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Sample records for glutamate msg-obese rats

  1. The PPARalpha/gamma dual agonist chiglitazar improves insulin resistance and dyslipidemia in MSG obese rats.

    PubMed

    Li, Ping-Ping; Shan, Song; Chen, Yue-Teng; Ning, Zhi-Qiang; Sun, Su-Juan; Liu, Quan; Lu, Xian-Ping; Xie, Ming-Zhi; Shen, Zhu-Fang

    2006-07-01

    1. The aim of this study was to investigate the capacity of chiglitazar to improve insulin resistance and dyslipidemia in monosodium L-glutamate (MSG) obese rats and to determine whether its lipid-lowering effect is mediated through its activation of PPARalpha. 2. Chiglitazar is a PPARalpha/gamma dual agonist. 3. The compound improved impaired insulin and glucose tolerance; decreased plasma insulin level and increased the insulin sensitivity index and decreased HOMA index. Euglycemic hyperinsulinemic clamp studies showed chiglitazar increased the glucose infusion rate in MSG obese rats. 4. Chiglitazar inhibited alanine gluconeogenesis, lowered the hepatic glycogen level in MSG obese rats. Like rosiglitazone, chiglitazar promoted the differentiation of adipocytes and decreased the maximal diameter of adipocytes. In addition, chiglitazar decreased the fibrosis and lipid accumulation in the islets and increased the size of islets. 5. Chiglitazar reduced plasma triglyceride, total cholesterol (TCHO), nonesterified fatty acids (NEFA) and low density lipoprotein-cholesterol levels; lowered hepatic triglyceride and TCHO contents; decreased muscular NEFA level. Unlike rosiglitazone, chiglitazar showed significant increase of mRNA expression of PPARalpha, CPT1, BIFEZ, ACO and CYP4A10 in the liver of MSG obese rats. 6. These data suggest that PPARalpha/gamma coagonist, such as chiglitazar, affect lipid homeostasis with different mechanisms from rosiglitazone, chiglitazar may have better effects on lipid homeostasis in diabetic patients than selective PPARgamma agonists. PMID:16751799

  2. Reproductive alterations in hyperinsulinemic but normoandrogenic MSG obese female rats.

    PubMed

    Gaspar, Renato Simões; Benevides, Renata Ohana Alves; Fontelles, João Lucas de Lima; Vale, Caroline Castro; França, Lucas Martins; Barros, Paulo de Tarso Silva; Paes, Antonio Marcus de Andrade

    2016-05-01

    Obesity and metabolic syndrome are the common causes of reproductive and fertility disorders in women. In particular, polycystic ovary syndrome, which is clinically characterized by hyperandrogenism, oligo/anovulation, and polycystic ovarian morphology, has been increasingly associated with metabolic disorders. However, given the broad interplay between metabolic and reproductive functions, this remains a field of intense research. In this study, we investigated the effect of monosodium l-glutamate (MSG)-induced obesity on reproductive biology of female rats. Newborn female rats were subcutaneously injected with MSG (4g/kg/day) or equiosmolar saline (CTR) each 2 days up to postnatal day (pnd) 10. On pnd 60, estrous cycle was evaluated using vaginal smears twice a day for 15 days, which showed MSG rats to be oligocyclic. Thereafter, animals were killed on estrous phase for blood and tissue collection. MSG rats had increased body mass, accumulation of retroperitoneal and visceral fat pads, and visceral adipocyte hypertrophy compared with CTR rats. MSG rats were also dyslipidemic and hyperinsulinemic but were normoglycemic and normoandrogenic. Ovarian morphology analysis showed that MSG rats had a two-fold decrease in oocyte count but a six-fold increase on ovarian follicular cysts, along with a higher number of total primordial and atretic follicles. Moreover, MSG rats had a four-fold increase in anti-Müllerian hormone immunohistochemical staining on antral follicles. Taken together, data presented here characterize MSG obesity as a unique model to study the metabolic pathways underlying reproductive disorders in the absence of overactivated hypothalamic-pituitary-gonadal axis. PMID:26952035

  3. Effects of fibre-enriched diets on tissue lipid profiles of MSG obese rats.

    PubMed

    Rotimi, O A; Olayiwola, I O; Ademuyiwa, O; Balogun, E A

    2012-11-01

    In order to investigate the influence of some fibre-enriched diets on tissue lipids in an animal model of obesity induced by the administration of monosodium glutamate (MSG), obese rats were fed diets containing 30% of Acha, Cassava, Maize and Plantain for five weeks and weight gain, feed intake and lee index were recorded. The lipid profiles of plasma, erythrocytes, kidney, heart and liver as well as hepatic 3-hydroxyl-3-methylglutaryl-CoA (HMG-CoA) reductase activity were measured. The diets significantly (p<0.05) reduced weight gain and lee index in the obese rats. Obesity-induced increase in plasma and erythrocytes lipid levels was significantly (p<0.05) reduced by these diets. MSG-induced obesity also resulted in a significant increase (p<0.05) in hepatic cholesterol level which was reduced by the diets. MSG-obesity was characterised by a significant (p<0.05) increase in cholesterol, triacylglycerol and phospholipids in kidney and this was reversed by the diets except Maize which did not reverse the increased cholesterol level. Only Acha reversed the obesity-induced increase in heart cholesterol and phospholipids. The increased activity of hepatic HMG-CoA reductase associated with obesity was also significantly (p<0.05) reduced by the diets. In conclusion, dyslipidemia associated with MSG-induced obesity could be attenuated by consumption of fibre-enriched diets. PMID:22898616

  4. Surgical removal of visceral fat decreases plasma free fatty acid and increases insulin sensitivity on liver and peripheral tissue in monosodium glutamate (MSG)-obese rats.

    PubMed

    Kim, Y W; Kim, J Y; Lee, S K

    1999-10-01

    In order to evaluate the role of visceral and subcutaneous fat tissue in insulin sensitivity and lipid metabolism, we measured the fasting levels of plasma free fatty acid (FFA) and insulin, glucose disappearance rate (Rd), and hepatic glucose production rate (HGP) after surgical removal of visceral (VF) or subcutaneous (SF) fat tissue in monosodium glutamate-obese (MSG-Ob) rats. Monosodium glutamate obesity was induced in rats by neonatal injection of MSG. Surgery to remove fat was done at 15 weeks of age. The experiments were done four weeks after the surgery. MSG-Ob rats showed increased levels of FFA, insulin, and HGP and decreased Rd compared to normal rats. In the VF group, the FFA level and HGP were decreased to normal values, Rd was partially normalized, but the level of insulin did not change significantly compared to MSG-Ob. In the SF group, FFA and Rd were partially normalized, but HGP was not suppressed significantly compared to MSG-Ob. These results suggest that visceral fat affects the insulin sensitivity of liver and FFA concentration more than subcutaneous fat; however, no significant difference was shown on whole body insulin sensitivity and fasting insulin concentration. PMID:10576150

  5. Vagotomy ameliorates islet morphofunction and body metabolic homeostasis in MSG-obese rats.

    PubMed

    Lubaczeuski, C; Balbo, S L; Ribeiro, R A; Vettorazzi, J F; Santos-Silva, J C; Carneiro, E M; Bonfleur, M L

    2015-05-01

    The parasympathetic nervous system is important for β-cell secretion and mass regulation. Here, we characterized involvement of the vagus nerve in pancreatic β-cell morphofunctional regulation and body nutrient homeostasis in 90-day-old monosodium glutamate (MSG)-obese rats. Male newborn Wistar rats received MSG (4 g/kg body weight) or saline [control (CTL) group] during the first 5 days of life. At 30 days of age, both groups of rats were submitted to sham-surgery (CTL and MSG groups) or subdiaphragmatic vagotomy (Cvag and Mvag groups). The 90-day-old MSG rats presented obesity, hyperinsulinemia, insulin resistance, and hypertriglyceridemia. Their pancreatic islets hypersecreted insulin in response to glucose but did not increase insulin release upon carbachol (Cch) stimulus, despite a higher intracellular Ca(2+) mobilization. Furthermore, while the pancreas weight was 34% lower in MSG rats, no alteration in islet and β-cell mass was observed. However, in the MSG pancreas, increases of 51% and 55% were observed in the total islet and β-cell area/pancreas section, respectively. Also, the β-cell number per β-cell area was 19% higher in MSG rat pancreas than in CTL pancreas. Vagotomy prevented obesity, reducing 25% of body fat stores and ameliorated glucose homeostasis in Mvag rats. Mvag islets demonstrated partially reduced insulin secretion in response to 11.1 mM glucose and presented normalization of Cch-induced Ca(2+) mobilization and insulin release. All morphometric parameters were similar among Mvag and CTL rat pancreases. Therefore, the higher insulin release in MSG rats was associated with greater β-cell/islet numbers and not due to hypertrophy. Vagotomy improved whole body nutrient homeostasis and endocrine pancreatic morphofunction in Mvag rats. PMID:25714886

  6. HPA axis and vagus nervous function are involved in impaired insulin secretion of MSG-obese rats.

    PubMed

    Miranda, Rosiane A; Torrezan, Rosana; de Oliveira, Júlio C; Barella, Luiz F; da Silva Franco, Claudinéia C; Lisboa, Patrícia C; Moura, Egberto G; Mathias, Paulo C F

    2016-07-01

    Neuroendocrine dysfunctions such as the hyperactivity of the vagus nerve and hypothalamus-pituitary-adrenal (HPA) axis greatly contribute to obesity and hyperinsulinemia; however, little is known about these dysfunctions in the pancreatic β-cells of obese individuals. We used a hypothalamic-obesity model obtained by neonatal treatment with monosodium l-glutamate (MSG) to induce obesity. To assess the role of the HPA axis and vagal tonus in the genesis of hypercorticosteronemia and hyperinsulinemia in an adult MSG-obese rat model, bilateral adrenalectomy (ADX) and subdiaphragmatic vagotomy (VAG) alone or combined surgeries (ADX-VAG) were performed. To study glucose-induced insulin secretion (GIIS) and the cholinergic insulinotropic process, pancreatic islets were incubated with different glucose concentrations with or without oxotremorine-M, a selective agonist of the M3 muscarinic acetylcholine receptor (M3AChR) subtype. Protein expression of M3AChR in pancreatic islets, corticosteronemia, and vagus nerve activity was also evaluated. Surgeries reduced 80% of the body weight gain. Fasting glucose and insulin were reduced both by ADX and ADX-VAG, whereas VAG was only associated with hyperglycemia. The serum insulin post-glucose stimulation was lower in all animals that underwent an operation. Vagal activity was decreased by 50% in ADX rats. In the highest glucose concentration, both surgeries reduced GIIS by 50%, whereas ADX-VAG decreased by 70%. Additionally, M3AChR activity was recovered by the individual surgeries. M3AChR protein expression was reduced by ADX. Both the adrenal gland and vagus nerve contribute to the hyperinsulinemia in the MSG model, although adrenal is more crucial as it appears to modulate parasympathetic activity and M3AChR expression in obesity. PMID:27113853

  7. Sex differences in brain cholinergic activity in MSG-obese rats submitted to exercise.

    PubMed

    Sagae, Sara Cristina; Grassiolli, Sabrina; Raineki, Charlis; Balbo, Sandra Lucinei; Marques da Silva, Ana Carla

    2011-11-01

    Obesity is an epidemic disease most commonly caused by a combination of increased energy intake and lack of physical activity. The cholinergic system has been shown to be involved in the regulation of food intake and energy expenditure. Moreover, physical exercise promotes a reduction of fat pads and body mass by increasing energy expenditure, but also influences the cholinergic system. The aim of this study is to evaluate the interaction between physical exercise (swimming) and central cholinergic activity in rats treated with monosodium glutamate (MSG, a model for obesity) during infancy. Our results show that MSG treatment is able to induce obesity in male and female rats. Specifically, MSG-treated rats presented a reduced body mass and nasoanal length, and increased perigonadal and retroperitoneal fat pads in relation to the body mass. Physical exercise was able to reduce body mass in both male and female rats, but did not change the fat pads in MSG-treated rats. Increased food intake was only seen in MSG-treated females submitted to exercise. Cholinergic activity was increased in the cortex of MSG-treated females and physical exercise was able to reduce this activity. Thalamic cholinergic activity was higher in sedentary MSG-treated females and exercised MSG-treated males. Hypothalamic cholinergic activity was higher in male and female MSG-treated rats, and was not reduced by exercise in the 2 sexes. Taken together, these results show that MSG treatment and physical exercise have different effects in the cholinergic activity of males and females. PMID:22039988

  8. Physical exercise introduced after weaning enhances pancreatic islet responsiveness to glucose and potentiating agents in adult MSG-obese rats.

    PubMed

    Ribeiro, R A; Bonfleur, M L; Vanzela, E C; Zotti, A I; Scomparin, D X; Boschero, A C; Balbo, S L

    2014-08-01

    Physical exercise represents an alternative way to prevent and/or ameliorate chronic metabolic diseases. Disruption of sympathetic nervous system (SNS) activity contributes to adiposity in obese subjects. Here, we verified the preventive effect of swimming training upon adiposity, adrenal catecholamine storage, and pancreatic islet function in obese monosodium glutamate (MSG)-treated rats. Male neonatal Wistar rats received MSG (4 mg/g body weight) during the first 5 days of life and, at weaning, half of the rats were submitted to swimming training, 30 min/day, 3 days a week, until 90 days of age (exercised rats: MSGex). Half of the rats were used as controls (sedentary group, MSGsd). Exercise training (ET) decreased insulinemia and fat deposition in MSGex, and increased adrenal catecholamine content, compared with MSGsd rats. Insulinemia during the ivGTT was lower in MSGex rats, despite a lack of difference in glycemia. Swimming training enhanced insulin release in islets challenged by 2.8-8.3 mmol/l glucose, whereas, at supraphysiological glucose concentrations (11.1-16.7 mmol/l), MSGex islets secreted less insulin than MSGsd. No differences in insulin secretion were observed following l-arginine (Arg) or K(+) stimuli. In contrast, islets from MSGex rats secreted more insulin when exposed to carbachol (100 μmol/l), forskolin (10 μmol/l), or IBMX (1 mmol/l) at 8.3 mmol/l glucose. Additionally, MSGex islets presented a better epinephrine inhibition upon insulin release. These results demonstrate that ET prevented the onset of obesity in MSG rats, probably by enhancing adrenal catecholamine levels. ET ameliorates islet responsiveness to several compounds, as well as insulin peripheral action. PMID:24554535

  9. Impaired muscarinic type 3 (M3) receptor/PKC and PKA pathways in islets from MSG-obese rats.

    PubMed

    Ribeiro, Rosane Aparecida; Balbo, Sandra Lucinei; Roma, Letícia Prates; Camargo, Rafael Ludemann; Barella, Luiz Felipe; Vanzela, Emerielle Cristine; de Freitas Mathias, Paulo Cesar; Carneiro, Everardo Magalhães; Boschero, Antonio Carlos; Bonfleur, Maria Lúcia

    2013-07-01

    Monosodium glutamate-obese rats are glucose intolerant and insulin resistant. Their pancreatic islets secrete more insulin at increasing glucose concentrations, despite the possible imbalance in the autonomic nervous system of these rats. Here, we investigate the involvement of the cholinergic/protein kinase (PK)-C and PKA pathways in MSG β-cell function. Male newborn Wistar rats received a subcutaneous injection of MSG (4 g/kg body weight (BW)) or hyperosmotic saline solution during the first 5 days of life. At 90 days of life, plasma parameters, islet static insulin secretion and protein expression were analyzed. Monosodium glutamate rats presented lower body weight and decreased nasoanal length, but had higher body fat depots, glucose intolerance, hyperinsulinemia and hypertrigliceridemia. Their pancreatic islets secreted more insulin in the presence of increasing glucose concentrations with no modifications in the islet-protein content of the glucose-sensing proteins: the glucose transporter (GLUT)-2 and glycokinase. However, MSG islets presented a lower secretory capacity at 40 mM K(+) (P < 0.05). The MSG group also released less insulin in response to 100 μM carbachol, 10 μM forskolin and 1 mM 3-isobutyl-1-methyl-xantine (P < 0.05, P < 0.0001 and P < 0.01). These effects may be associated with a the decrease of 46 % in the acetylcholine muscarinic type 3 (M3) receptor, and a reduction of 64 % in PKCα and 36 % in PKAα protein expressions in MSG islets. Our data suggest that MSG islets, whilst showing a compensatory increase in glucose-induced insulin release, demonstrate decreased islet M3/PKC and adenylate cyclase/PKA activation, possibly predisposing these prediabetic rodents to the early development of β-cell dysfunction. PMID:23652999

  10. Low fish oil intake improves insulin sensitivity, lipid profile and muscle metabolism on insulin resistant MSG-obese rats

    PubMed Central

    2011-01-01

    Background Obesity is commonly associated with diabetes, cardiovascular diseases and cancer. The purpose of this study was to determinate the effect of a lower dose of fish oil supplementation on insulin sensitivity, lipid profile, and muscle metabolism in obese rats. Methods Monosodium glutamate (MSG) (4 mg/g body weight) was injected in neonatal Wistar male rats. Three-month-old rats were divided in normal-weight control group (C), coconut fat-treated normal weight group (CO), fish oil-treated normal weight group (FO), obese control group (Ob), coconut fat-treated obese group (ObCO) and fish oil-treated obese group (ObFO). Obese insulin-resistant rats were supplemented with fish oil or coconut fat (1 g/kg/day) for 4 weeks. Insulin sensitivity, fasting blood biochemicals parameters, and skeletal muscle glucose metabolism were analyzed. Results Obese animals (Ob) presented higher Index Lee and 2.5 fold epididymal and retroperitoneal adipose tissue than C. Insulin sensitivity test (Kitt) showed that fish oil supplementation was able to maintain insulin sensitivity of obese rats (ObFO) similar to C. There were no changes in glucose and HDL-cholesterol levels amongst groups. Yet, ObFO revealed lower levels of total cholesterol (TC; 30%) and triacylglycerol (TG; 33%) compared to Ob. Finally, since exposed to insulin, ObFO skeletal muscle revealed an increase of 10% in lactate production, 38% in glycogen synthesis and 39% in oxidation of glucose compared to Ob. Conclusions Low dose of fish oil supplementation (1 g/kg/day) was able to reduce TC and TG levels, in addition to improved systemic and muscle insulin sensitivity. These results lend credence to the benefits of n-3 fatty acids upon the deleterious effects of insulin resistance mechanisms. PMID:21526994

  11. [A preliminary study on the mechanism of impaired beta cell function in monosodium glutamate obese rat with insulin resistance].

    PubMed

    Liu, Shuai-Nan; Liu, Quan; Shen, Zhu-Fang

    2008-11-01

    This study is to evaluate beta cell function and investigate the mechanism of impaired pancreatic islet beta cell function in monosodium glutamate (MSG) obese rat with insulin resistance, an animal model of metabolic syndrome. Insulin tolerance test was used to screen MSG obese rats with insulin resistance. Blood concentrations of glucose, triglyceride, total cholesterol and insulin were determined. Beta cell function was assessed with hyperglycemic clamp technique. The morphological alterations in pancreas and changes of islet beta cell mass were evaluated by hematoxylin-eosin (HE) and Gomori aldehyde fuchsin staining. Lipid, oxidative stress relevant factors, nitric oxide (NO) level and activity of ATPase in pancreas and pancreatic mitochondrial were tested. The MSG obese rats with insulin resistance could be validated as a typical metabolic syndrome animal model possessing increased fasting plasma triglycerides and insulin (P < 0. 001), markedly decreased weight indices of pancreas and impaired glucose-stimulated insulin secretion. Hematoxylin-eosin (HE) and Gomori aldehyde fuchsin staining showed increased adipocytes and fibroplasia deposition in pancreas and reduced beta cell mass. The increased contents of triglyceride and NO level, the decreased SOD levels and activities of total ATPase (P < 0.001), Na+-K+-ATPase (P < 0.001) and Ca2+-Mg2+-ATPase (P < 0.01) were observed in pancreas and its mitochondria versus normal rat. The study demonstrates that accumulation of lipids in pancreas could lead to increased systemic indicators of inflammation, such as NO, which may influence the activities of several kinds of ATPase in cell membranes and interfere the ion transport, substance metabolism and energy production in pancreas. Finally the MSG obese rats characterized with metabolic syndrome displayed an impairment of beta cell function. PMID:19239028

  12. Renal sympathetic nerve activity is increased in monosodium glutamate induced hyperadipose rats.

    PubMed

    da Silva Mattos, Alexandro Márcio; Xavier, Carlos Henrique; Karlen-Amarante, Marlusa; da Cunha, Natália Veronez; Fontes, Marco Antonio Peliky; Martins-Pinge, Marli Cardoso

    2012-08-01

    The literature suggests that both obesity and hypertension are associated with increased sympathetic nerve activity. In the present study we evaluated the renal sympathetic nerve activity (RSNA), mean arterial pressure (MAP) and heart rate (HR) in hyperadipose rats induced by neonatal administration of monosodium glutamate (MSG). Neonatal Wistar male rats were injected with MSG (4 mg/g body weight ID) or equimolar saline (control) for 5 days. At 90th day, all rats were anesthetized (urethane 1.4 g/kg) and prepared for MAP, HR and renal sympathetic nerve activity recordings. The anesthetized MSG rats presented baseline hypertension and increased baseline RSNA compared with control. Our results suggest the involvement of the renal sympathetic nervous system in the physiopathology of the MSG obesity. PMID:22705582

  13. Altered baroreflex and autonomic modulation in monosodium glutamate-induced hyperadipose rats.

    PubMed

    Karlen-Amarante, Marlusa; da Cunha, Natália Veronez; de Andrade, Ozahyr; de Souza, Hugo Celso Dutra; Martins-Pinge, Marli Cardoso

    2012-10-01

    We aimed to examine the cardiovascular function by tonic and baroreflex alterations in obese rats induced by monosodium glutamate (MSG). Neonatal male Wistar rats were injected with MSG (4 mg/g body weight) or equimolar saline (control, C). At 90 days, all rats were anesthetized for catheterization of the femoral artery for mean arterial pressure (MAP) and heart rate (HR) recordings in the conscious state. After baseline, we performed IV treatment with hexamethonium (25 mg/kg), or atropine (1 mg/kg) or propranolol (3 mg/kg). We also performed the spectral analysis of heart rate variability (HRV) and baroreflex sensitivity. Baseline comparison showed that obese rats are hypertensive compared with control (C=110±2 mmHg; MSG=: 123±3 mmHg, P<0.05). After ganglionic blockade with hexamethonium the differences in MAP between control and obese rats disappeared. Beta adrenergic blockade with propranolol induced a greater decrease in heart rate compared with control. The analysis of HRV showed that obese rats have increased modulation by both components of the autonomic nervous system compared with control rats. The baroreflex gain showed increased sensitivity for the parasympathetic component in the obese rats (C=-2.41±0.25; MSG=-3.34±0.23 bpm/mmHg) compared with control. Our data suggest that both components of autonomic cardiac tonus and the parasympathetic component of the baroreflex sensitivity are increased in the MSG obese rat. It is possible that the parasympathetic alterations observed in these MSG obese rats may have originated from central areas of cardiovascular control. PMID:22554831

  14. Anorexigenic effect of cholecystokinin is lost but that of CART (Cocaine and Amphetamine Regulated Transcript) peptide is preserved in monosodium glutamate obese mice.

    PubMed

    Zelezná, B; Maixnerová, J; Matysková, R; Haugvicová, R; Blokesová, D; Maletínská, L

    2009-01-01

    Monosodium glutamate (MSG) treatment of neonatal mice results in a selective damage to the arcuate nucleus (ARC) and development of obesity with increased adiposity at sustained body weight in the adulthood. Feeding pattern of the MSG obese mice is unusual. Our previous results showed that after 24-h fasting, MSG mice consumed negligible amount of food in several hours and therefore, it was impossible to register the effect of peptides attenuating food intake such as cholecystokinin (CCK) or cocaine- and amphetamine-regulated transcript (CART) peptide. To overcome this problem, two findings were used: firstly, orexigenic effect of neuropeptide Y (NPY) was attenuated both by CCK or CART peptide in lean fed mice and secondly, orexigenic effect of NPY was preserved in fed rats with MSG obesity. In this study, short-term food intake in fed lean and MSG obese C57BL/6 male mice was measured after simultaneous central administration of orexigenic NPY with either CART peptide or peripherally administered CCK. Anorexigenic action of exogenous CART peptide was preserved in MSG obese mice. On the other hand, satiety effect of exogenous CCK was completely lost in MSG obese mice. In conclusion, effective leptin signaling in ARC is necessary for satiety effect of CCK. PMID:19093718

  15. Recombinant murine fibroblast growth factor 21 ameliorates obesity-related inflammation in monosodium glutamate-induced obesity rats.

    PubMed

    Wang, Wen-Fei; Li, Si-Ming; Ren, Gui-Ping; Zheng, Wei; Lu, Yu-Jia; Yu, Yin-Hang; Xu, Wen-Juan; Li, Tian-He; Zhou, Li-Hong; Liu, Yan; Li, De-Shan

    2015-05-01

    The aim of this study is to investigate the role of FGF21 in obesity-related inflammation in livers of monosodium glutamate (MSG)-induced obesity rats. The MSG rats were injected with recombinant murine fibroblast growth factor 21(FGF21) or equal volumes of vehicle. Metabolic parameters including body weight, Lee's index, food intake, visceral fat and liver weight, intraperitoneal glucose tolerance, glucose, and lipid levels were dynamically measured at specific time points. Liver function and routine blood test were also analyzed. Further, systemic inflammatory cytokines such as glucose transporter 1 (GLUT-1), leptin, TNF-α, and IL-6 mRNAs were determined by real-time PCR. FGF21 independently decreased body weight and whole-body fat mass without reducing food intake in the MSG rats. FGF21 reduced blood glucose level, Lee's index, visceral fat, and liver weight, and improved glucose tolerance, lipid metabolic spectrum, and hepatic steatosis in the MSG-obesity rats. Liver function parameters including AST, ALT, ALP, TP, T.Bili, and D.Bili levels significantly reduced in the FGF21-treated obesity rats compared to the controls. Further, FGF21 ameliorated the total and differential white blood cell (WBC) count, serum C-reactive protein (CRP), IL-6, and TNF-α levels in adipose tissues of the obesity rats, suggesting inflammation amelioration in the in the obesity rats by FGF21. FGF21 improves multiple metabolic disorders and ameliorates obesity-related inflammation in the MSG-induced obesity rats. PMID:25306889

  16. Mechanisms underlying hypertriglyceridemia in rats with monosodium L-glutamate-induced obesity: evidence of XBP-1/PDI/MTP axis activation.

    PubMed

    França, Lucas Martins; Freitas, Larissa Nara Costa; Chagas, Vinicyus Teles; Coêlho, Caio Fernando Ferreira; Barroso, Wermerson Assunção; Costa, Graciomar Conceição; Silva, Lucilene Amorim; Debbas, Victor; Laurindo, Francisco Rafael Martins; Paes, Antonio Marcus de Andrade

    2014-01-10

    Non-alcoholic fatty liver disease (NAFLD) is intimately associated with insulin resistance and hypertriglyceridemia, whereas many of the mechanisms underlying this association are still poorly understood. In the present study, we investigated the relationship between microsomal triglyceride transfer protein (MTP) and markers of endoplasmic reticulum (ER) stress in the liver of rats subjected to neonatal monosodium L-glutamate (MSG)-induced obesity. At age 120 days old, the MSG-obese animals exhibited hyperglycemia, hypertriglyceridemia, insulin resistance, and liver steatosis, while the control (CTR) group did not. Analysis using fast protein liquid chromatography of the serum lipoproteins revealed that the triacylglycerol content of the very low-density lipoprotein (VLDL) particles was twice as high in the MSG animals compared with the CTR animals. The expression of ER stress markers, GRP76 and GRP94, was increased in the MSG rats, promoting a higher expression of X-box binding protein 1 (XBP-1), protein disulfide isomerase (PDI), and MTP. As the XBP-1/PDI/MTP axis has been suggested to represent a significant lipogenic mechanism in the liver response to ER stress, our data indicate that hypertriglyceridemia and liver steatosis occurring in the MSG rats are associated with increased MTP expression. PMID:24333444

  17. Regional brain glutamate transport in rats at normal and raised concentrations of circulating glutamate.

    PubMed

    Hawkins, R A; DeJoseph, M R; Hawkins, P A

    1995-08-01

    The permeability of the blood-brain barrier to glutamate was measured by quantitative autoradiography in brains of control rats (average plasma glutamate concentration of 95 microns) and rats infused with glutamate (average plasma glutamate concentration of 837 microns). Measurements of glutamate permeability were initiated by the injection of [14C]glutamate and stopped at 1 min to avoid the accumulation of [14C]glutamate metabolites. Glutamate entered the brain at a slow rate, with an average permeability-surface area product of 7 microliters.min-g-1, except in those areas known to have fenestrated capillaries. Glutamate accumulated in the choroid plexus of ventricles, but did not seem to enter the cerebrospinal fluid in detectable amounts regardless of the circulating concentration. Glutamate accumulated in circumventricular organs, such as the median eminence, where the radioactivity was localized without detectable spread. Infusion of glutamate to create high plasma concentrations did not result in greater spread of [14C]glutamate beyond the immediate vicinity of the circumventricular organs. PMID:7648616

  18. Glutamate-induced sensitization of rat masseter muscle fibers.

    PubMed

    Cairns, B E; Gambarota, G; Svensson, P; Arendt-Nielsen, L; Berde, C B

    2002-01-01

    In rats, intradermal or intraarticular injection of glutamate or selective excitatory amino acid receptor agonists acting at peripheral excitatory amino acid receptors can decrease the intensity of mechanical stimulation required to evoke nocifensive behaviors, an indication of hyperalgesia. Since excitatory amino acid receptors have been found on the terminal ends of cutaneous primary afferent fibers, it has been suggested that increased tissue glutamate levels may have a direct sensitizing effect on primary afferent fibers, in particular skin nociceptors. However, less is known about the effects of glutamate on deep tissue afferent fibers. In the present study, a series of experiments were undertaken to investigate the effect of intramuscular injection of glutamate on the excitability and mechanical threshold of masseter muscle afferent fibers in anesthetized rats of both sexes. Injection of 1.0 M, but not 0.1 M glutamate evoked masseter muscle afferent activity that was significantly greater than that evoked by isotonic saline. The mechanical threshold of masseter muscle afferent fibers, which was assessed with a Von Frey hair, was reduced by approximately 50% for a period of 30 min after injection of 1.0 M glutamate, but was unaffected by injections of 0.1 M glutamate or isotonic saline. Injection of 25% dextrose, which has the same osmotic strength as 1.0 M glutamate, did not evoke significant activity in or decrease the mechanical threshold of masseter muscle afferent fibers. Magnetic resonance imaging experiments confirmed that injection of 25% dextrose and 1.0 M glutamate produced similar edema volumes in the masseter muscle tissue. Co-injection of 0.1 M kynurenate, an excitatory amino acid receptor antagonist, and 1.0 M glutamate attenuated glutamate-evoked afferent activity and prevented glutamate-induced mechanical sensitization. When male and female rats were compared, no difference in the baseline mechanical threshold or in the magnitude of glutamate

  19. Polysaccharides from wolfberry antagonizes glutamate excitotoxicity in rat cortical neurons.

    PubMed

    Ho, Yuen-Shan; Yu, Man-Shan; Yik, Suet-Yi; So, Kwok-Fai; Yuen, Wai-Hung; Chang, Raymond Chuen-Chung

    2009-12-01

    Glutamate excitotoxicity is involved in many neurodegenerative diseases including Alzheimer's disease (AD). Attenuation of glutamate toxicity is one of the therapeutic strategies for AD. Wolfberry (Lycium barbarum) is a common ingredient in oriental cuisines. A number of studies suggest that wolfberry has anti-aging properties. In recent years, there is a trend of using dried Wolfberry as food supplement and health product in UK and North America. Previously, we have demonstrated that a fraction of polysaccharide from Wolfberry (LBA) provided remarkable neuroprotective effects against beta-amyloid peptide-induced cytotoxicity in primary cultures of rat cortical neurons. To investigate whether LBA can protect neurons from other pathological factors such as glutamate found in Alzheimer brain, we examined whether it can prevent neurotoxicity elicited by glutamate in primary cultured neurons. The glutamate-induced cell death as detected by lactate dehydrogenase assay and caspase-3-like activity assay was significantly reduced by LBA at concentrations ranging from 10 to 500 microg/ml. Protective effects of LBA were comparable to memantine, a non-competitive NMDA receptor antagonist. LBA provided neuroprotection even 1 h after exposure to glutamate. In addition to glutamate, LBA attenuated N-methyl-D-aspartate (NMDA)-induced neuronal damage. To further explore whether LBA might function as antioxidant, we used hydrogen peroxide (H(2)O(2)) as oxidative stress inducer in this study. LBA could not attenuate the toxicity of H(2)O(2). Furthermore, LBA did not attenuate glutamate-induced oxidation by using NBT assay. Western blot analysis indicated that glutamate-induced phosphorylation of c-jun N-terminal kinase (JNK) was reduced by treatment with LBA. Taken together, LBA exerted significant neuroprotective effects on cultured cortical neurons exposed to glutamate. PMID:19499323

  20. Opioid-glutamate interactions in rat locus coeruleus neurons.

    PubMed

    Oleskevich, S; Clements, J D; Williams, J T

    1993-09-01

    1. The effect of mu-opioids on the glutamate response was investigated in rat locus coeruleus (LC) neurons by intracellular recording in the brain slice preparation. Glutamate responses were evoked by bath application of selective glutamate agonists, glutamate iontophoresis, and stimulation of excitatory afferents. 2. The mu-opioid agonist D-Ala2-MePhe4-Gly-ol5-enkephalin (DAMGO; 1 microM) potentiated the response to bath application of N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazole proprionic acid by 91 and 142%, respectively, in slices cut in the horizontal plane. The mechanism of action of this effect was investigated under conditions that limited the DAMGO-induced hyperpolarization and improved the space clamp of the neuron through 1) addition of barium, 2) increase in extracellular potassium concentration, 3) sectioning of the LC in the coronal plane, and 4) addition of carbenoxolone. Each experimental manipulation decreased the DAMGO outward current and reduced the mu-opioid potentiation of the glutamate response. The results suggest that the mu-opioid-mediated potentiation of the glutamate response is dependent on membrane hyperpolarization. 3. Neither forskolin nor the phorbol ester 4b-phorbol 12,13-dibutyrate (PDBu) altered the glutamate-mediated inward currents. The potentiation of the glutamate response by DAMGO was not affected by PDBu. 4. The mu-opioids DAMGO and [met]5enkephalin (10 microM) did not significantly affect the NMDA receptor-mediated depolarization (mean 14%) evoked by local application of glutamate but inhibited the NMDA receptor-mediated synaptic potential (mean 25%).(ABSTRACT TRUNCATED AT 400 WORDS) PMID:7693886

  1. The mechanism of proline/glutamate antiport in rat kidney mitochondria. Energy dependence and glutamate-carrier involvement.

    PubMed

    Atlante, A; Passarella, S; Pierro, P; Di Martino, C; Quagliariello, E

    1996-10-01

    Proline/glutamate antiport in rat kidney mitochondria has been studied in terms of two different features: energy dependence and glutamate-carrier contribution to accomplish proline movement across the mitochondrial membrane. Energy dependence of the proline/glutamate antiporter in rat kidney mitochondria has been investigated by means of both spectroscopic measurements and isotopic techniques, using either normal or [14C]glutamate-loaded mitochondria. The sensitivity of the proline/glutamate antiport to the ionophores valinomycin and nigericin, under conditions in which delta psi and delta pH are selectively affected, shows that the exchange is energy dependent. Measurements of both membrane potential and proton movement across the mitochondrial membrane suggest that proline/glutamate antiport is driven by the electrochemical proton gradient via the delta psi dependent proline/glutamate translocator and delta pH-dependent glutamate/OH- carrier. Such a carrier provides for re-uptake of glutamate that has already passed out of the mitochondria in exchange with incoming proline, made possible by the existence of a separate pool of glutamate in the intermembrane space, directly shown by means of HPLC measurements. PMID:8898903

  2. Intragastric administration of glutamate increases REM sleep in rats.

    PubMed

    Datta, Karuna; Kumar, Deependra; Mallick, Hruda Nanda

    2013-10-01

    Monosodium glutamate, a umami taste substance is commonly used flavor enhancer. The effect of intragastric administration of 1.5 ml of 0.12M monosodium glutamate on sleep-wake was studied in 10 adult male Wistar rats. Sleep-wake parameters were recorded through chronically implanted electroencephalogram, electrooculogram and electromyogram electrodes using a digital recording system (BIOPAC system Inc. BSL PRO 36, USA). The sleep-wake was recorded for 6h after the intragastric administration of either glutamate or saline. Sleep-wake stages were analyzed as wake, slow wave sleep and REM sleep. Compared to saline, intragastric administration of glutamate significantly increased REM sleep duration and episode frequency. REM sleep duration was increased in all the three 2h bins, 10:00-12:00 h (p=0.037), 12:00-14:00 h (p=0.037) and 14:00-16:00 h (p=0.007). The slow wave sleep and total sleep time were not affected. It is concluded that intragastric glutamate administration increases REM sleep. PMID:24055576

  3. Rapid Microelectrode Measurements and the Origin and Regulation of Extracellular Glutamate in Rat Prefrontal Cortex

    PubMed Central

    Hascup, E.R.; Hascup, K.N.; Stephens, M.; Pomerleau, F.; Huettl, P.; Gratton, A.; Gerhardt, G.A.

    2010-01-01

    Glutamate in the prefrontal cortex (PFC) plays a significant role in several mental illnesses, including schizophrenia, addiction and anxiety. Previous studies on PFC glutamate-mediated function have used techniques that raise questions on the neuronal vs. astrocytic origin of glutamate. The present studies used enzyme-based microelectrode arrays (MEAs) to monitor second-by-second resting glutamate levels in the PFC of awake rats. Locally-applied drugs were employed in an attempt to discriminate between the neuronal or glial components of the resting glutamate signal. Local application of tetrodotoxin (TTX; sodium channel blocker), produced a significant (~40%) decline in resting glutamate levels. In addition significant reductions in extracellular glutamate were seen with locally-applied ω-conotoxin (MVIIC; ~50%; calcium channel blocker), and the mGluR⅔ agonist, LY379268 (~20%), and a significant increase with the mGluR⅔ antagonist LY341495 (~40%), effects all consistent with a large neuronal contribution to the resting glutamate levels. Local administration of D,L-threo-β-benzyloxyaspartate (TBOA; glutamate transporter inhibitor) produced an ~120% increase in extracellular glutamate levels, supporting that excitatory amino acid transporters, which are largely located on glia, modulate clearance of extracellular glutamate. Interestingly, local application of (S)-4-carboxyphenylglycine (CPG; cystine/glutamate antiporter inhibitor), produced small, non-significant bi-phasic changes in extracellular glutamate versus vehicle control. Finally, pre-administration of TTX completely blocked the glutamate response to tail pinch stress. Taken together, these results support that PFC resting glutamate levels in rats as measured by the MEA technology are at least 40-50% derived from neurons. Furthermore, these data support that the impulse flow-dependent glutamate release from a physiologically-evoked event is entirely neuronally derived. PMID:20969570

  4. Metabotropic glutamate receptors depress glutamate-mediated synaptic input to rat midbrain dopamine neurones in vitro.

    PubMed

    Wigmore, M A; Lacey, M G

    1998-02-01

    1. Glutamate (AMPA receptor-mediated) excitatory postsynaptic potentials (e.p.s.ps.), evoked by electrical stimulation rostral to the recording site, were examined by intracellular microelectrode recording from dopamine neurones in parasagittal slices of rat ventral midbrain. 2. The e.p.s.p. was depressed by the group III metabotropic glutamate (mGlu) receptor agonist L-2-amino-4-phosphonobutyric acid (L-AP4; 0.01-30 microM) by up to 60% with an EC50 of 0.82 microM. The depression induced by L-AP4 (3 microM) was reversed by the group III preferring mGlu receptor antagonist, alpha-methyl-4-phosphonophenylglycine (MPPG; 250 microM). 3. The group I and II mGlu agonist, 1S,3R-aminocyclopentanedicarboxylic acid (ACPD; 3-30 microM) also depressed the e.p.s.p. in a concentration-dependent manner. The effect of ACPD (10 microM) was reversed by (+)-alpha-methyl-4-carboxyphenylglycine (MCPG; 1 mM; 4 cells). This effect of ACPD was also partially antagonized (by 50.3+/-15.7%, 4 cells) by MPPG (250 microM). 4. The selective agonist at group I mGlu receptors, dihydroxyphenylglycine (DHPG; 100 microM), decreased e.p.s.p. amplitude by 27.1+/-8.2% (7 cells), as did the group II mGlu receptor-selective agonist (1S,1R,2'R,3'R)-2-(2,3-dicarboxycyclopropyl)glycine (DCG-IV; 1 microM) by 26.7+/-4.3% (5 cells). 5. DHPG (10-100 microM) caused a depolarization of the recorded cell, as did ACPD (3-30 microM), whereas no such postsynaptic effect of either L-AP4 or DCG-IV was observed. 6. These results provide evidence for the presence of presynaptic inhibitory metabotropic glutamate autoreceptors from the mGlu receptor groups II and III on descending glutamatergic inputs to midbrain dopamine neurones. Group I mGlu receptors mediate a postsynaptic depolarization, and can also depress glutamatergic transmission, but may not necessarily be localized presynaptically. These sites represent novel drug targets for treatment of schizophrenia and movement disorders of basal ganglia origin. PMID

  5. Metabotropic glutamate receptors depress glutamate-mediated synaptic input to rat midbrain dopamine neurones in vitro

    PubMed Central

    Wigmore, Mark A; Lacey, Michael G

    1998-01-01

    Glutamate (AMPA receptor-mediated) excitatory postsynaptic potentials (e.p.s.ps.), evoked by electrical stimulation rostral to the recording site, were examined by intracellular microelectrode recording from dopamine neurones in parasagittal slices of rat ventral midbrain. The e.p.s.p. was depressed by the group III metabotropic glutamate (mGlu) receptor agonist L-2-amino-4-phosphonobutyric acid (L-AP4; 0.01–30 μM) by up to 60% with an EC50 of 0.82 μM. The depression induced by L-AP4 (3 μM) was reversed by the group III preferring mGlu receptor antagonist, α-methyl-4-phosphonophenylglycine (MPPG; 250 μM). The group I and II mGlu agonist, 1S,3R-aminocyclopentanedicarboxylic acid (ACPD; 3–30 μM) also depressed the e.p.s.p. in a concentration-dependent manner. The effect of ACPD (10 μM) was reversed by (+)-α-methyl-4-carboxyphenylglycine (MCPG; 1 mM; 4 cells). This effect of ACPD was also partially antagonized (by 50.3±15.7%, 4 cells) by MPPG (250 μM). The selective agonist at group I mGlu receptors, dihydroxyphenylglycine (DHPG; 100 μM), decreased e.p.s.p. amplitude by 27.1±8.2% (7 cells), as did the group II mGlu receptor-selective agonist (1S,1′R,2′R,3′R)-2-(2,3-dicarboxycyclopropyl)glycine (DCG-IV; 1 μM) by 26.7±4.3% (5 cells). DHPG (10–100 μM) caused a depolarization of the recorded cell, as did ACPD (3–30 μM), whereas no such postsynaptic effect of either L-AP4 or DCG-IV was observed. These results provide evidence for the presence of presynaptic inhibitory metabotropic glutamate autoreceptors from the mGlu receptor groups II and III on descending glutamatergic inputs to midbrain dopamine neurones. Group I mGlu receptors mediate a postsynaptic depolarization, and can also depress glutamatergic transmission, but may not necessarily be localized presynaptically. These sites represent novel drug targets for treatment of schizophrenia and movement disorders of basal ganglia origin. PMID:9517386

  6. Ammonia triggers exocytotic release of L-glutamate from cultured rat astrocytes.

    PubMed

    Görg, Boris; Morwinsky, Anke; Keitel, Verena; Qvartskhava, Natalia; Schrör, Karsten; Häussinger, Dieter

    2010-04-15

    Ammonia toxicity to the brain involves NMDA receptor overactivation and glutamate excitotoxicity. The mechanisms underlying glutamate release from astrocytes in response to ammonia were addressed in this study. In cultured rat astrocytes, glutamate immunoreactivity (IR) was punctate and partly colocalized with transfected VAMP2-YFP. NH(4)Cl (5 mmol/L) and hypoosmotic exposure (205 mosmol/L) induced a rapid colchicine-sensitive loss of cellular glutamate and glutamate appearance in the extracellular space. The NH(4)Cl-induced glutamate loss from astrocytes was strongly blunted after transfection of the cells with VAMP2 siRNA. Ammonia-induced exocytosis of VAMP2-YFP expressing vesicles was shown by total internal reflection fluorescence microscopy (TIRF-M). Glutamate exocytosis in response to ammonia was sensitive to chelation of Ca(2+), cyclooxygenase inhibition by indomethacin and colchicine. Ammonia triggered the rapid formation of prostanoids, which were identified as upstream events in ammonia-induced glutamate exocytosis. Also, addition of prostaglandin E(2) or of tumor necrosis factor (TNF)-alpha triggered glutamate exocytosis. Inhibition of ammonia-induced glutamate exocytosis after transfection of VAMP2 siRNA inhibited ammonia-induced RNA oxidation. It is concluded that ammonia triggers a prostanoid- and Ca(2+)-dependent glutamate exocytosis, which is essential for induction of ammonia-induced RNA oxidation. PMID:20014275

  7. Hypoxia regulates glutamate metabolism and membrane transport in rat PC12 cells.

    PubMed

    Kobayashi, S; Millhorn, D E

    2001-03-01

    We investigated the effect of hypoxia on glutamate metabolism and uptake in rat pheochromocytoma (PC12) cells. Various key enzymes relevant to glutamate production, metabolism and transport were coordinately regulated by hypoxia. PC12 cells express two glutamate-metabolizing enzymes, glutamine synthetase (GS) and glutamate decarboxylase (GAD), as well as the glutamate-producing enzyme, phosphate-activated glutaminase (PAG). Exposure to hypoxia (1% O(2)) for 6 h or longer increased expression of GS mRNA and protein and enhanced GS enzymatic activity. In contrast, hypoxia caused a significant decrease in expression of PAG mRNA and protein, and also decreased PAG activity. In addition, hypoxia led to an increase in GAD65 and GAD67 protein levels and GAD enzymatic activity. PC12 cells express three Na(+)-dependent glutamate transporters; EAAC1, GLT-1 and GLAST. Hypoxia increased EAAC1 and GLT-1 protein levels, but had no effect on GLAST. Chronic hypoxia significantly enhanced the Na(+)-dependent component of glutamate transport. Furthermore, chronic hypoxia decreased cellular content of glutamate, but increased that of glutamine. Taken together, the hypoxia-induced changes in enzymes related to glutamate metabolism and transport are consistent with a decrease in the extracellular concentration of glutamate. This may have a role in protecting PC12 cells from the cytotoxic effects of glutamate during chronic hypoxia. PMID:11259512

  8. GLUTAMATE NEUROTOXICITY IN RAT AUDITORY SYSTEM: COCHLEAR NUCLEAR COMPLEX

    EPA Science Inventory

    In other systems such as the hypothalamus and hippocampus, it has been shown that cells postsynaptic with respect to glutamatergic inputs degenerate when exposed to large doses of glutamate ("glutamate neurotoxicity"). e have shown that large doses of glutamate administered intra...

  9. Local glutamate release in the rat ventral lateral thalamus evoked by high-frequency stimulation

    NASA Astrophysics Data System (ADS)

    Agnesi, Filippo; Blaha, Charles D.; Lin, Jessica; Lee, Kendall H.

    2010-04-01

    Thalamic deep brain stimulation (DBS) is proven therapy for essential tremor, Parkinson's disease and Tourette's syndrome. We tested the hypothesis that high-frequency electrical stimulation results in local thalamic glutamate release. Enzyme-linked glutamate amperometric biosensors were implanted in anesthetized rat thalamus adjacent to the stimulating electrode. Electrical stimulation was delivered to investigate the effect of frequency, pulse width, voltage-controlled or current-controlled stimulation, and charge balancing. Monophasic electrical stimulation-induced glutamate release was linearly dependent on stimulation frequency, intensity and pulse width. Prolonged stimulation evoked glutamate release to a plateau that subsequently decayed back to baseline after stimulation. Glutamate release was less pronounced with voltage-controlled stimulation and not present with charge balanced current-controlled stimulation. Using fixed potential amperometry in combination with a glutamate bioprobe and adjacent microstimulating electrode, the present study has shown that monophasic current-controlled stimulation of the thalamus in the anesthetized rat evoked linear increases in local extracellular glutamate concentrations that were dependent on stimulation duration, frequency, intensity and pulse width. However, the efficacy of monophasic voltage-controlled stimulation, in terms of evoking glutamate release in the thalamus, was substantially lower compared to monophasic current-controlled stimulation and entirely absent with biphasic (charge balanced) current-controlled stimulation. It remains to be determined whether similar glutamate release occurs with human DBS electrodes and similar charge balanced stimulation. As such, the present results indicate the importance of evaluating local neurotransmitter dynamics in studying the mechanism of action of DBS.

  10. Biochemical and immunological changes on oral glutamate feeding in male albino rats

    NASA Astrophysics Data System (ADS)

    Kumar, D.; Bansal, Anju; Thomas, Pauline; Sairam, M.; Sharma, S. K.; Mongia, S. S.; Singh, R.; Selvamurthy, W.

    High altitude stress leads to lipid peroxidation and free radical formation which results in cell membrane damage in organs and tissues, and associated mountain diseases. This paper discusses the changes in biochemical parameters and antibody response on feeding glutamate to male albino Sprague Dawley rats under hypoxic stress. Exposure of rats to simulated hypoxia at 7576 m, for 6 h daily for 5 consecutive days, in an animal decompression chamber at 32+/-2° C resulted in an increase in plasma malondialdehyde level with a concomitant decrease in blood glutathione (reduced) level. Supplementation of glutamate orally at an optimal dose (27 mg/kg body weight) in male albino rats under hypoxia enhanced glutathione level and decreased malondialdehyde concentration significantly. Glutamate feeding improved total plasma protein and glucose levels under hypoxia. The activities of serum glutamate oxaloacetate transaminase (SGOT) and serum glutamate pyruvate transaminase (SGPT) and the urea level remained elevated on glutamate supplementation under hypoxia. Glutamate supplementation increased the humoral response against sheep red blood cells (antibody titre). These results indicate a possible utility of glutamate in the amelioration of hypoxia-induced oxidative stress.

  11. Pharmacological modulation of brain levels of glutamate and GABA in rats exposed to total sleep deprivation

    PubMed Central

    Kamal, Sahar Mohamed

    2010-01-01

    Modulation of gamma-aminobutyric acid (GABA) and glutamate by selected antidepressants and anticonvulsants could play a beneficial role in total sleep deprivation (TSD) caused by depressed mood. In the present study, albino rats were exposed to TSD for five days. On the sixth day, the brains were removed, and GABA and glutamate levels were measured in the prefrontal cortex and thalamus to identify TSD-induced changes in untreated rats and in rats treated with carbamazepine 40 mg/kg intraperitoneally (IP), fluoxetine 20 mg/kg IP, or desipramine 10 mg/kg IP. Carbamazepine and fluoxetine significantly increased GABA and reduced glutamate levels in both brain areas. Desipramine administration did not affect GABA or glutamate concentrations in the tested brain areas; levels were comparable with those induced by TSD without treatment. These results suggest that administration of carbamazepine or fluoxetine could have a beneficial effect by increasing GABA levels during TSD.

  12. Resting Glutamate Levels and Rapid Glutamate Transients in the Prefrontal Cortex of the Flinders Sensitive Line Rat: A Genetic Rodent Model of Depression

    PubMed Central

    Hascup, Kevin N; Hascup, Erin R; Stephens, Michelle L; Glaser, Paul EA; Yoshitake, Takashi; Mathé, Aleksander A; Gerhardt, Greg A; Kehr, Jan

    2011-01-01

    Despite the numerous drugs targeting biogenic amines for major depressive disorder (depression), the search for novel therapeutics continues because of their poor response rates (∼30%) and slow onset of action (2–4 weeks). To better understand role of glutamate in depression, we used an enzyme-based microelectrode array (MEA) that was selective for glutamate measures with fast temporal (2 Hz) and high spatial (15 × 333 μm) resolution. These MEAs were chronically implanted into the prefrontal cortex of 3- to 6-month-old and 12- to 15-month-old Flinders Sensitive Line (FSL) and control Flinders Resistant Line (FRL) rats, a validated genetic rodent model of depression. Although no changes in glutamate dynamics were observed between 3 and 6 months FRL and FSL rats, a significant increase in resting glutamate levels was observed in the 12- to 15-month-old FSL rats compared with the 3- to 6-month-old FSL and age-matched FRL rats on days 3–5 post-implantation. Our MEA also recorded, for the first time, a unique phenomenon in all the four rat groups of fluctuations in resting glutamate, which we have termed glutamate transients. Although these events lasted only for seconds, they did occur throughout the testing paradigm. The average concentration of these glutamate-burst events was significantly increased in the 12- to 15-month-old FSL rats compared with 3- to 6-month-old FSL and age-matched FRL rats. These studies lay the foundation for future studies of both tonic and phasic glutamate signaling in rat models of depression to better understand the potential role of glutamate signaling in depression. PMID:21525860

  13. The efficacy of probiotics for monosodium glutamate-induced obesity: dietology concerns and opportunities for prevention

    PubMed Central

    2014-01-01

    Introduction Obesity becomes endemic today. Monosodium glutamate was proved as obesogenic food additive. Probiotics are discussed to impact on obesity development. Aims and objectives The aim was to study the effects of probiotics on the development of monosodium glutamate (MSG)-induced obesity in rats. Material and methods We included 45 Wistar male rats and divided into three groups (n = 15). Newborn rats of group 1 (control) received subcutaneously 8 μl/g saline. Group 2 received 3 to 4 mg/g MSG subcutaneously on the second, fourth, sixth, eighth and tenth day of life. Within 4 months after birth, rats were on a standard diet. Group 3 received an aqueous solution of probiotics mixture (2:1:1 Lactobacillus casei IMVB-7280, Bifidobacterium animalis VKL, B. animalis VKB) at the dose of 5 × 109 CFU/kg (50 mg/kg) intragastrically. Administration of probiotics was started at the age of 4 weeks just after weaning and continued for 3 months during 2-week courses. Group 2 received intragastrically 2.5 ml/kg water. Organometric and biochemical parameters in all groups of rats were analyzed over 4 months. The concentration of adiponectin was determined in serum, and leptin - in adipose tissue. Results Administration of MSG led to the development of obesity in rats; body weight had increased by 7.9% vs controls (p < 0.05); body length had increased by 5.4% (p < 0.05). Body mass index and Lee index and visceral fat mass had increased (p < 0.001). Under the neonatal injection of MSG, the concentration of total cholesterol, triglycerides, VLDL cholesterol and LDL cholesterol significantly increased (p < 0.001), in comparison with controls. Adipose-derived hormones changed in MSG obesity rats: adiponectin decreased by 58.8% (p < 0.01), and leptin concentration in adipose tissue had increased by 74.7% (p < 0.01). The probiotic therapy of rats from group 3 prevented obesity development. Parameters of rats treated with probiotic mixture did not differ from that in

  14. Blockade of spinal glutamate recycling produces paradoxical antinociception in rats with orofacial inflammatory pain.

    PubMed

    Yang, Kui Y; Mun, Jun H; Park, Ki D; Kim, Min J; Ju, Jin S; Kim, Seong T; Bae, Yong C; Ahn, Dong K

    2015-03-01

    In our current study, we investigated the role of spinal glutamate recycling in the development of orofacial inflammatory pain. DL-threo-β-benzyloxyaspartate (TBOA) or methionine sulfoximine (MSO) was administered intracisternally to block spinal glutamate transporter and glutamine synthetase activity in astroglia. Intracisternal administration of high dose TBOA (10 μg) produced thermal hyperalgesia in naïve rats but significantly attenuated the thermal hyperalgesia in rats that had been pretreated with interleukin (IL)-1β or Complete Freund's Adjuvant (CFA). In contrast, intracisternal injection of MSO produced anti-hyperalgesic effects against thermal stimuli in CFA-treated rats only. To confirm the paradoxical antinociceptive effects of TBOA and MSO, we examined changes in c-Fos expression in the medullary dorsal horn produced by thermal stimulation in naïve, IL-1β-, or CFA-treated rats, after intracisternal injections of TBOA and MSO. Intracisternal administration of TBOA significantly increased c-Fos immunoreactivity in naïve rats. In contrast, intracisternal administration of TBOA significantly decreased the up-regulation of c-Fos immunoreactivity in the medullary dorsal horn of IL-1β- and CFA-treated rats. However, intracisternal injection of MSO blocked the up-regulation of c-Fos immunoreactivity in CFA-treated rats only. We also investigated the effects of botulinum toxin type A (BoNT-A) on TBOA-induced paradoxical antinociception in CFA-treated rats, as BoNT-A inhibits the release of neurotransmitters, including glutamate. BoNT-A treatment reversed behavioral responses produced by intracisternal administration of TBOA in CFA-treated rats. These results suggest that the paradoxical responses produced by blocking glutamate transporters under inflammatory pain conditions are mediated by the modulation of glutamate release from presynaptic terminals. Moreover, blockade of glutamate reuptake could represent a new therapeutic target for the treatment of

  15. GLUTAMATE NEUROTOXICITY IN THE DEVELOPING RAT COCHLEA: PHYSIOLOGICAL AND MORPHOLOGICAL APPROACHES

    EPA Science Inventory

    The neurotoxic effects of exogenous glutamate were studied in the rat cochlea. lutamate-treated rats (4g/kg/day ip, postnatal days 2 through 9) exhibited electrophysiologically-measured elevations in high frequency thresholds usually associated with hair cell loss in the basal re...

  16. Rapid uncoupling of oxidative phosphorylation accompanies glutamate toxicity in rat cerebellar granule cells.

    PubMed

    Atlante, A; Gagliardi, S; Minervini, G M; Marra, E; Passarella, S; Calissano, P

    1996-11-01

    A 100 microM glutamate pulse administered to rat cerebellar granule cells causes a very rapid and progressive decrease in both cell and mitochondrial oxygen consumption caused by glucose and succinate addition, respectively. The respiratory control ratio, which reflects the ability of mitochondria to produce ATP, is reduced by 50% within the first 30 min after glutamate addition. Subsequent to glutamate exposure, a progressive decrease of respiratory control ratio to almost 1 was found within the following 3-5 h. The addition of extra calcium had no effect per se on oxygen consumption by cell homogenate. PMID:8981415

  17. [Glutamate metabolism in cerebral cortex obtained from chronic hepatic failure rats].

    PubMed

    Ito, M; Matsumoto, H; Kikuchi, S; Yachi, A

    1986-09-01

    The present investigation was carried out in order to elucidate the amino acid metabolism in hepatic failure with particular emphasis placed on glutamate. For this purpose, chronic hepatic failure models were produced in adult male Wistar rats by successive carbontetrachloride injection (0.20 ml/100 g. B. W., twice/week) for 13 weeks. They were confirmed to develop chemical changes compartible with hepatic failure, showing markedly elevated serum levels of NH3, GOT and ALP. Animals were killed by decapitation during fasting and the brains were removed immediately. After the parietal cortical slices were incubated for 45 min at 37 degrees C together with L-(U-14C) glutamate in O2-saturated Gey's balanced salt solution, they were homogenized in 75% ethanol and deproteinized with water saturated chloroform. The radioactivities of liberated CO2, glutamate and its metabolites (glutamine, aspartate and GABA) obtained from the slices were measured. The amount of radioactivity recovered from CO2, glutamine and aspartate revealed a significant increase (p less than 0.001), while that of glutamate and GABA remained unchanged. The main source of the CO2 is believed to originate from TCA cycle rather than the decarboxylation of glutamate to form GABA, and glutamate forms glutamine when it fixes ammonia. Furthermore, glutamate is converted into aspartate via TCA cycle when the carbon was labeled. Therefore, the results indicate that in chronic hepatic failure brains glutamate metabolism is enhanced through TCA cycle as well as ammonia fixation mechanism. PMID:3790365

  18. Time-dependent changes in extracellular glutamate in the rat dorsolateral striatum following a single cocaine injection.

    PubMed

    McKee, B L; Meshul, C K

    2005-01-01

    Acute cocaine administration has been shown to alter dorsal striatal plasticity [Proc Natl Acad Sci USA 87 (1990) 6912; Brain Res Bull 30 (1993) 173] and produce long-term neurochemical changes [Pharmacol Biochem Behav 27 (1987) 533]. To date, the effects of acute cocaine on extracellular glutamate and nerve terminal glutamate immunolabeling in the rat dorsolateral striatum have not been reported. To investigate cocaine-induced changes in extracellular glutamate, in vivo microdialysis was carried out in the dorsolateral striatum of rats 1-14 days after receiving a single injection of either vehicle or 15 mg/kg cocaine. There was an increase in the group injected with cocaine 1 day prior to measuring extracellular glutamate as compared with the control group. The group injected with cocaine 3 days prior to the microdialysis session had decreased extracellular glutamate levels. Furthermore, extracellular glutamate remained attenuated 14 days after acute cocaine treatment. Striatal glutamate decreased in the cocaine-treated rats after calcium removal, suggesting that cocaine-induced changes in extracellular glutamate were partially calcium-dependent. The density of nerve terminal glutamate immunolabeling was measured using immunogold electron microscopy in the contralateral striatum of the same rats that had been acutely treated with cocaine or vehicle. There were no changes in the density of glutamate immunolabeling within identified nerve terminals making an asymmetrical (excitatory) synaptic contact 1, 2, 3, or 14 days after acute cocaine exposure as compared with the control groups. Hence, these alterations in extracellular glutamate did not result from changes in glutamate immunolabeling within the synaptic vesicle pool. In addition, no changes in glutamate immunolabeling were found in rats that received cocaine 2 h previously or were withdrawn after 1 week of cocaine administration. The results demonstrate that a single injection of cocaine produces biphasic

  19. Functional and morphological characterization of glutamate transporters in the rat locus coeruleus

    PubMed Central

    Medrano, M C; Gerrikagoitia, I; Martínez-Millán, L; Mendiguren, A; Pineda, J

    2013-01-01

    Background and Purpose Excitatory amino acid transporters (EAATs) in the CNS contribute to the clearance of glutamate released during neurotransmission. The aim of this study was to explore the role of EAATs in the regulation of locus coeruleus (LC) neurons by glutamate. Experimental Approach We measured the effect of different EAAT subtype inhibitors/enhancers on glutamate- and KCl-induced activation of LC neurons in rat slices. EAAT2–3 expression in the LC was also characterized by immunohistochemistry. Key Results The EAAT2–5 inhibitor DL-threo-β-benzyloxaspartic acid (100 μM), but not the EAAT2, 4, 5 inhibitor L-trans-pyrrolidine-2,4-dicarboxylic acid (100 μM) or the EAAT2 inhibitor dihydrokainic acid (DHK; 100 μM), enhanced the glutamate- and KCl-induced activation of the firing rate of LC neurons. These effects were blocked by ionotropic, but not metabotrobic, glutamate receptor antagonists. DHK (100 μM) was the only EAAT inhibitor that increased the spontaneous firing rate of LC cells, an effect that was due to inhibition of EAAT2 and subsequent AMPA receptor activation. Chronic treatment with ceftriaxone (200 mg·kg−1 i.p., once daily, 7 days), an EAAT2 expression enhancer, increased the actions of glutamate and DHK, suggesting a functional impact of EAAT2 up-regulation on the glutamatergic system. Immuhistochemical data revealed the presence of EAAT2 and EAAT3 surrounding noradrenergic neurons and EAAT2 on glial cells in the LC. Conclusions and Implications These results remark the importance of EAAT2 and EAAT3 in the regulation of rat LC by glutamate. Neuronal EAAT3 would be responsible for terminating the action of synaptically released glutamate, whereas glial EAAT2 would regulate tonic glutamate concentrations in this nucleus. PMID:23638698

  20. L-glutamic acid: a neurotransmitter candidate for cone photoreceptors in human and rat retinas.

    PubMed Central

    Brandon, C; Lam, D M

    1983-01-01

    We have combined immunocytochemical localization of L-aspartate aminotransferase (L-aspartate:2-oxoglutarate aminotransferase, EC 2.6.1.1; glutamic-oxaloacetic transaminase) with autoradiographic localization of high-affinity uptake sites for L-glutamate or L-aspartate to identify the neurotransmitters of mammalian photoreceptors. In both human and rat retinas, high aspartate aminotransferase immunoreactivity is found in cones but not in rods; certain putative bipolar and amacrine cells are also heavily stained. In the human retina, and perhaps also in the rat retina, cones possess a high-affinity uptake mechanism for L-glutamate but not L-aspartate, whereas rods and Müller (glial) cells take up both L-glutamate and L-aspartate. Taken together, our results indicate that (i) L-glutamate is much more likely than L-aspartate to be the transmitter for human cones, and possibly for cones of other mammalian species as well, and (ii) major differences exist between mammalian cones and rods in the transport and metabolism or utilization of L-aspartate and L-glutamate. Images PMID:6136039

  1. Presynaptic kainate receptor facilitation of glutamate release involves protein kinase A in the rat hippocampus

    PubMed Central

    Rodríguez-Moreno, Antonio; Sihra, Talvinder S

    2004-01-01

    We have explored the mechanisms involved in the facilitation of glutamate release mediated by the activation of kainate receptors in the rat hippocampus using isolated nerve terminal (synaptosome) and slice preparations. In hippocampal nerve terminals, kainate (KA) produced an increase of glutamate release at concentrations of agonist ranging from 10 to 1000 μm. In hippocampal slices, KA at low nanomolar concentrations (20–50 nm) also produced an increase of evoked excitatory postsynaptic currents (eEPSCs) at mossy fibre–CA3 synapses. In both, synaptosomes and slices, the effect of KA was antagonized by CNQX, and persisted after pretreatment with a cocktail of antagonists for other receptors whose activation could potentially have produced facilitation of release. These data indicate that the facilitation of glutamate release observed is mediated by the activation of presynaptic glutamate receptors of the kainate type. Mechanistically, the observed effects of KA appear to be the same in synaptosomal and slice preparations. Thus, the effect of KA on glutamate release and mossy fibre–CA3 synaptic transmission was occluded by the stimulation of adenylyl cyclase by forskolin and suppressed by the inhibition of protein kinase A by H-89 or Rp-Br-cAMP. We conclude that kainate receptors present at presynaptic terminals in the rat hippocampus mediate the facilitation of glutamate release through a mechanism involving the activation of an adenylyl cyclase–second messenger cAMP–protein kinase A signalling cascade. PMID:15107475

  2. Quantitative autoradiographic distribution of L-(3H)glutamate-binding sites in rat central nervous system

    SciTech Connect

    Greenamyre, J.T.; Young, A.B.; Penney, J.B.

    1984-08-01

    Quantitative autoradiography was used to determine the distribution of L-(3H)glutamate-binding sites in the rat central nervous system. Autoradiography was carried out in the presence of Cl- and Ca2+ ions. Scatchard plots and Hill coefficients of glutamate binding suggested that glutamate was interacting with a single population of sites having a K-D of about 300 nM and a capacity of 14.5 pmol/mg of protein. In displacement studies, ibotenate also appeared to bind to a single class of non-interacting sites with a KI of 28 microM. However, quisqualate displacement of (3H)glutamate binding revealed two well-resolved sites with KIS of 12 nM and 114 microM in striatum. These sites were unevenly distributed, representing different proportions of specific glutamate binding in different brain regions. The distribution of glutamate-binding sites correlated very well with the projection areas of putative glutamatergic pathways. This technique provides an extremely sensitive assay which can be used to gather detailed pharmacological and anatomical information about L-(3H)glutamate binding in the central nervous system.

  3. Glutamine synthetase activity and glutamate uptake in hippocampus and frontal cortex in portal hypertensive rats

    PubMed Central

    Acosta, Gabriela Beatriz; Fernández, María Alejandra; Roselló, Diego Martín; Tomaro, María Luján; Balestrasse, Karina; Lemberg, Abraham

    2009-01-01

    AIM: To study glutamine synthetase (GS) activity and glutamate uptake in the hippocampus and frontal cortex (FC) from rats with prehepatic portal vein hypertension. METHODS: Male Wistar rats were divided into sham-operated group and a portal hypertension (PH) group with a regulated stricture of the portal vein. Animals were sacrificed by decapitation 14 d after portal vein stricture. GS activity was determined in the hippocampus and FC. Specific uptake of radiolabeled L-glutamate was studied using synaptosome-enriched fractions that were freshly prepared from both brain areas. RESULTS: We observed that the activity of GS increased in the hippocampus of PH rats, as compared to control animals, and decreased in the FC. A significant decrease in glutamate uptake was found in both brain areas, and was more marked in the hippocampus. The decrease in glutamate uptake might have been caused by a deficient transport function, significantly and persistent increase in this excitatory neurotransmitter activity. CONCLUSION: The presence of moderate ammonia blood levels may add to the toxicity of excitotoxic glutamate in the brain, which causes alterations in brain function. Portal vein stricture that causes portal hypertension modifies the normal function in some brain regions. PMID:19533812

  4. Chronic postnatal stress induces voluntary alcohol intake and modifies glutamate transporters in adolescent rats.

    PubMed

    Odeon, María Mercedes; Andreu, Marcela; Yamauchi, Laura; Grosman, Mauricio; Acosta, Gabriela Beatriz

    2015-01-01

    Postnatal stress alters stress responses for life, with serious consequences on the central nervous system (CNS), involving glutamatergic neurotransmission and development of voluntary alcohol intake. Several drugs of abuse, including alcohol and cocaine, alter glutamate transport (GluT). Here, we evaluated effects of chronic postnatal stress (CPS) on alcohol intake and brain glutamate uptake and transporters in male adolescent Wistar rats. For CPS from postnatal day (PD) 7, pups were separated from their mothers and exposed to cold stress (4 °C) for 1 h daily for 20 days; controls remained with their mothers. Then they were exposed to either voluntary ethanol (6%) or dextrose (1%) intake for 7 days (5-7 rats per group), then killed. CPS: (1) increased voluntary ethanol intake, (2) did not affect body weight gain or produce signs of toxicity with alcohol exposure, (3) increased glutamate uptake by hippocampal synaptosomes in vitro and (4) reduced protein levels (Western measurements) in hippocampus and frontal cortex of glial glutamate transporter-1 (GLT-1) and excitatory amino-acid transporter-3 (EAAT-3) but increased glutamate aspartate transporter (GLAST) levels. We propose that CPS-induced decrements in GLT-1 and EAAT-3 expression levels are opposed by activation of a compensatory mechanism to prevent excitotoxicity. A greater role for GLAST in total glutamate uptake to prevent enlarged extracellular glutamate levels is inferred. Although CPS strongly increased intake of ethanol, this had little impact on effects of CPS on brain glutamate uptake or transporters. However, the impact of early life adverse events on glutamatergic neurotransmission may underlie increased alcohol consumption in adulthood. PMID:26037264

  5. Mitochondria accumulate Ca2+ following intense glutamate stimulation of cultured rat forebrain neurones.

    PubMed Central

    White, R J; Reynolds, I J

    1997-01-01

    1. In cultures of rat forebrain neurones, mitochondria buffer glutamate-induced, NMDA receptor-mediated Ca2+ influx. Here, we have used the fluorescent calcium indicator, indo-1 AM to record [Ca2+]i from single cells. We varied either the glutamate concentration or the duration of exposure to investigate the cellular mechanisms recruited to buffer [Ca2+]i within different stimulation protocols. 2. For a 15 s stimulus, the recovery time doubled as the glutamate concentration was raised from 3 to 300 microM. Changing the duration of exposure from 15 s to 5 min increased the recovery time tenfold even when the glutamate concentration was held at 3 microM. 3. We used a selective inhibitor of the mitochondrial Na(+)-Ca2+ exchange, CGP-37157. When applied immediately after a 15 s, 100 microM glutamate challenge, CGP-37157 consistently caused a rapid fall in [Ca2+]i followed by a slow rise after the drug was washed out. A similar pattern was seen with the 5 min, 3 microM glutamate stimulus. The effects of CGP-37157 are consistent with the release of substantial mitochondrial Ca2+ stores during recovery from an intense glutamate stimulus. 4. These studies suggest that mitochondria become progressively more important for buffering glutamate-induced Ca2+ loads as the stimulus intensity increases. The recovery of [Ca2+]i to baseline following glutamate removal is critically regulated by the release of Ca2+ from mitochondrial stores via mitochondrial Na(+)-Ca2+ exchange. The data highlight a previously under-appreciated role for [Na+]i in the regulation of [Ca2+]i in central neurones. PMID:9023766

  6. Hispidulin inhibits the release of glutamate in rat cerebrocortical nerve terminals

    SciTech Connect

    Lin, Tzu-Yu; Lu, Cheng-Wei; Wang, Chia-Chuan; Lu, Jyh-Feng; Wang, Su-Jane

    2012-09-01

    Hispidulin, a naturally occurring flavone, has been reported to have an antiepileptic profile. An excessive release of glutamate is considered to be related to neuropathology of epilepsy. We investigated whether hispidulin affected endogenous glutamate release in rat cerebral cortex nerve terminals (synaptosomes) and explored the possible mechanism. Hispidulin inhibited the release of glutamate evoked by the K{sup +} channel blocker 4-aminopyridine (4-AP). The effects of hispidulin on the evoked glutamate release were prevented by the chelation of extracellular Ca{sup 2+} ions and the vesicular transporter inhibitor bafilomycin A1. However, the glutamate transporter inhibitor DL-threo-beta-benzyl-oxyaspartate did not have any effect on hispidulin action. Hispidulin reduced the depolarization-induced increase in cytosolic free Ca{sup 2+} concentration ([Ca{sup 2+}]{sub C}), but did not alter 4-AP-mediated depolarization. Furthermore, the effect of hispidulin on evoked glutamate release was abolished by blocking the Ca{sub v}2.2 (N-type) and Ca{sub v}2.1 (P/Q-type) channels, but not by blocking ryanodine receptors or mitochondrial Na{sup +}/Ca{sup 2+} exchange. Mitogen-activated protein kinase kinase (MEK) inhibition also prevented the inhibitory effect of hispidulin on evoked glutamate release. Western blot analyses showed that hispidulin decreased the 4-AP-induced phosphorylation of extracellular signal-regulated kinase 1 and 2 (ERK1/2) and synaptic vesicle-associated protein synapsin I, a major presynaptic substrate for ERK; this decrease was also blocked by the MEK inhibitor. Moreover, the inhibition of glutamate release by hispidulin was strongly attenuated in mice without synapsin I. These results show that hispidulin inhibits glutamate release from cortical synaptosomes in rats through the suppression of presynaptic voltage-dependent Ca{sup 2+} entry and ERK/synapsin I signaling pathway. -- Highlights: ► Hispidulin inhibited glutamate release from rat

  7. [Effect of cholinomimetics on L-glutamic acid release and uptake in the neostriatum of rats].

    PubMed

    Godukhin, O V; Budantsev, A Iu; Selifonova, O V; Agapova, V N

    1983-12-01

    The effects of cholinomimetics on release and uptake of exogenic glutamic acid in the rat brain neostriatum in vivo and in vitro were studied. Carbocholine and nicotin were shown to inhibit the release, carbocholine acting directly on the presynaptic receptors whereas nicotin acting indirectly through the interneurons of neostriatum. PMID:6141074

  8. EFFECTS OF PERINATAL MONOSODIUM GLUTAMATE ADMINISTRATIONON VISUAL EVOKED POTENTIALS OF JUVENILE AND ADULT RATS

    EPA Science Inventory

    Administration of high doses of monosodium glutamate (MSG) to rats during the first postnatal week results in severe losses of retinal ganglion cells and interneurons in the retina. his study was conducted to determine what effect this severe retinal damage would have upon the on...

  9. GLUTAMATE NEUROTOXICITY IN THE DEVELOPING RAT COCHLEA IS ANTAGONIZED BY KUNURENIC ACID AND MK-801

    EPA Science Inventory

    Glutamate (GLU) is neurotoxic in the neonatal rat cochlea, producing hearing impairment which is largely due to the death of spiral ganglion cells, whereas the receptor hair cells are spared. endritic fibers of the spiral ganglion are post-synaptic to the primary afferent synapse...

  10. Increased glutamate receptor gene expression in the cerebral cortex of insulin induced hypoglycemic and streptozotocin-induced diabetic rats.

    PubMed

    Joseph, A; Antony, S; Paulose, C S

    2008-10-01

    Hypoglycemia causes brain fuel deprivation, resulting in functional brain failure and brain death. It is a serious complication of insulin therapy in diabetic patients. A single intrafemoral dose of streptozotocin was administered to induce diabetes. Hypoglycemia was induced by appropriate doses of insulin s.c. in control and diabetic rats. Glutamate content and glutamate receptor kinetics were studied using [3H]glutamate. [3H]MK 801 was used to study the NMDA receptor kinetics. NMDA2B and metabotropic glutamate receptor (mGluR) 5 subunits receptor gene expressions were done using real time PCR. There was a significant (P<0.001) increase in the glutamate content in the cerebral cortex of hypoglycemic and diabetic rats when compared with control with more glutamate content in the hypoglycemic group. Scatchard analysis using [3H]glutamate and [3H]MK 801 in the cerebral cortex showed a significant (P<0.001) increase in the maximal binding (Bmax) in both hypoglycemic and diabetic rats when compared with control with no significant change in equilibrium dissociation constant. The glutamate and NMDA receptor binding parameters were significantly (P<0.001) enhanced in the hypoglycemic rats compared with hyperglycemic rats. Real time PCR analysis also showed a significant increase (P<0.001) in the gene expression of NMDA2B and mGluR5 subunits of glutamate receptor. This increased gene expression of NMDA2B and mGluR5 glutamate receptor subunits confirmed the enhanced mRNA of receptor subunits and subsequently at the protein level from the receptor kinetic studies. The enhanced glutamate receptors were more prominent in hypoglycemic group which is of significance in this study. Up-regulation of glutamate leads to Ca2+ overload in cells, potentially leading to cell damage and death. This functional damage during hypoglycemia is suggested to contribute to cognitive and memory deficits which has immense clinical relevance in the therapeutic management of diabetes. PMID:18761060

  11. Increased extracellular levels of glutamate in the hippocampus of chronically epileptic rats.

    PubMed

    Soukupova, M; Binaschi, A; Falcicchia, C; Palma, E; Roncon, P; Zucchini, S; Simonato, M

    2015-08-20

    An increase in the release of excitatory amino acids has consistently been observed in the hippocampus during seizures, both in humans and animals. However, very little or nothing is known about the extracellular levels of glutamate and aspartate during epileptogenesis and in the interictal chronic period of established epilepsy. The aim of this study was to systematically evaluate the relationship between seizure activity and changes in hippocampal glutamate and aspartate extracellular levels under basal and high K(+)-evoked conditions, at various time-points in the natural history of experimental temporal lobe epilepsy, using in vivo microdialysis. Hippocampal extracellular glutamate and aspartate levels were evaluated: 24h after pilocarpine-induced status epilepticus (SE); during the latency period preceding spontaneous seizures; immediately after the first spontaneous seizure; in the chronic (epileptic) period. We found that (i) basal (spontaneous) glutamate outflow is increased in the interictal phases of the chronic period, whereas basal aspartate outflow remains stable for the entire course of the disease; (ii) high K(+) perfusion increased glutamate and aspartate outflow in both control and pilocarpine-treated animals, and the overflow of glutamate was clearly increased in the chronic group. Our data suggest that the glutamatergic signaling is preserved and even potentiated in the hippocampus of epileptic rats, and thus may favor the occurrence of spontaneous recurrent seizures. Together with an impairment of GABA signaling (Soukupova et al., 2014), these data suggest that a shift toward excitation occurs in the excitation/inhibition balance in the chronic epileptic state. PMID:26073699

  12. Fangchinoline inhibits glutamate release from rat cerebral cortex nerve terminals (synaptosomes).

    PubMed

    Lin, Tzu-Yu; Lu, Cheng-Wei; Tien, Lu-Tai; Chuang, Shu-Han; Wang, Yu-Ru; Chang, Wen-Hsuan; Wang, Su-Jane

    2009-07-01

    Fangchinoline, an active component of radix stephaniae tetrandrinea, has been shown to possess neuroprotective properties. It has been reported that excessive glutamate release has been proposed to be involved in the pathogenesis of several neurological diseases. The primary purpose of the present study was to investigate the effect of fangchinoline on glutamate release in rat cerebral cortex nerve terminals and to explore the possible mechanism. Fangchinoline inhibited the release of glutamate evoked by 4-aminopyridine (4-AP) in a concentration-dependent manner, and this phenomenon resulted from a reduction of vesicular exocytosis but not from an inhibition of Ca(2+)-independent efflux via glutamate transporter. Fangchinoline did not alter the resting synaptosomal membrane potential or 4-AP-mediated depolarization, but significantly reduced depolarization-induced increase in [Ca(2+)](C). Fangchinoline-mediated inhibition of glutamate release was significantly prevented by the N- and P/Q-type Ca(2+) channel blocker omega-conotoxin MVIIC, and by the PKC inhibitors, GF109203X and Ro318220. In addition, the glutamate release mediated by direct Ca(2+) entry with Ca(2+) ionophore (ionomycin) was unaffected by fangchinoline, which suggests that the inhibitory effect of fangchinoline is not due to directly interfering with the release process at some point subsequent to Ca(2+) influx. These results suggest that fangchinoline inhibits glutamate release from the rat cortical synaptosomes through the suppression of voltage-dependent Ca(2+) channel activity and subsequent reduces Ca(2+) entry into nerve terminals, rather than any upstream effect on nerve terminal excitability. This inhibition appears to involve the suppression of PKC signal transduction pathway. This finding may explain the neuroprotective effects of fangchinoline against neurotoxicity. PMID:19428795

  13. Berberine Inhibits the Release of Glutamate in Nerve Terminals from Rat Cerebral Cortex

    PubMed Central

    Lu, Cheng-Wei; Huang, Shu-Kuei; Wang, Su-Jane

    2013-01-01

    Berberine, an isoquinoline plant alkaloid, protects neurons against neurotoxicity. An excessive release of glutamate is considered to be one of the molecular mechanisms of neuronal damage in several neurological diseases. In this study, we investigated whether berberine could affect endogenous glutamate release in nerve terminals of rat cerebral cortex (synaptosomes) and explored the possible mechanism. Berberine inhibited the release of glutamate evoked by the K+ channel blocker 4-aminopyridine (4-AP), and this phenomenon was prevented by the chelating extracellular Ca2+ ions and the vesicular transporter inhibitor bafilomycin A1, but was insensitive to the glutamate transporter inhibitor DL-threo-beta-benzyl-oxyaspartate. Inhibition of glutamate release by berberine was not due to it decreasing synaptosomal excitability, because berberine did not alter 4-AP-mediated depolarization. The inhibitory effect of berberine on glutamate release was associated with a reduction in the depolarization-induced increase in cytosolic free Ca2+ concentration. Involvement of the Cav2.1 (P/Q-type) channels in the berberine action was confirmed by blockade of the berberine-mediated inhibition of glutamate release by the Cav2.1 (P/Q-type) channel blocker ω-agatoxin IVA. In addition, the inhibitory effect of berberine on evoked glutamate release was prevented by the mitogen-activated/extracellular signal-regulated kinase kinase (MEK) inhibitors. Berberine decreased the 4-AP-induced phosphorylation of extracellular signal-regulated kinase 1 and 2 (ERK1/2) and synapsin I, the main presynaptic target of ERK; this decrease was also blocked by the MEK inhibition. Moreover, the inhibitory effect of berberine on evoked glutamate release was prevented in nerve terminals from mice lacking synapsin I. Together, these results indicated that berberine inhibits glutamate release from rats cortical synaptosomes, through the suppression of presynaptic Cav2.1 channels and ERK/synapsin I signaling

  14. Effects of Amoxicillin and Augmentin on Cystine-Glutamate Exchanger and Glutamate Transporter 1 Isoforms as well as Ethanol Intake in Alcohol-Preferring Rats.

    PubMed

    Hakami, Alqassem Y; Hammad, Alaa M; Sari, Youssef

    2016-01-01

    Alcohol dependence is associated with alteration of glutamate transport and glutamate neurotransmission. Glutamate transporter 1 (GLT-1) is a major transporter that regulates the majority of extracellular glutamate concentration, which is also regulated by cystine-glutamate exchanger (xCT). Importantly, we recently reported that amoxicillin and Augmentin (amoxicillin/clavulanate) upreglulated GLT-1 expression in nucleus accumbens (NAc) and prefrontal cortex (PFC) as well as reduced ethanol consumption in male P rats. In this study, we examined the effects of amoxicillin and Augmentin on GLT-1 isoforms (GLT-1a and GLT-1b), xCT, and glutamate/aspartate transporter (GLAST) expression in NAc and PFC as well as ethanol intake in male P rats. We found that both compounds significantly reduced ethanol intake, and increased GLT-1a, GLT-1b, and xCT expression in NAc. However, only Augmentin increased GLT-1a, GLT-1b, and xCT expression in PFC. There were no effects of these compounds on GLAST expression in NAc and PFC. These findings demonstrated that Augmentin and amoxicillin have the potential to upregulate GLT-1 isoforms and xCT expression, and consequently attenuate ethanol dependence. PMID:27199635

  15. Effects of Amoxicillin and Augmentin on Cystine-Glutamate Exchanger and Glutamate Transporter 1 Isoforms as well as Ethanol Intake in Alcohol-Preferring Rats

    PubMed Central

    Hakami, Alqassem Y.; Hammad, Alaa M.; Sari, Youssef

    2016-01-01

    Alcohol dependence is associated with alteration of glutamate transport and glutamate neurotransmission. Glutamate transporter 1 (GLT-1) is a major transporter that regulates the majority of extracellular glutamate concentration, which is also regulated by cystine-glutamate exchanger (xCT). Importantly, we recently reported that amoxicillin and Augmentin (amoxicillin/clavulanate) upreglulated GLT-1 expression in nucleus accumbens (NAc) and prefrontal cortex (PFC) as well as reduced ethanol consumption in male P rats. In this study, we examined the effects of amoxicillin and Augmentin on GLT-1 isoforms (GLT-1a and GLT-1b), xCT, and glutamate/aspartate transporter (GLAST) expression in NAc and PFC as well as ethanol intake in male P rats. We found that both compounds significantly reduced ethanol intake, and increased GLT-1a, GLT-1b, and xCT expression in NAc. However, only Augmentin increased GLT-1a, GLT-1b, and xCT expression in PFC. There were no effects of these compounds on GLAST expression in NAc and PFC. These findings demonstrated that Augmentin and amoxicillin have the potential to upregulate GLT-1 isoforms and xCT expression, and consequently attenuate ethanol dependence. PMID:27199635

  16. [The effect of probiotic therapy on development of experimental obesity in rats caused by monosodium glutamate].

    PubMed

    Savcheniuk, O A; Virchenko, O V; Falalieieva, T M; Beregova, T V; Babenko, L P; Lazarenko, L M; Spivak, M Ia

    2014-01-01

    The effect of a mixture of probiotic strains (2:1:1 Lactobacillus casei IMVB-7280, Bifidobacterium animalis VKL, Bifidobacterium animalis VKB) on the development of experimental obesity in rats induced by neonatal administration of monosodium glutamate has been studied. It was shown that in rats of 4 months age, the injection of monosodium glutamate (4 mg/g) at 2, 4, 6, 8, 10 days after birth elicited abdominal obesity and metabolic syndrome. An intermittent administration of a probiotic mixture to rats treated with monosodium prevented the development of obesity. In the group of rats treated with probiotics, anthropometric parameters (weight and body length, Lee index, body mass index) did not differ from the level of intact rats. Visceral fat mass was decreased by probiotics by 38.5% (P < 0.05) compared to rats treated with water. Probiotics improved lipid metabolism: reduced the level of VLDL by 32.2% (P < 0,05), the level of LDL by 30.6% (P < 0.05), increased HDL by 25.7% (P <0,05) compared to obese control rats. Probiotic strains restored the secretion of adipocytes hormones (leptin and adiponectin) to the normal level of intact animals. The results show the effectiveness of probiotics for the prevention of obesity. PMID:25007523

  17. Perinatal thiamine restriction affects central GABA and glutamate concentrations and motor behavior of adult rat offspring.

    PubMed

    Ferreira-Vieira, Talita Hélen; de Freitas-Silva, Danielle Marra; Ribeiro, Andrea Frozino; Pereira, Sílvia Rejane Castanheira; Ribeiro, Ângela Maria

    2016-03-23

    The purposes of the present study were to investigate the effects of perinatal thiamine deficiency, from the 11th day of gestation until the 5th day of lactation, on motor behavior and neurochemical parameters in adult rat offspring, using 3-month-old, adult, male Wistar rats. All rats were submitted to motor tests, using the rotarod and paw print tasks. After behavioral tests, their thalamus, cerebellum and spinal cord were dissected for glutamate and GABA quantifications by high performance liquid chromatography. The thiamine-restricted mothers (RM) group showed a significant reduction of time spent on the rotarod at 25 rpm and an increase in hind-base width. A significant decrease of glutamate concentration in the cerebellum and an increase of GABA concentrations in the thalamus were also observed. For the offspring from control mothers (CM) group there were significant correlations between thalamic GABA concentrations and both rotarod performance and average hind-base width. In addition, for rats from the RM group a significant correlation between stride length and cerebellar GABA concentration was found. These results show that the deficiency of thiamine during an early developmental period affects certain motor behavior parameters and GABA and glutamate levels in specific brain areas. Hence, a thiamine deficiency episode during an early developmental period can induce motor impairments and excitatory and inhibitory neurotransmitter changes that are persistent and detectable in later periods of life. PMID:26836141

  18. Epilepsy and hippocampal neurodegeneration induced by glutamate decarboxylase inhibitors in awake rats.

    PubMed

    Salazar, Patricia; Tapia, Ricardo

    2015-10-01

    Glutamic acid decarboxylase (GAD), the enzyme responsible for GABA synthesis, requires pyridoxal phosphate (PLP) as a cofactor. Thiosemicarbazide (TSC) and γ-glutamyl-hydrazone (PLPGH) inhibit the free PLP-dependent isoform (GAD65) activity after systemic administration, leading to epilepsy in mice and in young, but not in adult rats. However, the competitive GAD inhibitor 3-mercaptopropionic acid (MPA) induces convulsions in both immature and adult rats. In the present study we tested comparatively the epileptogenic and neurotoxic effects of PLPGH, TSC and MPA, administered by microdialysis in the hippocampus of adult awake rats. Cortical EEG and motor behavior were analyzed during the next 2h, and aspartate, glutamate and GABA were measured by HPLC in the microdialysis-collected fractions. Twenty-four hours after drug administration rats were fixed for histological analysis of the hippocampus. PLPGH or TSC did not affect the motor behavior, EEG or cellular morphology, although the extracellular concentration of GABA was decreased. In contrast, MPA produced intense wet-dog shakes, EEG epileptiform discharges, a >75% reduction of extracellular GABA levels and remarkable neurodegeneration of the CA1 region, with >80% neuronal loss. The systemic administration of the NMDA glutamate receptor antagonist MK-801 30 min before MPA did not prevent the MPA-induced epilepsy but significantly protected against its neurotoxic effect, reducing neuronal loss to <30%. We conclude that in adult awake rats, drugs acting on PLP availability have only a weak effect on GABA neurotransmission, whereas direct GAD inhibition produced by MPA induces hyperexcitation leading to epilepsy and hippocampal neurodegeneration. Because this degeneration was prevented by the blockade of NMDA receptors, we conclude that it is due to glutamate-mediated excitotoxicity consequent to disinhibition of the hippocampal excitatory circuits. PMID:26354164

  19. Glutamate uptake block triggers deadly rhythmic bursting of neonatal rat hypoglossal motoneurons

    PubMed Central

    Sharifullina, Elina; Nistri, Andrea

    2006-01-01

    In the brain the extracellular concentration of glutamate is controlled by glial transporters that restrict the neurotransmitter action to synaptic sites and avoid excitotoxicity. Impaired transport of glutamate occurs in many cases of amyotrophic lateral sclerosis, a devastating motoneuron disease. Motoneurons of the brainstem nucleus hypoglossus are among the most vulnerable, giving early symptoms like slurred speech and dysphagia. However, the direct consequences of extracellular glutamate build-up, due to uptake block, on synaptic transmission and survival of hypoglossal motoneurons remain unclear and have been studied using the neonatal rat brainstem slice preparation as a model. Patch clamp recording from hypoglossal motoneurons showed that, in about one-third of these cells, inhibition of glutamate transport with the selective blocker dl-threo-β-benzyloxyaspartate (TBOA; 50 μ m) unexpectedly led to the emergence of rhythmic bursting consisting of inward currents of long duration with superimposed fast oscillations and synaptic events. Synaptic inhibition block facilitated bursting. Bursts had a reversal potential near 0 mV, and were blocked by tetrodotoxin, the gap junction blocker carbenoxolone, or antagonists of AMPA, NMDA or mGluR1 glutamate receptors. Intracellular Ca2+ imaging showed bursts as synchronous discharges among motoneurons. Synergy of activation of distinct classes of glutamate receptor plus gap junctions were therefore essential for bursting. Ablating the lateral reticular formation preserved bursting, suggesting independence from propagated network activity within the brainstem. TBOA significantly increased the number of dead motoneurons, an effect prevented by the same agents that suppressed bursting. Bursting thus represents a novel hallmark of motoneuron dysfunction triggered by glutamate uptake block. PMID:16455692

  20. Effect of 8-bromo-cAMP and dexamethasone on glutamate metabolism in rat astrocytes

    SciTech Connect

    Zielke, H.R.; Tildon, J.T.; Landry, M.E.; Max, S.R. )

    1990-11-01

    Glutamine synthetase (GS) activity in cultured rat astrocytes was measured in extracts and compared to the intracellular rate of glutamine synthesis by intact control astrocytes or astrocytes exposed to 1 mM 8-bromo-cAMP (8Br-cAMP) + 1 microM dexamethasone (DEX) for 4 days. GS activity in extracts of astrocytes treated with 8Br-cAMP + DEX was 7.5 times greater than the activity in extracts of control astrocytes. In contrast, the intracellular rate of glutamine synthesis by intact cells increased only 2-fold, suggesting that additional intracellular effectors regulate the expression of GS activity inside the intact cell. The rate of glutamine synthesis by astrocytes was 4.3 times greater in MEM than in HEPES buffered Hank's salts. Synthesis of glutamine by intact astrocytes cultured in MEM was independent of the external glutamine or ammonia concentrations but was increased by higher extracellular glutamate concentrations. In studies with intact astrocytes 80% of the original (U-{sup 14}C)glutamate was recovered in the medium as radioactive glutamine, 2-3% as aspartate, and 7% as glutamate after 2 hours for both control and treated astrocytes. The results suggest: (1) astrocytes are highly efficient in the conversion of glutamate to glutamine; (2) induction of GS activity increases the rate of glutamate conversion to glutamine by astrocytes and the rate of glutamine release into the medium; (3) endogenous intracellular regulators of GS activity control the flux of glutamate through this enzymatic reaction; and (4) the composition of the medium alters the rate of glutamine synthesis from external glutamate.

  1. Prenatal monosodium glutamate (MSG) treatment given through the mother's diet causes behavioral deficits in rat offspring.

    PubMed

    Frieder, B; Grimm, V E

    1984-04-01

    The present study reports various developmental and behavioral changes in the offspring of rat dams that received monosodium glutamate (MSG) in the drinking water all through the second and third trimesters of pregnancy. Three main effects were observed in the MSG exposed offspring: (1) juvenile obesity; (2) reduced general activity levels; (3) a specific type of learning disability in discrimination learning involving choice between simultaneously present positive and negative stimuli. PMID:6541212

  2. Region-specific changes in presynaptic agmatine and glutamate levels in the aged rat brain.

    PubMed

    Jing, Y; Liu, P; Leitch, B

    2016-01-15

    During the normal aging process, the brain undergoes a range of biochemical and structural alterations, which may contribute to deterioration of sensory and cognitive functions. Age-related deficits are associated with altered efficacy of synaptic neurotransmission. Emerging evidence indicates that levels of agmatine, a putative neurotransmitter in the mammalian brain, are altered in a region-specific manner during the aging process. The gross tissue content of agmatine in the prefrontal cortex (PFC) of aged rat brains is decreased whereas levels in the temporal cortex (TE) are increased. However, it is not known whether these changes in gross tissue levels are also mirrored by changes in agmatine levels at synapses and thus could potentially contribute to altered synaptic function with age. In the present study, agmatine levels in presynaptic terminals in the PFC and TE regions (300 terminals/region) of young (3month; n=3) and aged (24month; n=3) brains of male Sprague-Dawley rats were compared using quantitative post-embedding immunogold electron-microscopy. Presynaptic levels of agmatine were significantly increased in the TE region (60%; p<0.001) of aged rats compared to young rats, however no significant differences were detected in synaptic levels in the PFC region. Double immunogold labeling indicated that agmatine and glutamate were co-localized in the same synaptic terminals, and quantitative analyses revealed significantly reduced glutamate levels in agmatine-immunopositive synaptic terminals in both regions in aged rats compared to young animals. This study, for the first time, demonstrates differential effects of aging on agmatine and glutamate in the presynaptic terminals of PFC and TE. Future research is required to understand the functional significance of these changes and the underlying mechanisms. PMID:26548412

  3. The combination of organoselenium compounds and guanosine prevents glutamate-induced oxidative stress in different regions of rat brains.

    PubMed

    Dalla Corte, Cristiane L; Bastos, Luíza L; Dobrachinski, Fernando; Rocha, João B T; Soares, Félix A A

    2012-01-01

    This study was designed to investigate the protective effects of the combination of guanosine and 2 organoselenium compounds (ebselen and diphenyl diselenide) against glutamate-induced oxidative stress in different regions of rat brains. Glutamate caused an increase in reactive oxygen species (ROS) generation and a decrease in [(3)H]-glutamate uptake in striatal, cortical, and hippocampal slices. Guanosine, ebselen, and diphenyl diselenide prevented glutamate-induced ROS production in striatal, cortical and hippocampal slices. The combination of guanosine with organoselenium compounds was more effective against glutamate-induced ROS production than the individual compounds alone. Guanosine prevented [(3)H]-glutamate uptake inhibition in striatal, cortical, and hippocampal slices. Thus, protection against the harmful effects of glutamate is possibly due to the combination of the antioxidant properties of organoselenium compounds and the stimulatory effect of guanosine on glutamate uptake. In conclusion, the combination of antioxidants and glutamatergic system modulators could be considered a potential therapy against the prooxidant effects of glutamate. PMID:22133308

  4. Differing effects of transport inhibitor on glutamate uptake by nerve terminals before and after exposure of rats to artificial gravity.

    NASA Astrophysics Data System (ADS)

    Borisova, T.; Krisanova, N.; Himmelreich, N.

    Glutamate is the major excitatory neurotransmitter in the brain. Subsequent to its release from glutamatergic neurons and activation of receptors, it is removed from extracellular space by high affinity Na^+-dependent glutamate transporters, which utilize the Na^+/K^+ electrochemical gradient as a driving force and located in nerve terminals and astrocytes. The glutamate transporters may modify the time course of synaptic events. Like glutamate itself, glutamate transporters are somehow involved in almost all aspects of normal and abnormal brain activity (e.g. cerebral ischemia, amyotrophic lateral sclerosis, Alzheimer's disease, traumatic brain injury, epilepsy and schizophrenia). The present study assessed transporter inhibitor for the ability to inhibit glutamate uptake by synaptosomes at the normal and hypergravity conditions (rats were rotated in a long-arm centrifuge at ten-G during one-hour period). DL-threo-beta-benzyloxyaspartate (DL-TBOA) is a newly developed competitive inhibitor of the high-affinity, Na^+-dependent glutamate transporters. As a potent, non- transported inhibitor of glutamate transporters, DL-TBOA promises to be a valuable new compound for the study of glutamatergic mechanisms. We demonstrated that DL-TBOA inhibited glutamate uptake ( 100 μM glutamate, 30 sec incubation period) in dose-dependent manner as in control as in hypergravity. The effect of this transport inhibitor on glutamate uptake by control synaptosomes and synaptosomes prepared of animals exposed to hypergravity was different. IC50 values calculated on the basis of curves of non-linear regression kinetic analysis was 18±2 μM and 11±2 μM ((P≤0,05) before and after exposure to artificial gravity, respectively. Inhibition caused by 10 μM DL-TBOA was significantly increased from 38,0±3,8 % in control group to 51,0±4,1 % in animals, exposed to hypergravity (P≤0,05). Thus, DL-TBOA had complex effect on glutamate uptake process and perhaps, became more potent under

  5. Anorexigenic lipopeptides ameliorate central insulin signaling and attenuate tau phosphorylation in hippocampi of mice with monosodium glutamate-induced obesity.

    PubMed

    Špolcová, Andrea; Mikulášková, Barbora; Holubová, Martina; Nagelová, Veronika; Pirnik, Zdenko; Zemenová, Jana; Haluzík, Martin; Železná, Blanka; Galas, Marie-Christine; Maletínská, Lenka

    2015-01-01

    Numerous epidemiological and experimental studies have demonstrated that patients who suffer from metabolic disorders, such as type 2 diabetes mellitus (T2DM) or obesity, have higher risks of cognitive dysfunction and of Alzheimer's disease (AD). Impaired insulin signaling in the brain could contribute to the formation of neurofibrillary tangles, which contain an abnormally hyperphosphorylated tau protein. This study aimed to determine whether potential tau hyperphosphorylation could be detected in an obesity-induced pre-diabetes state and whether anorexigenic agents could affect this state. We demonstrated that 6-month-old mice with monosodium glutamate (MSG) obesity, which represent a model of obesity-induced pre-diabetes, had increased tau phosphorylation at Ser396 and Thr231 in the hippocampus compared with the controls, as determined by western blots. Two weeks of subcutaneous treatment with a lipidized analog of prolactin-releasing peptide (palm-PrRP31) or with the T2DM drug liraglutide, which both had a central anorexigenic effect, resulted in increased phosphorylation of the insulin cascade kinases PDK1 (Ser241), Akt (Thr308), and GSK-3β (Ser9). Furthermore, these drugs attenuated phosphorylation at Ser396, Thr231, and Thr212 of tau and of the primary tau kinases in the hippocampi of 6-month-old MSG-obese mice. We identified tau hyperphosphorylation in the obesity-induced pre-diabetes state in MSG-obese mice and demonstrated the beneficial effects of palm-PrRP31 and liraglutide, both of known central anorexigenic effects, on hippocampal insulin signaling and on tau phosphorylation. PMID:25624414

  6. Inhibition of vesicular glutamate transporters contributes to attenuate methamphetamine-induced conditioned place preference in rats.

    PubMed

    He, Zongsheng; Chen, Yuan; Dong, Huajin; Su, Ruibin; Gong, Zehui; Yan, Lingdi

    2014-07-01

    Accumulating evidence suggests that glutamatergic system plays a crucial role in methamphetamine (METH) addiction. In the glutamatergic transmission, vesicular glutamate transporters (VGLUTs) are responsible for transporting glutamate into synaptic vesicles and affect the glutamate concentrations in the synaptic cleft. It is well documented that VGLUTs play an essential role in pathophysiology of several psychiatric and neurological diseases, however, whether VGLUTs also have a role in addiction caused by psychostimulant drugs is still unknown. The present study was underwent to investigate the effect of inhibition of VGLUTs on METH-induced induce conditioned place preference in rats. Rats were induced to conditioned place preference with METH (0.5, 1.0 and 2.0mg/kg) by intraperitoneal injection. Intracerebroventricular administration of 1.0 or 5.0μg Chicago sky blue 6B (CSB6B), a VGLUTs inhibitor, and 2.5h prior to METH was to observe its effect on METH-induced conditioned place preference in rats. The rats receiving METH showed stronger place preference at the dose of 1.0mg/kg than that of other doses. The intracerebroventricular administration of CSB6B (1.0, 5.0μg) 2.5h prior to the exposure to METH attenuated the acquisition of METH-induced conditioned place preference, while CSB6B itself had no effect on place preference. These results indicate that VGLUTs are involved in the effect of METH-induced conditioned place preference and may be a new target against METH addiction. PMID:24613241

  7. The effects of development of a food-related operant reflex on the receptor binding of glutamate in the rat brain.

    PubMed

    Karpova, I V

    1999-01-01

    Receptor binding of glutamate was studied in the striatum, hippocampus, and cerebral cortex of rats with different abilities to acquire an operant food-related reflex in a Skinner box. The striatum of rapidly-learning rats and rats unable to learn showed significantly higher levels of glutamate binding than controls were not trained in the Skinner box (p < 0.05). Striatal receptor binding of glutamate in slow-learning rats was lower than that in rapidly-learning rats and rats which were unable to learn (p < 0.05). In the hippocampus, all groups of rats (rapidly-learning, slow-learning, and those unable to learn) showed increased receptor binding of glutamate as compared with controls (p < 0.05), in the cerebral cortex, there was a significant decrease in glutamate binding as compared with controls in all groups of animals subjected to training (p < 0.05). PMID:10651326

  8. Monosodium Glutamate Dietary Consumption Decreases Pancreatic β-Cell Mass in Adult Wistar Rats

    PubMed Central

    Boonnate, Piyanard; Waraasawapati, Sakda; Hipkaeo, Wiphawi; Pethlert, Supattra; Sharma, Amod; Selmi, Carlo; Prasongwattana, Vitoon; Cha’on, Ubon

    2015-01-01

    Background The amount of dietary monosodium glutamate (MSG) is increasing worldwide, in parallel with the epidemics of metabolic syndrome. Parenteral administration of MSG to rodents induces obesity, hyperglycemia, hyperlipidemia, insulin resistance, and type 2 diabetes. However, the impact of dietary MSG is still being debated. We investigated the morphological and functional effects of prolonged MSG consumption on rat glucose metabolism and on pancreatic islet histology. Methods Eighty adult male Wistar rats were randomly subdivided into 4 groups, and test rats in each group were supplemented with MSG for a different duration (1, 3, 6, or 9 months, n=20 for each group). All rats were fed ad libitum with a standard rat chow and water. Ten test rats in each group were provided MSG 2 mg/g body weight/day in drinking water and the 10 remaining rats in each group served as non-MSG treated controls. Oral glucose tolerance tests (OGTT) were performed and serum insulin measured at 9 months. Animals were sacrificed at 1, 3, 6, or 9 months to examine the histopathology of pancreatic islets. Results MSG-treated rats had significantly lower pancreatic β-cell mass at 1, 6 and 9 months of study. Islet hemorrhages increased with age in all groups and fibrosis was significantly more frequent in MSG-treated rats at 1 and 3 months. Serum insulin levels and glucose tolerance in MSG-treated and untreated rats were similar at all time points we investigated. Conclusion Daily MSG dietary consumption was associated with reduced pancreatic β-cell mass and enhanced hemorrhages and fibrosis, but did not affect glucose homeostasis. We speculate that high dietary MSG intake may exert a negative effect on the pancreas and such effect might become functionally significant in the presence or susceptibility to diabetes or NaCl; future experiments will take these crucial cofactors into account. PMID:26121281

  9. Single Prolonged Stress Decreases Glutamate, Glutamine, and Creatine Concentrations In The Rat Medial Prefrontal Cortex

    PubMed Central

    Knox, Dayan; Perrine, Shane A.; George, Sophie A.; Galloway, Matthew P.; Liberzon, Israel

    2010-01-01

    Application of Single Prolonged Stress (SPS) in rats induces changes in neuroendocrine function and arousal that are characteristic of Post Traumatic Stress Disorder (PTSD). PTSD, in humans, is associated with decreased neural activity in the prefrontal cortex, increased neural activity in the amygdala complex, and reduced neuronal integrity in the hippocampus. However, the extent to which SPS models these aspects of PTSD has not been established. In order to address this, we used high-resolution magic angle spinning proton magnetic resonance spectroscopy (HR-MAS 1H MRS) ex vivo to assay levels of neurochemicals critical for energy metabolism (creatine and lactate), excitatory (glutamate and glutamine) and inhibitory (gamma amino butyric acid (GABA)) neurotransmission, and neuronal integrity (N-acetyl aspartate (NAA)) in the medial prefrontal cortex (mPFC), amygdala complex, and hippocampus of SPS and control rats. Glutamate, glutamine, and creatine levels were decreased in the mPFC of SPS rats when compared to controls, which suggests decreased excitatory tone in this region. SPS did not alter the neurochemical profiles of either the hippocampus or amygdala. These data suggest that SPS selectively attenuates excitatory tone, without a disruption of neuronal integrity, in the mPFC. PMID:20546834

  10. Elevated spectroscopic glutamate/gamma-amino butyric acid in rats bred for learned helplessness.

    PubMed

    Sartorius, Alexander; Mahlstedt, Magdalena M; Vollmayr, Barbara; Henn, Fritz A; Ende, Gabriele

    2007-09-17

    The theory of depression is dominated by the monoamine hypothesis but there is increasing evidence that beyond monoamines, glutamate (Glu) and gamma-aminobutyric acid (GABA) play an essential role in the pathogenesis of depression. In this study, the effect of alterations of GABA and Glu were investigated in the congenital learned helplessness paradigm. Proton magnetic resonance spectroscopy is an important monitoring tool to bridge the findings in clinical and preclinical studies. We found increased Glu/GABA ratios in the hippocampus and prefrontal cortex of placebo-treated (saline intraperitoneally) congenital learned helplessness rats versus wild-type rats, and a treatment-induced (desipramine 10 mg/kg intraperitoneally or electroconvulsive shock) decrease of this monoamine ratio in both brain regions. Our results corroborate previous findings of an amino-acid influence on the pathomechanisms of mood disorders. PMID:17712276

  11. Characterization of metabotropic glutamate receptor-stimulated phosphoinositide hydrolysis in rat cultured cerebellar granule cells.

    PubMed Central

    Toms, N. J.; Jane, D. E.; Tse, H. W.; Roberts, P. J.

    1995-01-01

    1. The pharmacology of excitatory amino acid (EAA)-stimulated phosphoinositide (PI) hydrolysis, monitored via [3H]-inositol monophosphate accumulation, was investigated in primary cultures of rat cerebellar granule cells. 2. EAA-stimulated PI hydrolysis peaked after 4-5 days in vitro and subsequently declined. 3. The agonist order of potency was found to be (EC50): L-quisqualic acid (Quis) (2 microM) >> L-glutamate (50 microM) > (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid ((1S,3R)-ACPD) (102 microM). L-Glutamate (Emax = 873% of basal activity) elicited the largest stimulation of PI hydrolysis, whereas Quis (Emax = 603%) and (1S,3R)-ACPD (Emax = 306%) produced somewhat lower stimulations. 4. Several phenylglycine derivatives were found to be active in inhibiting 2 microM Quis-stimulated PI hydrolysis, in order of potency (IC50): (S)-4-carboxy-3-hydroxyphenylglycine (41 microM) > or = (S)-4-carboxyphenylglycine (51 microM) >> (+)-alpha-methyl-4-carboxyphenylglycine (243 microM). 5. Cultured cerebellar granule cells of the rat appear to have Group I mGluR pharmacology similar to that reported for cloned mGluR1 and provide an ideal system for investigating novel mGluR1 ligands in a native environment. PMID:8680712

  12. Diphenyl ditelluride induces anxiogenic-like behavior in rats by reducing glutamate uptake.

    PubMed

    Stangherlin, Eluza Curte; Nogueira, Cristina Wayne

    2014-06-01

    Anxiety-related disorders are a common public health issue. Several lines of evidence suggest that altered glutamatergic neurotransmission underlies anxiety. The present study evaluated the effect of diphenyl ditelluride [(PhTe)2] exposure on the behavioral performance of rats and examined whether the behavioral effects could be attributed to changes in the modulation of glutamatergic function. Rats were exposed to (PhTe)2 (subcutaneously) during 8 weeks-final dose one third LD50 (124 μg/kg). The testing schedule included elevated plus-maze, open-field, T-maze, rotorod, and Morris water maze tests. Synaptosomal basal [(3)H] glutamate release and uptake were also evaluated. The time spent in the open arm and the ratio of time spent in the open arm/total were decreased in the (PhTe)2 group. Furthermore, the [(3)H] glutamate uptake was decreased in this experimental group. The results suggest that exposure to (PhTe)2 did not change motor abilities whereas it may result in anxiogenic-like behavior, induced by changes in the glutamatergic system at the pre-synaptic level. PMID:24715661

  13. The effect of combined glutamate receptor blockade in the NTS on the hypoxic ventilatory response in awake rats differs from the effect of individual glutamate receptor blockade.

    PubMed

    Pamenter, Matthew E; Nguyen, Jetson; Carr, John A; Powell, Frank L

    2014-08-01

    Ventilatory acclimatization to hypoxia (VAH) increases the hypoxic ventilatory response (HVR) and causes persistent hyperventilation when normoxia is restored, which is consistent with the occurrence of synaptic plasticity in acclimatized animals. Recently, we demonstrated that antagonism of individual glutamate receptor types (GluRs) within the nucleus tractus solitarii (NTS) modifies this plasticity and VAH (J. Physiol. 592(8):1839-1856); however, the effects of combined GluR antagonism remain unknown in awake rats. To evaluate this, we exposed rats to room air or chronic sustained hypobaric hypoxia (CSH, PiO2 = 70 Torr) for 7-9 days. On the experimental day, we microinjected artificial cerebrospinal fluid (ACSF: sham) and then a "cocktail" of the GluR antagonists MK-801 and DNQX into the NTS. The location of injection sites in the NTS was confirmed by glutamate injections on a day before the experiment and with histology following the experiment. Ventilation was measured in awake, unrestrained rats breathing normoxia or acute hypoxia (10% O2) in 15-min intervals using barometric pressure plethysmography. In control (CON) rats, acute hypoxia increased ventilation; NTS microinjections of GluR antagonists, but not ACSF, significantly decreased ventilation and breathing frequency in acute hypoxia but not normoxia (P < 0.05). CSH increased ventilation in hypoxia and acute normoxia. In CSH-conditioned rats, GluR antagonists in the NTS significantly decreased ventilation in normoxia and breathing frequency in hypoxia. A persistent HVR after combined GluR blockade in the NTS contrasts with the effect of individual GluR blockade and also with results in anesthetized rats. Our findings support the hypotheses that GluRs in the NTS contribute to, but cannot completely explain, VAH in awake rats. PMID:25107985

  14. Down-regulation of astroglial glutamate transporter-1 in the locus coeruleus impairs pain-evoked endogenous analgesia in rats.

    PubMed

    Kimura, Masafumi; Suto, Takashi; Eisenach, James C; Hayashida, Ken-ichiro

    2015-11-01

    Descending noradrenergic inhibition to the spinal cord from the locus coeruleus (LC) is an important endogenous pain-relief mechanism which can be activated by local glutamate signaling. Here we tested whether dysregulation of extracellular glutamate level in the LC induced by down-regulating astroglial glutamate transporter-1(GLT-1) impairs endogenous analgesia. In rats treated with repeated LC injections of GLT-1 selective or non-targeting small interfering RNA (siRNA), a subdermal injection of capsaicin was used to examine noxious stimulation-induced analgesia (NSIA), evoked LC glutamate and spinal noradrenaline release, and evoked LC neuronal activity. LC-injected GLT-1 siRNA reduced expression of GLT-1 in the LC (P=0.02), increased basal activity of LC neurons (P<0.01), and increased basal extracellular concentrations of LC glutamate (P<0.01) and spinal noradrenaline (P<0.01), but did not affect mechanical withdrawal thresholds in the hindpaw (P=0.83), compared to non-targeting siRNA. LC-injected GLT-1 siRNA impaired capsaicin-evoked release of LC glutamate and spinal noradrenaline, capsaicin-evoked LC neuronal activation, and NSIA. These results suggest that astroglial GLT-1 is essential to normal LC function and that increased extracellular glutamate by down-regulating GLT-1 impairs evoked LC activity and NSIA, essentially taking the LC "off-line". PMID:26450532

  15. Modulation of ( sup 3 H)-glutamate binding by serotonin in the rat hippocampus: An autoradiographic study

    SciTech Connect

    Mennini, T.; Miari, A. )

    1991-01-01

    Serotonin (5-HT) added in vitro increased ({sup 3}H)-glutamate specific binding in the rat hippocampus, reaching statistical significance in layers rich in N-Methyl-D-Aspartate sensitive glutamate receptors. This effect was explained by a significant increase in the apparent affinity of ({sup 3}H)-glutamate when 5-HT is added in vitro. Two days after lesion of serotonergic afferents to the hippocampus with 5,7- Dihydroxytryptamine ({sup 3}H)-glutamate binding was significantly decreased in the CA3 region and stratum lacunosum moleculare of the hippocampus, this reduction being reversed by in vitro addition of 10 {mu}M 5-HT. The decrease observed is due to a significant reduction of quisqualate-insensitive (radiatum CA3) and kainate receptors (strata oriens, radiatum, pyramidal of CA3). Five days after lesion ({sup 3}H)-glutamate binding increased significantly in the CA3 region of the hippocampus but was not different from sham animals in the other hippocampal layers. Two weeks after lesion ({sup 3}H)-glutamate binding to quisqualate-insensitive receptors was increased in all the hippocampal layers, while kainate and quisqualate-sensitive receptors were not affected. These data are consistent with the possibility that 5-HT is a direct positive modulator of glutamate receptor subtypes.

  16. Effect of the protonophore carbonyl cyanide-p-trifluoromethoxyphenyl-hydrazon on the glutamate release from rat brain nerve terminals under altered gravity conditions.

    NASA Astrophysics Data System (ADS)

    Borisova, T.; Krisanova, N.

    L-glutamate acts within the mammalian central nervous system as the predominant excitatory neurotransmitter and as a potent neurotoxin The balance between these physiological and pathological actions of glutamate is thought to be kept in check by the rapid removal of the neurotransmitter from the synaptic cleft The majority of uptake is mediated by the high-affinity Na -dependent glutamate transporters Depolarization leads to stimulation of glutamate efflux mediated by reversal of the high-affinity glutamate transporters The effects of the protonophore carbonyl cyanide-p-trifluoromethoxyphenyl-hydrazon FCCP on the glutamate release from isolated nerve terminals rat brain synaptosomes were investigated in control and after centrifuge-induced hypergravity rats were rotated in a long-arm centrifuge at ten-G during one-hour period The treatment of synaptosomes with 1 mu M FCCP during 11 min resulted in the increase in L- 14 C glutamate release by 23 0 pm 2 3 of total accumulated synaptosomal label in control animals and 24 0 pm 2 3 animals subjected to hypergravity FCCP evoked release of L- 14 C glutamate from synaptosomes was not altered in animals exposed to hypergravity as compared to control Glutamate transport is of electrogenic nature and thus depends on the membrane potential The high-KCl stimulated L- 14 C glutamate release in Ca 2 -free media occurred due to reversal of the glutamate transporters Carrier --mediated release of L- 14 C glutamate 6 min slightly increased as a result of

  17. Differential expression of vesicular glutamate transporters by vagal afferent terminals in rat nucleus of the solitary tract: projections from the heart preferentially express vesicular glutamate transporter 1.

    PubMed

    Corbett, E K A; Sinfield, J K; McWilliam, P N; Deuchars, J; Batten, T F C

    2005-01-01

    The central projections and neurochemistry of vagal afferent neurones supplying the heart in the rat were investigated by injecting cholera toxin B-subunit into the pericardium. Transganglionically transported cholera toxin B-subunit was visualized in the medulla oblongata in axons and varicosities that were predominantly aggregated in the dorsomedial, dorsolateral, ventrolateral and commissural subnuclei of the caudal nucleus of the solitary tract. Unilateral vagal section in control rats prevented cholera toxin B-subunit labeling on the ipsilateral side of the nucleus of the solitary tract. Fluorescent and electron microscopic dual labeling showed colocalization of immunoreactivity for vesicular glutamate transporter 1, but only rarely vesicular glutamate transporters 2 or 3 with cholera toxin B-subunit in terminals in nucleus of the solitary tract, suggesting that cardiac vagal axons release glutamate as a neurotransmitter. In contrast, populations of vagal afferent fibers labeled by injection of cholera toxin B-subunit, tetra-methylrhodamine dextran or biotin dextran amine into the aortic nerve, stomach or nodose ganglion colocalized vesicular glutamate transporter 2 more frequently than vesicular glutamate transporter 1. The presence of other neurochemical markers of primary afferent neurones was examined in nucleus of the solitary tract axons and nodose ganglion cells labeled by pericardial cholera toxin B-subunit injections. Immunoreactivity for a 200-kDa neurofilament protein in many large, cholera toxin B-subunit-labeled nodose ganglion cells indicated that the cardiac afferent fibers labeled are mostly myelinated, whereas binding of Griffonia simplicifolia isolectin B4 to fewer small cholera toxin B-subunit-labeled ganglion cells suggested that tracer was also taken up by some non-myelinated axons. A few labeled nucleus of the solitary tract axons and ganglion cells were positive for substance P and calcitonin gene-related peptide, which are considered as

  18. Naloxone-precipitated morphine withdrawal increases pontine glutamate levels in the rat.

    PubMed

    Zhang, T; Feng, Y; Rockhold, R W; Ho, I K

    1994-01-01

    Extracellular fluid (ECF) levels of glutamate (Glu) and aspartate (Asp) were measured in the locus coeruleus (LC) during morphine withdrawal by using microdialysis in conscious morphine-dependent Sprague-Dawley rats. Guide cannulae were implanted chronically and rats were given intracerebroventricular (i.c.v.) infusions of morphine (26 nmol/1 microliters/hr) or saline (1 microliters/hr) for 3 days. Microdialysis probes (2 mm tip) were inserted into the LC 24 hr before precipitation of withdrawal by i.c.v. injection of naloxone (12 or 48 nmol/5 microliters). Behavioral evidence of withdrawal (teeth-chattering, wet-dog shakes, etc.) was detected following naloxone challenge in morphine, but not in saline-infused rats. Increases (P < 0.01) in ECF levels of Glu (and Asp, to a lesser degree) were noted after naloxone-precipitated withdrawal only in the morphine group. The ECF Glu levels in the LC increased from 9.6 +/- 2.7 to 15.5 +/- 5.0 microM following 12 nmol/5 microliters naloxone, and from 9.5 +/- 1.9 to 20.5 +/- 3.3 microM following 48 nmol/5 microliters naloxone, before and in the first 15 min sample after the precipitation of withdrawal in the morphine-dependent rats, respectively. These results provide direct evidence to support the role of excitatory amino acids within the LC in morphine withdrawal. PMID:7912397

  19. Nitric oxide induces rapid, calcium-dependent release of vesicular glutamate and ATP from cultured rat astrocytes.

    PubMed

    Bal-Price, Anna; Moneer, Zahid; Brown, Guy C

    2002-12-01

    Nitric oxide (NO; 1 microM) or an NO donor (500 microM diethylenetriamine-nitric oxide, DETA-NONOate) caused rapid glutamate and ATP release from cultured rat cortical astrocytes. NO-induced glutamate release was prevented by calcium chelators (EGTA or BAPTA-AM) and an inhibitor of vesicular exocytosis (botulinum neurotoxin C, BoTx-C), but not by a glutamate transport inhibitor, L-trans-pyrrolidine-2,4-dicarboxylate (t-PDC), a cyclooxygenase inhibitor (indomethacin), or an inhibitor of soluble guanylate cyclase 1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one (ODQ), and was not induced by mitochondrial respiratory inhibitors (myxothiazol or azide). Similarly to glutamate, NO-induced ATP release was also completely blocked by BAPTA-AM and BoTx-C, suggesting again a vesicular, calcium-dependent mechanism of release. Addition of DETA-NONOate (500 microM) to fura-2-loaded astrocytes induced a rapid, transient increase in intracellular calcium levels followed by a lower, sustained level of calcium entry. The latter was blocked by gadolinium (1 microM), an inhibitor of capacitative Ca(2+) entry. Thus, NO appears to cause rapid exocytosis of vesicular glutamate and ATP from astrocytes by raising intracellular calcium levels. Astrocytes activated by lipopolysaccharide/endotoxin and interferon-gamma to express inducible NO synthase (iNOS) maintained substantially higher extracellular glutamate levels than nonactivated cells or activated cells treated with an iNOS inhibitor (1400W), but the rate of glutamate uptake by these cells was similar. This suggests that NO from inflammatory-activated astrocytes causes release of astrocytic glutamate. NO-induced release of astrocytic glutamate and ATP may be important in physiological or pathological communication between astrocytes and neurons. PMID:12420311

  20. Effects of CB1 receptor blockade on monosodium glutamate induced hypometabolic and hypothalamic obesity in rats.

    PubMed

    Chen, Wei; Chen, Zhenhua; Xue, Nina; Zheng, Zhibing; Li, Song; Wang, Lili

    2013-08-01

    Effects of cannabinoid receptor 1 (CB1R) blockade were observed by comparing 9-day and 6-week SR141716 treatments in monosodium glutamate (MSG)-induced hypometabolic and hypothalamic obesity (HO) in rats for the first time and molecular mechanisms were investigated. Compared with normal rats, the MSG rats display typical symptoms of the metabolic syndrome, i.e., excessive abdominal obesity, hypertriglyceridemia, hyperinsulinemia, insulin resistance, and hepatic steatosis, but with lower food intake. Although both the 9-day and 6-week treatments with the specific CB1R antagonist SR141716 effectively lowered body weight, intraperitoneal adipose tissue mass, serum triglyceride (TG), and insulin level, the effect of chronic treatment is more impressive. Moreover, serum cholesterol, free fatty acids (FFA), fasted and postprandial blood glucose, and insulin insensitivity were more effectively improved by 6-week exposure to SR141716, whereas hypophagia was only effective within the initial 2 weeks. In addition, hepatic steatosis as well as hepatic and adipocyte morphology was improved. Western blot analysis revealed that the markedly increased CB1R expression and decreased insulin receptor (INR) expression in liver and adipose tissues were effectively corrected by SR141716. Consistent with this, deregulated gene expression of lipogenesis and lipolysis as well as glucose metabolic key enzymes were also restored by SR141716. In conclusion, based on present data we found that: (1) alteration of the hypothalamus in MSG rats leads to a lower expression of INR in crucially insulin-targeted tissues and hyperinsulinemia that was reversed by SR141716, (2) the abnormally increased expression of CB1R in liver and adipose tissues plays a vital role in the pathophysiological process of MSG rats, and (3) chronic CB1R blockade leads to a sustained improvement of the metabolic dysfunctions of MSG rats. PMID:23620336

  1. Glutamate presynaptic vesicular transporter and postsynaptic receptor levels correlate with spatial memory status in aging rat models.

    PubMed

    Ménard, Caroline; Quirion, Rémi; Vigneault, Erika; Bouchard, Sylvain; Ferland, Guylaine; El Mestikawy, Salah; Gaudreau, Pierrette

    2015-03-01

    In humans, memory capacities are generally affected with aging, even without any reported neurologic disorders. The mechanisms behind cognitive decline are not well understood. We studied here whether postsynaptic glutamate receptor and presynaptic vesicular glutamate transporters (VGLUTs) levels may change in the course of aging and be related to cognitive abilities using various age-impaired (AI) or age-unimpaired rat strains. Twenty-four-month-old Long-Evans (LE) rats with intact spatial memory maintained postsynaptic ionotropic glutamate receptor levels in the hippocampal-adjacent cortex similar to those of young animals. In contrast, AI rats showed significantly reduced expression of ionotropic glutamate receptor GluR2, NR2A and NR2B subunits. In AI LE rats, VGLUT1 and VGLUT2 levels were increased and negatively correlated with receptor levels as shown by principal component analysis and correlation matrices. We also investigated whether glutamatergic receptors and VGLUT levels were altered in the obesity-resistant LOU/C/Jall (LOU) rat strain which is characterized by intact memory despite aging. No difference was observed between 24-month-old LOU rats and their young counterparts. Taken together, the unaltered spatial memory performance of 24-month-old age-unimpaired LE and LOU rats suggests that intact coordination of the presynaptic and postsynaptic hippocampal-adjacent cortex glutamatergic networks may be important for successful cognitive aging. Accordingly, altered expression of presynaptic and postsynaptic glutamatergic components, such as in AI LE rats, could be considered a marker of age-related cognitive deficits. PMID:25556161

  2. Mobility of NMDA autoreceptors but not postsynaptic receptors at glutamate synapses in the rat entorhinal cortex

    PubMed Central

    Yang, Jian; Chamberlain, Sophie E L; Woodhall, Gavin L; Jones, Roland S G

    2008-01-01

    NMDA receptors (NMDAr) are known to undergo recycling and lateral diffusion in postsynaptic spines and dendrites. However, NMDAr are also present as autoreceptors on glutamate terminals, where they act to facilitate glutamate release, but it is not known whether these receptors are also mobile. We have used functional pharmacological approaches to examine whether NMDA receptors at excitatory synapses in the rat entorhinal cortex are mobile at either postsynaptic sites or in presynaptic terminals. When NMDAr-mediated evoked EPSCs (eEPSCs) were blocked by MK-801, they showed no evidence of recovery when the irreversible blocker was removed, suggesting that postsynaptic NMDAr were relatively stably anchored at these synapses. However, using frequency-dependent facilitation of AMPA receptor (AMPAr)-mediated eEPSCs as a reporter of presynaptic NMDAr activity, we found that when facilitation was blocked with MK-801 there was a rapid (∼30–40 min) anomalous recovery upon removal of the antagonist. This was not observed when global NMDAr blockade was induced by combined perfusion with MK-801 and NMDA. Anomalous recovery was accompanied by an increase in frequency of spontaneous EPSCs, and a variable increase in frequency-facilitation. Following recovery from blockade of presynaptic NMDAr with a competitive antagonist, frequency-dependent facilitation of AMPAr-mediated eEPSCs was also transiently enhanced. Finally, an increase in frequency of miniature EPSCs induced by NMDA was succeeded by a persistent decrease. Our data provide the first evidence for mobility of NMDAr in the presynaptic terminals, and may point to a role of this process in activity-dependent control of glutamate release. PMID:18718983

  3. [Studying specific effects of nootropic drugs on glutamate receptors in the rat brain].

    PubMed

    Firstova, Iu Iu; Vasil'eva, E V; Kovalev, G I

    2011-01-01

    The influence of nootropic drugs of different groups (piracetam, phenotropil, nooglutil, noopept, semax, meclofenoxate, pantocalcine, and dimebon) on the binding of the corresponding ligands to AMPA, NMDA, and mGlu receptors of rat brain has been studied by the method of radio-ligand binding in vitro. It is established that nooglutil exhibits pharmacologically significant competition with a selective agonist of AMPA receptors ([G-3H]Ro 48-8587) for the receptor binding sites (with IC50 = 6.4 +/- 0.2 microM), while the competition of noopept for these receptor binding sites was lower by an order of magnitude (IC50 = 80 +/- 5.6 microM). The heptapeptide drug semax was moderately competitive with [G-3H]LY 354740 for mGlu receptor sites (IC50 = 33 +/- 2.4 microM). Dimebon moderately influenced the specific binding of the ligand of NMDA receptor channel ([G-3H]MK-801) at IC50 = 59 +/- 3.6 microM. Nootropic drugs of the pyrrolidone group (piracetam, phenotropil) as well as meclofenoxate, pantocalcine (pantogam) in a broad rage of concentrations (10(-4)-10(-10) M) did not affect the binding of the corresponding ligands to glutamate receptors (IC50 100 pM). Thus, the direct neurochemical investigation was used for the first time to qualitatively characterize the specific binding sites for nooglutil and (to a lower extent) noopept on AMPA receptors, for semax on metabotropic glutamate receptors, and for dimebon on the channel region of NMDA receptors. The results are indicative of a selective action of some nootropes on the glutamate family. PMID:21476267

  4. Transient receptor potential-like channels mediate metabotropic glutamate receptor EPSCs in rat dopamine neurones.

    PubMed

    Bengtson, C Peter; Tozzi, Alessandro; Bernardi, Giorgio; Mercuri, Nicola B

    2004-03-01

    Transient receptor potential (TRP) channels form cationic channels activated by diverse factors including mechanical stimuli, changes in osmolarity, pH and temperature, as well as the exogenous irritant, capsaicin. Metabotropic glutamate receptors have also recently been linked to TRP channel activation in neurones of the substantia nigra, hippocampus and cerebellum, suggesting a novel role for such channels in synaptic communication via endogenous neurotransmitters. We tested this for dopamine neurones in rat brain slices by characterizing the current-voltage relationship and pharmacology of EPSCs mediated by group I metabotropic glutamate receptor subtype 1 (mGluR1). Slow inward currents (273 +/- 35 pA peak amplitude, 381 +/- 25 ms latency, holding potential (V(h)) =-73 mV) representing evoked mGluR1 EPSCs were isolated in the presence of antagonists of AMPA, NMDA, GABA(A), GABA(B), muscarinic and glycine receptors. CPCCOEt (100 microM), an mGluR1 antagonist, blocked the residual EPSC in all recordings. mGluR1-activated EPSCs reversed polarity near -10 mV, consistent with the involvement of a cationic channel. Extracellular application of the non-selective TRP channel blockers SKF 96365, flufenamic acid and ruthenium red caused reversible inhibition of mGluR1-activated EPSCs. These characteristics parallel those of mGluR1 activation with an agonist and indicate the involvement of a TRP-like channel in mGluR1-mediated EPSCs. PMID:14724196

  5. Inhibition of glutamate carboxypeptidase II (NAALADase) protects against dynorphin A-induced ischemic spinal cord injury in rats.

    PubMed

    Long, Joseph B; Yourick, Debra L; Slusher, Barbara S; Robinson, Michael B; Meyerhoff, James L

    2005-01-31

    Glutamate carboxypeptidase (GCP) II (EC 3.4.17.21), which is also known as N-acetylated-alpha-linked acidic dipeptidase (NAALADase), hydrolyses the endogenous acidic dipeptide N-acetylaspartylglutamate (NAAG), yielding N-acetyl-aspartate and glutamate. Inhibition of this enzyme by 2-(phosphonomethyl) pentanedioic acid (2-PMPA) has been shown to protect against ischemic injury to the brain and hypoxic and metabolic injury to neuronal cells in culture, presumably by increasing and decreasing the extracellular concentrations of NAAG and glutamate, respectively. Since both NAAG and GCP II are found in especially high concentrations in the spinal cord, injuries to the spinal cord involving pathophysiological elevations in extracellular glutamate might be particularly responsive to GCP II inhibition. Lumbar subarachnoid injections of dynorphin A in rats cause ischemic spinal cord injury, elevated extracellular glutamate and a persistent hindlimb paralysis that is mediated through excitatory amino acid receptors. We therefore used this injury model to evaluate the protective effects of 2-PMPA. When coadministered with dynorphin A, 2-PMPA significantly attenuated the dynorphin A-induced elevations in cerebrospinal fluid glutamate levels and by 24 h postinjection caused significant dose-dependent improvements in motor scores that were associated with marked histopathological improvements. These results indicate that 2-PMPA provides effective protection against excitotoxic spinal cord injury. PMID:15680261

  6. Energy substrates protect hippocampus against endogenous glutamate-mediated neurodegeneration in awake rats.

    PubMed

    Netzahualcoyotzi, Citlalli; Tapia, Ricardo

    2014-07-01

    Excitotoxicity due to excessive glutamatergic neurotransmission is a well-studied phenomenon that has been related to the mechanisms of neuronal death occurring in some disorders of the CNS. We have previously shown that the intrahippocampal perfusion by microdialysis of 4-aminopyridine (4-AP) in rats stimulates endogenous glutamate release from nerve endings and this results in excitotoxic effects such as immediate seizures and delayed neuronal death, due to the overactivation of N-methyl-D-aspartate (NMDA) receptors. To study whether mitochondrial energy dysfunction and oxidative stress could be involved in this 4-AP-induced excitotoxicity, we evaluated in awake rats the protective effect of several energy substrates and antioxidant compounds, using microdialysis, electroencephalographic (EEG) recording and histological analysis. The 4-AP-induced behavioral and EEG seizures, which progressed to status epilepticus in about 30 min, were prevented by the NMDA receptor antagonist MK-801, whereas acetoacetate, DL- and L-β-hydroxybutyrate did not protect against seizures but increased the latency to the onset of status epilepticus; pyruvate, α-ketoglutarate and glutathione ethyl ester did not show any protective effect. 4-AP also produced nearly complete loss of pyramidal neurons in CA1 and CA3 regions of the ipsilateral hippocampus 24 h after the experiment. MK-801 totally prevented this neuronal death and the energy substrates tested protected by about 50%, whereas the antioxidants showed only a weak protection. We conclude that ketone bodies possess weak anticonvulsant effects and that energy metabolism impairment plays a more important role than oxidative stress in the delayed hippocampal neurodegeneration resulting from the excitotoxic action of 4-AP mediated by endogenous glutamate. PMID:24789366

  7. [Oxidative stress development in the tissues of salivary glands of rats in conditions of monosodium glutamate-induced obesity].

    PubMed

    Hordiienko, L P; Berehova, T V; Neporada, K S; Falalieieva, T M

    2014-01-01

    Pathogenic mechanisms of damage of salivary glands under obesity are an insufficiently studied problem of modem medicine. On experimental model of obesity induced by monosodium glutamate, free-radical processes and antioxidant defense system were studied in the tissues of salivary glands of rats. Under experimental obesity induced by monosodium glutamate there is a significant increase of the content of thio-barbituric acid reactive substances and a significant decrease in the activity of superoxide dismutase and catalase. Thus, it indicates to the misbalance of prooxidant and antioxidant systems and the development of oxidative stress. PMID:25335241

  8. Swimming Training Modulates Nitric Oxide-Glutamate Interaction in the Rostral Ventrolateral Medulla in Normotensive Conscious Rats.

    PubMed

    Raquel, Hiviny de A; Masson, Gustavo S; Barna, Barbara Falquetto; Zanluqui, Nágela G; Pinge-Filho, Phileno; Michelini, Lisete C; Martins-Pinge, Marli C

    2016-01-01

    We evaluated the effects of swimming training on nitric oxide (NO) modulation to glutamate microinjection within the rostral ventrolateral medulla (RVLM) in conscious freely moving rats. Male Wistar rats were submitted to exercise training (Tr) by swimming or kept sedentary (Sed) for 4 weeks. After the last training session, RVLM guide cannulas and arterial/venous catheters were chronically implanted. Arterial pressure (AP), heart rate (HR), and baroreflex control of HR (loading/unloading of baroreceptors) were recorded in conscious rats at rest. Pressor response to L-glutamate in the RVLM was compared before and after blockade of local nitric oxide (NO) production. In other Tr and Sed groups, brain was harvested for gene (qRT-PCR) and protein (immunohistochemistry) expression of NO synthase (NOS) isoforms and measurement of NO content (nitrite assay) within the RVLM. Trained rats exhibited resting bradycardia (average reduction of 9%), increased baroreflex gain (Tr: -4.41 ± 0.5 vs. Sed: -2.42 ± 0.31 b/min/mmHg), and unchanged resting MAP. The pressor response to glutamate was smaller in the Tr group (32 ± 4 vs. 53 ± 2 mmHg, p < 0.05); this difference disappeared after RVLM pretreatment with carboxy-PTIO (NO scavenger), Nw-Propyl-L-Arginine and L-NAME (NOS inhibitors). eNOS immunoreactivity observed mainly in RVLM capillaries was higher in Tr, but eNOS gene expression was reduced. nNOS gene and protein expression was slightly reduced (-29 and -9%, respectively, P > 0.05). Also, RVLM NO levels were significantly reduced in Tr (-63% vs. Sed). After microinjection of a NO-donor, the attenuated pressor response of L-glutamate in Tr group was restored. Data indicate that swimming training by decreasing RVLM NO availability and glutamatergic neurotransmission to locally administered glutamate may contribute to decreased sympathetic activity in trained subjects. PMID:27378935

  9. Swimming Training Modulates Nitric Oxide-Glutamate Interaction in the Rostral Ventrolateral Medulla in Normotensive Conscious Rats

    PubMed Central

    Raquel, Hiviny de A.; Masson, Gustavo S.; Barna, Barbara Falquetto; Zanluqui, Nágela G.; Pinge-Filho, Phileno; Michelini, Lisete C.; Martins-Pinge, Marli C.

    2016-01-01

    We evaluated the effects of swimming training on nitric oxide (NO) modulation to glutamate microinjection within the rostral ventrolateral medulla (RVLM) in conscious freely moving rats. Male Wistar rats were submitted to exercise training (Tr) by swimming or kept sedentary (Sed) for 4 weeks. After the last training session, RVLM guide cannulas and arterial/venous catheters were chronically implanted. Arterial pressure (AP), heart rate (HR), and baroreflex control of HR (loading/unloading of baroreceptors) were recorded in conscious rats at rest. Pressor response to L-glutamate in the RVLM was compared before and after blockade of local nitric oxide (NO) production. In other Tr and Sed groups, brain was harvested for gene (qRT-PCR) and protein (immunohistochemistry) expression of NO synthase (NOS) isoforms and measurement of NO content (nitrite assay) within the RVLM. Trained rats exhibited resting bradycardia (average reduction of 9%), increased baroreflex gain (Tr: −4.41 ± 0.5 vs. Sed: −2.42 ± 0.31 b/min/mmHg), and unchanged resting MAP. The pressor response to glutamate was smaller in the Tr group (32 ± 4 vs. 53 ± 2 mmHg, p < 0.05); this difference disappeared after RVLM pretreatment with carboxy-PTIO (NO scavenger), Nw-Propyl-L-Arginine and L-NAME (NOS inhibitors). eNOS immunoreactivity observed mainly in RVLM capillaries was higher in Tr, but eNOS gene expression was reduced. nNOS gene and protein expression was slightly reduced (−29 and −9%, respectively, P > 0.05). Also, RVLM NO levels were significantly reduced in Tr (−63% vs. Sed). After microinjection of a NO-donor, the attenuated pressor response of L-glutamate in Tr group was restored. Data indicate that swimming training by decreasing RVLM NO availability and glutamatergic neurotransmission to locally administered glutamate may contribute to decreased sympathetic activity in trained subjects. PMID:27378935

  10. Glutamate receptor binding in the frontal cortex and dorsal striatum of aged rats with impaired attentional set-shifting.

    PubMed

    Nicolle, Michelle M; Baxter, Mark G

    2003-12-01

    Aged Long-Evans rats exhibit deficits in attentional set shifting, an aspect of executive function, relative to adult rats. Impairments in set shifting and spatial learning are uncorrelated in aged rats, indicating a possible dissociation of the effects of ageing in prefrontal versus hippocampal systems. Ionotropic glutamate receptor binding was assessed using an in vitro autoradiography method in young and aged rats. The rats had been tested on a set-shifting task that measured attentional set shifts and reversal learning, as well as in a spatial learning task in the Morris water maze. [3H]Kainate, [3H]AMPA and NMDA-displaceable [3H]glutamate receptor binding were quantified in orbital cortex, cingulate cortex, medial frontal cortex, dorsolateral and dorsomedial striatum. Age-related decreases in [3H]kainate binding were apparent in all regions measured. Similarly, NMDA-displaceable [3H]glutamate binding was decreased in the aged rats in all the regions measured except for the medial frontal area where no age effects were observed. [3H]AMPA receptor binding was preserved with age in all the regions measured. Lower levels of [3H]kainate binding in the cingulate cortex were significantly correlated with poorer set-shifting performance, whereas higher levels of NMDA binding in the dorsomedial striatum were correlated with poorer set-shifting performance. There were no significant correlations between the levels of ionotropic glutamate receptors and performance in the reversal task or spatial learning in the Morris water maze. These results indicate that age-related behavioural deficits in attentional set shifting are selectively associated with neurobiological alterations in the cingulate cortex and dorsomedial striatum. PMID:14686906

  11. Up-regulation of DRP-3 long isoform during the induction of neural progenitor cells by glutamate treatment in the ex vivo rat retina

    SciTech Connect

    Tokuda, Kazuhiro; Kuramitsu, Yasuhiro; Byron, Baron; Kitagawa, Takao; Tokuda, Nobuko; Kobayashi, Daiki; Nagayama, Megumi; Araki, Norie; Sonoda, Koh-Hei; Nakamura, Kazuyuki

    2015-08-07

    Glutamate has been shown to induce neural progenitor cells in the adult vertebrate retina. However, protein dynamics during progenitor cell induction by glutamate are not fully understood. To identify specific proteins involved in the process, we employed two-dimensional electrophoresis-based proteomics on glutamate untreated and treated retinal ex vivo sections. Rat retinal tissues were incubated with 1 mM glutamate for 1 h, followed by incubation in glutamate-free media for a total of 24 h. Consistent with prior reports, it was found that mitotic cells appeared in the outer nuclear layer without any histological damage. Immunohistological evaluations and immunoblotting confirmed the emergence of neuronal progenitor cells in the mature retina treated with glutamate. Proteomic analysis revealed the up-regulation of dihydropyrimidinase-related protein 3 (DRP-3), DRP-2 and stress-induced-phosphoprotein 1 (STIP1) during neural progenitor cell induction by glutamate. Moreover, mRNA expression of DRP-3, especially, its long isoform, robustly increased in the treated retina compared to that in the untreated retina. These results may indicate that glutamate induces neural progenitor cells in the mature rat retina by up-regulating the proteins which mediate cell mitosis and neurite growth. - Highlights: • Glutamate induced neuronal progenitor cells in the mature rat retina. • Proteomic analysis revealed the up-regulation of DRP-3, DRP-2 and STIP1. • mRNA expression of DRP-3, especially, its long isoform, robustly increased.

  12. In vivo release of glutamate in nucleus tractus solitarii of the rat during hypoxia.

    PubMed Central

    Mizusawa, A; Ogawa, H; Kikuchi, Y; Hida, W; Kurosawa, H; Okabe, S; Takishima, T; Shirato, K

    1994-01-01

    1. An attempt has been made to test the hypothesis that, in the caudal part of nucleus tractus solitarii (NTS) where carotid sinus nerve (CSN) afferents project, L-glutamate (Glut) modulates the hypoxic ventilatory response. 2. Unanaesthetized, peripherally chemodenervated (carotid body denervated; CBD) and sham-operated, freely moving rats were used. During peripheral chemoreceptor stimulation by hypoxia (10% O2 for 30 min) or doxapram (Dox) infusion (2 mg kg-1 (30 min)-1), ventilation was recorded and successively, under the same conditions, the extracellular Glut concentration ([Glut]o) in the caudal NTS was measured by in vivo microdialysis. [Glut]o was also measured during hyperoxic hypercapnia (10% CO2-30% O2 for 30 min). 3. Furthermore, the effects on ventilation of exogenous Glut, the NMDA (N-methyl-D-aspartate) receptor antagonist MK-801 or the ionotropic receptor antagonist kynurenate microinjected into the caudal NTS were investigated in sham-operated rats. 4. In sham-operated rats, both ventilation and [Glut]o in NTS were increased during peripheral chemoreceptor stimulation. On the other hand, no increases in either ventilation or Glut release were observed in CBD rats. In spite of ventilatory augmentation during hypercapnia, no response of [Glut]o to hypercapnia was observed in either group. 5. Local Glut application into NTS increased ventilation. Pretreatment with MK-801 or kynurenate reduced the hypoxic ventilatory response. This reduction in ventilation was mainly due to the decrease in tidal volume. 6. These results suggest that hypoxia induced the release of Glut in NTS and that this effect was mediated by arterial chemosensory input. Images Figure 2 PMID:7965835

  13. Enhanced expression of glutamate decarboxylase 65 improves symptoms of rat parkinsonian models.

    PubMed

    Lee, B; Lee, H; Nam, Y R; Oh, J H; Cho, Y H; Chang, J W

    2005-08-01

    In this study, we report the amelioration of parkinsonian symptoms in rat Parkinson's disease (PD) models, as a result of the expression of glutamate decarboxylase (GAD) 65 with a modified cytomegalovirus (CMV) promoter. The transfer of the gene for gamma-amino butryic acid (GAD), the rate-limiting enzyme in gama-amino butrylic acid (GABA) production, has been investigated as a means to increase inhibitory synaptic activity. Electrophysiological evidence suggests that the transfer of the GAD65 gene to the subthalamic nucleus (STN) can change the excitatory output of this nucleus to inhibitory output. Our in vitro results also demonstrated higher GAD65 expression in cells transfected with the JDK promoter, as compared to cells transfected with the CMV promoter. Also, a rat PD model in which recombinant adeno-associated virus-2 (rAAV2)-JDK-GAD65 was delivered into the STN exhibited significant behavioral improvements, as compared to the saline-injected group. Interestingly, we observed that these behavioral improvements were more obvious in rat PD models in which rAAV2-JDK-GAD65 was injected into the STN than in rat PD models in which rAAV2-CMV-GAD65 was injected into the STN. Moreover, according to electrophysiological data, the rAAV2-JDK-GAD65-injected group exhibited more constant improvements in firing rates than did the rAAV2-CMV-GAD65-injected group. These data indicate that the JDK promoter, when coupled with GAD65 expression, is more effective with regard to parkinsonian symptoms than is the CMV promoter. PMID:15829994

  14. Acamprosate {monocalcium bis(3-acetamidopropane-1-sulfonate)} reduces ethanol-drinking behavior in rats and glutamate-induced toxicity in ethanol-exposed primary rat cortical neuronal cultures.

    PubMed

    Oka, Michiko; Hirouchi, Masaaki; Tamura, Masaru; Sugahara, Seishi; Oyama, Tatsuya

    2013-10-15

    Acamprosate, the calcium salt of bis(3-acetamidopropane-1-sulfonate), contributes to the maintenance of abstinence in alcohol-dependent patients, but its mechanism of action in the central nervous system is unclear. Here, we report the effect of acamprosate on ethanol-drinking behavior in standard laboratory Wistar rats, including voluntary ethanol consumption and the ethanol-deprivation effect. After forced ethanol consumption arranged by the provision of only one drinking bottle containing 10% ethanol, the rats were given a choice between two drinking bottles, one containing water and the other containing 10% ethanol. In rats selected for high ethanol preference, repeated oral administration of acamprosate diminished voluntary ethanol drinking. After three months of continuous access to two bottles, rats were deprived of ethanol for three days and then presented with two bottles again. After ethanol deprivation, ethanol preference was increased, and the increase was largely abolished by acamprosate. After exposure of primary neuronal cultures of rat cerebral cortex to ethanol for four days, neurotoxicity, as measured by the extracellular leakage of lactate dehydrogenase (LDH), was induced by incubation with glutamate for 1h followed by incubation in the absence of ethanol for 24h. The N-methyl-D-aspartate receptor blocker 5-methyl-10,11-dihydro-5H-dibenzo[a,d]-cyclohepten-5,10-imine, the metabotropic glutamate receptor subtype 5 antagonist 6-methyl-2-(phenylethynyl)pyridine and the voltage-gated calcium-channel blocker nifedipine all inhibited glutamate-induced LDH leakage from ethanol-exposed neurons. Acamprosate inhibited the glutamate-induced LDH leakage from ethanol-exposed neurons more strongly than that from intact neurons. In conclusion, acamprosate showed effective reduction of drinking behavior in rats and protected ethanol-exposed neurons by multiple blocking of glutamate signaling. PMID:24012782

  15. Binge Toluene Exposure Alters Glutamate, Glutamine and GABA in the Adolescent Rat Brain as Measured by Proton Magnetic Resonance Spectroscopy*

    PubMed Central

    Perrine, Shane A.; O'Leary-Moore, Shonagh K.; Galloway, Matthew P.; Hannigan, John H.; Bowen, Scott E.

    2010-01-01

    Despite the high incidence of toluene abuse in adolescents, little is known regarding the effect of binge exposure on neurochemical profiles during this developmental stage. In the current study, the effects of binge toluene exposure during adolescence on neurotransmitter levels were determined using high-resolution proton magnetic resonance spectroscopy ex vivo at 11.7 T. Adolescent male Sprague-Dawley rats were exposed to toluene (0, 8,000 , or 12,000 ppm) for 15 min twice daily from postnatal day 28 (P28) through P34 and then euthanized either one or seven days later (on P35 or P42) to assess glutamate, glutamine, and GABA levels in intact tissue punches from the medial prefrontal cortex (mPFC), anterior striatum and hippocampus. In the mPFC, toluene reduced glutamate one day after exposure, with no effect on GABA, while after seven days, glutamate was no longer affected but there was an increase in GABA levels. In the hippocampus, neither GABA nor glutamate was altered one day after exposure, whereas seven days after exposure, increases were observed in GABA and glutamate. Striatal glutamate and GABA levels measured after either one or seven days were not altered after toluene exposure. These findings show that one week of binge toluene inhalation selectively alters these neurotransmitters in the mPFC and hippocampus in adolescent rats, and that some of these effects endure at least one week after the exposure. The results suggest that age-dependent, differential neurochemical responses to toluene may contribute to the unique behavioral patterns associated with drug abuse among older children and young teens. PMID:21126832

  16. Increased Expression of GM1 Detected by Electrospray Mass Spectrometry in Rat Primary Embryonic Cortical Neurons Exposed to Glutamate Toxicity.

    PubMed

    Park, Dae Hee; Wang, Lynn; Pittock, Paula; Lajoie, Gilles; Whitehead, Shawn Narain

    2016-08-01

    Neurons within different brain regions have varying levels of vulnerability to external stress and respond differently to injury. A potential reason to explain this may lie within a key lipid class of the cell's plasma membrane called gangliosides. These glycosphingolipid species have been shown to play various roles in the maintenance of neuronal viability. The purpose of this study is to use electrospray ionization mass spectrometry (ESI-MS) and immunohistochemistry to evaluate the temporal expression profiles of gangliosides during the course of neurodegeneration in rat primary cortical neurons exposed to glutamate toxicity. Primary embryonic (E18) rat cortical neurons were cultured to DIV (days in vitro) 14. Glutamate toxicity was induced for 1, 3, 6, and 24 h to injure and kill neurons. Immunofluorescence was used to stain for GM1 and GM3 species, and ESI-MS was used to quantify the ganglioside species expressed within these injured neurons. ESI-MS data revealed that GM1, GM2, and GM3 were up-regulated in neurons exposed to glutamate. Interestingly, using immunofluorescence, we demonstrated that the GM1 increase following glutamate exposure occurred in viable neurons, possibly indicating a potential intrinsic neuroprotective response. To test this potential neuroprotective property, neurons were pretreated with GM1 for 24 h prior to glutamate exposure. Pretreatment with GM1 conferred significant neuroprotection against glutamate-induced cell death. Overall, work from this study validates the use of ESI-MS for cell-derived gangliosides and supports the further development of lipid based strategies to protect against neuron cell death. PMID:27376483

  17. Glutamate transporters alterations in the reorganizing dentate gyrus are associated with progressive seizure activity in chronic epileptic rats.

    PubMed

    Gorter, Jan A; Van Vliet, Erwin A; Proper, Evelien A; De Graan, Pierre N E; Ghijsen, Wim E J M; Lopes Da Silva, Fernando H; Aronica, Eleonora

    2002-01-21

    The expression of glial and neuronal glutamate transporter proteins was investigated in the hippocampal region at different time points after electrically induced status epilepticus (SE) in the rat. This experimental rat model for mesial temporal lobe epilepsy is characterized by cell loss, gliosis, synaptic reorganization, and chronic seizures after a latent period. Despite extensive gliosis, immunocytochemistry revealed only an up-regulation of both glial transporters localized at the outer aspect of the inner molecular layer (iml) in chronic epileptic rats. The neuronal EAAC1 transporter was increased in many somata of individual CA1-3 neurons and granule cells that had survived after SE; this up-regulation was still present in the chronic epileptic phase. In contrast, a permanent decrease of EAAC1 immunoreactivity was observed in the iml of the dentate gyrus. This permanent decrease in EAAC1 expression, which was only observed in rats that experienced progressive spontaneous seizure activity, could lead to abnormal glutamate levels in the iml once new abnormal glutamatergic synaptic contacts are formed by means of sprouted mossy fibers. Considering the steady growth of reorganizing mossy fibers in the iml, the absence of a glutamate reuptake mechanism in this region could contribute to progression of spontaneous seizure activity, which occurs with a similar time course. PMID:11793340

  18. K+ depolarization evokes ATP, adenosine and glutamate release from glia in rat hippocampus: a microelectrode biosensor study

    PubMed Central

    Heinrich, A; Andó, RD; Túri, G; Rózsa, B; Sperlágh, B

    2012-01-01

    BACKGROUND AND PURPOSE This study was undertaken to characterize the ATP, adenosine and glutamate outflow evoked by depolarization with high K+ concentrations, in slices of rat hippocampus. EXPERIMENTAL APPROACH We utilized the microelectrode biosensor technique and extracellular electrophysiological recording for the real-time monitoring of the efflux of ATP, adenosine and glutamate. KEY RESULTS ATP, adenosine and glutamate sensors exhibited transient and reversible current during depolarization with 25 mM K+, with distinct kinetics. The ecto-ATPase inhibitor ARL67156 enhanced the extracellular level of ATP and inhibited the prolonged adenosine efflux, suggesting that generation of adenosine may derive from the extracellular breakdown of ATP. Stimulation-evoked ATP, adenosine and glutamate efflux was inhibited by tetrodotoxin, while exposure to Ca2+-free medium abolished ATP and adenosine efflux from hippocampal slices. Extracellular elevation of ATP and adenosine were decreased in the presence of NMDA receptor antagonists, D-AP-5 and ifenprodil, whereas non-NMDA receptor blockade by CNQX inhibited glutamate but not ATP and adenosine efflux. The gliotoxin fluoroacetate and P2X7 receptor antagonists inhibited the K+-evoked ATP, adenosine and glutamate efflux, while carbenoxolone in low concentration and probenecid decreased only the adenosine efflux. CONCLUSIONS AND IMPLICATIONS Our results demonstrated activity-dependent gliotransmitter release in the hippocampus in response to ongoing neuronal activity. ATP and glutamate were released by P2X7 receptor activation into extracellular space. Although the increased extracellular levels of adenosine did derive from released ATP, adenosine might also be released directly via pannexin hemichannels. LINKED ARTICLE This article is commented on by Sershen, pp. 1000–1002 of this issue. To view this commentary visit http://dx.doi.org/10.1111/j.1476-5381.2012.02072.x PMID:22394324

  19. Ceftriaxone attenuates ethanol drinking and restores extracellular glutamate concentration through normalization of GLT-1 in nucleus accumbens of male alcohol-preferring rats.

    PubMed

    Das, Sujan C; Yamamoto, Bryan K; Hristov, Alexandar M; Sari, Youssef

    2015-10-01

    Alteration of glutamatergic-neurotransmission is a hallmark of alcohol dependence. We have previously reported that chronic ethanol-drinking downregulated glutamate transporter 1 (GLT-1) in nucleus accumbens (NAc) in male P rats in a manner that was reversed by ceftriaxone treatment. However, the effect of ceftriaxone on extracellular glutamate concentrations in NAc after chronic ethanol-drinking has not yet been studied. In the present study, male P rats were treated with ceftriaxone (100 mg/kg/day, i.p.) for five consecutive days following five-weeks of free choice ethanol (15% and 30%) drinking. In vivo microdialysis was performed to measure the extracellular glutamate concentrations in NAc and the effect of blockade of GLT-1 with dihydrokainic acid (DHK) on extracellular glutamate in NAc of ceftriaxone-treated rats was determined. Ceftriaxone treatment attenuated ethanol intake as well as ethanol preference. Extracellular glutamate was significantly higher in NAc after five-weeks of ethanol drinking in saline-treated compared to water control rats. Ceftriaxone treatment blocked the increase extracellular glutamate produced by ethanol intake. Blockade of GLT-1 by DHK reversed the effects of ceftriaxone on glutamate and implicated the role of GLT-1 in the normalization of extracellular glutamate by ceftriaxone. In addition, GLT-1 protein was decreased in ethanol exposed animals and ceftriaxone treatment reversed this deficit. Ceftriaxone treatment also increased glutamine synthetase activity in NAc but not in PFC as compared to ethanol drinking saline-treated rats. Our present study demonstrates that ceftriaxone treatment prevents ethanol drinking in part through normalization of extracellular glutamate concentrations in NAc of male P rats via GLT-1. PMID:26002627

  20. Chronobiological variations in the convulsive effect of monosodium L-glutamate when administered to adult rats.

    PubMed

    Feria-Velasco, A; Feria-Cuevas, Y; Gutiérrez-Padilla, R

    1995-01-01

    Monosodium L-glutamate (MSG) when administered intraperitoneally (i.p.) to rodents induces convulsions and has been used as a model to study various aspects of status epilepticus of multifocal origin. There are circadian variations of susceptibility to convulsions induced by various factors in some animal species. The aim of this work was to learn whether the convulsive effect of MSG in rats would vary when the drug is given at different times of the day. Three subgroups of Wistar rats were given i.p. 5 mg/g MSG at 07:00, 15:00 and 23:00 h, whereas two groups of rats divided into three subgroups of five animals each were used as controls, also being injected at 07:00, 15:00 and 23:00 h. One group was injected with NaCI solution, equimolar to that of MSG (eqNaCI); the other was injected with physiological saline solution (PSS) in proportional volumes to those of the experimental group. Motor behavior was recorded for 4 h following injections in the three groups of animals. Neither signs of brain hyperexcitability, nor convulsions appeared in animals injected with PSS or eqNaCl. With MSG, no variations were seen in the latency period when data from the three subgroups studied were compared among them. Duration of convulsive period when rats were injected at 07:00 h was shorter than that seen at 15:00 and 23:00 h. No significant variations were seen in total number of convulsive episodes in the three subgroups, while the number of seizures per hour and their intensity were significantly greater when animals were injected at 07:00 h than those seen when rats were studied at 15:00 and 23:00 h. Nearly 70% of animals injected at 07:00 h died in status epilepticus, whereas no deaths were recorded in animals injected at 15:00 and 23:00 h. Results could be explained in terms of variations of physiological processes at both the brain and extracerebral tissues involved in MSG metabolism and cerebral excitability, related to circadian rhythms. PMID:8845636

  1. Glutamate co-transmission from developing medial nucleus of the trapezoid body - Lateral superior olive synapses is cochlear dependent in kanamycin-treated rats

    SciTech Connect

    Lee, Jae Ho; Pradhan, Jonu; Maskey, Dhiraj; Park, Ki Sup; Hong, Sung Hwa; Suh, Myung-Whan; Kim, Myeung Ju; Ahn, Seung Cheol

    2011-02-11

    Research highlights: {yields} Glutamate co-transmission is enhanced in kanamycin-treated rats. {yields} VGLUT3 expression is increased in kanamycin-treated rats. {yields} GlyR expression is decreased in kanamycin-treated rats. {yields} GlyR, VGLUT3 expression patterns are asymmetric in unilaterally cochlear ablated rat. -- Abstract: Cochlear dependency of glutamate co-transmission at the medial nucleus of the trapezoid body (MNTB) - the lateral superior olive (LSO) synapses was investigated using developing rats treated with high dose kanamycin. Rats were treated with kanamycin from postnatal day (P) 3 to P8. A scanning electron microscopic study on P9 demonstrated partial cochlear hair cell damage. A whole cell voltage clamp experiment demonstrated the increased glutamatergic portion of postsynaptic currents (PSCs) elicited by MNTB stimulation in P9-P11 kanamycin-treated rats. The enhanced VGLUT3 immunoreactivities (IRs) in kanamycin-treated rats and asymmetric VGLUT3 IRs in the LSO of unilaterally cochlear ablated rats supported the electrophysiologic data. Taken together, it is concluded that glutamate co-transmission is cochlear-dependent and enhanced glutamate co-transmission in kanamycin-treated rats is induced by partial cochlear damage.

  2. Developmental lead exposure alters gene expression of metabotropic glutamate receptors in rat hippocampal neurons.

    PubMed

    Xu, Jian; Yan, Chong-Huai; Wu, Sheng-Hu; Yu, Xiao-Dan; Yu, Xiao-Gang; Shen, Xiao-Ming

    2007-02-21

    Exposure to lead in utero and in infancy is associated with a risk of impaired cognitive development. Increasing evidence suggests that the family of metabotropic glutamate receptors (mGluRs) plays an important role in synaptic plasticity and memory formation. We determined whether mGluRs subtypes 1, 3, and 7 (mGluR1, mGluR3, and mGluR7) were involved in developmental neurotoxicity due to lead. Embryonic rat hippocampal neurons were cultured for 21 days and exposed to lead chloride beginning on the fourth day of incubation. We investigated levels of mGluR1, mGluR3, and mGluR7 mRNA expression by using quantitative real-time reverse-transcription polymerase chain reaction (RT-PCR) with lead exposure at 10 nM, 1 microM, and 100 microM. Lead exposure in vitro downregulated the expression of mGluR1 mRNA and upregulated the expression of mGluR3 and mGluR7 mRNA in a dose-dependent manner. We speculate that mGluRs may be involved in lead neurotoxicity. Pathways that likely contribute to lead neurotoxicity by means of mGluRs are impairment of long-term potentiation, effects on N-methyl-D-aspartate (NMDA) receptor functions, and depotentiation. PMID:17267122

  3. Neonatal exposure to monosodium glutamate induces morphological alterations in suprachiasmatic nucleus of adult rat.

    PubMed

    Rojas-Castañeda, Julio César; Vigueras-Villaseñor, Rosa María; Chávez-Saldaña, Margarita; Rojas, Patricia; Gutiérrez-Pérez, Oscar; Rojas, Carolina; Arteaga-Silva, Marcela

    2016-02-01

    Neonatal exposure to monosodium glutamate (MSG) induces circadian disorders in several physiological and behavioural processes regulated by the suprachiasmatic nucleus (SCN). The objective of this study was to evaluate the effects of neonatal exposure to MSG on locomotor activity, and on morphology, cellular density and expression of proteins, as evaluated by optical density (OD), of vasopressin (VP)-, vasoactive intestinal polypeptide (VIP)- and glial fibrillary acidic protein (GFAP)-immunoreactive cells in the SCN. Male Wistar rats were used: the MSG group was subcutaneously treated from 3 to 10 days of age with 3.5 mg/g/day. Locomotor activity was evaluated at 90 days of age using 'open-field' test, and the brains were processed for immunohistochemical studies. MSG exposure induced a significant decrease in locomotor activity. VP- and VIP-immunoreactive neuronal densities showed a significant decrease, while the somatic OD showed an increase. Major axes and somatic area were significantly increased in VIP neurons. The cellular and optical densities of GFAP-immunoreactive sections of SCN were significantly increased. These results demonstrated that newborn exposure to MSG induced morphological alterations in SCN cells, an alteration that could be the basis for behavioural disorders observed in the animals. PMID:26799547

  4. Chronotropic and dromotropic responses to localized glutamate microinjections in the rat nucleus ambiguus☆

    PubMed Central

    Sampaio, Karla N.; Mauad, Hélder; Michael Spyer, K.; Ford, Timothy W.

    2014-01-01

    The cardioinhibitory effects of cardiac vagal motoneurons (CVMs) are mediated by activation of postganglionic neurons in the epicardial ganglia which have been shown to exert functionally selective effects on heart rate and atrioventricular conduction in the rat. Here we investigate whether CVMs producing these responses may occupy different rostrocaudal positions within the nucleus ambiguus. Excitation of CVMs was attempted by microinjections of glutamate into the nucleus ambiguus of an arterially perfused preparation in a grid extending over 2 mm in the rostrocaudal plane using the obex as a reference point. Microinjections were paired, one made during pacing to measure changes in atrioventricular conduction (P-R interval) independent of changes in heart rate and the other looking for changes in heart period (P-P interval) un-paced. Although evidence of a differential distribution was found in 7 cases, in the majority (13/20), sites producing maximal effects on both variables coincided. Maximal changes in atrioventricular conduction resulted from more rostral sites in 6 cases and from a more caudal site in only one. Overall, the ratio of the change in atrioventricular conduction to the change in heart rate for a given site was significantly greater 1 mm rostral to the obex than at either end of the test grid. We conclude that while CVMs controlling atrioventricular conduction are distributed with a peak somewhat rostral to those controlling heart rate in a number of animals, there is a significant overlap and much greater variability in this distribution in the rat than in cats and dogs. PMID:24177045

  5. Glutamate carboxypeptidase inhibition reduces the severity of chemotherapy-induced peripheral neurotoxicity in rat.

    PubMed

    Carozzi, Valentina A; Chiorazzi, Alessia; Canta, Annalisa; Lapidus, Rena G; Slusher, Barbara S; Wozniak, Krystyna M; Cavaletti, Guido

    2010-05-01

    Chemotherapy is the most common method to treat cancer. The use of certain antineoplastic drugs, however, is associated with the development of peripheral neuropathy that can be dose-limiting. Excitotoxic glutamate release, leading to excessive glutamatergic neurotransmission and activation of N-methyl-D-aspartate (NMDA) receptors, is associated with neuronal damage and death in several nervous system disorders. N-Acetyl-aspartyl-glutamate (NAAG) is an abundant neuropeptide widely distributed in the central and peripheral nervous system which is physiologically hydrolyzed by the enzyme glutamate carboxypeptidase into N-Acetyl-aspartyl (NAA) and glutamate. Pharmacological inhibition of glutamate carboxypeptidase results in decreased glutamate and increased endogenous NAAG and has been shown to provide neuroprotection in several preclinical models. Here, we report the neuroprotective effect of an orally available glutamate carboxypeptidase inhibitor on three well-established animal models of chemotherapy (cisplatin, paclitaxel, bortezomib)-induced peripheral neuropathy. In all cases, glutamate carboxypeptidase inhibition significantly improved the chemotherapy-induced nerve conduction velocity deficits. In addition, morphological and morphometrical alterations induced by cisplatin and bortezomib in dorsal root ganglia (DRG) were improved by glutamate carboxypeptidase inhibition. Our data support a novel approach for the treatment of chemotherapy-induced peripheral neuropathy. PMID:19763734

  6. Distribution of radiolabeled L-glutamate and D-aspartate from blood into peripheral tissues in naive rats: Significance for brain neuroprotection

    SciTech Connect

    Klin, Yael; Zlotnik, Alexander; Boyko, Matthew; Ohayon, Sharon; Shapira, Yoram; Teichberg, Vivian I.

    2010-09-03

    Research highlights: {yields} Blood glutamate has a half-life time of 2-3 min. {yields} Blood glutamate is submitted to rapid decarboxylation. {yields} Blood glutamate and its metabolites are mainly absorbed in skeletal muscle and liver. {yields} The skeletal muscle and liver are now targets for potential drugs affording brain neuroprotection. -- Abstract: Excess L-glutamate (glutamate) levels in brain interstitial and cerebrospinal fluids (ISF and CSF, respectively) are the hallmark of several neurodegenerative conditions such as stroke, traumatic brain injury or amyotrophic lateral sclerosis. Its removal could prevent the glutamate excitotoxicity that causes long-lasting neurological deficits. As in previous studies, we have established the role of blood glutamate levels in brain neuroprotection, we have now investigated the contribution of the peripheral organs to the homeostasis of glutamate in blood. We have administered naive rats with intravenous injections of either L-[1-{sup 14}C] Glutamic acid (L-[1-{sup 14}C] Glu), L-[G-{sup 3}H] Glutamic acid (L-[G-{sup 3}H] Glu) or D-[2,3-{sup 3}H] Aspartic acid (D-[2,3-{sup 3}H] Asp), a non-metabolized analog of glutamate, and have followed their distribution into peripheral organs. We have observed that the decay of the radioactivity associated with L-[1-{sup 14}C] Glu and L-[G-{sup 3}H] Glu was faster than that associated with glutamate non-metabolized analog, D-[2,3-{sup 3}H] Asp. L-[1-{sup 14}C] Glu was subjected in blood to a rapid decarboxylation with the loss of {sup 14}CO{sub 2}. The three major sequestrating organs, serving as depots for the eliminated glutamate and/or its metabolites were skeletal muscle, liver and gut, contributing together 92% or 87% of total L-[U-{sup 14}C] Glu or D-[2,3-{sup 3}H] Asp radioactivity capture. L-[U-{sup 14}C] Glu and D-[2,3-{sup 3}H] Asp showed a different organ sequestration pattern. We conclude that glutamate is rapidly eliminated from the blood into peripheral tissues

  7. Expression of Vesicular Glutamate Transporters VGLUT1 and VGLUT2 in the Rat Dental Pulp and Trigeminal Ganglion following Inflammation

    PubMed Central

    Hong, Jae Hyun; Kim, Yun Sook; Choi, So Young; Kim, Tae Heon; Cho, Yi Sul; Bae, Yong Chul

    2014-01-01

    Background There is increasing evidence that peripheral glutamate signaling mechanism is involved in the nociceptive transmission during pathological conditions. However, little is known about the glutamate signaling mechanism and related specific type of vesicular glutamate transporter (VGLUT) in the dental pulp following inflammation. To address this issue, we investigated expression and protein levels of VGLUT1 and VGLUT2 in the dental pulp and trigeminal ganglion (TG) following complete Freund’s adjuvant (CFA) application to the rat dental pulp by light microscopic immunohistochemistry and Western blot analysis. Results The density of VGLUT2− immunopositive (+) axons in the dental pulp and the number of VGLUT2+ soma in the TG increased significantly in the CFA-treated group, compared to control group. The protein levels of VGLUT2 in the dental pulp and TG were also significantly higher in the CFA-treated group than control group by Western blot analysis. The density of VGLUT1+ axons in the dental pulp and soma in the TG remained unchanged in the CFA-treated group. Conclusions These findings suggest that glutamate signaling that is mediated by VGLUT2 in the pulpal axons may be enhanced in the inflamed dental pulp, which may contribute to pulpal axon sensitization leading to hyperalgesia following inflammation. PMID:25290694

  8. Decreased endothelial nitric oxide, systemic oxidative stress, and increased sympathetic modulation contribute to hypertension in obese rats.

    PubMed

    da Cunha, Natalia Veronez; Pinge-Filho, Phileno; Panis, Carolina; Silva, Bruno Rodrigues; Pernomian, Laena; Grando, Marcella Daruge; Cecchini, Rubens; Bendhack, Lusiane Maria; Martins-Pinge, Marli Cardoso

    2014-05-15

    We investigated the involvement of nitric oxide (NO) and reactive oxygen species (ROS) on autonomic cardiovascular parameters, vascular reactivity, and endothelial cells isolated from aorta of monosodium glutamate (MSG) obese rats. Obesity was induced by administration of 4 mg/g body wt of MSG or equimolar saline [control (CTR)] to newborn rats. At the 60th day, the treatment was started with N(G)-nitro-L-arginine methyl ester (L-NAME, 20 mg/kg) or 0.9% saline. At the 90th day, after artery catheterization, mean arterial pressure (MAP) and heart rate were recorded. Plasma was collected to assess lipid peroxidation. Endothelial cells isolated from aorta were evaluated by flow cytometry and fluorescence intensity (FI) emitted by NO-sensitive dye [4,5-diaminofluoresceindiacetate (DAF-2DA)] and by ROS-sensitive dye [dihydroethidium (DHE)]. Vascular reactivity was made by concentration-response curves of acetylcholine. MSG showed hypertension compared with CTR. Treatment with L-NAME increased MAP only in CTR. The MSG induced an increase in the low-frequency (LF) band and a decrease in the high-frequency band of pulse interval. L-NAME treatment increased the LF band of systolic arterial pressure only in CTR without changes in MSG. Lipid peroxidation levels were higher in MSG and were attenuated after L-NAME. In endothelial cells, basal FI to DAF was higher in CTR than in MSG. In both groups, acetylcholine increased FI for DAF from basal. The FI baseline to DHE was higher in MSG than in CTR. Acetylcholine increased FI to DHE in the CTR group, but decreased in MSG animals. We suggest that reduced NO production and increased production of ROS may contribute to hypertension in obese MSG animals. PMID:24633548

  9. Glutamate Stimulates Local Protein Synthesis in the Axons of Rat Cortical Neurons by Activating α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid (AMPA) Receptors and Metabotropic Glutamate Receptors*

    PubMed Central

    Hsu, Wei-Lun; Chung, Hui-Wen; Wu, Chih-Yueh; Wu, Huei-Ing; Lee, Yu-Tao; Chen, En-Chan; Fang, Weilun; Chang, Yen-Chung

    2015-01-01

    Glutamate is the principal excitatory neurotransmitter in the mammalian CNS. By analyzing the metabolic incorporation of azidohomoalanine, a methionine analogue, in newly synthesized proteins, we find that glutamate treatments up-regulate protein translation not only in intact rat cortical neurons in culture but also in the axons emitting from cortical neurons before making synapses with target cells. The process by which glutamate stimulates local translation in axons begins with the binding of glutamate to the ionotropic AMPA receptors and metabotropic glutamate receptor 1 and members of group 2 metabotropic glutamate receptors on the plasma membrane. Subsequently, the activated mammalian target of rapamycin (mTOR) signaling pathway and the rise in Ca2+, resulting from Ca2+ influxes through calcium-permeable AMPA receptors, voltage-gated Ca2+ channels, and transient receptor potential canonical channels, in axons stimulate the local translation machinery. For comparison, the enhancement effects of brain-derived neurotrophic factor (BDNF) on the local protein synthesis in cortical axons were also studied. The results indicate that Ca2+ influxes via transient receptor potential canonical channels and activated the mTOR pathway in axons also mediate BDNF stimulation to local protein synthesis. However, glutamate- and BDNF-induced enhancements of translation in axons exhibit different kinetics. Moreover, Ca2+ and mTOR signaling appear to play roles carrying different weights, respectively, in transducing glutamate- and BDNF-induced enhancements of axonal translation. Thus, our results indicate that exposure to transient increases of glutamate and more lasting increases of BDNF would stimulate local protein synthesis in migrating axons en route to their targets in the developing brain. PMID:26134564

  10. Immunohistochemical evaluation of hippocampal CA1 region astrocytes in 10-day-old rats after monosodium glutamate treatment.

    PubMed

    Krawczyk, A; Jaworska-Adamu, J; Rycerz, K

    2015-01-01

    High concentration of glutamate (Glu) is excitotoxic for nervous system structures. This may lead to glial reactivity ie. increased expression of glial fibrillary acidic protein (GFAP) and S100β protein, and also to hypertrophy and proliferation of cells which are determined by the presence of Ki-67 antigen. The aim of the study was to analyse the immunoreactivity of the GFAP, S100β and Ki-67 proteins in astrocytes of hippocampal CA1 region in young rats after administration of monosodium glutamate (MSG) at two doses: 2 g/kg b.w. (I group) and 4 g/kg b.w. (II group). In rats from I and II group morphologically altered astrocytes with the GFAP expression were observed in the SLM of the hippocampal CA1 region. The cells had eccentrically located nuclei and on the opposite site of the nuclei there were single or double, long and weakly branched processes. Moreover, in the SLM the increase of the number of GFAP and S100β immunopositive astrocytes and nuclei with Ki-67 expression, in contrary to control individuals, was observed. These results suggest the increased expression of the proteins in early reactions or hyperplasia which, together with cell hypertrophy, indicate late reactivity of astroglia in response to glutamate noxious effect. PMID:26812818

  11. The influence of ionotropic and metabotropic glutamate receptor ligands on anxiety-like effect of amphetamine withdrawal in rats.

    PubMed

    Koltunowska, D; Gibula-Bruzda, E; Kotlinska, J H

    2013-08-01

    Chronic amphetamine use results in anxiety-like states after drug cessation. The aim of the study was to determine a role of ionotropic and metabotropic glutamate receptor ligands in amphetamine-evoked withdrawal anxiety in the elevated plus-maze test in rats. In our study memantine (8 and 12 mg/kg), a noncompetitive N-methyl-d-aspartate (NMDA) receptor antagonist did not reduce amphetamine withdrawal anxiety. Acamprosate (NMDA and metabotropic glutamate 5 receptor (mGluR5) antagonist) at the dose 200 and 400mg/kg showed anxiolytic-like effect, thus increasing the percent of time spent in open arms and a number of open arm entries. mGluR5 selective antagonist, MTEP (3-[(2-methyl-1,3-thiazol-4-yl)ethynyl]pyridine hydrochloride) and mGluR2/3 agonist, LY354740 (1S,2S,5R,6S)-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylic acid), caused effects similar to acamprosate at doses 1.25-5mg/kg and 2.5-5mg/kg, respectively. None of the glutamate ligands influenced locomotor activity of rats when given to the saline-treated group. Taking into account the positive correlation between amphetamine withdrawal-induced anxiety and relapse to amphetamine taking, our results suggest that modulation of mGluRs may prevent relapse to amphetamine and might pose a new direction in amphetamine abuse therapy. PMID:23623810

  12. A toxic extract of the marine phytoflagellate Prymnesium parvum induces calcium-dependent release of glutamate from rat brain synaptosomes.

    PubMed

    Mariussen, Espen; Nelson, George Nicholas; Fonnum, Frode

    2005-01-01

    Blooms of the marine phytoflagellate Prymnesium parvum produced mass mortality of fish in Norway and many other parts of the world. The effects of a purified algae extract of P. parvum on transmitter release from rat brain synaptosomes were studied to characterize its toxic action. Synaptosomes are detached nerve terminals and represent a simple system that has retained the machinery for uptake, synthesis, storage, and release of neurotransmitters. A crude methanol extract of P. parvum was purified by reverse-phase column for fast protein liquid chromatography (FPLC). The purified extract stimulated Ca2+-dependent spontaneous release of glutamate in a concentration-dependent manner. The release was increased by addition of extracellular Ca2+. The release of glutamate was suppressed by the Ca2+-channel blockers flunarizine (10 microM), diltiazem (10 microM), and verapamil (10 microM). The stimulation of release of glutamate from rat brain synaptosomes induced by the toxin may be due to an ionophorelike property of the algae extract such as previously reported for the potent algal toxin maitotoxin. At high concentrations the toxin primarily acts as a powerful lytic agent. PMID:15739805

  13. Changes in metabolic proteins in ex vivo rat retina during glutamate-induced neural progenitor cell induction.

    PubMed

    Tokuda, Kazuhiro; Kuramitsu, Yasuhiro; Baron, Byron; Kitagawa, Takao; Tokuda, Nobuko; Kobayashi, Masaaki; Kimura, Kazuhiro; Sonoda, Koh-Hei; Nakamura, Kazuyuki

    2016-08-01

    Understanding how energy metabolism and related proteins influence neural progenitor cells in adult tissues is critical for developing new strategies in clinical tissue regeneration therapy. We have recently reported that a subtoxic concentration of glutamate-induced neural progenitor cells in the mature ex vivo rat retina. We herein explore changes in the metabolic pathways during the process. We firstly observed an increase in lactate and lactate dehydrogenase concentration in the glutamate-treated retina. We then investigated the levels of glycolytic enzymes and confirmed significant upregulation of pyruvate kinase M type (PKM), especially PKM2, enolase, phosphoglycerate mutase 1 (PGAM1), and inosine-5'-monophosphate dehydrogenase (IMPDH1) in the glutamate-treated retina compared to the untreated retina. An analysis of the subcellular localization of PKM2 revealed nuclear translocation in the treated retina, which has been reported to regulate cell cycle proliferation and glycolytic enzymes. Our findings indicate that the mature rat retina undergoes an increase in aerobic glycolysis. PKM2, both in the cytoplasm and in the nucleus, may thus play an important role during neural progenitor cell induction, as it does in other proliferating cells. PMID:27421851

  14. Intra-amygdala microinjection of TNF-α impairs the auditory fear conditioning of rats via glutamate toxicity.

    PubMed

    Jing, He; Hao, Yongxin; Bi, Qiang; Zhang, Jiaozhen; Yang, Pingting

    2015-02-01

    During an inflammatory or infectious process, innate immune cells produce large amount of pro-inflammatory cytokines that act on the brain to cause cognitive dysfunctions. Tumor necrosis factor alpha (TNF-α) is one of the main pro-inflammatory cytokines. Thus, it is important to study how the excessive TNF-α affects the cognitive functions of central nervous system and possible antagonists to its effects. In the present study, we conducted behavioral experiments of rats to determine whether murine TNF-α administered directly into the brain would elicit behavioral effects related to learning and memory impairments. Rats subjected to single-dose intra-amygdala TNF-α infusion showed a significant delay in the acquisition and extinction of auditory fear conditioning. Accordingly, the glutamate level of the tissue samples from amygdala was elevated after the TNF-α treatment. Furthermore, pharmacological blockade of NMDAR before the TNF-α treatment reversed the TNF-α induced impairments in fear learning. Our findings suggest that TNF-α can impair the learning and memory functions through glutamate-NMDAR neurotoxicity, and present the possibility to develop therapeutic modalities directing at glutamate transmission for the treatment of neuro-inflammative dysfunctions. PMID:25448547

  15. Comparison of fractal dimension and Shannon entropy in myocytes from rats treated with histidine-tryptophan-glutamate and histidine-tryptophan cetoglutarate

    PubMed Central

    de Oliveira, Marcos Aurélio Barboza; Brandi, Antônio Carlos; dos Santos, Carlos Alberto; Botelho, Paulo Henrique Husseni; Cortez, José Luís Lasso; de Godoy, Moacir Fernandes; Braile, Domingo Marcolino

    2014-01-01

    Introduction Solutions that cause elective cardiac arrest are constantly evolving, but the ideal compound has not yet been found. The authors compare a new cardioplegic solution with histidine-tryptophan-glutamate (Group 2) and other one with histidine-tryptophan-cetoglutarate (Group 1) in a model of isolated rat heart. Objective To quantify the fractal dimension and Shannon entropy in rat myocytes subjected to cardioplegia solution using histidine-tryptophan with glutamate in an experimental model, considering the caspase markers, IL-8 and KI-67. Methods Twenty male Wistar rats were anesthetized and heparinized. The chest was opened, the heart was withdrawn and 40 ml/kg of cardioplegia (with histidine-tryptophan-cetoglutarate or histidine-tryptophan-glutamate solution) was infused. The hearts were kept for 2 hours at 4ºC in the same solution, and thereafter placed in the Langendorff apparatus for 30 min with Ringer-Locke solution. Analyzes were performed for immunohistochemical caspase, IL-8 and KI-67. Results The fractal dimension and Shannon entropy were not different between groups histidine-tryptophan-glutamate and histidine-tryptophan-acetoglutarate. Conclusion The amount of information measured by Shannon entropy and the distribution thereof (given by fractal dimension) of the slices treated with histidine-tryptophan-cetoglutarate and histidine-tryptophan-glutamate were not different, showing that the histidine-tryptophan-glutamate solution is as good as histidine-tryptophan-acetoglutarate to preserve myocytes in isolated rat heart. PMID:25140464

  16. The function of the glutamate-nitric oxide-cGMP pathway in brain in vivo and learning ability decrease in parallel in mature compared with young rats.

    PubMed

    Piedrafita, Blanca; Cauli, Omar; Montoliu, Carmina; Felipo, Vicente

    2007-04-01

    Aging is associated with cognitive impairment, but the underlying mechanisms remain unclear. We have recently reported that the ability of rats to learn a Y-maze conditional discrimination task depends on the function of the glutamate-nitric oxide-cGMP pathway in brain. The aims of the present work were to assess whether the ability of rats to learn this task decreases with age and whether this reduction is associated with a decreased function of the glutamate-nitric oxide-cGMP pathway in brain in vivo, as analyzed by microdialysis in freely moving rats. We show that 7-mo-old rats need significantly more (192 +/- 64%) trials than do 3-mo-old rats to learn the Y-maze task. Moreover, the function of the glutamate-nitric oxide-cGMP pathway is reduced by 60 +/- 23% in 7-mo-old rats compared with 3-mo-old rats. The results reported support the idea that the reduction in the ability to learn the Y-maze task (and likely other types of learning) of mature compared with young rats would be a consequence of reduced function of the glutamate-nitric oxide-cGMP pathway. PMID:17412964

  17. The Function of the Glutamate-Nitric Oxide-cGMP Pathway in Brain in Vivo and Learning Ability Decrease in Parallel in Mature Compared with Young Rats

    ERIC Educational Resources Information Center

    Piedrafita, Blanca; Cauli, Omar; Montoliu, Carmina; Felipo, Vicente

    2007-01-01

    Aging is associated with cognitive impairment, but the underlying mechanisms remain unclear. We have recently reported that the ability of rats to learn a Y-maze conditional discrimination task depends on the function of the glutamate-nitric oxide-cGMP pathway in brain. The aims of the present work were to assess whether the ability of rats to…

  18. Effect of taurine on the concentrations of glutamate, GABA, glutamine and alanine in the rat striatum and hippocampus.

    PubMed

    Molchanova, Svetlana M; Oja, Simos S; Saransaari, Pirjo

    2007-01-01

    Taurine, a non-protein amino acid, acts as an osmoregulator and inhibitory neuromodulator in the brain. Here we studied the effects of intraperitoneal injections of taurine on the concentrations of glutamate and GABA, and their precursors, glutamine and alanine, in the rat striatum and hippocampus. Injections of 0.25, 0.5 and 1 g/kg taurine led to a gradual increase in taurine tissue concentrations in both hippocampus and striatum. Glutamate and GABA also increased in the hippocampus, but not in the striatum. Glutamine increased and alanine decreased markedly in both brain structures. The results corroborate the neuromodulatory role of taurine in the brain. Taurine administration results in an imbalance in inhibitory and excitatory neurotransmission in the glutamatergic (hippocampus) and GABAergic (striatum) brain structures, affecting more markedly the neurotransmitter precursors. PMID:18605241

  19. Metabotropic glutamate receptor subtypes modulating neurotransmission at parallel fibre-Purkinje cell synapses in rat cerebellum.

    PubMed

    Neale, S A; Garthwaite, J; Batchelor, A M

    2001-07-01

    The actions of reportedly group-selective metabotropic glutamate (mGlu) receptor agonists and antagonists on neurotransmission at parallel fibre-Purkinje cell synapses in the rat cerebellum have been characterised using sharp microelectrode recording and an in vitro slice preparation. Application of the group I agonist (S)-3,5-dihydroxyphenylglycine (DHPG) or the group III selective agonist L(+)-2-amino-4-phosphonobutyric acid (L-AP4) depressed synaptic transmission in a reversible and concentration-dependent manner (EC(50)=18 and 5 microM, respectively). The depression produced by DHPG was unrelated to the depolarisation observed in some Purkinje cells. The group II agonist (2S,2'R,3'R)-2-(2',3'-dicarboxycyclopropyl)glycine (DCG IV, 1 microM) had no effect. The effects of DHPG were inhibited by the group I-selective antagonist 7-hydroxyiminocyclopropan[b]chromen-1a-carboxylic acid ethyl ester (CPCCOEt), but not by the group II/III antagonist alpha-methyl-4-phosphonophenylglycine (MPPG). The effect of L-AP4 was inhibited by MPPG, but not by the group I/II antagonist (S)-alpha-methyl-4-carboxyphenylglycine (MCPG). By themselves, the antagonists did not affect the EPSPs, suggesting that neither receptor is activated during low frequency neurotransmission. It is concluded that, in addition to the excitatory role for group I receptors described previously, both group I and III (but not group II) mGlu receptors operate at this synapse to inhibit synaptic transmission. The specific receptor subtypes involved are likely to be mGlu1 and mGlu4. PMID:11445184

  20. Glutamate carboxypeptidase II inhibition behaviorally and physiologically improves pyridoxine-induced neuropathy in rats.

    PubMed

    Potter, Michelle C; Wozniak, Krystyna M; Callizot, Noelle; Slusher, Barbara S

    2014-01-01

    Pyridoxine is used as a supplement for treating conditions such as vitamin deficiency as well as neurological disorders such as depression, epilepsy and autism. A significant neurologic complication of pyridoxine therapy is peripheral neuropathy thought to be a result of long-term and high dose usage. Although pyridoxine-induced neuropathy is transient and can remit after its withdrawal, the process of complete recovery can be slow. Glutamate carboxypeptidase II (GCP II) inhibition has been shown to improve symptoms of both chemotherapy- and diabetic-induced neuropathy. This study evaluated if GCP II inhibition could behaviorally and physiologically improve pyridoxine-induced neuropathy. In the current study, high doses of pyridoxine (400 mg/kg, twice a day for seven days) were used to induce neuropathy in rats. An orally bioavailable GCP II inhibitor, 2-(3-mercaptopropyl) pentanedioic acid (2-MPPA), was administered daily at a dose of 30 mg/kg starting from the onset of pyridoxine injections. Body weight, motor coordination, heat sensitivity, electromyographical (EMG) parameters and nerve morphological features were monitored. The results show beneficial effects of GCP II inhibition including normalization of hot plate reaction time, foot fault improvements and increased open field distance travelled. H wave frequency, amplitude and latency as well as sensory nerve conduction velocity (SNCV) were also significantly improved by 2-MPPA. Lastly, GCP II inhibition resulted in morphological protection in the spinal cord and sensory fibers in the lumbar region dorsal root ganglia (DRG). In conclusion, inhibition of GCP II may be beneficial against the peripheral sensory neuropathy caused by pyridoxine. PMID:25254647

  1. Metabolism and disposition of a potent group II metabotropic glutamate receptor agonist, in rats, dogs, and monkeys.

    PubMed

    James, Joyce K; Nakamura, Masato; Nakazato, Atsuro; Zhang, Kanyin E; Cramer, Merryl; Brunner, Janice; Cook, Jacquelynn; Chen, Weichao G

    2005-09-01

    Metabolism and disposition of MGS0028 [(1R,2S,5S,6S)-2-amino-6-fluoro-4-oxobicyclo[3.1.0]hexane-2,6-dicarboxylic acid monohydrate], a potent group II metabotropic glutamate receptor agonist, were examined in three preclinical species (Sprague-Dawley rats, beagle dogs, and rhesus monkeys). In rats, MGS0028 was widely distributed and primarily excreted in urine as parent and as a single reductive metabolite, identified as the 4R-isomer MGS0034 [(1R,2S,4R,5S,6S)-2-amino-6-fluoro-4-hydroxybicyclo[3.1.0]-hexane-2,6-dicarboxylic acid]. MGS0028 had a low brain to plasma ratio at efficacious doses in rats and was eliminated more slowly in rat brain than in plasma. Exposure increased proportionally (1--10 mg/kg p.o.) in rats, with bioavailability>60% at all doses. However, bioavailability was only approximately 20% in monkeys, and MGS0034 was found in relatively high abundance in plasma. In dogs, oral bioavailability was >60%, and the metabolite was not detected. In vitro metabolism was examined in liver subcellular fractions (microsomes and cytosol) from rat, dog, monkey, and human. Reductive metabolism was observed in rat, monkey, and human liver cytosol incubations, but not in dog liver cytosol incubations. No metabolism of MGS0028 was detected in incubations with liver microsomes from any species. Similar to in vivo results, MGS0028 was reduced in cytosol stereospecifically to MGS0034. The rank order of in vitro metabolite formation (monkey > rat approximately human > dog) was in agreement with in vivo observations in rats, dogs, and monkeys. Based on the observation of species difference in reductive metabolism, rat and monkey were recommended to be the preclinical species for further characterization prior to testing in humans. Finally, allometric scaling predicts that human pharmacokinetic parameters would be acceptable for further development. PMID:15980102

  2. Vesicular Glutamate Transporter 2 Expression in the Rat Pineal Gland: Detailed Analysis of Expression Pattern and Regulatory Mechanism

    NASA Astrophysics Data System (ADS)

    Yoshida, Sachine; Hisano, Setsuji

    Melatonin, a hormone secreted by the pineal gland, is closely related physiologically to circadian rhythm, sleep and reproduction, and also psychiatrically to mood disorders in humans. Under circadian control, melatonin secretion is modulated via nocturnal autonomic (adrenergic) stimulation to the gland, which expresses vesicular glutamate transporter (VGLUT) 1, VGLUT2 and a VGLUT1 splice variant (VGLUT1v), glutamatergic markers. Expression of VGLUT2 gene and protein in the intact gland has been reported to exhibit a rhythmic change during a day. To study VGLUT2 expression is under adrenergic control, we here performed an in vitro experiment using dispersed pineal cells of rats. Stimulation of either β-adrenergic receptor or cAMP production to the pineal cells was shown to increase mRNA level of VGLUT2, but not VGLUT1 and VGLUT1v. Because an ability of glutamate to inhibit melatonin production was previously reported in the cultured gland, it is likely that pineal VGLUT2 transports glutamate engaged in the inhibition of melatonin production.

  3. Metabotropic glutamate receptor antagonists but not NMDA antagonists affect conditioned taste aversion acquisition in the parabrachial nucleus of rats.

    PubMed

    Vales, Karel; Zach, Petr; Bielavska, Edita

    2006-02-01

    The effect of glutamate receptor antagonists on conditioned taste aversion (CTA) was studied in rats. The association of the short-term memory of a gustatory conditioned stimulus (CS) with visceral malaise (unconditioned stimulus, US) in the CTA paradigm takes place in the parabrachial nuclei (PBN) of the brainstem. The first direct evidence of participation of glutamatergic neurotransmission in the PBN during CTA demonstrated that the extracellular level of glutamate rises during saccharin drinking (Bielavska et al. in Brain Res 887:413-417, 2000). Our results show an effect of microdialysis administration of selective GluR antagonists into the PBN on the formation of CTA engram. We used four glutamate receptor (GluR) antagonists of different types (D-AP5, MK-801 as antagonists of ionotropic GluR and L-AP3, MSPG as antagonists of metabotropic GluR). The disruptive effect of MK-801 on CTA formation in the PBN is concentration-dependent, with the greatest inhibition under the higher concentrations eliciting significant disruption. The application of D-AP5 (0.1, 1, 5 mM) did not elicit a statistically significant blockade of CTA acquisition. This indicates that the association of the US-CS in the PBN is not dependent on NMDA receptors. On the contrary, application of L-AP3 (0.1, 1, 5 mM) blocked the CS-US association. PMID:16273405

  4. Thiopental sodium preserves the responsiveness to glutamate but not acetylcholine in rat primary cultured neurons exposed to hypoxia.

    PubMed

    Morita, Tomotaka; Shibuta, Satoshi; Kosaka, Jun; Fujino, Yuji

    2016-06-15

    Although many in vitro studies demonstrated that thiopental sodium (TPS) is a promising neuroprotective agent, clinical attempts to use TPS showed mainly unsatisfactory results. We investigated the neuroprotective effects of TPS against hypoxic insults (HI), and the responses of the neurons to l-glutamate and acetylcholine application. Neurons prepared from E17 Wistar rats were used after 2weeks in culture. The neurons were exposed to 12-h HI with or without TPS. HI-induced neurotoxicity was evaluated morphologically. Moreover, we investigated the dynamics of the free intracellular calcium ([Ca(2+)]i) in the surviving neurons after HI with or without TPS pretreatment following the application of neurotransmitters. TPS was neuroprotective against HI according to the morphological examinations (0.73±0.06 vs. 0.52±0.07, P=0.04). While the response to l-glutamate was maintained (0.89±0.08 vs. 1.02±0.09, P=0.60), the [Ca(2+)]i response to acetylcholine was notably impaired (0.59±0.02 vs. 0.94±0.04, P<0.01). Though TPS to cortical cultures was neuroprotective against HI morphologically, the [Ca(2+)]i response not to l-glutamate but to acetylcholine was impaired. This may partially explain the inconsistent results regarding the neuroprotective effects of TPS between experimental studies and clinical settings. PMID:27206889

  5. Influence of glutamate on the content and metabolism of dopamine in the nigrostriatal system of rats distinguished by capacity for learning.

    PubMed

    Karpova, I V; Yakimovskii, A F

    1994-01-01

    The effect of repeated (over the course of nine days) intrastriatal microinjections of glutamate (5 or 0.5 micrograms in 0.75 microliters of physiological solution daily) were investigated in 42 male Sprague-Dawley rats. Twenty-nine rats were preliminarily trained in a Skinner box using food reinforcement. It was demonstrated that the administration of glutamate to rats not subjected to training increases the content of homovanillic acid in the striatum. A similar influence in rats that are capable of learning leads to an increase in the content of dopamine and a decrease in the level of homovanillic acid in this nucleus, while it does not induce changes in the biochemical indicators under investigation in those rats that are incapable of learning. Microinjections of glutamate also do not alter the capacity for learning in any of the groups of animals. The possible causes for the different influence of intrastriatal microinjections of glutamate on the activity of the nigrostriatal system of rats differing by capacity for learning are discussed. PMID:7808643

  6. Characterization of the inward current induced by metabotropic glutamate receptor stimulation in rat ventromedial hypothalamic neurones.

    PubMed Central

    Lee, K; Boden, P R

    1997-01-01

    1. Whole-cell patch clamp recordings were made from rat ventromedial hypothalamic neurones in slices of brain tissue in vitro. Bath application of 50 microM (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD) depolarized all neurones tested by activation of an inward current of approximately 55 pA at -60 mV. 2. The inward current elicited by 1S,3R-ACPD was unaffected by K+ channel blockade with external Cs+, Ba2+ or TEA. However, the current was significantly reduced by replacement of the external NaCl with either Tris-HCl or LiCl. 3. The 1S,3R-ACPD-induced current was reduced by the heavy metal ions Ni2+ or La3+ and also by the Na(+)-Ca2+ exchange current inhibitor 3',4'-dichlorobenzamil. 4. The effects of 1S,3R-ACPD were mimicked by the group I metabotropic agonist 3,5-dihydroxyphenylglycine (DHPG) but not by the group III selective agonist, L-2-amino-4-phosphonobutanoate (L-AP4). Furthermore, the effects of 1S,3R-ACPD were inhibited by the metabotropic antagonists alpha-methyl-4-carboxyphenylglycine (MCPG) and 1-aminoindan-1,5-dicarboxylic acid (AIDA) but not by the presynaptic metabotropic receptor antagonists alpha-methyl-4-phosphonophenylglycine (MPPG) or alpha-methyl-4-tetrazolylphenylglycine (MTPG). 5. Photorelease of caged GDP beta S inside neurones irreversibly blocked the 1S,3R-ACPD-induced current whilst photolysis of caged GTP gamma S inside neurones irreversibly potentiated this current. 6. The PLC inhibitor U-73,122 significantly reduced the size of the inward current induced by 1S,3R-ACPD. This effect was not mimicked by the inactive analogue U-73,343. 7. Flash photolysis of the caged calcium chelator diazo-2 inside neurones diminished the response to 1S,3R-ACPD. 8. It is concluded that group I metabotropic glutamate receptors depolarize neurones in the VMH by activation of a Na(+)-Ca2+ exchange current through a G-protein coupled increase in intracellular Ca2+. PMID:9401972

  7. Characterization of the inward current induced by metabotropic glutamate receptor stimulation in rat ventromedial hypothalamic neurones.

    PubMed

    Lee, K; Boden, P R

    1997-11-01

    1. Whole-cell patch clamp recordings were made from rat ventromedial hypothalamic neurones in slices of brain tissue in vitro. Bath application of 50 microM (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD) depolarized all neurones tested by activation of an inward current of approximately 55 pA at -60 mV. 2. The inward current elicited by 1S,3R-ACPD was unaffected by K+ channel blockade with external Cs+, Ba2+ or TEA. However, the current was significantly reduced by replacement of the external NaCl with either Tris-HCl or LiCl. 3. The 1S,3R-ACPD-induced current was reduced by the heavy metal ions Ni2+ or La3+ and also by the Na(+)-Ca2+ exchange current inhibitor 3',4'-dichlorobenzamil. 4. The effects of 1S,3R-ACPD were mimicked by the group I metabotropic agonist 3,5-dihydroxyphenylglycine (DHPG) but not by the group III selective agonist, L-2-amino-4-phosphonobutanoate (L-AP4). Furthermore, the effects of 1S,3R-ACPD were inhibited by the metabotropic antagonists alpha-methyl-4-carboxyphenylglycine (MCPG) and 1-aminoindan-1,5-dicarboxylic acid (AIDA) but not by the presynaptic metabotropic receptor antagonists alpha-methyl-4-phosphonophenylglycine (MPPG) or alpha-methyl-4-tetrazolylphenylglycine (MTPG). 5. Photorelease of caged GDP beta S inside neurones irreversibly blocked the 1S,3R-ACPD-induced current whilst photolysis of caged GTP gamma S inside neurones irreversibly potentiated this current. 6. The PLC inhibitor U-73,122 significantly reduced the size of the inward current induced by 1S,3R-ACPD. This effect was not mimicked by the inactive analogue U-73,343. 7. Flash photolysis of the caged calcium chelator diazo-2 inside neurones diminished the response to 1S,3R-ACPD. 8. It is concluded that group I metabotropic glutamate receptors depolarize neurones in the VMH by activation of a Na(+)-Ca2+ exchange current through a G-protein coupled increase in intracellular Ca2+. PMID:9401972

  8. Cytokine regulation of glutamate decarboxylase biosynthesis in isolated rat islets of Langerhans.

    PubMed Central

    Schmidli, R S; Faulkner-Jones, B E; Harrison, L C; James, R F; DeAizpurua, H J

    1996-01-01

    Insulin-dependent diabetes mellitus (IDDM) is an autoimmune disease in which cytokines are thought to play an important role in beta-cell destruction and immune regulation. A major target of beta-cell autoimmunity in IDDM is the enzyme glutamate decarboxylase (GAD). We hypothesized that cytokines in the insulitis lesion modulate the synthesis of GAD. This may, in turn, modify the rate of beta-cell destruction. Accordingly we cultured rat islets in the presence and absence of cytokines, and measured synthesis of both isoforms of GAD, GAD65 and GAD67, by [35S]methionine incorporation and immunoprecipitation with a rabbit antiserum that recognizes both GAD65 and GAD67. Incubation of islets with interleukin (IL)-1 beta (1 ng/ml, 24 h), tumour necrosis factor alpha (TNF-alpha; 200 units/ml, 24 h) or interferon gamma (IFN-gamma; 500 units/ml, 72 h) significantly decreased the synthesis of both GAD65 and GAD67, but reduced neither total protein synthesis nor insulin accumulation in the medium or content. Incubation of islets for 24 h in IFN-alpha (1000 units/ml), TNF-beta (50 ng/ml), IL 2 (1000 units/ml), IL-4 (100 ng/ml), IL-6 (10 ng/ml), IL-10 (20 ng/ml), IL-12 (10 ng/ml) or transforming growth factor beta 2 (TGF-beta 2; 5 ng/ml) did not significantly alter GAD65 or GAD67 synthesis. Inhibition of GAD65 and GAD67 protein synthesis by IL-1 beta, TNF-alpha or IFN-gamma was reversed by co-incubation with the nitric oxide synthase inhibitor, NG-monomethyl arginine (NMMA). Expression of both GAD65 and GAD67 mRNA, measured by RNase protection assay, was also decreased by IL-1 beta and completely restored to baseline levels by NMMA. Thus the synthesis of both isoforms of islet GAD is selectively decreased in the presence of IL-1 beta, TNF-alpha or IFN-gamma by a NO-mediated mechanism, probably at the level of cytokine gene transcription. As GAD autoimmunity has been previously shown to have a pathogenic role in an animal model of IDDM, its inhibition by cytokines might limit

  9. Chronic second-by-second measures of l-glutamate in the central nervous system of freely moving rats

    PubMed Central

    Rutherford, Erin C.; Pomerleau, Francois; Huettl, Peter; Strömberg, Ingrid; Gerhardt, Greg A.

    2012-01-01

    l-glutamate (Glu) is the main excitatory neurotransmitter in the central nervous system (CNS) and is associated with motor behavior and sensory perception. While microdialysis methods have been used to record tonic levels of Glu, little is known about the more rapid changes in Glu signals that may be observed in awake rats. We have reported acute recording methods using enzyme-based microelectrode arrays (MEA) with fast response time and low detection levels of Glu in anesthetized animals with minimal interference. The current paper concerns modification of the MEA design to allow for reliable measures in the brain of conscious rats. In this study, we characterized the effects of chronic implantation of the MEA into the brains of rats. We were capable of measuring Glu levels for 7 days without loss of sensitivity. We performed studies of tail-pinch induced stress, which caused a robust biphasic increase in Glu. Histological data show chronic implantation of the MEAs caused minimal injury to the CNS. Taken together, our data show that chronic recordings of tonic and phasic Glu can be carried out in awake rats for up to 17 days in vivo allowing longer term studies of Glu regulation in behaving rats. PMID:17630982

  10. Antinociceptive action of diphenyl diselenide in the nociception induced by neonatal administration of monosodium glutamate in rats.

    PubMed

    Rosa, Suzan G; Quines, Caroline B; da Rocha, Juliana T; Bortolatto, Cristiani F; Duarte, Thiago; Nogueira, Cristina W

    2015-07-01

    Monosodium glutamate (MSG) is a neuroexcitatory amino acid commonly used as flavoring of foods. MSG neonatal administration to animals leads to behavioral and physiological disorders in adulthood, including increased pain sensitivity. This study aimed to investigate the effect of diphenyl diselenide (PhSe)2, an organoselenium compound with pharmacological properties already documented, on nociception induced by MSG. Newborn Wistar rats received 10 subcutaneous injections of MSG at a dose of 4.0g/kg or saline (once daily). At the 60th day of life, the rats were daily treated with (PhSe)2 (1mg/kg) or vehicle (canola oil) by the intragastric route for 7 days. The behavioral tests (locomotor activity, hot plate, tail-immersion and mechanical allodynia) were carried out. Ex vivo assays were performed in samples of hippocampus to determine Na(+), K(+)-ATPase and Ca(2+)-ATPase activities, cytokine levels and [(3)H]glutamate uptake. The results demonstrated that MSG increased nociception in the hot plate test and in the mechanical allodynia stimulated by Von-Frey hair but did not alter the tail immersion test. (PhSe)2 reversed all nociceptive behaviors altered by MSG. MSG caused an increase in Na(+),K(+)-ATPase and Ca(2+)-ATPase activities and in pro-inflammatory cytokine levels and a decrease in the anti-inflammatory cytokine and in the [(3)H]glutamate uptake. (PhSe)2 was effective in reversing all alterations caused by MSG. The results indicate that (PhSe)2 had a potential antinociceptive and anti-inflammatory action in the MSG model. PMID:25841878

  11. The role of spinal nitric oxide and glutamate in nociceptive behaviour evoked by high-dose intrathecal morphine in rats.

    PubMed

    Watanabe, Chizuko; Sakurada, Tsukasa; Okuda, Kazuhiro; Sakurada, Chikai; Ando, Ryuichiro; Sakurada, Shinobu

    2003-12-01

    Injection of high-dose of morphine into the spinal lumbar intrathecal (i.t.) space of rats elicits a nociceptive behavioural syndrome characterized by periodic bouts of spontaneous agitation and severe vocalization. The induced behavioural response such as vocalization and agitation was observed dose-dependently by i.t. administration of morphine (125-500 nmol). Pretreatment with naloxone (s.c. and i.t.), an opioid receptor antagonist, failed to reverse the morphine-induced behavioural response. The excitatory effect of morphine was inhibited dose-dependently by pretreatment with 3-((+)2-carboxy-piperazin-4-yl)-propyl-1-phosphonic acid (CPP), a competitive N-methyl-D-aspartate (NMDA) receptor antagonist and MK-801, a non-competitive NMDA receptor antagonist. The non-selective nitric oxide (NO) synthase inhibitor N(G)-nitro L-arginine methyl ester (L-NAME) inhibited dose-dependently the behavioural response to high-dose i.t. morphine (500 nmol), whereas D-NAME was without affecting the response to high-dose i.t. morphine. In the present study, we measured NO metabolites (nitrite/nitrate) in the extracellular fluid of rat dorsal spinal cord using in vivo microdialysis. The i.t. injection of morphine (500 nmol) evoked significant increases in NO metabolites and glutamate from the spinal cord. Not only NO metabolites but also glutamate released by high-dose morphine were reduced significantly by pretreatment with L-NAME (400 nmol). Pretreatment with CPP and MK-801 showed a significant reduction of the NO metabolites and glutamate levels elevated by high-dose i.t. morphine. These results suggest that the excitatory action of high-dose i.t. morphine may be mediated by an NMDA-NO cascade in the spinal cord. PMID:14659510

  12. Neuroprotective effects of a sesquiterpene lactone and flavanones from Paulownia tomentosa Steud. against glutamate-induced neurotoxicity in primary cultured rat cortical cells.

    PubMed

    Kim, Soo-Ki; Cho, Sang-Buem; Moon, Hyung-In

    2010-12-01

    The neuroprotective effects of Paulownia tomentosa against glutamate-induced neurotoxicity were studied in primary cultured rat cortical cells. It was found that the aqueous extract of this medicinal plant significantly attenuated glutamate-induced toxicity. In order to clarify the mechanism(s) underlying this neuroprotective effect, the active fractions and components were isolated and identified. Five compounds were isolated as the methanol extracts from air-dried flowers of P. tomentosa. Isoatriplicolide tiglate exhibited significant neuroprotective activity against glutamate-induced toxicity at concentrations ranging from 1 μM to 10 μM, and exhibited cell viability of approximately 43-78%. Therefore, the neuroprotective effect of P. tomentosa might be due to the inhibition of glutamate-induced toxicity by the sesquiterpene lactone derivative it contains. PMID:20683844

  13. The effects of aqueous extract of Lavandula angustifolia flowers in glutamate-induced neurotoxicity of cerebellar granular cell culture of rat pups.

    PubMed

    Büyükokuroğlu, Mehmet Emin; Gepdiremen, Akçahan; Hacimüftüoğlu, Ahmet; Oktay, Münir

    2003-01-01

    In the present study, neuroprotective effect of Lavandula angustifolia flower aqueous extract in glutamate-induced neurotoxicity in rat pups cerebellar granular cell culture was investigated. The extract at doses of 10 microg ml(-1), 100 microg ml(-1), 1 mg ml(-1) and 10 mg ml(-1) was applied to culture flasks. The extract at doses of 100 microg ml(-1) and 1 mg ml(-1) significantly blocked glutamate-induced neurotoxicity, with the most effective dose being 1 mg ml(-1). On the other hand, 10 mg ml(-1) dose of extract increased the dead cell with respect to glutamate group, despite being found insignificant statistically. As a result, L. angustifolia protected the neurons against glutamate toxicity. PMID:12499081

  14. Immunohistochemical localization of the neuron-specific glutamate transporter EAAC1 (EAAT3) in rat brain and spinal cord revealed by a novel monoclonal antibody.

    PubMed

    Shashidharan, P; Huntley, G W; Murray, J M; Buku, A; Moran, T; Walsh, M J; Morrison, J H; Plaitakis, A

    1997-10-31

    Neuronal regulation of glutamate homeostasis is mediated by high-affinity sodium-dependent and highly hydrophobic plasma membrane glycoproteins which maintain low levels of glutamate at central synapses. To further elucidate the molecular mechanisms that regulate glutamate metabolism and glutamate flux at central synapses, a monoclonal antibody was produced to a synthetic peptide corresponding to amino acid residues 161-177 of the deduced sequence of the human neuron-specific glutamate transporter III (EAAC1). Immunoblot analysis of human and rat brain total homogenates and isolated synaptosomes from frontal cortex revealed that the antibody immunoreacted with a protein band of apparent Mr approximately 70 kDa. Deglycosylation of immunoprecipitates obtained using the monoclonal antibody yielded a protein with a lower apparent Mr (approximately 65 kDa). These results are consistent with the molecular size of the human EAAC1 predicted from the cloned cDNA. Analysis of the transfected COS-1 cells by immunocytochemistry confirmed that the monoclonal antibody is specific for the neuron-specific glutamate transporter. Immunocytochemical studies of rat cerebral cortex, hippocampus, cerebellum, substantia nigra and spinal cord revealed intense labeling of neuronal somata, dendrites, fine-caliber fibers and puncta. Double-label immunofluorescence using antibody to glial fibrillary acidic protein as a marker for astrocytes demonstrated that astrocytes were not co-labeled for EAAC1. The localization of EAAC1 immunoreactivity in dendrites and particularly in cell somata suggests that this transporter may function in the regulation of other aspects of glutamate metabolism in addition to terminating the action of synaptically released glutamate at central synapses. PMID:9409715

  15. Metabolism of 3H- and 14C-labeled glutamate, proline, and alanine in normal and adrenalectomized rats using different sites of tracer administration and sampling.

    PubMed

    Said, H M; Chenoweth, M; Dunn, A

    1989-08-01

    Alanine, glutamate and proline labeled with 14C and 3H were infused into fasted normal and adrenalectomized rats. Alanine was administered by the A-V mode (arterial administration-venous sampling), and glutamate and proline by both the A-V and V-A (venous administration-arterial sampling) modes. The kinetics of 14C alanine and 14C glutamate differed markedly from those of the tritium-labeled compounds, but there was little difference in the kinetics of 3H and 14C proline. The replacement rate calculated from the A-V mode for glutamate was about half that obtained in the V-A mode, but there was little difference with proline. The masses of the amino acids (total content of amino acids in the body) were calculated from the washout curves of the tritium-labeled compounds after the infusion of tracer was terminated. The masses for the normal rats were 407 mumol/kg for alanine, 578 mumol/kg for glutamate and 296 mumol/kg for proline. The so-called distribution spaces calculated conventionally from total masses and the amino acid concentrations in plasma are much greater than the volume of the body, reflecting the fact that amino acid concentrations in tissues greatly exceed those in plasma. Adrenalectomy markedly affected the kinetics of the three amino acids, and their replacement rates were greatly reduced. The proline and glutamate masses were reduced by at least one half, while that of alanine was unchanged. Adrenalectomy markedly reduced the conversion of proline to glutamate. The hydrocortisone regimen used in this study restored the metabolism of alanine and glutamate to normal, but had no effect on that of proline. PMID:2569659

  16. Protective Effect of Calendula officinalis L. Flowers Against Monosodium Glutamate Induced Oxidative Stress and Excitotoxic Brain Damage in Rats.

    PubMed

    Shivasharan, B D; Nagakannan, P; Thippeswamy, B S; Veerapur, V P

    2013-07-01

    Monosodium glutamate (MSG) is a popular flavour enhancer used in food industries; however, excess MSG is neurotoxic. Oxidative stress is well documented in MSG induced neurotoxicity. The compounds having antioxidant and anti-inflammatory properties reportedly possess beneficial effects against various neurotoxic insults. Calendula officinalis Linn. flower extract (COE) is known for its potent antioxidant and anti-inflammatory activities. Hence, this present study has been designed to evaluate the neuroprotective effect of COE on MSG-induced neurotoxicity in rats. Adult Wistar rats were administered systemically for 7 days with MSG and after one h of MSG injection, rats were treated with COE (100 and 200 mg/kg) orally. At the end the treatment period, animals were assessed for locomotor activity and were sacrificed; brains were isolated for estimation of LPO, GSH, CAT, TT, GST, Nitrite and histopathological studies. MSG caused a significant alteration in animal behavior, oxidative defense (raised levels of LPO, nitrite concentration, depletion of antioxidant levels) and hippocampal neuronal histology. Treatment with COE significantly attenuated behavioral alterations, oxidative stress, and hippocampal damage in MSG-treated animals. Hence, this study demonstrates that COE protects against MSG-induced neurotoxicity in rats. The antioxidant and anti-inflammatory properties of COE may be responsible for its observed neuroprotective action. PMID:24426226

  17. High dosage of monosodium glutamate causes deficits of the motor coordination and the number of cerebellar Purkinje cells of rats.

    PubMed

    Prastiwi, D; Djunaidi, A; Partadiredja, G

    2015-11-01

    Monosodium glutamate (MSG) has been widely used throughout the world as a flavoring agent of food. However, MSG at certain dosages is also thought to cause damage to many organs, including cerebellum. This study aimed at investigating the effects of different doses of MSG on the motor coordination and the number of Purkinje cells of the cerebellum of Wistar rats. A total of 24 male rats aged 4 to 5 weeks were divided into four groups, namely, control (C), T2.5, T3, and T3.5 groups, which received intraperitoneal injection of 0.9% sodium chloride solution, 2.5 mg/g body weight (bw) of MSG, 3.0 mg/g bw of MSG, and 3.5 mg/g bw of MSG, respectively, for 10 consecutive days. The motor coordination of the rats was examined prior and subsequent to the treatment. The number of cerebellar Purkinje cells was estimated using physical fractionator method. It has been found that the administration of MSG at a dosage of 3.5 mg/g bw, but not at lower dosages, caused a significant decrease of motor coordination and the estimated total number of Purkinje cells of rats. There was also a significant correlation between motor coordination and the total number of Purkinje cells. PMID:25697849

  18. The urinary excretion of orally administered pteroyl-l-glutamic acid by the rat

    PubMed Central

    Blair, J. A.; Dransfield, E.

    1971-01-01

    1. The urinary excretion of folates after oral administration of [2-14C]pteroyl-l-glutamic acid was studied by assaying the radioactivity in the urine and in materials purified and characterized by t.l.c. 2. Radioactivity excreted was 6.8, 5.9 and 30.7% of the oral dose in the first 24h after doses of 3.1, 32 and 320μg/kg respectively. 3. Extensive decomposition of urinary folates to pteroyl-l-glutamic acid was prevented by antioxidants or collection of urine frozen. 4. At the three dosages, two major and one minor radioactive compounds were isolated. One of the major metabolites was 5-methyltetrahydropteroylglutamic acid. The others were unidentified but were not pteroylglutamic acid, 7,8-dihydro-, 5,6,7,8-tetrahydro-, 5- or 10-formyl-tetrahydro-, 5,10-methylidyne-tetrahydro-, 5-formimidoyl-tetrahydro-, 5,10-methylene-tetrahydro-, 5-methyltetrahydro-pteroylglutamic acid, nor any decomposition products of these compounds formed during isolation. Labelled unconjugated pteridines were absent. 5. Labelled pteroyl-l-glutamic acid was displaced by oral administration of unlabelled pteroyl-l-glutamic acid (1.6mg/kg) when given 3.5h after, but not when given 24h after the labelled dose. 6. The results show that orally administered [2-14C]pteroyl-l-glutamic acid is absorbed without metabolism and is then metabolized into naturally occurring tetrahydro-folates. 7. These findings are discussed with reference to previous work. PMID:5124394

  19. Local synaptic release of glutamate from neurons in the rat hypothalamic arcuate nucleus.

    PubMed Central

    Belousov, A B; van den Pol, A N

    1997-01-01

    1. The hypothalamic arcuate nucleus (ARC) contains neuroendocrine neurons that regulate endocrine secretions by releasing substances which control anterior pituitary hormonal release into the portal blood stream. Many neuroactive substances have been identified in the ARC, but the existence of excitatory neurons in the ARC and the identity of an excitatory transmitter have not been investigated physiologically. 2. In the present experiments using whole-cell current- and voltage-clamp recording of neurons from cultures and slices of the ARC, we demonstrate for the first time that some of the neurons in the ARC secrete glutamate as their transmitter. 3. Using microdrop stimulation of presynaptic neurons in ARC slices, we found that local axons from these glutamatergic neurons make local synaptic contact with other neurons in the ARC and that all evoked excitatory postsynaptic potentials could be blocked by the selective ionotropic glutamate receptor antagonists 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 10 microM) and D,L-2-amino-5-phosphonovalerate (AP5; 100 microM). To determine the identity of ARC neurons postsynaptic to local glutamatergic neurons, we used antidromic stimulation to reveal that many of these cells were neuroendocrine neurons by virtue of their maintaining axon terminals in the median eminence. 4. In ARC cultures, postsynaptic potentials, both excitatory and inhibitory, were virtually eliminated by the glutamate receptor antagonists AP5 and CNQX, underlining the functional importance of glutamate within this part of the neuroendocrine brain. 5. GABA was secreted by a subset of ARC neurons from local axons. The GABAA receptor antagonist bicuculline released glutamatergic neurons from chronic inhibition mediated by synaptically released GABA, resulting in further depolarization and an increase in the amplitude and frequency of glutamate-mediated excitatory postsynaptic potentials. Images Figure 1 PMID:9130170

  20. The effect of clonidine on cell survival, glutamate, and aspartate release in normo- and hyperglycemic rats after near complete forebrain ischemia.

    PubMed

    Jellish, W Scott; Murdoch, John; Kindel, Gisela; Zhang, Xin; White, Fletcher A

    2005-12-01

    The present study was undertaken to investigate the effects of the alpha2 adrenergic agonist, clonidine, on the near complete cerebral ischemia (NCFI) evoked release of glutamate and aspartate from normo- and hyperglycemic rodent brain tissue using microdialysis tissue techniques. Hemodynamic variables, blood lactate, and glucose levels were monitored throughout the 40 min NCFI occlusion period. After 48 h, rats were killed and the extent of neuronal injury was determined in the cortex, striatum, and hippocampus. Hemodynamic variables recorded during ischemia improved with clonidine treatment in both normo- and hyperglycemic groups. Glutamate and aspartate levels were greatly increased over control values during normo- and hyperglycemic NCFI treatment. Clonidine pretreatment suppressed the release of both glutamate and aspartate during NCFI in normo- and hyperglycemic rodents when compared with NCFI-treated normo- and hyperglycemic rats without the drug. Significant neuroprotection of cells in the cortex, striatum, and hippocampus was also observed in drug-treated animals 48 h postischemia. The combined effects of diminished glutamate release after NCFI and reduced neuronal injury in both normo- and hyperglycemic states suggests that clonidine treatment during NCFI is neuroprotective. The neuroprotective effect of clonidine during ischemia may be ascribed to both a sensitization of central sympathetic activity and a reduced release of glutamate thereby reducing NMDA receptor activation and neuronal damage. PMID:16044300

  1. [Studying the neuroprotective effect of the novel glutamic acid derivative neiroglutam on focal cerebral ischemia in rats].

    PubMed

    Tiurenkov, I N; Kurkin, D V; Bakulin, D A; Volotova, E V

    2014-01-01

    We have studied the neuroprotective effect of the novel glutamic acid derivative neiroglutam on reversible focal cerebral ischemia in rats. The neuroprotective drug action was assessed by the ability to reduce the severity of neurological deficit (1, 2, 3, 5 and 7 days), forelimb fine-motor disorders (in the ladder test), hind limb motor activity (beam-walking test), and volume of the infarct zone upon 7-day pathologic exposure. It was found that the therapeutic administration of neiroglutam (26 mg/kg, i.p., for 7 days) reduces the volume of necrosis of cerebral tissues in case of focal brain ischemia in animals (on the average by 38%, (p < 0.05) and decreases the severity of motor disorders, which indicates the presence of neuroprotective effect of this compound. PMID:25365863

  2. No effects of monosodium glutamate consumption on the body weight or composition of adult rats and mice.

    PubMed

    Tordoff, Michael G; Aleman, Tiffany R; Murphy, Michelle C

    2012-10-10

    Monosodium glutamate (MSG) is pervasively consumed as a flavor enhancer so there are important implications to understanding its physiological actions, particularly its effects on body weight. Previous studies suggest that MSG increases, decreases, or has no effect on the body weight of rodents. However, most of these studies involved administration of MSG to immature rodents and consequently may not be relevant for understanding human obesity. We report here five experiments in which we measured the body weights of a total of 32 groups of 10-12 adult rats or mice given various diets to eat and MSG to eat or drink. We found no evidence that MSG influenced body weight, energy intake, or body composition. To the extent that experiments in rodents illuminate mechanisms involved in human obesity and body weight control, our results suggest that MSG is unlikely to be a useful anti-obesity supplement but neither is it responsible for exacerbating obesity. PMID:22868067

  3. Effects of glutamate and {alpha}2-noradrenergic receptor antagonists on the development of neurotoxicity produced by chronic rotenone in rats

    SciTech Connect

    Alam, Mesbah Danysz, Wojciech; Schmidt, Werner Juergen; Dekundy, Andrzej

    2009-10-15

    Systemic inhibition of complex I by rotenone in rats represents a model of Parkinson's disease (PD). The aim of this study was to elucidate whether neramexane (NMDA, nicotinic {alpha}9/{alpha}10 and 5-HT{sub 3} receptor antagonist), idazoxan ({alpha}{sub 2}-adrenoceptor antagonist) or 2-methyl-6-(phenyl-ethyl)-pyrimidine (MPEP, metabotropic glutamate receptor 5 antagonist) prevents rotenone-induced parkinsonian-like behaviours and neurochemical changes in rats. Rotenone (2.5 mg/kg i.p. daily) was administered over 60 days together with saline, neramexane (5 mg/kg i.p., b.i.d.), idazoxan (2.5 mg/kg i.p., b.i.d.) or MPEP (2.5 mg/kg i.p., b.i.d.). The same doses of neramexane, idazoxan and MPEP were administered to rats treated with vehicle instead of rotenone. Treatment-related effects on parkinsonian-like behaviours, such as hypokinesia/rigidity and locomotor activity, were evaluated. Moreover, concentrations of dopamine, serotonin and their metabolites were measured in rats from each experimental group. Over the 60-day treatment period, the rotenone + saline treated animals developed hypokinesia, expressed as an increase in the bar and grid descent latencies in the catalepsy test, and a decrease in locomotor activity. Neramexane and idazoxan partially prevented the development of catalepsy in rotenone-treated rats. Co-administration of MPEP with rotenone resulted only in a decrease in descent latency in the grid test on day 60. Chronic rotenone treatment reduced concentrations of dopamine and serotonin in the anterior striatum, which was blocked by co-treatment with neramexane or idazoxan but not with MPEP. Only neramexane treatment blocked the rotenone-induced decrease in dopamine levels in the substantia nigra pars compacta. In conclusion, neramexane and idazoxan counteracted to some extent the development of parkinsonian symptoms and neurochemical alterations in the rotenone model of Parkinson's disease.

  4. Differential effects of arginine, glutamate and phosphoarginine on Ca(2+)-activation properties of muscle fibres from crayfish and rat.

    PubMed

    Jame, David W; West, Jan M; Dooley, Philip C; Stephenson, D George

    2004-01-01

    The effects of two amino acids, arginine which has a positively charged side-chain and glutamate which has a negatively charged side-chain on the Ca2+-activation properties of the contractile apparatus were examined in four structurally and functionally different types of skeletal muscle; long- and short-sarcomere fibres from the claw muscle of the yabby (a freshwater decapod crustacean), and fast- and slow-twitch fibres from limb muscles of the rat. Single skinned fibres were activated in carefully balanced solutions of different pCa (-log10[Ca2+]) that either contained the test solute ("test") or not ("control"). The effect of phosphoarginine, a phosphagen that bears a nett negative charge, was also compared to the effects of arginine. Results show that (i) arginine (33-36 mmol l(-1)) significantly shifted the force-pCa curve by 0.08-0.13 pCa units in the direction of increased sensitivity to Ca2+-activated contraction in all fibre types; (ii) phosphoarginine (9-10 mmol l(-1)) induced a significant shift of the force-pCa curve by 0.18-0.24 pCa units in the direction of increased sensitivity to Ca2+ in mammalian fast- and slow-twitch fibres, but had no significant effects on the force-pCa relation in either long- or short-sarcomere crustacean fibres; (iii) glutamate (36-40 mmol l(-1)), like arginine affected the force-pCa relation of all fibre types investigated, but in the opposite direction, causing a significant decrease in the sensitivity to Ca2+-activated contraction by 0.08-0.19 pCa units; (iv) arginine, phosphoarginine and glutamate had little or no effect on the maximum Ca2+-activated force of crustacean and mammalian fibres. The results suggest that the opposing effects of glutamate and arginine are not related to simply their charge structure, but must involve complex interactions between these molecules, Ca2+ and the regulatory and other myofibrillar proteins. PMID:15711880

  5. Involvement of a cyclic-AMP pathway in group I metabotropic glutamate receptor responses in neonatal rat cortex.

    PubMed

    Schaffhauser, H; de Barry, J; Muller, H; Heitz, M P; Gombos, G; Mutel, V

    1997-09-10

    3,5-Dihydroxyphenylglycine (DHPG), (S)-3-hydroxyphenylglycine and (S)-4-carboxy-3-hydroxyphenylglycine (S-4C3HPG) stimulated phosphoinositide hydrolysis in neonatal rat cortical slices, but with lower maximal effect, in comparison with 2S,1'S,2'S-2-(2'-carboxycyclopropyl)glycine (L-CCG I) or (1S,3R)-1-aminocyclo-pentane-1,3-dicarboxylic acid (1S,3R-ACPD). DHPG, 1S,3R-ACPD, and S-4C3HPG also evoked a rapidly desensitizing increase in [Ca2+]i in cortical layers of neonatal brain slices. (R,S)-alpha-methyl-4-tetrazolyl-phenylglycine (MTPG), and (R,S)-alpha-methyl-4-phosphono-phenylglycine (MPPG) inhibited the increase of phosphoinositide hydrolysis elicited by 1S,3R-ACPD but not that by R,S-DHPG. In contrast, the selective group II receptor agonist (1S,2S,5R,6S)-2-amino-bicyclo-[3.1.0]-hexane-2,6-dicarboxylate (LY 354740) potentiated the response of R,S-DHPG. Finally, 8-(4-chlorophenylthio)-cAMP, a membrane permeant analogue of cAMP, reversed the stimulatory effect of 1S,3R-ACPD and S-4C3HPG on phosphoinositide hydrolysis and [Ca2+]i mobilization, without affecting the response induced by R,S-DHPG. These data suggest that, in neonatal rat cortex, the activation of group II metabotropic glutamate receptors potentiates the phosphoinositide hydrolysis and [Ca2+]i responses mediated by group I metabotropic glutamate receptors. PMID:9369360

  6. Uptake and metabolism of L-(/sup 3/H)glutamate and L-(/sup 3/H)glutamine in adult rat cerebellar slices

    SciTech Connect

    de Barry, J.; Vincendon, G.; Gombos, G.

    1983-10-01

    Using very low concentrations (1 mumol range) of L-2-3-(/sup 3/H)glutamate, (/sup 3/H-Glu) or L-2-3-(/sup 3/H)glutamine (/sup 3/H-Gln), the authors have previously shown by autoradiography that these amino acids were preferentially taken up in the molecular layer of the cerebellar cortex. Furthermore, the accumulation of /sup 3/H-Glu was essentially glial in these conditions. Uptake and metabolism of either (/sup 3/H-Glu) or (/sup 3/H-Gln) were studied in adult rat cerebellar slices. Both amino acids were rapidly converted into other metabolic compounds: after seven minutes of incubation in the presence of exogenous /sup 3/H-Glu, 70% of the tissue accumulated radioactivity was found to be in compounds other than glutamate. The main metabolites were Gln (42%), alpha-ketoglutarate (25%) and GABA (1,4%). In the presence of exogenous /sup 3/H-Gln the rate of metabolism was slightly slower (50% after seven minutes of incubation) and the metabolites were also Glu (29%), alpha-ketoglutarate (15%) and GABA (5%). Using depolarizing conditions (56 mM KCl) with either exogenous /sup 3/H-Glu or /sup 3/H-Gln, the radioactivity was preferentially accumulated in glutamate compared to control. From these results we conclude: i) there are two cellular compartments for the neurotransmission-glutamate-glutamine cycle; one is glial, the other neuronal; ii) these two cellular compartments contain both Gln and Glu; iii) transmitter glutamate is always in equilibrium with the so-called ''metabolic'' pool of glutamate; iv) the regulation of the glutamate-glutamine cycle occurs at least at two different levels: the uptake of glutamate and the enzymatic activity of the neuronal glutaminase.

  7. Convulsant and subconvulsant doses of norfloxacin in the presence and absence of biphenylacetic acid alter extracellular hippocampal glutamate but not gamma-aminobutyric acid levels in conscious rats.

    PubMed

    Smolders, I; Gousseau, C; Marchand, S; Couet, W; Ebinger, G; Michotte, Y

    2002-02-01

    Fluoroquinolones are antibiotics with central excitatory side effects. These adverse effects presumably result from inhibition of gamma-aminobutyric acid (GABA) binding to GABA(A) receptors. This GABA antagonistic effect is greatly potentiated by the active metabolite of fenbufen, biphenylacetic acid (BPAA). Nevertheless, it remains questionable whether GABA receptor antagonism alone can explain the convulsant activity potentials of these antimicrobial agents. The present study was undertaken to investigate the possible effects of norfloxacin, both in the absence and in the presence of BPAA, on the extracellular hippocampal levels of GABA and glutamate, the main central inhibitory and excitatory amino acid neurotransmitters, respectively. This in vivo microdialysis approach with conscious rats allows monitoring of behavioral alterations and concomitant transmitter modulation in the hippocampus. Peroral administration of 100 mg of BPAA per kg of body weight had no effect on behavior and did not significantly alter extracellular GABA or glutamate concentrations. Intravenous perfusion of 300 mg of norfloxacin per kg did not change the rat's behavior or the concomitant neurotransmitter levels in about half of the experiments, while the remaining animals exhibited severe seizures. These norfloxacin-induced convulsions did not affect extracellular hippocampal GABA levels but were accompanied by enhanced glutamate concentrations. Half of the rats receiving both 100 mg of BPAA per kg and 50 mg of norfloxacin per kg displayed lethal seizures, while the remaining animals showed no seizure-related behavior. In the latter subgroup, again no significant alterations in extracellular GABA levels were observed, but glutamate overflow remained significantly elevated for at least 3 h. In conclusion, norfloxacin exerts convulsant activity in rats, accompanied by elevations of extracellular hippocampal glutamate levels but not GABA levels, even in the presence of BPAA. PMID:11796360

  8. Convulsant and Subconvulsant Doses of Norfloxacin in the Presence and Absence of Biphenylacetic Acid Alter Extracellular Hippocampal Glutamate but Not Gamma-Aminobutyric Acid Levels in Conscious Rats

    PubMed Central

    Smolders, I.; Gousseau, C.; Marchand, S.; Couet, W.; Ebinger, G.; Michotte, Y.

    2002-01-01

    Fluoroquinolones are antibiotics with central excitatory side effects. These adverse effects presumably result from inhibition of γ-aminobutyric acid (GABA) binding to GABAA receptors. This GABA antagonistic effect is greatly potentiated by the active metabolite of fenbufen, biphenylacetic acid (BPAA). Nevertheless, it remains questionable whether GABA receptor antagonism alone can explain the convulsant activity potentials of these antimicrobial agents. The present study was undertaken to investigate the possible effects of norfloxacin, both in the absence and in the presence of BPAA, on the extracellular hippocampal levels of GABA and glutamate, the main central inhibitory and excitatory amino acid neurotransmitters, respectively. This in vivo microdialysis approach with conscious rats allows monitoring of behavioral alterations and concomitant transmitter modulation in the hippocampus. Peroral administration of 100 mg of BPAA per kg of body weight had no effect on behavior and did not significantly alter extracellular GABA or glutamate concentrations. Intravenous perfusion of 300 mg of norfloxacin per kg did not change the rat's behavior or the concomitant neurotransmitter levels in about half of the experiments, while the remaining animals exhibited severe seizures. These norfloxacin-induced convulsions did not affect extracellular hippocampal GABA levels but were accompanied by enhanced glutamate concentrations. Half of the rats receiving both 100 mg of BPAA per kg and 50 mg of norfloxacin per kg displayed lethal seizures, while the remaining animals showed no seizure-related behavior. In the latter subgroup, again no significant alterations in extracellular GABA levels were observed, but glutamate overflow remained significantly elevated for at least 3 h. In conclusion, norfloxacin exerts convulsant activity in rats, accompanied by elevations of extracellular hippocampal glutamate levels but not GABA levels, even in the presence of BPAA. PMID:11796360

  9. Group II metabotropic glutamate receptor type 2 allosteric potentiators prevent sodium lactate-induced panic-like response in panic-vulnerable rats

    PubMed Central

    Johnson, Philip L; Fitz, Stephanie D; Engleman, Eric A; Svensson, Kjell A; Schkeryantz, Jeffrey M; Shekhar, Anantha

    2015-01-01

    Rats with chronic inhibition of GABA synthesis by infusion of l-allyglycine, a glutamic acid decarboxylase inhibitor, into their dorsomedial/perifornical hypothalamus are anxious and exhibit panic-like cardio-respiratory responses to treatment with intravenous (i.v.) sodium lactate (NaLac) infusions, in a manner similar to what occurs in patients with panic disorder. We previously showed that either NMDA receptor antagonists or metabotropic glutamate receptor type 2/3 receptor agonists can block such a NaLac response, suggesting that a glutamate mechanism is contributing to this panic-like state. Using this animal model of panic, we tested the efficacy of CBiPES and THIIC, which are selective group II metabotropic glutamate type 2 receptor allosteric potentiators (at 10–30mg/kg i.p.), in preventing NaLac-induced panic-like behavioral and cardiovascular responses. The positive control was alprazolam (3mg/kg i.p.), a clinically effective anti-panic benzodiazepine. As predicted, panic-prone rats given a NaLac challenge displayed NaLac-induced panic-like cardiovascular (i.e. tachycardia and hypertensive) responses and “anxiety” (i.e. decreased social interaction time) and “flight” (i.e. increased locomotion) -associated behaviors; however, systemic injection of the panic-prone rats with CBiPES, THIIC or alprazolam prior to the NaLac dose blocked all NaLac-induced panic-like behaviors and cardiovascular responses. These data suggested that in a rat animal model, selective group II metabotropic glutamate type 2 receptor allosteric potentiators show an anti-panic efficacy similar to alprazolam. PMID:22914798

  10. Neonatal administration of N-acetyl-L-aspartyl-L-glutamate induces early neurodegeneration in hippocampus and alters behaviour in young adult rats.

    PubMed

    Bubeníková-Valesová, Vera; Balcar, Vladimir J; Tejkalová, Hana; Langmeier, Milos; St'astný, Frantisek

    2006-01-01

    N-acetyl-L-aspartyl-L-glutamate (NAAG) is a dipeptide that could be considered a sequestered form of L-glutamate. As much as 25% of L-glutamate in brain may be present in the form of NAAG. NAAG is also one of the most abundant neuroactive small molecules in the CNS: it is an agonist at Group II metabotropic glutamate receptors (mGluR II) and, at higher concentrations, at the N-methyl-D-aspartate (NMDA) type of ionotropic glutamate receptors. As such, NAAG can be either neuroprotective or neurotoxic and, in fact, both characteristics have been discussed and described in the literature. In the present studies, 250 nmol NAAG was infused into each lateral cerebral ventricle of 12-day-old rat pups and, using Nissl-stained sections, neurodegeneration in the hippocampus was evaluated 24 or 96 h after the infusion. In several experiments, the neuronal death was also visualised by Fluoro-Jade B staining and studied by TUNEL technique. Some of the NAAG-treated animals were allowed to survive until 50 days post partum and subjected to behavioural (open field) tests. The administration of NAAG to 12-day-old rats resulted in extensive death of neurons particularly in the dentate gyrus of the hippocampus. The neurodegeneration was, in part, prevented by administration of an NMDA receptor antagonist MK-801 (0.1 mg/kg). The nuclear DNA-fragmentation demonstrated by TUNEL technique pointed to the presence of non-specific single-strand DNA cleavage. The NAAG-associated neonatal neuronal damage may have perturbed development of synaptic circuitry during adolescence as indicated by an altered performance of the experimental animals in the open field testing (changes in grooming activity) at postnatal day 50. The results underscore the potential neurotoxicity of NAAG in neonatal rat brain and implicate neonatally induced, NMDA receptor-mediated neuronal loss in the development of abnormal behaviour in young adult rats. PMID:16540202

  11. Compounds extracted from Phyllantus and Jatropha elliptica inhibit the binding of [3H]glutamate and [3H]GMP-PNP in rat cerebral cortex membrane.

    PubMed

    Martini, L H; Souza, C R; Marques, P B; Calixto, J B; Yunes, R A; Souza, D O

    2000-02-01

    Glutamate is to be considered a nociceptive neurotransmitter and glutamatergic antagonists present antinoceptive activity. In this study we investigated the effects of the naturally occurring antinociceptive compounds rutin, geraniin and quercetine extracted from Phyllanthus, as well as the diterpene jatrophone, extracted from Jatropha elliptica on the binding of [3H]glutamate and [3H]GMP-PNP [a GTP analogue which binds to extracellular site(s), modulating the glutamatergic transmission] in rat brain membrane. Jatrophone inhibited [3H]glutamate binding and geraniin inhibited [3H]GMP-PNP binding. Quercetine inhibited the binding of both ligands. These results may indicate a neurochemical parameter possibly related to the antinoceptive activity of these natural compounds. PMID:10786704

  12. Metabotropic glutamate receptors inhibit microglial glutamate release

    PubMed Central

    McMullan, Stephen M; Phanavanh, Bounleut; Guo Li, Gary; Barger, Steven W

    2012-01-01

    Pro-inflammatory stimuli evoke an export of glutamate from microglia that is sufficient to contribute to excitotoxicity in neighbouring neurons. Since microglia also express various glutamate receptors themselves, we were interested in the potential feedback of glutamate on this system. Several agonists of mGluRs (metabotropic glutamate receptors) were applied to primary rat microglia, and the export of glutamate into their culture medium was evoked by LPS (lipopolysaccharide). Agonists of group-II and -III mGluR ACPD [(1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid] and L-AP4 [L-(+)-2-amino-4-phosphonobutyric acid] were both capable of completely blocking the glutamate export without interfering with the production of NO (nitric oxide); the group-I agonist tADA (trans-azetidine-2,4-dicarboxylic acid) was ineffective. Consistent with the possibility of feedback, inhibition of mGluR by MSPG [(R,S)-α-2-methyl-4sulfonophenylglycine] potentiated glutamate export. As the group-II and -III mGluR are coupled to Gαi-containing G-proteins and the inhibition of adenylate cyclase, we explored the role of cAMP in this effect. Inhibition of cAMP-dependent protein kinase [also known as protein kinase A (PKA)] by H89 mimicked the effect of ACPD, and the mGluR agonist had its actions reversed by artificially sustaining cAMP through the PDE (phosphodiesterase) inhibitor IBMX (isobutylmethylxanthine) or the cAMP mimetic dbcAMP (dibutyryl cAMP). These data indicate that mGluR activation attenuates a potentially neurotoxic export of glutamate from activated microglia and implicate cAMP as a contributor to this aspect of microglial action. PMID:22770428

  13. Neuroprotective Effects of the Glutamate Transporter Activator (R)-(-)-5-methyl-1-nicotinoyl-2-pyrazoline (MS-153) following Traumatic Brain Injury in the Adult Rat.

    PubMed

    Karklin Fontana, Andréia Cristina; Fox, Douglas P; Zoubroulis, Argie; Valente Mortensen, Ole; Raghupathi, Ramesh

    2016-06-01

    Traumatic brain injury (TBI) in humans and in animals leads to an acute and sustained increase in tissue glutamate concentrations within the brain, triggering glutamate-mediated excitotoxicity. Excitatory amino acid transporters (EAATs) are responsible for maintaining extracellular central nervous system glutamate concentrations below neurotoxic levels. Our results demonstrate that as early as 5 min and up to 2 h following brain trauma in brain-injured rats, the activity (Vmax) of EAAT2 in the cortex and the hippocampus was significantly decreased, compared with sham-injured animals. The affinity for glutamate (KM) and the expression of glutamate transporter 1 (GLT-1) and glutamate aspartate transporter (GLAST) were not altered by the injury. Administration of (R)-(-)-5-methyl-1-nicotinoyl-2-pyrazoline (MS-153), a GLT-1 activator, beginning immediately after injury and continuing for 24 h, significantly decreased neurodegeneration, loss of microtubule-associated protein 2 and NeuN (+) immunoreactivities, and attenuated calpain activation in both the cortex and the hippocampus at 24 h after the injury; the reduction in neurodegeneration remained evident up to 14 days post-injury. In synaptosomal uptake assays, MS-153 up-regulated GLT-1 activity in the naïve rat brain but did not reverse the reduced activity of GLT-1 in traumatically-injured brains. This study demonstrates that administration of MS-153 in the acute post-traumatic period provides acute and long-term neuroprotection for TBI and suggests that the neuroprotective effects of MS-153 are related to mechanisms other than GLT-1 activation, such as the inhibition of voltage-gated calcium channels. PMID:26200170

  14. Upregulation of metabotropic glutamate receptor 8 mRNA expression in the rat forebrain after repeated amphetamine administration

    PubMed Central

    Parelkar, Nikhil K; Wang, John Q.

    2008-01-01

    Metabotropic glutamate receptors (mGluRs) are G-protein-coupled receptors and are densely expressed in the forebrain of adult rats. Accumulative evidence suggests a critical role of mGluRs in the regulation of normal physiological activity of neurons and pathogenesis of mental illnesses such as schizophrenia, depression, and substance addiction. In this study, we investigated alterations in mGluR8 subtype mRNA expression in the rat forebrain in response to repeated intraperitoneal administration of amphetamine (twice daily for 12 days, 5 mg/kg per injection) using quantitative in situ hybridization. We found that mGluR8 mRNA levels were profoundly increased in the dorsal (caudate putamen) and ventral (nucleus accumbens) striatum 1 day after the discontinuation of amphetamine treatments. Such increases were sustained up to 21 days of withdrawal. Increases in mGluR8 mRNAs were also found in the cerebral cortex, including the cingulate and sensory cortex but not the piriform cortex, at 1 and 21 days. These data demonstrate a positive response of mGluR8 in mRNA abundance in most forebrain regions to repeated stimulant exposure. PMID:18255232

  15. New phenylglycine derivatives with potent and selective antagonist activity at presynaptic glutamate receptors in neonatal rat spinal cord.

    PubMed

    Jane, D E; Pittaway, K; Sunter, D C; Thomas, N K; Watkins, J C

    1995-08-01

    The depression of the monosynaptic excitation of neonatal rat motoneurones produced by the metabotropic glutamate receptor (mGluR) agonists (1S,3S)-1-aminocyclopentane-1, 3-dicarboxylate (ACPD) or L-2-amino-4-phosphonobutyrate (L-AP4) was antagonized by three novel phenylglycine analogues: (RS)-alpha-methyl-4-sulphonophenylglycine (MSPG), (RS)-alpha-methyl-4-phosphonophenylglycine (MPPG) and (RS)-alpha-methyl-4-tetrazolylphenylglycine (MTPG). The potencies of all the new compounds were greater than that of the previously reported (RS)-alpha-methyl-4-carboxyphenylglycine (MCPG). For L-AP4-sensitive presynaptic mGluRs, the order of antagonist potency found was MPPG > MSPG > MTPG > MCPG. In contrast, the order of antagonist potency found for (1S,3S)-ACPD-sensitive presynaptic mGluRs was MTPG > MPPG > MSPG > MCPG. To date, MPPG (KD 9.2 microM) is the most potent L-AP4-sensitive receptor antagonist yet tested on the neonatal rat spinal cord. In addition, MTPG (KD 77 microM) is the most potent antagonist yet tested for (1S,3S)-ACPD-sensitive receptors in this preparation. PMID:8532166

  16. Gamma-glutamyltransferase of rat kidney. Simultaneous assay of the hydrolysis and transfer reactions with (glutamate-14C)glutathione.

    PubMed Central

    Elce, J S; Broxmeyer, B

    1976-01-01

    1. The hydrolytic and transfer reactions catalysed by rat kidney-gamma-glutamyltransferase (EC 2.3.2.2) were studied in vitro with substrates [U-14C]glutamic acid-labelled glutathione and methionine. Initial-velocity patterns, isotope-exchange and binding studies were consistent with a branched non-sequential mechanism in which a gamma-glutamyl-enzyme intermediate may react either with water (hydrolysis) or with methionine (gamma-glutamyl transfer). 2. The Michaelis constant for glutathione in hydrolysis was 13.9 +/- 1.4 mum, for glutathione in transfer it was 113 +/- 15 muM and for methionine as substrate it was 4.7 +/- 0.7 mM. At substrate concentrations in the ranges of their respective Michaelis constants, the rate of transfer was about ten times higher than that of hydrolysis, but at concentrations of methionine approximating to the physiological (64 muM in rat plasma) the transfer is negligible. 3. The enzyme is reported to lie on the luminal surface of the proximal straight kidney tubule. In this situation, if the kinetic results obtained with the detergent-solubilized enzyme are relevant to the behavior of the enzyme in vivo, it appears likely that the main function of renal gamma-glutamyltransferase is not in amino acid transport, but rather to hydrolyse glutathione in the renal filtrate. PMID:6004

  17. Effect of different doses of monosodium glutamate on the thyroid follicular cells of adult male albino rats: a histological study

    PubMed Central

    Khalaf, Hanaa A; Arafat, Eetmad A

    2015-01-01

    Monosodium glutamate (MSG) is a major flavor enhancer used as a food additive. The present study investigates the effects of different doses of MSG on the morphometric and histological changes of the thyroid gland. 28 male albino rats were used. The rats were divided into four groups: group I control, group II, III and IV treated with MSG (0.25 g/kg, 3 g/kg, 6 g/kg daily for one month) respectively. The thyroid glands were dissected out and prepared for light and electron microscopic examination. Light microscopic examination of thyroid gland of group II revealed increase in follicular epithelial height. Groups III & IV showed decrease in the follicular diameter and irregularity in the shape of some follicles with discontinuity of basement membrane. Follicular hyperplasia was detected in some follicles with appearance of multiple pyknotic nuclei in follicular and interfollicular cells and multiple exfoliated cells in the colloid. In addition, areas of loss of follicular pattern were appeared in group IV. Immunohistochemical examination of BCL2 immunoexpression of the thyroid glands of groups III & IV reveals weak positive reaction in the follicular cells cytoplasm. Ultrathin sections examination of groups III & IV revealed follicular cells with irregular hyperchromatic nuclei, marked dilatation of rER and increased lysosomes with areas of short or lost apical microvilli. In addition, vacuolation of mitochondria was detected in group IV. The results displayed that MSG even at low doses is capable of producing alterations in the body weights and thyroid tissue function and histology. PMID:26884820

  18. Comparison of the solution of histidine-tryptophan-alfacetoglutarate with histidine-tryptophan-glutamate as cardioplegic agents in isolated rat hearts: an immunohistochemical study

    PubMed Central

    de Oliveira, Marcos Aurélio Barboza; Ferreira, Lívia Carvalho; Zuccari, Débora Aparecida Pires de Campos; Brandi, Antônio Carlos; dos Santos, Carlos Alberto; Botelho, Paulo Henrique Husseni; Petrucci, Orlando; Braile, Domingo Marcolino

    2014-01-01

    Introduction Cardiac arrest during heart surgery is a common procedure and allows the surgeon to perform surgical procedures in an environment free of blood and movement. Using a model of isolated rat heart, the authors compare a new cardioplegic solution containing histidine-tryptophan-glutamate (group 2) with the histidine-tryptophan-alphacetoglutarate (group 1) routinely used by some cardiac surgeons. Objective To assess caspase, IL-8 and KI-67 in isolated rat hearts using immunohistochemistry. Methods 20 Wistar male rats were anesthetized and heparinized. The chest was opened, cardioctomy was performed and 40 ml/kg of the appropriate cardioplegic solution was infused. The hearts were kept for 2 hours at 4ºC in the same solution, and thereafter, placed in the Langendorff apparatus for 30 minutes with Ringer-Locke solution. Immunohistochemistry analysis of caspase, IL-8, and KI-67 were performed. Results The concentration of caspase was lower in group 2 and Ki-67 was higher in group 2, both P<0.05. There was no statistical difference between the values of IL-8 between the groups. Conclusion Histidine-tryptophan-glutamate solution was better than histidine-tryptophan-alphacetoglutarate solution because it reduced caspase (apoptosis), increased KI-67 (cell proliferation), and showed no difference in IL-8 levels compared to group 1. This suggests that the histidine-tryptophan-glutamate solution was more efficient than the histidine-tryptophan-alphacetoglutarate for the preservation of hearts of rat cardiomyocytes. PMID:24896167

  19. Echinacoside Inhibits Glutamate Release by Suppressing Voltage-Dependent Ca2+ Entry and Protein Kinase C in Rat Cerebrocortical Nerve Terminals

    PubMed Central

    Lu, Cheng Wei; Lin, Tzu Yu; Huang, Shu Kuei; Wang, Su Jane

    2016-01-01

    The glutamatergic system may be involved in the effects of neuroprotectant therapies. Echinacoside, a phenylethanoid glycoside extracted from the medicinal Chinese herb Herba Cistanche, has neuroprotective effects. This study investigated the effects of echinacoside on 4-aminopyridine-evoked glutamate release in rat cerebrocortical nerve terminals (synaptosomes). Echinacoside inhibited Ca2+-dependent, but not Ca2+-independent, 4-aminopyridine-evoked glutamate release in a concentration-dependent manner. Echinacoside also reduced the 4-aminopyridine-evoked increase in cytoplasmic free Ca2+ concentration but did not alter the synaptosomal membrane potential. The inhibitory effect of echinacoside on 4-aminopyridine-evoked glutamate release was prevented by ω-conotoxin MVIIC, a wide-spectrum blocker of Cav2.2 (N-type) and Cav2.1 (P/Q-type) channels, but was insensitive to the intracellular Ca2+ release-inhibitors dantrolene and 7-chloro-5-(2-chloropheny)-1,5-dihydro-4,1-benzothiazepin-2(3H)-one (CGP37157). Furthermore, echinacoside decreased the 4-aminopyridine-induced phosphorylation of protein kinase C, and protein kinase C inhibitors abolished the effect of echinacoside on glutamate release. According to these results, we suggest that the inhibitory effect of echinacoside on evoked glutamate release is associated with reduced voltage-dependent Ca2+ entry and subsequent suppression of protein kinase C activity. PMID:27347934

  20. MDMA increases glutamate release and reduces parvalbumin-positive GABAergic cells in the dorsal hippocampus of the rat: role of cyclooxygenase

    PubMed Central

    Anneken, John H.; Cunningham, Jacobi I.; Collins, Stuart A.; Yamamoto, Bryan K.; Gudelsky, Gary A.

    2012-01-01

    3,4-Methylenedioxymethamphetamine (MDMA; Ecstasy) is a popular drug of abuse with well-documented acute effects on serotonergic, dopaminergic, and cholinergic transmitter systems, as well as evidence of long-term disruption of serotoninergic systems in the rat brain. Recently, it was demonstrated that MDMA evokes a delayed and sustained increase in glutamate release in the hippocampus. The purpose of the present study was to determine the role of inflammatory mediators in the MDMA-induced increase in glutamate release, as well as the contribution of inflammatory pathways in the persistent neurochemical toxicity associated with repeated MDMA treatment. Treatment with the non-selective cyclooxygenase (COX) inhibitor ketoprofen and the COX-2 selective inhibitor nimesulide attenuated the increase in extracellular glutamate in the hippocampus evoked by repeated MDMA exposure (10 mg/kg, i.p., every 2 h); no attenuation was observed in rats treated with the COX-1 selective inhibitor piroxicam. Reverse dialysis of a major product of COX activity, prostaglandin E2, also resulted in a significant increase in extracellular glutamate in the hippocampus. Repeated exposure to MDMA diminished the number of parvalbumin-positive GABA interneurons in the dentate gyrus of the hippocampus, an effect that was attenuated by ketoprofen treatment. However, COX inhibition with ketoprofen did not prevent the long-term depletion of 5-HT in the hippocampus evoked by MDMA treatment. These data are supportive of the view that cyclooxygenase activity contributes to the mechanism underlying both the increased release of glutamate and decreased number of GABA interneurons in the rat hippocampus produced by repeated MDMA exposure. PMID:23179355

  1. Beneficial effect of magnesium lithospermate B on cerebral ischemia-reperfusion injury in rats involves the regulation of miR-107/glutamate transporter 1 pathway.

    PubMed

    Yang, Zhong-Bao; Luo, Xiu-Ju; Ren, Kai-Di; Peng, Jing-Jie; Tan, Bin; Liu, Bin; Lou, Zheng; Xiong, Xiao-Ming; Zhang, Xiao-Jie; Ren, Xian; Peng, Jun

    2015-11-01

    Recent studies uncovered that glutamate accumulation following cerebral ischemia-reperfusion (I/R) was related to the dysfunction of miR-107/glutamate transporter-1(GLT-1) pathway and magnesium lithospermate B (MLB) possesses the pharmacological activity of anti-excitotoxicity. This study aims to explore whether MLB is able to protect rat brain from excitatory neurotoxicity during I/R by modulating miR-107/GLT-1 pathway. Rats were subjected to 2h of cerebral ischemia following by 24h of reperfusion to establish an I/R injury model, which showed an increase in neurological deficit score, infarct volume and cellular apoptosis concomitant with glutamate accumulation, miR-107 elevation and GLT-1 down-regulation. Administration of MLB reduced I/R-induced cerebral injury accompanied by a reverse in glutamate accumulation, miR-107 and GLT-1 expression. Next, we examined the association of MLB with miR-107/GLT-1 pathway in a nerve cell hypoxia/reoxygenation (H/R) injury model. H/R treatment increased the nerve cells apoptosis concomitant with glutamate accumulation and miR-107 elevation, and suppressed GLT-1 expression, mimicking our in vivo findings. All these effects were reversed in the presence of MLB, confirming a strong correlation between MLB and miR-107/GLT-1 pathway. Based on these observations, we conclude that MLB is able to protect the rat brain from excitatory neurotoxicity during I/R through the regulation of miR-107/GLT-1 pathway. PMID:26420356

  2. Propofol differentially inhibits the release of glutamate, γ-aminobutyric acid and glycine in the spinal dorsal horn of rats

    PubMed Central

    Yang, Jing; Wang, Wei; Yong, Zheng; Mi, Weidong; Zhang, Hong

    2015-01-01

    Objective(s): Propofol (2, 6-diisopropylphenol) is an intravenous anesthetic that is commonly used for the general anesthesia. It is well known that the spinal cord is one of the working targets of general anesthesia including propofol. However, there is a lack of investigation of the effects of propofol on spinal dorsal horn which is important for the sensory transmission of nociceptive signals. The objective of this study was to investigate the effects of increasing dosage of propofol on the release of glutamate (Glu), γ-aminobutyric acid (GABA) and glycine (Gly) in the spinal dorsal horn. Materials and Methods: The efflux of Glu, GABA or Gly in the spinal dorsal horn of rats was detected using transverse spinal microdialysis under an awake condition and various depths of propofol anesthesia. The infusion rates of propofol were, in order, 400 µg/(kg·min), 600 µg/(kg·min) and 800 µg/(kg·min), with a 20 min infusion period being maintained at each infusion rate. Results: Propofol decreased the glutamate efflux within spinal dorsal horn in a dose-dependent manner, and the maximum decrease was 56.8 ± 6.0% at high-dose propofol infusion producing immobility. The inhibitory GABA and Gly efflux was also decreased about 15–20% at low-dose propofol infusion only producing sedation, but did not continue to drop with higher doses of propofol. Conclusion: Propofol decreased both excitatory and inhibitory amino acids efflux in spinal dorsal horn, and the preferential suppression of the excitatory amino acid might be associated with the analgesic effect of propofol. PMID:26557972

  3. Physiological role of group III metabotropic glutamate receptors in visually responsive neurons of the rat superficial superior colliculus.

    PubMed

    Cirone, J; Salt, T E

    2000-03-01

    There is evidence from immunohistochemical and in situ hybridization studies for the presence of Group I, II and III metabotropic glutamate receptors (mGluRs) in the rat superficial superior colliculus (SSC). The purpose of this study was to investigate if manipulation of Group III mGluRs affects visual responses in the SSC. Drugs were applied by iontophoresis and single neuron activity was recorded extracellularly. L-AP4 (Group III agonist) resulted in a reduction of visual responses in most neurons, but also a potentiation in others. The effect of L-AP4 is drug- and stereospecific in that application of D-AP4 did not significantly affect visual responses. L-AP4 application also resulted in a potentiation of the response to iontophoretically applied NMDA. The effects of MPPG and CPPG (Group III antagonists) were compared with the effect of L-AP4 in the same neuron and were found to produce the opposite effect to L-AP4. Furthermore, the effect of L-AP4 could be blocked by coapplication of MPPG or CPPG. Presynaptic depression of glutamate release is a possible mechanism by which L-AP4 could reduce visual responses in the SSC whereas the potentiation of visual responses by L-AP4 could be due to a reduction of GABAergic inhibition. The finding that MPPG and CPPG, as well as antagonizing the L-AP4 effect, have a direct effect on visual responses suggests that Group III mGluRs are activated by endogenous transmitter released during visual stimulation. PMID:10762314

  4. Group II and III metabotropic glutamate receptors contribute to different aspects of visual response processing in the rat superior colliculus

    PubMed Central

    Cirone, Jennifer; Salt, Thomas E

    2001-01-01

    Neurones in the superior colliculus (SC) respond to novel sensory stimuli and response habituation is a key feature of this. It is known that both ionotropic and metabotropic glutamate (mGlu) receptors participate in visual responses of superficial SC neurones. A feature of Group II and Group III mGlu receptors is that they may modulate specific neural pathways, possibly via presynaptic mechanisms. However, less is known about how this may relate to functions of systems in whole animals. We have therefore investigated whether these receptors affect specific attributes of visual responses in the superficial SC. Recordings were made from visually responsive neurones in anaesthetised rats, and agonists and antagonists of Group II and III mGlu receptors were applied iontophoretically at the recording site. We found that application of the Group III metabotropic glutamate receptor agonist l-2-amino-4-phosphonobutyric acid (l-AP4) produced an increase in visual response habituation, whilst Group III antagonists decreased habituation. These effects were independent of the response habituation mediated via GABAB receptors. In contrast, modulation of Group II mGlu receptors with the specific agonist LY354740 or the antagonist LY341495 did not affect response habituation, although these compounds did modulate visual responses. This suggests a specific role for Group III mGlu receptors in visual response habituation. The magnitude of Group II effects was smaller during presentation of low contrast stimuli compared with high contrast stimuli. This suggests that activation of Group II receptors may be activity dependent and that these receptors can translate this into a functional effect in adapting to high contrast stimuli. PMID:11433000

  5. Decreasing nicotinic receptor activity and the spatial learning impairment caused by the NMDA glutamate antagonist dizocilpine in rats

    PubMed Central

    Burke, Dennis A.; Heshmati, Pooneh; Kholdebarin, Ehsan; Levin, Edward D.

    2014-01-01

    Nicotinic systems have been shown by a variety of studies to be involved in cognitive function. Nicotinic receptors have an inherent property to become desensitized after activation. The relative role of nicotinic receptor activation vs. net receptor inactivation by desensitization in the cognitive effects of nicotinic drugs remains to be fully understood. In these studies, we tested the effects of the α7 nicotinic receptor antagonist methyllycaconitine (MLA), the α4β2 nicotinic receptor antagonist dihydro-β-erythroidine (DHβE), the nonspecific nicotinic channel blocker mecamylamine and the α4β2 nicotinic receptor desensitizing agent sazetidine-A on learning in a repeated acquisition test. Adult female Sprague-Dawley rats were trained on a repeated acquisition learning procedure in an 8-arm radial maze. MLA (1–4 mg/kg), DHβE (1–4 mg/kg), mecamylamine (0.125–0.5 mg/kg) or sazetidine-A (1 and 3 mg/kg) were administered in four different studies either alone or together with the NMDA glutamate antagonist dizocilpine (0.05 and 0.10 mg/kg). MLA significantly counteracted the learning impairment caused by dizocilpine. The overall choice accuracy impairment caused by dizocilpine was significantly attenuated by co-administration of DHβE. Low doses of the non-specific nicotinic antagonist mecamylamine also reduced dizocilpine-induced repeated acquisition impairment. Sazetidine-A reversed the accuracy impairment caused by dizocilpine. These studies provide evidence that a net decrease in nicotinic receptor activity can improve learning by attenuating learning impairment induced by NMDA glutamate blockade. This adds to evidence in cognitive tests that nicotinic antagonists can improve cognitive function. Further research characterizing the efficacy and mechanisms underlying nicotinic antagonist and desensitization induced cognitive improvement is warranted. PMID:25064338

  6. Subcellular and subsynaptic localization of group I metabotropic glutamate receptors in the nucleus accumbens of cocaine-treated rats

    PubMed Central

    Mitrano, D.A.; Arnold, C.; Smith, Y.

    2008-01-01

    There is significant pharmacological and behavioral evidence that group I metabotropic glutamate receptors (mGluR1a and mGluR5) in the nucleus accumbens play an important role in the neurochemical and pathophysiological mechanisms that underlie addiction to psychostimulants. To further address this issue, we undertook a detailed ultrastructural analysis to characterize changes in the subcellular and subsynaptic localization of mGluR1a and mGluR5 in the core and shell of nucleus accumbens following acute or chronic cocaine administration in rats. After a single cocaine injection (30mg/kg) and 45 minutes withdrawal, there was a significant decrease in the proportion of plasma membrane-bound mGluR1a in accumbens shell dendrites. Similarly, the proportion of plasma membrane-bound mGluR1a was decreased in large dendrites of accumbens core neurons following chronic cocaine exposure (i.e. 1 week treatment followed by three weeks withdrawal). However, neither acute nor chronic cocaine treatments induced significant change in the localization of mGluR5 in accumbens core and shell, which is in contrast with the significant reduction of plasma membrane-bound mGluR1a and mGluR5 induced by local intra-accumbens administration of the group I mGluR agonist, DHPG. In conclusion, these findings demonstrate that cocaine-induced glutamate imbalance (Smith et al., 1995; Pierce et al., 1996; Reid et al., 1997) has modest effects on the trafficking of group I mGluRs in the nucleus accumbens. These results provide valuable information on the neuroadaptive mechanisms of accumbens group I mGluRs in response to cocaine administration. PMID:18479833

  7. Modulation of GABAergic inhibition in the rat superior colliculus by a presynaptic group II metabotropic glutamate receptor.

    PubMed

    Neale, S A; Salt, T E

    2006-12-01

    Previous work has indicated that metabotropic glutamate receptors (mGluRs) modulate visual responses of superior colliculus (SC) neurones in vivo in a variety of ways, in a manner that can be dependent upon visual stimulus properties. How this occurs remains unclear. In this study we aimed to determine how activation of mGluR2 and mGluR3 receptors (Group II) might modulate visual responses, by using field potential and whole-cell patch clamp recording techniques in rat SC slice. Stimulation within the superficial layers of the SC, in the presence of ionotropic glutamate receptor antagonists, evoked IPSCs that were blocked by bicuculline indicating that they are mediated via GABAA receptors. It is likely that these IPSCs were of heterogeneous origin as they showed substantial variation in paired-pulse behaviour. Nevertheless, activation of Group II mGluRs with the group-selective agonist LY354740 (300 nM, bath application) resulted in a reduction of these IPSCs (to 56% of control amplitude), and this was associated with a decrease in paired-pulse depression. At the same concentration, LY354740 did not reduce the EPSC or field-EPSP evoked by stimulation of the retinal input to the SC. The effects of LY354740 on IPSCs were not mimicked by the mGluR3-selective agonist N-acetyl-aspartyl-glutamate (NAAG, 200-500 microM). Stimulation of IPSCs with trains of impulses (10 at 20 Hz) in order to mimic natural activation patterns resulted in sequences of IPSCs that were reduced in amplitude towards the end of the stimulus train. Application of the Group II antagonist LY341495 (100 nM) under these conditions resulted in an increase in later IPSCs in a third of neurones tested. These findings indicate that mGluR2 (but not mGluR3) can selectively modulate GABAergic inhibition in SC, probably via a presynaptic mechanism. Furthermore, these receptors may be activated by synaptically released transmitter during patterns of activation similar to those seen during visual processing

  8. Pregnenolone sulfate restores the glutamate-nitric-oxide-cGMP pathway and extracellular GABA in cerebellum and learning and motor coordination in hyperammonemic rats.

    PubMed

    Gonzalez-Usano, Alba; Cauli, Omar; Agusti, Ana; Felipo, Vicente

    2014-02-19

    Around 40% of cirrhotic patients show minimal hepatic encephalopathy (MHE), with mild cognitive impairment which reduces their quality of life and life span. Treatment of MHE is unsatisfactory, and there are no specific treatments for the neurological alterations in MHE. Hyperammonemia is the main contributor to neurological alterations in MHE. New agents acting on molecular targets involved in brain mechanisms leading to neurological alterations are needed to treat MHE. Chronic hyperammonemia impairs learning of a Y-maze task by impairing the glutamate-nitric-oxide (NO)-cGMP pathway in cerebellum, in part by enhancing GABA(A) receptor activation, which also induces motor in-coordination. Acute pregnenolone sulfate (PregS) restores the glutamate-NO-cGMP pathway in hyperammonemic rats. This work aimed to assess whether chronic treatment of hyperammonemic rats with PregS restores (1) motor coordination; (2) extracellular GABA in cerebellum; (3) learning of the Y-maze task; (4) the glutamate-NO-cGMP pathway in cerebellum. Chronic intracerebral administration of PregS normalizes motor coordination likely due to extracellular GABA reduction. PregS restores learning ability by restoring the glutamate-NO-cGMP pathway, likely due to both enhanced NMDA receptor activation and reduced GABA(A) receptor activation. Similar treatments would improve cognitive and motor alterations in patients with MHE. PMID:24256194

  9. Pregnenolone Sulfate Restores the Glutamate-Nitric-Oxide-cGMP Pathway and Extracellular GABA in Cerebellum and Learning and Motor Coordination in Hyperammonemic Rats

    PubMed Central

    2013-01-01

    Around 40% of cirrhotic patients show minimal hepatic encephalopathy (MHE), with mild cognitive impairment which reduces their quality of life and life span. Treatment of MHE is unsatisfactory, and there are no specific treatments for the neurological alterations in MHE. Hyperammonemia is the main contributor to neurological alterations in MHE. New agents acting on molecular targets involved in brain mechanisms leading to neurological alterations are needed to treat MHE. Chronic hyperammonemia impairs learning of a Y-maze task by impairing the glutamate-nitric-oxide (NO)-cGMP pathway in cerebellum, in part by enhancing GABAA receptor activation, which also induces motor in-coordination. Acute pregnenolone sulfate (PregS) restores the glutamate-NO-cGMP pathway in hyperammonemic rats. This work aimed to assess whether chronic treatment of hyperammonemic rats with PregS restores (1) motor coordination; (2) extracellular GABA in cerebellum; (3) learning of the Y-maze task; (4) the glutamate-NO-cGMP pathway in cerebellum. Chronic intracerebral administration of PregS normalizes motor coordination likely due to extracellular GABA reduction. PregS restores learning ability by restoring the glutamate-NO-cGMP pathway, likely due to both enhanced NMDA receptor activation and reduced GABAA receptor activation. Similar treatments would improve cognitive and motor alterations in patients with MHE. PMID:24256194

  10. Involvement of Glutamate NMDA Receptors in the Acute, Long-Term, and Conditioned Effects of Amphetamine on Rat 50kHz Ultrasonic Vocalizations

    PubMed Central

    Costa, Giulia; Morelli, Micaela

    2015-01-01

    Background: Rats emit 50kHz ultrasonic vocalizations (USVs) in response to either natural or pharmacological pleasurable stimuli, and these USVs have emerged as a new behavioral measure for investigating the motivational properties of drugs. Earlier studies have indicated that activation of the dopaminergic system is critically involved in 50kHz USV emissions. However, evidence also exists that non-dopaminergic neurotransmitters participate in this behavioral response. Methods: To ascertain whether glutamate transmission plays a role in 50kHz USV emissions stimulated by amphetamine, rats received five amphetamine (1–2mg/kg, i.p.) administrations on alternate days in a test cage, either alone or combined with the glutamate N-methyl-D-aspartate receptor antagonist MK-801 (0.1–0.5mg/kg, i.p.). Seven days after treatment discontinuation, rats were re-exposed to the test cage to assess drug conditioning, and afterwards received a drug challenge. USVs and locomotor activity were evaluated, along with immunofluorescence for Zif-268 in various brain regions and spontaneous alternation in a Y maze. Results: Amphetamine-treated rats displayed higher 50kHz USV emissions and locomotor activity than vehicle-treated rats, and emitted conditioned vocalizations on test cage re-exposure. Rats co-administered amphetamine and MK-801 displayed lower and dose-dependent 50kHz USV emissions, but not lower locomotor activity, during repeated treatment and challenge, and scarce conditioned vocalization compared with amphetamine-treated rats. These effects were associated with lower levels of Zif-268 after amphetamine challenge and spontaneous alternation deficits. Conclusions: These results indicate that glutamate transmission participates in the acute, long-term, and conditioned effects of amphetamine on 50kHz USVs, possibly by influencing amphetamine-induced long-term neuronal changes and/or amphetamine-associated memories. PMID:25991653

  11. Coincident Glutamatergic and Cholinergic Inputs Transiently Depress Glutamate Release at Rat Schaffer Collateral Synapses

    PubMed Central

    Gipson, Keith E.; Yeckel, Mark F.

    2010-01-01

    The mammalian hippocampus, together with subcortical and cortical areas, is responsible for some forms of learning and memory. Proper hippocampal function depends on the highly dynamic nature of its circuitry, including the ability of synapses to change their strength for brief to long periods of time. In this study, we focused on a transient depression of glutamatergic synaptic transmission at Schaffer collateral synapses in acute hippocampal slices. The depression of evoked excitatory postsynaptic current (EPSC) amplitudes, herein called transient depression, follows brief trains of synaptic stimulation in stratum radiatum of CA1 and lasts for 2–3 min. Depression results from a decrease in presynaptic glutamate release, as NMDA-receptor–mediated EPSCs and composite EPSCs are depressed similarly and depression is accompanied by an increase in the paired-pulse ratio. Transient depression is prevented by blockade of metabotropic glutamate and acetylcholine receptors, presumably located presynaptically. These two receptor types—acting together— cause depression. Blockade of a single receptor type necessitates significantly stronger conditioning trains for triggering depression. Addition of an acetylcholinesterase inhibitor enables depression from previously insufficient conditioning trains. Furthermore, a strong coincident, but not causal, relationship existed between presynaptic depression and postsynaptic internal Ca2+ release, emphasizing the potential importance of functional interactions between presynaptic and postsynaptic effects of convergent cholinergic and glutamatergic inputs to CA1. These convergent afferents, one intrinsic to the hippocampus and the other likely originating in the medial septum, may regulate CA1 network activity, the induction of long-term synaptic plasticity, and ultimately hippocampal function. PMID:17303811

  12. Neurotoxic Potential of Lunar and Martian Dust: Influence on Em, Proton Gradient, Active Transport, and Binding of Glutamate in Rat Brain Nerve Terminals

    PubMed Central

    Krisanova, Natalia; Kasatkina, Ludmila; Sivko, Roman; Borysov, Arseniy; Nazarova, Anastasiya; Slenzka, Klaus; Borisova, Tatiana

    2013-01-01

    Abstract The harmful effects of lunar dust (LD) on directly exposed tissues are documented in the literature, whereas researchers are only recently beginning to consider its effects on indirectly exposed tissues. During inhalation, nano-/microsized particles are efficiently deposited in nasal, tracheobronchial, and alveolar regions and transported to the central nervous system. The neurotoxic potential of LD and martian dust (MD) has not yet been assessed. Glutamate is the main excitatory neurotransmitter involved in most aspects of normal brain function, whereas disturbances in glutamate homeostasis contribute to the pathogenesis of major neurological disorders. The research was focused on the analysis of the effects of LD/MD simulants (JSC-1a/JSC, derived from volcanic ash) on the key characteristics of glutamatergic neurotransmission. The average size of LD and MD particles (even minor fractions) before and after sonication was determined by dynamic light scattering. With the use of radiolabeled l-[14C]glutamate, it was shown that there is an increase in l-[14C]glutamate binding to isolated rat brain nerve terminals (synaptosomes) in low [Na+] media and at low temperature in the presence of LD. MD caused significantly lesser changes under the same conditions, whereas nanoparticles of magnetite had no effect at all. Fluorimetric experiments with potential-sensitive dye rhodamine 6G and pH-sensitive dye acridine orange showed that the potential of the plasma membrane of the nerve terminals and acidification of synaptic vesicles were not altered by LD/MD (and nanoparticles of magnetite). Thus, the unique effect of LD to increase glutamate binding to the nerve terminals was shown. This can have deleterious effects on extracellular glutamate homeostasis in the central nervous system and cause alterations in the ambient level of glutamate, which is extremely important for proper synaptic transmission. During a long-term mission, a combination of constant irritation

  13. Genetic predisposition and early life experience interact to determine glutamate transporter (GLT1) and solute carrier family 12 member 5 (KCC2) levels in rat hippocampus.

    PubMed

    Sterley, Toni-Lee; Howells, Fleur M; Dimatelis, Jacqueline J; Russell, Vivienne A

    2016-02-01

    Attention-deficit/hyperactivity disorder (ADHD) is one of the most common child psychiatric disorders. While it is typically treated with medications that target dopamine and norepinephrine transmission, there is increasing evidence that other neurotransmitter systems, such as glutamate and GABA, may be involved. The aetiology of ADHD is unknown; however, there is evidence that early life stress may contribute to the development of the disorder. In the present study we used proteomic analysis (iTRAQ) followed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and Western blot analysis to investigate hippocampal protein profiles of three rat strains: an animal model of ADHD, spontaneously hypertensive rats (SHR), their control Wistar-Kyoto rats (WKY), and Sprague-Dawley rats (SD). We additionally investigated how these protein profiles are affected by maternal separation, a model of early life stress. Our findings show that solute carrier family 12 member 5 (KCC2) is increased in SHR hippocampus. The glutamate transporter GLT1 splice variant, GLT1b, was increased (proteomic analysis) while total GLT1 (comprised mostly of GLT1a splice variant) was reduced (Western blot analysis) in SHR hippocampus, compared to WKY and SD--a pattern that is consistent with elevated extracellular glutamate levels. Maternal separation increased total GLT1 in hippocampi of SHR, WKY, and SD, and reduced GLT1b in SHR hippocampus. Together these findings provide evidence for disturbed glutamatergic and GABAergic transmission in SHR hippocampus, maternal separation effects on glutamate uptake in hippocampi of all three strains, as well a unique effect of maternal separation on GLT1b levels in SHR hippocampus. These data suggest significant involvement of glutamatergic and GABAergic transmission in the neuropathophysiology of ADHD, and implicates changes in glutamatergic transmission as a result of early life stress. PMID:26464063

  14. Enhanced Extracellular Glutamate and Dopamine in the Ventral Pallidum of Alcohol-Preferring AA and Alcohol-Avoiding ANA Rats after Morphine

    PubMed Central

    Kemppainen, Heidi; Nurmi, Harri; Raivio, Noora; Kiianmaa, Kalervo

    2015-01-01

    The purpose of the present study was to investigate the role of ventral pallidal opioidergic mechanisms in the control of ethanol intake by studying the effects of acute administration of morphine on the levels of GABA, glutamate, and dopamine in the ventral pallidum. The study was conducted using the alcohol-preferring Alko Alcohol (AA) and alcohol-avoiding Alko Non-Alcohol (ANA) rat lines that have well-documented differences in their voluntary ethanol intake and brain opioidergic systems. Therefore, examination of neurobiological differences between the lines is supposed to help to identify the neuronal mechanisms underlying ethanol intake, since selection pressure is assumed gradually to lead to enrichment of alleles promoting high or low ethanol intake, respectively. The effects of an acute dose of morphine (1 or 10 mg/kg s.c.) on the extracellular levels of GABA and glutamate in the ventral pallidum were monitored with in vivo microdialysis. The concentrations of GABA and glutamate in the dialyzates were determined with a high performance liquid chromatography system using fluorescent detection, while electrochemical detection was used for dopamine. The levels of glutamate in the rats injected with morphine 1 mg/kg were significantly above the levels found in the controls and in the rats receiving morphine 10 mg/kg. Morphine 10 mg/kg also increased the levels of dopamine. Morphine could not, however, modify the levels of GABA. The rat lines did not differ in any of the effects of morphine. The data suggest that the glutamatergic and dopaminergic systems in the ventral pallidum may mediate some effects of morphine. Since there were no differences between the AA and ANA lines, the basic hypothesis underlying the use of the genetic animal model suggests that the effects of morphine detected probably do not underlie the different intake of ethanol by the lines and contribute to the control of ethanol intake in these animals. PMID:25653621

  15. L-glutamate diethyl ester and deaminated analogues as excitatory amino acid antagonists in rat cerebral cortex.

    PubMed

    Turner, J P; Meldrum, B S

    1991-10-01

    1. The effects of L-glutamate diethyl ester (GDEE) HCl, glutarate diethyl ester (GlrDEE) and glutarate dimethyl ester (GlrDME) on depolarizing responses to alpha-amino-3-hydroxy-5- methyl-4-isoxazolepropionate (AMPA), kainate (Kain), N-methyl-D-aspartate (NMDA) and quisqualate (Quis), and spontaneous paroxysmal discharges (SPDs) were examined. Experiments were performed on slices of rat cingulate cortex using the in vitro grease gap recording technique in nominally Mg(2+)-free Krebs medium. 2. GDEE HCl (3-14 mM) caused a concentration-dependent depolarization of the d.c. baseline potential. L-Glutamate (0.1-0.5 mM), HCl (15 mM) and sucrose (30 mM) also depolarized the baseline. GlrDEE (3-12 mM) and GlrDME (4-26 mM) had no consistent effect on baseline potential. 3. GDEE HCl (10 mM) had no effect on depolarizing responses to AMPA, Kain and NMDA, but caused potentiation of those to Quis with a dose-ratio of 0.53 (0.44-0.63) (n = 4). In two other experiments, where the depolarization of the baseline induced by GDEE HCl was large, a depression of Quis response amplitude was observed. 4. GlrDEE (10 mM) antagonized depolarizing responses to Kain, and to a lesser extent NMDA, with dose-ratios of 2.14 (1.92-2.38) and 1.61 (1.39-1.87), respectively. This concentration of GlrDEE had no effect on AMPA responses, but potentiated Quis responses, with a dose-ratio of 0.64 (0.58-0.71). 5. GlrDME (10 mM) antagonized depolarizing responses to Kain and to Quis, with dose-ratios of 1.66 (1.48-1.85) and 1.22 (1.15-1.29), respectively, and had no effect on responses to NMDA. 6. The SPDs were inhibited by GDEE HCI (IC50 6.7 +/- 0.37mM), GlrDEE (IC50 5.6 +/- 0.38 mM) and GlrDME (IC50 10.4 +/- 0.73 mM). 7. In conclusion, there is little evidence that GDEE HCI is an antagonist of the postsynaptic excitatory amino acid receptors in the rat neocortex, and its effects may result from its contamination with Lglutamate and increased osmolarity of the bathing medium at high concentrations. The

  16. Modafinil restores methamphetamine induced object-in-place memory deficits in rats independent of glutamate N-methyl d-aspartate receptor expression

    PubMed Central

    Reichel, Carmela M.; Gilstrap, Meghin G.; Ramsey, Lauren A.; See, Ronald E.

    2013-01-01

    Background Chronic methamphetamine (meth) abuse in humans can lead to various cognitive deficits, including memory loss. We previously showed that chronic meth self-administration impairs memory for objects relative to their location and surrounding objects. Here, we demonstrate that the cognitive enhancer, modafinil, reversed this cognitive impairment independent of glutamate N-methyl d-aspartate (GluN) receptor expression. Methods Male, Long-Evans rats underwent a noncontingent (Experiment 1) or contingent (Experiment 2) meth regimen. After one week of abstinence, rats were tested for object-in-place recognition memory. Half the rats received either vehicle or modafinil (100 mg/kg) immediately after object familiarization. Rats (Experiment 2) were sacrificed immediately after the test and brain areas that comprise the key circuitry for object in place performance were manually dissected. Subsequently, glutamate receptor expression was measured from a crude membrane fraction using western blot procedures. Results Saline-treated rats spent more time interacting with the objects in changed locations, while meth-treated rats distributed their time equally among all objects. Meth-treated rats that received modafinil showed a reversal in the deficit, whereby they spent more time exploring the objects in the new locations. GluN2B receptor subtype was decreased in the perirhinal cortex, yet remained unaffected in the prefrontal cortex and hippocampus of meth rats. This meth-induced down regulation occurred whether or not meth experienced rats received vehicle or modafinil. Conclusions These data support the use of modafinil for memory impairment in meth addiction. Further studies are needed to elucidate the neural mechanisms of modafinil reversal of cognitive impairments. PMID:24120858

  17. Glutamate-induced activation of nitric oxide synthase is impaired in cerebral cortex in vivo in rats with chronic liver failure.

    PubMed

    Rodrigo, Regina; Erceg, Slaven; Rodriguez-Diaz, Jesus; Saez-Valero, Javier; Piedrafita, Blanca; Suarez, Isabel; Felipo, Vicente

    2007-07-01

    It has been proposed that impairment of the glutamate-nitric oxide-cyclic guanosine monophosphate (cGMP) pathway in brain contributes to cognitive impairment in hepatic encephalopathy. The aims of this work were to assess whether the function of this pathway and of nitric oxide synthase (NOS) are altered in cerebral cortex in vivo in rats with chronic liver failure due to portacaval shunt (PCS) and whether these alterations are due to hyperammonemia. The glutamate-nitric oxide-cGMP pathway function and NOS activation by NMDA was analysed by in vivo microdialysis in cerebral cortex of PCS and control rats and in rats with hyperammonemia without liver failure. Similar studies were done in cortical slices from these rats and in cultured cortical neurons exposed to ammonia. Basal NOS activity, nitrites and cGMP are increased in cortex of rats with hyperammonemia or liver failure. These increases seem due to increased inducible nitric oxide synthase expression. NOS activation by NMDA is impaired in cerebral cortex in both animal models and in neurons exposed to ammonia. Chronic liver failure increases basal NOS activity, nitric oxide and cGMP but reduces activation of NOS induced by NMDA receptors activation. Hyperammonemia is responsible for both effects which will lead, independently, to alterations contributing to neurological alterations in hepatic encephalopathy. PMID:17286583

  18. Glutamate and glycine modulation of 3H-MK801 binding to the NMDA receptor-ion channel complex in the vitamin B-6 deficient neonatal rat brain

    SciTech Connect

    Guilarte, T.R. )

    1990-02-26

    The authors have previously shown that the concentrations of the neuroactive amino acids glutamate (GLU) and glycine (GLY) are significantly altered in the seizure-prone vitamin B-6 deficient neonatal rat brain. Recently, it has been shown that GLU and GLY modulate the binding of {sup 3}H-MK801 to the ion channel associated with the N-methyl-D-aspartate (NMDA)-glutamate receptor subtype. The present investigation was undertaken to determine if GLU or GLY modulation of {sup 3}H-MK801 binding was altered in B-6 deficient neonatal rat brain. Preparation of cortical membranes from control and deficient 14 day old rats and {sup 3}H-MK801 binding assay were done as described by Ransom and Stec. The results show a significant reduction in the potency and efficacy of GLU modulation of {sup 3}H-MK801 binding, as well as a reduction in the efficacy of GLY, in membrane preparations from deficient rats compared to controls. These results indicate a reduced ability of GLU and GLY to potentiate the binding of {sup 3}H-MK801 to the NMDA receptor-ion channel in the B-6 deficient neonatal rat brain.

  19. The effects of combined application of inorganic Martian dust simulant and carbon dots on glutamate transport rat brain nerve terminals

    NASA Astrophysics Data System (ADS)

    Borisova, Tatiana; Krisanova, Natalia; Nazarova, Anastasiya; Borysov, Arseniy; Pastukhov, Artem; Pozdnyakova, Natalia; Dudarenko, Marina

    2016-07-01

    During inhalation, nano-/microsized particles are efficiently deposited in nasal, tracheobronchial, and alveolar regions and can be transported to the central nervous system (Oberdorster et al., 2004). Recently, the research team of this study found the minor fractions of nanoparticles with the size ~ 50 -60 nm in Lunar and Martian dust stimulants (JSC-1a and JSC, ORBITEC Orbital Technologies Corporation, Madison, Wisconsin), whereas the average size of the simulants was 1 mm and 4mm, respectively (Krisanova et al., 2013). Also, the research team of this study discovered new phenomenon - the neuromodulating and neurotoxic effect of carbon nano-sized particles - Carbon dots (C-dots), originated from ash of burned carbon-containing product (Borisova et al, 2015). The aims of this study was to analyse acute effects of upgraded stimulant of inorganic Martian dust derived from volcanic ash (JSC-1a/JSC, ORBITEC Orbital Technologies Corporation, Madison, Wisconsin) by the addition of carbon components, that is, carbon dots, on the key characteristic of synaptic neurotransmission. Acute administration of carbon-containing Martian dust analogue resulted in a significant decrease in transporter-mediated uptake of L-[14C]glutamate (the major excitatory neurotransmitter) by isolated rat brain nerve terminals. The ambient level of the neurotransmitter in the preparation of nerve terminals increased in the presence of carbon dot-contained Martian dust analogue. These effects were associated with action of carbon component of the upgraded Martian dust stimulant but not with its inorganic constituent.

  20. Distribution of immunoreactive GABA and glutamate receptors in the gustatory portion of the nucleus of the solitary tract in rat.

    PubMed

    King, Michael S

    2003-05-15

    The distribution of glutamate (GLU) and gamma-aminobutyric acid (GABA) receptors within the gustatory portion of the rat nucleus of the solitary tract (gNST) was investigated using immunohistochemical, histological and neural tract tracing techniques. Numerous somata throughout the gNST were immunoreactive for alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) and N-methyl-D-aspartate (NMDA) receptors, while few were labeled for kainate receptors. AMPA and NMDA receptors were particularly abundant in the rostral central (RC) subdivision of the gNST, which receives most of the primary afferent input from the oral cavity and contains most of the gNST neurons that project to the parabrachial nuclei (PBN). This finding supports electrophysiological evidence that AMPA and NMDA receptors are involved in responses to orosensory input and indicates that their action may influence ascending taste signals as well. Compared to the ionotropic GLU receptors, few cell bodies were immunoreactive for metabotropic GLU receptors. Somata immunoreactive for GABA(A) and GABA(B) receptors were located throughout the nucleus. The densest neuropil labeling was for GABA(A) receptors in the ventral (V) subnucleus, the gNST subdivision that sends output to brainstem oromotor centers. The distributions of immunolabeling for GLU and GABA receptors imply that different functional roles may exist for specific receptors within this nucleus. PMID:12754086

  1. The vesicular glutamate transporter-1 upstream promoter and first intron each support glutamatergic-specific expression in rat postrhinal cortex

    PubMed Central

    Zhang, Guo-rong; Li, Xu; Cao, Haiyan; Zhao, Hua; Geller, Alfred I.

    2011-01-01

    Multiple applications of direct gene transfer into neurons require restricting expression to glutamatergic neurons, or specific subclasses of glutamatergic neurons. Thus, it is desirable to develop and analyze promoters that support glutamatergic-specific expression. The three vesicular glutamate transporters (VGLUTs) are found in different populations of neurons, and VGLUT1 is the predominant VGLUT in the neocortex, hippocampus, and cerebellar cortex. We previously reported on a plasmid (amplicon) Herpes Simplex Virus vector that contains a VGLUT1 promoter. This vector supports long-term expression in VGLUT1-containing glutamatergic neurons in rat postrhinal (POR) cortex, but does not support expression in VGLUT2-containing glutamatergic neurons in the ventral medial hypothalamus. This VGLUT1 promoter contains both the VGLUT1 upstream promoter and the VGLUT1 first intron. In this study, we begin to isolate and analyze the glutamatergic-specific regulatory elements in this VGLUT1 promoter. We show that the VGLUT1 upstream promoter and first intron each support glutamatergic-specific expression. We isolated a small, basal VGLUT1 promoter that does not support glutamatergic-specific expression. Next, we fused either the VGLUT1 upstream promoter or the first intron to this basal promoter. The VGLUT1 upstream promoter or the first intron, fused to the basal promoter, each supported glutamatergic-specific expression in POR cortex. PMID:21172319

  2. EXPRESS: Histone hyperacetylation modulates spinal type II metabotropic glutamate receptor alleviating stress-induced visceral hypersensitivity in female rats.

    PubMed

    Cao, Dong-Yuan; Bai, Guang; Ji, Yaping; Karpowicz, Jane M; Traub, Richard J

    2016-01-01

    Stress is often a trigger to exacerbate chronic pain including visceral hypersensitivity associated with irritable bowel syndrome, a female predominant functional bowel disorder. Epigenetic mechanisms that mediate stress responses are a potential target to interfere with visceral pain. The purpose of this study was to examine the effect of a histone deacetylase inhibitor, suberoylanilide hydroxamic acid, on visceral hypersensitivity induced by a subchronic stressor in female rats and to investigate the involvement of spinal glutamate receptors. Three daily sessions of forced swim induced visceral hypersensitivity. Intrathecal suberoylanilide hydroxamic acid prevented or reversed the stress-induced visceral hypersensitivity, increased spinal histone 3 acetylation and increased mGluR2 and mGluR3 expression. Chromatin immunoprecipitation (ChIP) analysis revealed enrichment of H3K9Ac and H3K18Ac at several promoter Grm2 and Grm3 regions. The mGluR2/3 antagonist LY341495 reversed the inhibitory effect of suberoylanilide hydroxamic acid on the stress-induced visceral hypersensitivity. In surprising contrast, stress and/or suberoylanilide hydroxamic acid had no effect on spinal NMDA receptor expression or function. These data reveal histone modification modulates mGluR2/3 expression in the spinal cord to attenuate stressinduced visceral hypersensitivity. HDAC inhibitors may provide a potential approach to relieve visceral hypersensitivity associated with irritable bowel syndrome. PMID:27385724

  3. Acute administration of cocaine reduces metabotropic glutamate receptor 8 protein expression in the rat striatum in vivo

    PubMed Central

    Zhang, Guo-Chi; Vu, Khang; Parelkar, Nikhil K; Mao, Li-Min; Stanford, Ian M.; Fibuch, Eugene E.; Wang, John Q.

    2009-01-01

    Metabotropic glutamate receptors (mGluRs) are densely expressed in the limbic system of mammalian brain. Increasing evidence suggests a critical role of mGluRs in the pathogenesis of various mental illnesses, including drug abuse and addiction. In this study, we investigated the effect of psychostimulant cocaine on protein expression of a specific mGluR subtype, mGluR8, in the rat forebrain in vivo. A rabbit antibody against the extracellular N-terminus of mGluR8 was developed to detect changes in mGluR8 proteins in immunoblot assays. With this antibody, we found that acute systemic injection of cocaine reduced mGluR8 protein levels in the striatum. The reduction of mGluR8 proteins was rapid and transient as it was induced 25 min after cocaine injection and returned to the normal level by 6 h. No significant change in mGluR8 protein levels in the prefrontal cortex and the hippocampus was observed following cocaine administration. These data demonstrate that protein expression of mGluR8 is subject to the modulation by dopamine stimulation. Acute exposure to cocaine results in a dynamic and region-specific downregulation of mGluR8 expression in the striatum. PMID:19010389

  4. Functional topography of respiratory, cardiovascular and pontine-wave responses to glutamate microstimulation of the pedunculopontine tegmentum of the rat

    PubMed Central

    Topchiy, Irina; Waxman, Jonathan; Radulovacki, Miodrag; Carley, David W.

    2010-01-01

    Functionally distinct areas were mapped within the pedunculopontine tegmentum (PPT) of 42 ketamine/xylazine anesthetized rats using local stimulation by glutamate microinjection (10 mM, 5–12 nl). Functional responses were classified as: 1) apnea; 2) tachypnea; 3) hypertension (HTN); 4) sinus tachycardia; 5) genioglossus electromyogram activation or 6) pontine-waves (p-waves) activation. We found that short latency apneas were predominantly elicited by stimulation in the lateral portion of the PPT, in close proximity to cholinergic neurons. Tachypneic responses were elicited from ventral regions of the PPT and HTN predominated in the ventral portion of the antero-medial PPT. We observed sinus tachycardia after stimulation of the most ventral part of the medial PPT at the boundary with nucleus reticularis pontis oralis, whereas p-waves were registered predominantly following stimulation in the dorso-caudal portion of the PPT. Genioglossus EMG activation was evoked from the medial PPT. Our results support the existence of the functionally distinct areas within the PPT affecting respiration, cardio-vascular function, EEG and genioglossus EMG. PMID:20601208

  5. Histone hyperacetylation modulates spinal type II metabotropic glutamate receptor alleviating stress-induced visceral hypersensitivity in female rats

    PubMed Central

    Cao, Dong-Yuan; Bai, Guang; Ji, Yaping; Karpowicz, Jane

    2016-01-01

    Stress is often a trigger to exacerbate chronic pain including visceral hypersensitivity associated with irritable bowel syndrome, a female predominant functional bowel disorder. Epigenetic mechanisms that mediate stress responses are a potential target to interfere with visceral pain. The purpose of this study was to examine the effect of a histone deacetylase inhibitor, suberoylanilide hydroxamic acid, on visceral hypersensitivity induced by a subchronic stressor in female rats and to investigate the involvement of spinal glutamate receptors. Three daily sessions of forced swim induced visceral hypersensitivity. Intrathecal suberoylanilide hydroxamic acid prevented or reversed the stress-induced visceral hypersensitivity, increased spinal histone 3 acetylation and increased mGluR2 and mGluR3 expression. Chromatin immunoprecipitation (ChIP) analysis revealed enrichment of H3K9Ac and H3K18Ac at several promoter Grm2 and Grm3 regions. The mGluR2/3 antagonist LY341495 reversed the inhibitory effect of suberoylanilide hydroxamic acid on the stress-induced visceral hypersensitivity. In surprising contrast, stress and/or suberoylanilide hydroxamic acid had no effect on spinal NMDA receptor expression or function. These data reveal histone modification modulates mGluR2/3 expression in the spinal cord to attenuate stress-induced visceral hypersensitivity. HDAC inhibitors may provide a potential approach to relieve visceral hypersensitivity associated with irritable bowel syndrome. PMID:27385724

  6. Apoptosis-inducing factor and calpain upregulation in glutamate-induced injury of rat spiral ganglion neurons.

    PubMed

    Ding, Zhong-Jia; Chen, Xin; Tang, Xiao-Xu; Wang, Xi; Song, Yong-Li; Chen, Xiao-Dong; Wang, Jian; Wang, Ren-Feng; Mi, Wen-Juan; Chen, Fu-Quan; Qiu, Jian-Hua

    2015-08-01

    Spiral ganglion neuron (SGN) damage and apoptosis can lead to noise-induced hearing loss, age-associated hearing loss and, in certain cases, auditory neuropathy. The apoptosis-inducing factor (AIF)-associated pathway may be important in this process. The present study aimed to investigate the expression levels of AIF and calpain in damaged SGNs. Glutamate (Glu) perfusion and cell culture in different concentrations of Glu were performed to damage the SGNs of Sprague-Dawley (SD) rats, with saline water used as a control Different concentrations (5, 10, 20 and 40 mM) of Glu were injected into the cochlear tympanic canal of 18 SD rats, and 10, 20 and 40 mM Glu were added to SGN cultures. Auditory brainstem responses (ABR) were measured prior to and 2 days following the injection of Glu. Immunofluorescent staining was used to detect the SGN damage and the expression levels of AIF and calpain in vivo and in in vitro. Transmission electron microscopy (TEM) was used to measure cell apoptosis and reverse transcription-quantitative polymerase chain reaction was used to analyse the gene expression levels of AIF and calpain in the damaged SGNs. The TEM identified mitochondrial vacuolisation, swelling of the SGN and heterochromatin formation. Injection of Glu reduced the number of SGNs and induced apoptosis. AIF was observed to translocate into the nuclei of the SGNs in the 20 and 40 mM Glu groups, and the expression levels of AIF and calpain were markedly upregulated in the modiolus of the Glu-damaged SGNs. The upregulation of AIF and calpain may be important in the process of SGN damage and apoptosis. PMID:25891494

  7. Apoptosis-inducing factor and calpain upregulation in glutamate-induced injury of rat spiral ganglion neurons

    PubMed Central

    DING, ZHONG-JIA; CHEN, XIN; TANG, XIAO-XU; WANG, XI; SONG, YONG-LI; CHEN, XIAO-DONG; WANG, JIAN; WANG, REN-FENG; MI, WEN-JUAN; CHEN, FU-QUAN; QIU, JIAN-HUA

    2015-01-01

    Spiral ganglion neuron (SGN) damage and apoptosis can lead to noise-induced hearing loss, age-associated hearing loss and, in certain cases, auditory neuropathy. The apoptosis-inducing factor (AIF)-associated pathway may be important in this process. The present study aimed to investigate the expression levels of AIF and calpain in damaged SGNs. Glutamate (Glu) perfusion and cell culture in different concentrations of Glu were performed to damage the SGNs of Sprague-Dawley (SD) rats, with saline water used as a control Different concentrations (5, 10, 20 and 40 mM) of Glu were injected into the cochlear tympanic canal of 18 SD rats, and 10, 20 and 40 mM Glu were added to SGN cultures. Auditory brainstem responses (ABR) were measured prior to and 2 days following the injection of Glu. Immunofluorescent staining was used to detect the SGN damage and the expression levels of AIF and calpain in vivo and in in vitro. Transmission electron microscopy (TEM) was used to measure cell apoptosis and reverse transcription-quantitative polymerase chain reaction was used to analyse the gene expression levels of AIF and calpain in the damaged SGNs. The TEM identified mitochondrial vacuolisation, swelling of the SGN and hetero-chromatin formation. Injection of Glu reduced the number of SGNs and induced apoptosis. AIF was observed to translocate into the nuclei of the SGNs in the 20 and 40 mM Glu groups, and the expression levels of AIF and calpain were markedly upregulated in the modiolus of the Glu-damaged SGNs. The upregulation of AIF and calpain may be important in the process of SGN damage and apoptosis. PMID:25891494

  8. The effect of adenosine A(2A) receptor antagonists on hydroxyl radical, dopamine, and glutamate in the striatum of rats with altered function of VMAT2.

    PubMed

    Gołembiowska, Krystyna; Dziubina, Anna

    2012-08-01

    It has been shown that a decreased vesicular monoamine transporter (VMAT2) function and the disruption of dopamine (DA) storage is an early contributor to oxidative damage of dopamine neurons in Parkinson's disease (PD). In our previous study, we demonstrated that adenosine A(2A) receptor antagonists suppressed oxidative stress in 6-hydroxydopamine-treated rats suggesting that this effect may account for neuroprotective properties of drugs. In the present study, rats were injected with reserpine (10 mg/kg sc) and 18 h later the effect of the adenosine A(2A) receptor antagonists 8-(3-chlorostyryl)caffeine (CSC) and 4-(2-[7-amino-2-(2-furyl)[1,2,4]triazolo[2,3-a][1,3,5]triazin-5-ylamino]ethyl)phenol (ZM 241385) on extracellular DA, glutamate and hydroxyl radical formation was studied in the rat striatum using in vivo microdialysis. By disrupting VMAT2 function, reserpine depleted DA stores, and increased glutamate and hydroxyl radical levels in the rat striatum. CSC (1 mg/kg) but not ZM 241385 (3 mg/kg) increased extracellular DA level and production of hydroxyl radical in reserpinised rats. Both antagonists decreased the reserpine-induced increase in extracellular glutamate. L-3,4-Dihydroxyphenylalanine (L-DOPA) (25 mg/kg) significantly enhanced extracellular DA, had no effect on reserpine-induced hydroxyl radical production and decreased extracellular glutamate concentration. CSC but not ZM 241385 given jointly with L-DOPA increased the effect of L-DOPA on extracellular DA and augmented the reserpine-induced hydroxyl radical production. CSC and ZM 241385 did not influence extracellular glutamate level, which was decreased by L-DOPA. It seems that by decreasing the MAO-dependent DA metabolism rate, CSC raised cytosolic DA and by DA autoxidation, it induced hydroxyl radical overproduction. Thus, the methylxanthine A(2A) receptor antagonists bearing properties of MAO-B inhibitor, like CSC, may cause a risk of oxidative stress resulting from dysfunctional DA storage

  9. Increased glutamate-stimulated release of dopamine in substantia nigra of a rat model for attention-deficit/hyperactivity disorder--lack of effect of methylphenidate.

    PubMed

    Warton, Fleur L; Howells, Fleur M; Russell, Vivienne A

    2009-12-01

    Attention-deficit/hyperactivity disorder (ADHD) is a behavioural disorder that has been associated with dysfunction of the dopaminergic system. Abnormal dopamine function could be the result of a primary defect in dopamine neurons (neuronal firing, dopamine transporter, synthesis, receptor function) or an indirect result of impaired glutamate and/or noradrenergic regulation of dopamine neurons. There is considerable evidence to suggest that dopamine release is impaired at mesolimbic and nigrostriatal dopaminergic terminals. However, it is not known whether dysregulation occurs at the level of the cell bodies in the ventral tegmental area of the midbrain (VTA) and substantia nigra (SN). An in vitro superfusion technique was used to measure dopamine release in a widely used model of ADHD, the spontaneously hypertensive rat (SHR), and its normotensive Wistar-Kyoto (WKY) control. At approximately 30 days of age, rats were analysed for behavioural differences in the open field in response to acute treatment with methylphenidate (0.5 to 2 mg/kg in condensed milk, oral self-administration). In addition, rats were treated chronically with methylphenidate (2 mg/kg, oral self-administration, twice daily for 14 days from postnatal day 21 to 34) before the VTA and the SN were analysed for glutamate-stimulated and depolarization-evoked release of dopamine in these areas. In support of its use as an animal model for ADHD, SHR were more active in the open field and displayed less anxiety-like behaviour than WKY. Neither strain showed any effect of treatment with methylphenidate. A significant difference was observed in glutamate-stimulated release of dopamine in the SN of SHR and WKY, with SHR releasing more dopamine, consistent with the hypothesis of altered glutamate regulation of dopamine neurons in SHR. PMID:19821016

  10. Chronic Treatment with a Clinically Relevant Dose of Methylphenidate Increases Glutamate Levels in Cerebrospinal Fluid and Impairs Glutamatergic Homeostasis in Prefrontal Cortex of Juvenile Rats.

    PubMed

    Schmitz, Felipe; Pierozan, Paula; Rodrigues, André F; Biasibetti, Helena; Coelho, Daniella M; Mussulini, Ben Hur; Pereira, Mery S L; Parisi, Mariana M; Barbé-Tuana, Florencia; de Oliveira, Diogo L; Vargas, Carmen R; Wyse, Angela T S

    2016-05-01

    The understanding of the consequences of chronic treatment with methylphenidate is very important since this psychostimulant is extensively prescribed to preschool age children, and little is known about the mechanisms underlying the persistent changes in behavior and neuronal function related with the use of methylphenidate. In this study, we initially investigate the effect of early chronic treatment with methylphenidate on amino acids profile in cerebrospinal fluid and prefrontal cortex of juvenile rats, as well as on glutamatergic homeostasis, Na(+),K(+)-ATPase function, and balance redox in prefrontal cortex of rats. Wistar rats at early age received intraperitoneal injections of methylphenidate (2.0 mg/kg) or an equivalent volume of 0.9 % saline solution (controls), once a day, from the 15th to the 45th day of age. Twenty-four hours after the last injection, the animals were decapitated and the cerebrospinal fluid and prefrontal cortex were obtained. Results showed that methylphenidate altered amino acid profile in cerebrospinal fluid, increasing the levels of glutamate. Glutamate uptake was decreased by methylphenidate administration, but GLAST and GLT-1 were not altered by this treatment. In addition, the astrocyte marker GFAP was not altered by MPH. The activity and immunocontent of catalytic subunits (α1, α2, and α3) of Na(+),K(+)-ATPase were decreased in prefrontal cortex of rats subjected to methylphenidate treatment, as well as changes in α1 and α2 gene expression of catalytic α subunits of Na(+),K(+)-ATPase were also observed. CAT activity was increased and SOD/CAT ratio and sulfhydryl content were decreased in rat prefrontal cortex. Taken together, our results suggest that chronic treatment with methylphenidate at early age induces excitotoxicity, at least in part, due to inhibition of glutamate uptake probably caused by disturbances in the Na(+),K(+)-ATPase function and/or in protein damage observed in the prefrontal cortex. PMID:26001762

  11. [Reduction in hypoxia-derived neuroinflammation and dysfunctional glutamate transporters by minocycline may restore hypoxia-injured cognition of neonatal rat].

    PubMed

    Li, Hong-Chun; Xiao, Jie; Huang, Yi-Long; Li, Long-Jun; Jiang, Hong; Huang, Li-Xuan; Yang, Ting; Yang, Ling; Li, Fan

    2016-04-25

    The aim of the present study was to investigate the effects of minocycline on cognitive functions in neonatal rat after hypoxia exposure and the underlying mechanism. A model of hypoxic brain damage (HBD) was developed by exposing postnatal 1 day (P1) rats to systemic hypoxia. The rats were intraperitoneally injected with normal saline (Hy group) or minocycline (Hy + M group) 2 h after hypoxia exposure. Some other P1 rats that were not subjected to systemic hypoxia were used as normal control (NG group). The Y-maze test was used to evaluate learning and memory ability on postnatal day 30. Inflammatory mediators (Iba-1, IL-1β, TNF-α and TGF-β1), glutamate transporters (EAAT1 and EAAT2), total Tau and phosphorylated Tau (phosphorylation sites: Tyr18, Thr205, Thr231, Ser396 and Ser404) protein expressions in the hippocampus were detected by Western blot 7 d after hypoxic exposure. The results showed that hypoxia induced learning and memory impairments of the neonatal rats, and minocycline administration could reverse the effects of hypoxia. The protein expression levels of Iba-1, IL-1β, TNF-α, EAAT2 and Tau phosphorylated at T231 were increased, but the total Tau expression was decreased in the hippocampus of the rats from Hy group 7 d after hypoxia exposure. In the hypoxia-treated rats, minocycline down-regulated Iba-1, IL-1β, TNF-α and EAAT2 protein expressions significantly, but did not affect total Tau and phosphorylated Tau protein expressions. Our results suggest that minocycline can prevent cognitive deficits of rats with hypoxia exposure, and the underlying mechanism may involve the inhibition of neuroinflammation and dysfunctional glutamate transporters but not the regulation of the Tau hyperphosphorylation. PMID:27108901

  12. Expressions of caspase-3, Tunel, and Hsp72 immunoreactivities in cultured spinal cord neurons of rat after exposure to glutamate, nitric oxide, or peroxynitrite.

    PubMed

    Manabe, Y; Wang, J; Warita, H; Shiro, Y; Abe, K

    2001-07-01

    Although excitotoxic and oxidative stress play important roles in spinal neuron death, the exact mechanisms are not fully understood. We examined cell damage of primary culture of 11 day-old rat spinal cord by addition of glutamate, nitric oxice (NO) or peroxynitrite (PN) with detection of caspase-3, terminal deoxynucleotidyl transferase-mediated dUTP-biotin in situ nick end labeling (TUNEL) or 72 kDa heat shock protein (HSP72). With addition of glutamate, NOC18 (a slow NO releaser) or PN, immunoreactivity for caspase-3 became stronger in the cytoplasm of large motor neurons in the ventral horn at 6 to 24 hr. TUNEL positive nuclei were found in spinal large motor neurons from 24 h and the positive cell proportion greatly increased at 48 h in contrast to the vehicle. On the other hand, the immunoreactivity of HSP72 in the ventral horn was already positive at 0 h, and gradually decreased in the course of time with glutamate, NOC18 or PN than vehicle treatment. In the dorsal horn, the proportion of caspase-3 positive small neurons greatly increased at 6 to 48 h after addition of glutamate. The present results suggest that both excitotoxic and oxidative stress play important roles in the apoptotic pathway in cultured spinal neurons. PMID:15111253

  13. Reactive oxygen species induced by presynaptic glutamate receptor activation is involved in [(3)H]GABA release from rat brain cortical nerve terminals.

    PubMed

    Tarasenko, A; Krupko, O; Himmelreich, N

    2012-12-01

    We investigated the production of reactive oxygen species (ROS) as a response to presynaptic glutamate receptor activation, and the role of ROS in neurotransmitter (GABA) release. Experiments were performed with rat brain cortical synaptosomes using glutamate, NMDA and kainate as agonists of glutamate receptors. ROS production was evaluated with the fluorogenic compound dichlorodihydrofluorescein diacetate (H(2)DCF-DA), and GABA release was studied using synaptosomes loaded with [(3)H]GABA. All agonists were found to stimulate ROS production, and specific antagonists of NMDA and kainate/AMPA receptors, dizocilpine hydrogen maleate (MK-801) and 6-cyano-7-nitroquinoxaline-2,3-done (CNQX), significantly inhibited the ROS increase. Spontaneous as well as agonist-evoked ROS production was effectively attenuated by diphenyleneiodonium (DPI), a commonly used potent inhibitor of NADPH oxidase activity, that suggests a high contribution of NADPH-oxidase to this process. The replacement of glucose with pyruvate or the simultaneous presence of both substrates in the medium led to the decrease in spontaneous and NMDA-evoked ROS production, but to the increase in ROS production induced by kainate. Scavenging of agonist-evoked ROS production by a potent antioxidant N-acetylcysteine was tightly correlated with the inhibition of agonist-evoked GABA release. Together, these findings show that the activation of presynaptic glutamate receptors induces an increase in ROS production, and there is a tight correlation between ROS production and GABA secretion. The pivotal role of kainate/AMPA receptors in ROS production is under discussion. PMID:22864357

  14. Effects of rasagiline, its metabolite aminoindan and selegiline on glutamate receptor mediated signalling in the rat hippocampus slice in vitro

    PubMed Central

    2011-01-01

    Background Rasagiline, a new drug developed to treat Parkinson's disease, is known to inhibit monoamine oxidase B. However, its metabolite R-(-)-aminoindan does not show this kind of activity. The present series of in vitro experiments using the rat hippocampal slice preparation deals with effects of both compounds on the pyramidal cell response after electric stimulation of the Schaffer Collaterals in comparison to selegiline, another MAO B inhibitor. Method Stimulation of the Schaffer Collaterals by single stimuli (SS) or theta burst stimulation (TBS) resulted in stable responses of pyramidal cells measured as population spike amplitude (about 1 mV under control SS conditions or about 2 mV after TBS). Results During the first series, this response was attenuated in the presence of rasagiline and aminoindan-to a lesser degree of selegiline-in a concentration dependent manner (5-50 μM) after single stimuli as well as under TBS. During oxygen/glucose deprivation for 10 min the amplitude of the population spike breaks down by 75%. The presence of rasagiline and aminoindan, but rarely the presence of selegiline, prevented this break down. Following glutamate receptor mediated enhancements of neuronal transmission in a second series of experiments very clear differences could be observed in comparison to the action of selegiline: NMDA receptor, AMPA receptor as well as metabotropic glutamate receptor mediated increases of transmission were concentration dependently (0,3 - 2 μM) antagonized by rasagiline and aminoindan, but not by selegiline. On the opposite, only selegiline attenuated kainate receptor mediated increases of excitability. Thus, both monoamino oxidase (MAO) B inhibitors show attenuation of glutamatergic transmission in the hippocampus but interfere with different receptor mediated excitatory modulations at low concentrations. Conclusions Since aminoindan does not induce MAO B inhibition, these effects must be regarded as being independent from MAO B

  15. The metabolism of 5-methyltetrahydropteroyl-L-glutamic acid and its oxidation products in the rat.

    PubMed Central

    Kennelly, J C; Blair, J A; Pheasant, A E

    1982-01-01

    Folate metabolism in the rat was investigated using radiolabelled 5-methyltetrahydropteroylglutamate (5-CH3-H4PteGlu) and its oxidation products. 5-CH3-H4PteGlu is absorbed completely from the intestine, although in some preparations it is an equimolecular mixture of C-6 epimers, only one of which is naturally present in biological systems. The methyl group is incorporated into non-folate compounds, including methionine and creatine. No evidence was observed for the oxidation of the methyl group of 5-CH3-H4PteGlu to form other folate types. The tetrahydrofolate moiety of 5-CH3-H4PteGlu is metabolized in a similar manner to folic acid, forming formyl folates and tissue polyglutamates, and is catabolized by scission. The triazine oxidation product of 5-CH3-H4PteGlu is not metabolized by the rat or its gut microflora. 5-Methyl-5,6-dihydropteroylglutamate, however, is assimilated into the folate pool, but is substantially broken down by passage through the gut. The possible implication of this in scorbutic diets is discussed. PMID:7150248

  16. Effect of adenosine A(2A) receptor antagonists and L-DOPA on hydroxyl radical, glutamate and dopamine in the striatum of 6-OHDA-treated rats.

    PubMed

    Gołembiowska, Krystyna; Dziubina, Anna

    2012-02-01

    A(2A) adenosine receptor antagonists have been proposed as a new therapy of PD. Since oxidative stress plays an important role in the pathogenesis of PD, we studied the effect of the selective A(2A) adenosine receptor antagonists 8-(-3-chlorostyryl)caffeine (CSC) and 4-(2-[7-amino-2-(2-furyl)[1,2,4]triazolo[2,3-a][1,3,5]triazin-5-ylamino]ethyl)phenol (ZM 241385) on hydroxyl radical generation, and glutamate (GLU) and dopamine (DA) extracellular level using a microdialysis in the striatum of 6-OHDA-treated rats. CSC (1 mg/kg) and ZM 241385 (3 mg/kg) given repeatedly for 14 days decreased the production of hydroxyl radical and extracellular GLU level, both enhanced by prior 6-OHDA treatment in dialysates from the rat striatum. CSC and ZM 241385 did not affect DA and its metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanilic acid (HVA) extracellular levels in the striatum of 6-OHDA-treated rats. L-DOPA (6 mg/kg) given twice daily for two weeks in the presence of benserazide (3 mg/kg) decreased striatal hydroxyl radical and glutamate extracellular level in 6-OHDA-treated rats. At the same time, L-DOPA slightly but significantly increased the extracellular levels of DOPAC and HVA. A combined repeated administration of L-DOPA and CSC or ZM 241385 did not change the effect of L-DOPA on hydroxyl radical production and glutamate extracellular level in spite of an enhancement of extracellular DA level by CSC and elevation of extracellular level of DOPAC and HVA by ZM 241385. The data suggest that the 6-OHDA-induced damage of nigrostriatal DA-terminals is related to oxidative stress and excessive release of glutamate. Administration of L-DOPA in combination with CSC or ZM 241385, by restoring striatal DA-glutamate balance, suppressed 6-OHDA-induced overproduction of hydroxyl radical. PMID:21830163

  17. Effects of a metabotropic glutamate receptor subtype 7 negative allosteric modulator in the periaqueductal grey on pain responses and rostral ventromedial medulla cell activity in rat

    PubMed Central

    2013-01-01

    The metabotropic glutamate receptor 7 (mGluR7) negative allosteric modulator, 6-(4-methoxyphenyl)-5-methyl-3-pyridin-4-ylisoxazolo[4,5-c]pyridin-4(5H)-one (MMPIP), was locally microinjected into the ventrolateral periaqueductal gray (VL PAG) and the effect on pain responses in formalin and spare nerve injury (SNI) -induced neuropathic pain models was monitored in the rat. The activity of rostral ventromedial medulla (RVM) “pronociceptive” ON and “antinociceptive” OFF cells was also evaluated. Intra–VL PAG MMPIP blocked the first and second phase of nocifensive behaviour in the formalin pain model. MMPIP increased the tail flick latency and simultaneously increased the activity of the OFF cells while inhibiting that of ON cells in rats with SNI of the sciatic nerve. MMPIP failed to modify nociceptive responses and associated RVM ON and OFF cell activity in sham rats. An increase in mGluR7 gene, protein and staining, the latter being associated with vesicular glutamate transporter-positive profiles, has been found in the VL PAG in SNI rats. Blockade of mGluR7 within the VL PAG has an antinociceptive effect in formalin and neuropathic pain models. VL PAG mGluR7 blockade offers a target for dis-inhibiting the VL PAG-RVM pathway and silencing pain in inflammatory and neuropathic pain models. PMID:24004843

  18. Influence of metabotropic glutamate receptor agonists on the inhibitory effects of adenosine A1 receptor activation in the rat hippocampus.

    PubMed

    de Mendonça, A; Ribeiro, J A

    1997-08-01

    1. Glutamate and other amino acids are the main excitatory neurotransmitters in many brain regions, including the hippocampus, by activating ion channel-coupled glutamate receptors, as well as metabotropic receptors linked to G proteins and second messenger systems. Several conditions which promote the release of glutamate, like frequency stimulation and hypoxia, also lead to an increase in the extracellular levels of the important neuromodulator, adenosine. We studied whether the activation of different subgroups of metabotropic glutamate receptors (mGluR) could modify the known inhibitory effects of a selective adenosine A1 receptor agonist on synaptic transmission in the hippocampus. The experiments were performed on hippocampal slices taken from young (12-14 days old) rats. Stimulation was delivered to the Schaffer collateral/commissural fibres, and evoked field excitatory postsynaptic potentials (fe. p.s.p.) recorded extracellularly from the stratum radiatum in the CAI area. 2. The concentration-response curve for the inhibitory effects of the selective adenosine A1 receptor agonist, N6-cyclopentyladenosine (CPA; 2-50 nM), on the fe.p.s.p. slope (EC50 = 12.5 (9.2-17.3; 95% confidence intervals)) was displaced to the right by the group I mGluR selective agonist, (R,S)-3,5-dihydroxyphenylglycine (DPHG; 10 microM) (EC50 = 27.2 (21.4-34.5) nM, n = 4). The attenuation of the inhibitory effect of CPA (10 nM) on the fe.p.s.p. slope by DHPG (10 microM) was blocked in the presence of the mGluR antagonist (which blocks group I and II mGluR), (R,S)-alpha-methyl-4-carboxyphenylglycine (MCPG; 500 microM). DHPG (10 microM) itself had an inhibitory effect of 20.1 +/- 1.9% (n = 4) on the fe.p.s.p. slope. 3. The concentration-response curves for the inhibitory effects of CPA (2-20 nM) on the fe.p.s.p. slope were not modified either in the presence of the group II mGluR selective agonist, (2S,3S,4S)-alpha-(carboxycyclopropyl)glycine (L-CCG-I; 1 microM), or in the presence of

  19. Influence of metabotropic glutamate receptor agonists on the inhibitory effects of adenosine A1 receptor activation in the rat hippocampus

    PubMed Central

    de Mendonça, Alexandre; Ribeiro, J A

    1997-01-01

    Glutamate and other amino acids are the main excitatory neurotransmitters in many brain regions, including the hippocampus, by activating ion channel-coupled glutamate receptors, as well as metabotropic receptors linked to G proteins and second messenger systems. Several conditions which promote the release of glutamate, like frequency stimulation and hypoxia, also lead to an increase in the extracellular levels of the important neuromodulator, adenosine. We studied whether the activation of different subgroups of metabotropic glutamate receptors (mGluR) could modify the known inhibitory effects of a selective adenosine A1 receptor agonist on synaptic transmission in the hippocampus. The experiments were performed on hippocampal slices taken from young (12–14 days old) rats. Stimulation was delivered to the Schaffer collateral/commissural fibres, and evoked field excitatory postsynaptic potentials (fe.p.s.p.) recorded extracellularly from the stratum radiatum in the CA1 area. The concentration-response curve for the inhibitory effects of the selective adenosine A1 receptor agonist, N6-cyclopentyladenosine (CPA; 2–50 nM), on the fe.p.s.p. slope (EC50=12.5 (9.2–17.3; 95% confidence intervals)) was displaced to the right by the group I mGluR selective agonist, (R,S)-3,5-dihydroxyphenylglycine (DPHG; 10 μM) (EC50=27.2 (21.4–34.5) nM, n=4). The attenuation of the inhibitory effect of CPA (10 nM) on the fe.p.s.p. slope by DHPG (10 μM) was blocked in the presence of the mGluR antagonist (which blocks group I and II mGluR), (R,S)-α-methyl-4-carboxyphenylglycine (MCPG; 500 μM). DHPG (10 μM) itself had an inhibitory effect of 20.1±1.9% (n=4) on the fe.p.s.p. slope. The concentration-response curves for the inhibitory effects of CPA (2–20 nM) on the fe.p.s.p. slope were not modified either in the presence of the group II mGluR selective agonist, (2S,3S,4S)-α-(carboxycyclopropyl)glycine (L-CCG-I; 1 μM), or in the presence of the non

  20. COMPARISON OF THE ONTOGENY OF THE VESICULAR GLUTAMATE TRANSPORTER 3 (VGLUT3) WITH VGLUT1 AND VGLUT2 IN THE RAT RETINA

    PubMed Central

    Stella, Salvatore L.; Li, Stefanie; Sabatini, Andrea; Vila, Alejandro; Brecha, Nicholas C.

    2008-01-01

    Glutamate is the major excitatory neurotransmitter in the retina, and most glutamatergic neurons express one of the three known vesicular glutamate transporters (VGLUT1, 2, or 3). However, the expression profiles of these transporters vary greatly in the retina. VGLUT1 is expressed by photoreceptor and bipolar cell terminals, and VGLUT2 appears to be predominately expressed by ganglion cells, and perhaps Müller cells, cone photoreceptor terminals, and horizontal cells in some species. The discovery of a third vesicular glutamate transporter, VGLUT3, has brought about speculation concerning its role and function based on its expression in amacrine cells. To address this we studied the postnatal development of VGLUT3 from day 0 through adult in the rat retina, and compared this with the expression patterns of VGLUT1 and VGLUT2. VGLUT3 expression was restricted to a population of amacrine cells. Expression of VGLUT3 was first observed at postnatal day 10 (P10) in the soma and some processes, which extensively arborized in both the ON and OFF sublamina of the IPL by P15. In contrast, VGLUT1 and VGLUT2 expression appeared earlier than VGLUT3; with VGLUT1 initially detected at P5 in photoreceptor terminals and P6 in bipolar terminals, and VGLUT2 immunoreactivity initially detected at P0 in ganglion cell bodies, and remained prominent throughout all stages of development. Interestingly, VGLUT3 has extensive somatic expression throughout development, which could be involved in non-synaptic modulation by glutamate in developing retina, and could influence trophic and extra-synaptic neuronal signaling by glutamate in the inner retina. PMID:18482716

  1. Binge ethanol withdrawal: Effects on post-withdrawal ethanol intake, glutamate-glutamine cycle and monoamine tissue content in P rat model.

    PubMed

    Das, Sujan C; Althobaiti, Yusuf S; Alshehri, Fahad S; Sari, Youssef

    2016-04-15

    Alcohol withdrawal syndrome (AWS) is a medical emergency situation which appears after abrupt cessation of ethanol intake. Decreased GABA-A function and increased glutamate function are known to exist in the AWS. However, the involvement of glutamate transporters in the context of AWS requires further investigation. In this study, we used a model of ethanol withdrawal involving abrupt cessation of binge ethanol administration (4g/kg/gavage three times a day for three days) using male alcohol-preferring (P) rats. After 48h of withdrawal, P rats were re-exposed to voluntary ethanol intake. The amount of ethanol consumed was measured during post-withdrawal phase. In addition, the expression of GLT-1, GLAST and xCT were determined in both medial prefrontal cortex (mPFC) and nucleus accumbens (NAc). We also measured glutamine synthetase (GS) activity, and the tissue content of glutamate, glutamine, dopamine and serotonin in both mPFC and NAc. We found that binge ethanol withdrawal escalated post-withdrawal ethanol intake, which was associated with downregulation of GLT-1 expression in both mPFC and NAc. The expression of GLAST and xCT were unchanged in the ethanol-withdrawal (EW) group compared to control group. Tissue content of glutamate was significantly lower in both mPFC and NAc, whereas tissue content of glutamine was higher in mPFC but unchanged in NAc in the EW group compared to control group. The GS activity was unchanged in both mPFC and NAc. The tissue content of DA was significantly lower in both mPFC and NAc, whereas tissue content of serotonin was unchanged in both mPFC and NAc. These findings provide important information of the critical role of GLT-1 in context of AWS. PMID:26821293

  2. Neuroendocrine, metabolic, and immune functions during the acute phase response of inflammatory stress in monosodium L-glutamate-damaged, hyperadipose male rat.

    PubMed

    Castrogiovanni, Daniel; Gaillard, Rolf C; Giovambattista, Andrés; Spinedi, Eduardo

    2008-01-01

    In rats, neonatal treatment with monosodium L-glutamate (MSG) induces several metabolic and neuroendocrine abnormalities, which result in hyperadiposity. No data exist, however, regarding neuroendocrine, immune and metabolic responses to acute endotoxemia in the MSG-damaged rat. We studied the consequences of MSG treatment during the acute phase response of inflammatory stress. Neonatal male rats were treated with MSG or vehicle (controls, CTR) and studied at age 90 days. Pituitary, adrenal, adipo-insular axis, immune, metabolic and gonadal functions were explored before and up to 5 h after single sub-lethal i.p. injection of bacterial lipopolysaccharide (LPS; 150 microg/kg). Our results showed that, during the acute phase response of inflammatory stress in MSG rats: (1) the corticotrope-adrenal, leptin, insulin and triglyceride responses were higher than in CTR rats, (2) pro-inflammatory (TNFalpha) cytokine response was impaired and anti-inflammatory (IL-10) cytokine response was normal, and (3) changes in peripheral estradiol and testosterone levels after LPS varied as in CTR rats. These data indicate that metabolic and neroendocrine-immune functions are altered in MSG-damaged rats. Our study also suggests that the enhanced corticotrope-corticoadrenal activity in MSG animals could be responsible, at least in part, for the immune and metabolic derangements characterizing hypothalamic obesity. PMID:18382067

  3. Glutamate receptors in the dorsal hippocampus mediate the acquisition, but not the expression, of conditioned place aversion induced by acute morphine withdrawal in rats

    PubMed Central

    Hou, Yuan-yuan; Liu, Yao; Kang, Shuo; Yu, Chuan; Chi, Zhi-qiang; Liu, Jing-gen

    2009-01-01

    Aim: To evaluate the role of glutamate receptors in the dorsal hippocampus (DH) in the motivational component of morphine withdrawal. Methods: NMDA receptor antagonist D-AP5 (5 μg/0.5 μL per side) or AMPA receptor antagonist NBQX (2 μg/0.5 μL per side) was microinjected into DH of rats. Conditioned place aversion (CPA) induced by naloxone-precipitated morphine withdrawal were assessed. Results: Preconditioning microinjection of D-AP5 or NBQX into the DH impaired the acquisition of CPA in acute morphine-dependent rats. However, intra-DH microinjection of D-AP5 or NBQX after conditioning but before the testing session had no effect on the expression of CPA. Conclusion: Our results suggest that NMDA and AMPA receptors in the dorsal hippocampus are involved in the acquisition, but not in the expression, of the negative motivational components of acute morphine withdrawal in rats. PMID:19767765

  4. Lesions of nucleus accumbens affect morphine-induced release of ascorbic acid and GABA but not of glutamate in rats.

    PubMed

    Sun, Ji Y; Yang, Jing Y; Wang, Fang; Wang, Jian Y; Song, Wu; Su, Guang Y; Dong, Ying X; Wu, Chun F

    2011-10-01

    Our previous studies have shown that local perfusion of morphine causes an increase of extracellular ascorbic acid (AA) levels in nucleus accumbens (NAc) of freely moving rats. Lines of evidence showed that glutamatergic and GABAergic were associated with morphine-induced effects on the neurotransmission of the brain, especially on the release of AA. In the present study, the effects of morphine on the release of extracellular AA, γ-aminobutyric acid (GABA) and glutamate (Glu) in the NAc following bilateral NAc lesions induced by kainic acid (KA) were studied by using the microdialysis technique, coupled to high performance liquid chromatography with electrochemical detection (HPLC-ECD) and fluorescent detection (HPLC-FD). The results showed that local perfusion of morphine (100 µM, 1 mM) in NAc dose-dependently increased AA and GABA release, while attenuated Glu release in the NAc. Naloxone (0.4 mM) pretreated by local perfusion to the NAc, significantly blocked the effects of morphine. After NAc lesion by KA (1 µg), morphine-induced increase in AA and GABA were markedly eliminated, while decrease in Glu was not affected. The loss effect of morphine on AA and GABA release after KA lesion could be recovered by GABA agonist, musimol. These results indicate that morphine-induced AA release may be mediated at least by µ-opioid receptor. Moreover, this effect of morphine possibly depend less on the glutamatergic afferents, but more on the GABAergic circuits within this nucleus. Finally, AA release induced by local perfusion of morphine may be GABA-receptor mediated and synaptically localized in the NAc. PMID:20731632

  5. Interaction of mechanisms involving epoxyeicosatrienoic acids, adenosine receptors, and metabotropic glutamate receptors in neurovascular coupling in rat whisker barrel cortex

    PubMed Central

    Shi, Yanrong; Liu, Xiaoguang; Gebremedhin, Debebe; Falck, John R; Harder, David R; Koehler, Raymond C

    2008-01-01

    Adenosine, astrocyte metabotropic glutamate receptors (mGluRs), and epoxyeicosatrienoic acids (EETs) have been implicated in neurovascular coupling. Although A2A and A2B receptors mediate cerebral vasodilation to adenosine, the role of each receptor in the cerebral blood flow (CBF) response to neural activation remains to be fully elucidated. In addition, adenosine can amplify astrocyte calcium, which may increase arachidonic acid metabolites such as EETs. The interaction of these pathways was investigated by determining if combined treatment with antagonists exerted an additive inhibitory effect on the CBF response. During whisker stimulation of anesthetized rats, the increase in cortical CBF was reduced by approximately half after individual administration of A2B, mGluR and EET antagonists and EET synthesis inhibitors. Combining treatment of either a mGluR antagonist, an EET antagonist, or an EET synthesis inhibitor with an A2B receptor antagonist did not produce an additional decrement in the CBF response. Likewise, the CBF response also remained reduced by ~50% when an EET antagonist was combined with an mGluR antagonist or an mGluR antagonist plus an A2B receptor antagonist. In contrast, A2A and A3 receptor antagonists had no effect on the CBF response to whisker stimulation. We conclude that (1) adenosine A2B receptors, rather than A2A or A3 receptors, play a significant role in coupling cortical CBF to neuronal activity, and (2) the adenosine A2B receptor, mGluR, and EETs signaling pathways are not functionally additive, consistent with the possibility of astrocytic mGluR and adenosine A2B receptor linkage to the synthesis and release of vasodilatory EETs. PMID:17519974

  6. Presynaptic group I metabotropic glutamate receptors modulate synaptic transmission in the rat superior colliculus via 4-AP sensitive K+ channels

    PubMed Central

    White, Anne-Marie; Kylänpää, Risto A; Christie, Louisa A; McIntosh, Simon J; Irving, Andrew J; Platt, Bettina

    2003-01-01

    Group I metabotropic glutamate receptors (mGluRs) are thought to be important modulators of neuronal function in the superior colliculus (SC). Here, we investigated the pharmacology and signalling mechanisms underlying group I mGluR-mediated inhibition of neuronal excitability and synaptic transmission in the rat SC slice. The group I agonist (RS)-3,5-dihydroxyphenylglycine (DHPG) potently depressed synaptically evoked excitatory postsynaptic potentials (EPSPs), currents (EPSCs), and action potentials in a dose-dependent manner (IC50: 6.3 μM). This was strongly reduced by the broad-spectrum antagonist (+)-alpha-methyl-4-carboxyphenylglycine (MCPG, 1 mM, ∼95% reduction), by the mGluR1 antagonist LY367385 (100 μM, ∼80% reduction) but not by the mGluR5 antagonist 6-methyl-2-(phenylethynyl)-pyridine (MPEP, 1–100 μM). The putative mGluR5-specific agonist (RS)-2-chloro-5-hydroxyphenylglycine (CHPG, 500 μM) also inhibited EPSPs. Interestingly, CHPG's actions were not blocked by MPEP, but LY367385 (100 μM) reduced the effect of CHPG by 50%. Inhibition induced by DHPG was independent of phospholipase C (PLC)/protein kinase C pathways, and did not require intact intracellular Ca2+ stores. It was not abolished but enhanced by the GABAA antagonist bicuculline (5 μM), suggesting that DHPG's action was not due to facilitated inhibition or changes in neuronal network activity. The K+ channel antagonist 4-aminopyridine (4-AP, 50–100 μM) converted the inhibitory effect of DHPG into facilitation. Paired-pulse depression was strongly reduced by DHPG, an effect that was also prevented by 4-AP. Our data indicate that group I agonists regulate transmitter release, presumably via an autoreceptor in the SC. This receptor may be involved in adaptation to repetitive stimulation via a non-PLC mediated pathway. PMID:14623765

  7. Regulation of synaptic transmission in the mossy fibre-granule cell pathway of rat cerebellum by metabotropic glutamate receptors.

    PubMed

    Vetter, P; Garthwaite, J; Batchelor, A M

    1999-06-01

    The role of metabotropic glutamate receptors (mGluRs) in the mossy fibre-granule cell pathway in rat cerebellum was studied using slice preparations and electrophysiological techniques. Application of the group I selective agonist (S)-3,5-dihydroxyphenylglycine (DHPG) evoked, in a concentration-dependent manner (EC50 = 33 microM), a depolarising/hyperpolarising complex response from granule cells which was preferentially inhibited by the group I selective antagonist (S)-4-carboxyphenylglycine (4CPG). The group III selective agonist L-amino-4-phosphonobutyrate (AP4) evoked a hyperpolarising response (EC50 = 10 microM) which was inhibited by the group II/III selective antagonist (S)-alpha-methyl-4-phosphonophenylglycine (MPPG). The group II agonist (2S,2'R,3'R)-2-(2',3'-dicarboxylcyclopropyl)glycine (DCG-IV) elicited no measurable voltage change. The amplitude of the synaptically-mediated mossy fibre response in granule cells was unaffected during application of AP4, was reduced by DHPG and was enhanced by DCG-IV (EC50 = 80 nM). These effects were inhibited by the group selective antagonists 4CPG and (2S,1'S,2'S,3'R)-2-(2'-carboxy-3'-phenylcyclopropyl)glycine (PCCG-4), respectively. Further investigation using patch-clamp recording revealed that DCG-IV potently inhibited spontaneous GABAergic currents. We conclude that group I and III (but not group II) mGluRs are functionally expressed by granule cells, whereas unexpectedly group II or III mGluRs do not appear to be present presynaptically on mossy fibre terminals. Group II mGluRs are located on Golgi cell terminals; when activated these receptors cause disinhibition, a function which may be important for gating information transfer from the mossy fibres to the granule cells. PMID:10465684

  8. 5-HT1B receptors inhibit glutamate release from primary afferent terminals in rat medullary dorsal horn neurons

    PubMed Central

    Choi, I-S; Cho, J-H; An, C-H; Jung, J-K; Hur, Y-K; Choi, J-K; Jang, I-S

    2012-01-01

    BACKGROUND AND PURPOSE Although 5-HT1B receptors are expressed in trigeminal sensory neurons, it is still not known whether these receptors can modulate nociceptive transmission from primary afferents onto medullary dorsal horn neurons. EXPERIMENTAL APPROACH Primary afferent-evoked EPSCs were recorded from medullary dorsal horn neurons of rat horizontal brain stem slices using a conventional whole-cell patch clamp technique under a voltage-clamp condition. KEY RESULTS CP93129, a selective 5-HT1B receptor agonist, reversibly and concentration-dependently decreased the amplitude of glutamatergic EPSCs and increased the paired-pulse ratio. In addition, CP93129 reduced the frequency of spontaneous miniature EPSCs without affecting the current amplitude. The CP93129-induced inhibition of EPSCs was significantly occluded by GR55562, a 5-HT1B/1D receptor antagonist, but not LY310762, a 5-HT1D receptor antagonist. Sumatriptan, an anti-migraine drug, also decreased EPSC amplitude, and this effect was partially blocked by either GR55562 or LY310762. On the other hand, primary afferent-evoked EPSCs were mediated by the Ca2+ influx passing through both presynaptic N-type and P/Q-type Ca2+ channels. The CP93129-induced inhibition of EPSCs was significantly occluded by ω-conotoxin GVIA, an N-type Ca2+ channel blocker. CONCLUSIONS AND IMPLICATIONS The present results suggest that the activation of presynaptic 5-HT1B receptors reduces glutamate release from primary afferent terminals onto medullary dorsal horn neurons, and that 5-HT1B receptors could be, at the very least, a potential target for the treatment of pain from orofacial tissues. LINKED ARTICLE This article is commented on by Connor, pp. 353–355 of this issue. To view this commentary visit http://dx.doi.org/10.1111/j.1476-5381.2012.01963.x PMID:22462474

  9. Discriminative stimulus effects of NMDA, AMPA and mGluR5 glutamate receptor ligands in methamphetamine-trained rats

    PubMed Central

    Wooters, Thomas E.; Dwoskin, Linda P.; Bardo, Michael T.

    2011-01-01

    Glutamate contributes to the reinforcing and stimulant effects of methamphetamine, yet its potential role in the interoceptive stimulus properties of methamphetamine is unknown. In the current study, adult male Sprague-Dawley rats were trained to discriminate methamphetamine (1.0 mg/kg, i.p.) from saline in a standard operant discrimination task. The effects of methamphetamine (0.1-1.0 mg/kg, i.p.), the N-methyl-D-aspartate (NMDA) receptor channel blockers MK-801 (0.03-0.3 mg/kg, i.p.) and ketamine (1.0-10.0 mg/kg, i.p.), the low-affinity NMDA antagonist memantine (1.0-10 mg/kg, i.p.), the polyamine site NMDA receptor antagonist ifenprodil (1-10 mg/kg), the α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate (AMPA) receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 1-10 mg/kg, i.p.), and the metabotropic 5 (mGluR5) receptor antagonist 6-methyl-2-(phenylethynyl)pyridine (MPEP; 1-10 mg/kg) given alone were determined in substitution tests. The effects of MK-801 (0.03 and 0.1 mg/kg), ketamine (1.0 and 3.0 mg/kg), ifenprodil (5.6 mg/kg), CNQX (5.6 mg/kg) and MPEP (5.6 mg/kg) were also tested in combination with methamphetamine to assess for alterations in the methamphetamine cue. In substitution tests, none of the test drugs generalized to the methamphetamine cue. However, ketamine and ifenprodil produced significant leftward shifts in the methamphetamine dose-response curve; pretreatment with 3 mg/kg of ketamine, for example, decreased the ED50 value for methamphetamine by half. These results suggest that blockade of the NMDA receptor augments the interoceptive stimulus properties of methamphetamine. PMID:21836462

  10. Effect of neurotrophin-3 precursor on glutamate-induced calcium homeostasis deregulation in rat cerebellum granule cells.

    PubMed

    Safina, Dina R; Surin, Alexander M; Pinelis, Vsevolod G; Kostrov, Sergey V

    2015-12-01

    Neurotrophin-3 (NT-3) belongs to the family of highly conserved dimeric growth factors that controls the differentiation and activity of various neuronal populations. Mammals contain both the mature (NT-3) and the precursor (pro-NT-3) forms of neurotrophin. Members of the neurotrophin family are involved in the regulation of calcium homeostasis in neurons; however, the role of NT-3 and pro-NT-3 in this process remains unclear. The current study explores the effects of NT-3 and pro-NT-3 on disturbed calcium homeostasis and decline of mitochondrial potential induced by a neurotoxic concentration of glutamate (Glu; 100 µM) in the primary culture of rat cerebellar granule cells. In this Glu excitotoxicity model, mature NT-3 had no effect on the induced changes in Ca²⁺ homeostasis. In contrast, pro-NT-3 decreased the period of delayed calcium deregulation (DCD) and concurrent strong mitochondrial depolarization. According to the amplitude of the increase in the intracellular free Ca²⁺ concentration ([Ca²⁺]i ) and Fura-2 fluorescence quenching by Mn²⁺ within the first 20 sec of exposure to Glu, pro-NT-3 had no effect on the initial rate of Ca²⁺ entry into neurons. During the lag period preceding DCD, the mean amplitude of [Ca²⁺]i rise was 1.2-fold greater in the presence of pro-NT-3 than in the presence of Glu alone (1.67 ±  0.07 and 1.39 ± 0.04, respectively, P < 0.05). The Glu-induced changes in Са²⁺ homeostasis in the presence of pro-NT-3 likely are due to the decreased rate of Са²⁺ removal from the cytosol during the DCD latency period. PMID:26346533

  11. Neurotoxic potential of lunar and martian dust: influence on em, proton gradient, active transport, and binding of glutamate in rat brain nerve terminals.

    PubMed

    Krisanova, Natalia; Kasatkina, Ludmila; Sivko, Roman; Borysov, Arseniy; Nazarova, Anastasiya; Slenzka, Klaus; Borisova, Tatiana

    2013-08-01

    The harmful effects of lunar dust (LD) on directly exposed tissues are documented in the literature, whereas researchers are only recently beginning to consider its effects on indirectly exposed tissues. During inhalation, nano-/microsized particles are efficiently deposited in nasal, tracheobronchial, and alveolar regions and transported to the central nervous system. The neurotoxic potential of LD and martian dust (MD) has not yet been assessed. Glutamate is the main excitatory neurotransmitter involved in most aspects of normal brain function, whereas disturbances in glutamate homeostasis contribute to the pathogenesis of major neurological disorders. The research was focused on the analysis of the effects of LD/MD simulants (JSC-1a/JSC, derived from volcanic ash) on the key characteristics of glutamatergic neurotransmission. The average size of LD and MD particles (even minor fractions) before and after sonication was determined by dynamic light scattering. With the use of radiolabeled l-[(14)C]glutamate, it was shown that there is an increase in l-[(14)C]glutamate binding to isolated rat brain nerve terminals (synaptosomes) in low [Na(+)] media and at low temperature in the presence of LD. MD caused significantly lesser changes under the same conditions, whereas nanoparticles of magnetite had no effect at all. Fluorimetric experiments with potential-sensitive dye rhodamine 6G and pH-sensitive dye acridine orange showed that the potential of the plasma membrane of the nerve terminals and acidification of synaptic vesicles were not altered by LD/MD (and nanoparticles of magnetite). Thus, the unique effect of LD to increase glutamate binding to the nerve terminals was shown. This can have deleterious effects on extracellular glutamate homeostasis in the central nervous system and cause alterations in the ambient level of glutamate, which is extremely important for proper synaptic transmission. During a long-term mission, a combination of constant irritation due

  12. L-theanine administration results in neuroprotection and prevents glutamate receptor agonist-mediated injury in the rat model of cerebral ischemia-reperfusion.

    PubMed

    Zukhurova, Mavdzhuda; Prosvirnina, Maria; Daineko, Anastasia; Simanenkova, Anna; Petrishchev, Nikolay; Sonin, Dmitry; Galagudza, Michael; Shamtsyan, Mark; Juneja, Lekh R; Vlasov, Timur

    2013-09-01

    While the neuroprotective effect of green tea (Camellia sinensis) might be explained by the presence of amino acid L-theanine in the tea leaves, it is not known whether postischemic administration of L-theanine could also provide neuroprotection. In the present study, we investigated the neuroprotective effect of L-theanine (1 and 4 mg/kg) administered at 3, 12, and 24 h after reperfusion in the rat model of stroke. We also studied the effect of L-theanine on brain injury caused by exogenous administration of N-methyl-D-aspartate and α-amino-3-hydroxy-5-methyl-isoxazole-4-propionate/kainate receptor agonists during reperfusion. Rats were subjected to 30-min middle cerebral artery occlusion followed by 48-h reperfusion. Neurological deficit and infarct size were determined at the end of reperfusion. At 3 and 12 h, but not at 24 h of reperfusion, L-theanine substantially reduced the size of brain infarct. Neurological status was improved when L-theanine was administered 3, 12, and 24 h after reperfusion. Repeated intrastriatal injections of L-theanine at a total dose of 800 µg/kg during reperfusion prevented brain injury caused by glutamate receptor agonists. In conclusion, L-theanine at reperfusion exerts neuroprotective effect in the in vivo rat model of stroke. Local treatment with L-theanine at reperfusion prevents glutamate receptor agonist-mediated brain injury. PMID:23097345

  13. Glutamate neurotoxicity in rat cerebellar granule cells: a major role for xanthine oxidase in oxygen radical formation.

    PubMed

    Atlante, A; Gagliardi, S; Minervini, G M; Ciotti, M T; Marra, E; Calissano, P

    1997-05-01

    To gain insight into the mechanism through which the neurotransmitter glutamate causally participates in several neurological diseases, in vitro cultured cerebellar granule cells were exposed to glutamate and oxygen radical production was investigated. To this aim, a novel procedure was developed to detect oxygen radicals; the fluorescent dye 2',7'-dichlorofluorescein was used to detect production of peroxides, and a specific search for the possible conversion of the enzyme xanthine dehydrogenase into xanthine oxidase after the excitotoxic glutamate pulse was undertaken. A 100 microM glutamate pulse administered to 7-day-old cerebellar granule cells is accompanied by the onset of neuronal death, the appearance of xanthine oxidase, and production of oxygen radicals. Xanthine oxidase activation and superoxide (O2.-) production are completely inhibited by concomitant incubation of glutamate with MK-801, a specific NMDA receptor antagonist, or by chelation of external calcium with EGTA. Partial inhibition of both cell death and parallel production of reactive oxygen species is achieved with allopurinol, a xanthine oxidase inhibitor, leupeptin, a protease inhibitor, reducing agents such as glutathione or dithiothreitol, antioxidants such as vitamin E and vitamin C, and externally added superoxide dismutase. It is concluded that glutamate-triggered, NMDA-mediated, massive Ca2+ influx induces rapid conversion of xanthine dehydrogenase into xanthine oxidase with subsequent production of reactive oxygen species that most probably have a causal involvement in the initial steps of the series of intracellular events leading to neuronal degeneration and death. PMID:9109530

  14. Neuroprotective effect of exercise in rat hippocampal slices submitted to in vitro ischemia is promoted by decrease of glutamate release and pro-apoptotic markers.

    PubMed

    Mourão, Flávio Afonso Gonçalves; Leite, Hércules Ribeiro; de Carvalho, Luciana Estefani Drumond; Ferreira E Vieira, Talita Hélen; Pinto, Mauro Cunha Xavier; de Castro Medeiros, Daniel; Andrade, Ian Lara Lamounier; Gonçalves, Daniela Fontes; Pereira, Grace Schenatto; Dutra Moraes, Márcio Flávio; Massensini, André Ricardo

    2014-10-01

    The role of physical exercise as a neuroprotective agent against ischemic injury has been extensively discussed. Nevertheless, the mechanisms underlying the effects of physical exercise on cerebral ischemia remain poorly understood. Here, we investigate the hypothesis that physical exercise increases ischemic tolerance by decreasing the induction of cellular apoptosis and glutamate release. Rats (n = 50) were submitted to a swimming exercise protocol for 8 weeks. Hippocampal slices were then submitted to oxygen and glucose deprivation. Cellular viability, pro-apoptotic markers (Caspase 8, Caspase 9, Caspase 3, and apoptosis-inducing factor), and glutamate release were analyzed. The percentage of cell death, the amount of glutamate release, and the expression of the apoptotic markers were all decreased in the exercise group when compared to the sedentary group after oxygen and glucose deprivation. Our results suggest that physical exercise protects hippocampal slices from the effects of oxygen and glucose deprivation, probably by a mechanism involving both the decrease of glutamatergic excitotoxicity and apoptosis induction. PMID:24903976

  15. [The role of non-NMDA glutamate receptors in the EEG effects of chronic administration of noopept GVS-111 in awake rats].

    PubMed

    Kovalev, G I; Vorob'ev, V V

    2002-01-01

    Participation of the non-NMDA glutamate receptor subtype in the formation of the EEG frequency spectrum was studied in wakeful rats upon a long-term (10 x 0.2 mg/kg, s.c.) administration of the nootropic dipeptide GVS-111 (noopept or N-phenylacetyl-L-prolyglycine ethylate). The EEGs were measured with electrodes implanted into somatosensor cortex regions, hippocampus, and a cannula in the lateral ventricle. The acute reactions (characteristic of nootropes) in the alpha and beta ranges of EEG exhibited inversion after the 6th injection of noopept and almost completely vanished after the 9th injection. Preliminary introduction of the non-NMDA antagonist GDEE (glutamic acid diethyl ester) in a dose of 1 mumole into the lateral ventricle restored the EEG pattern observed upon the 6th dose of GVS-111. The role of glutamate receptors in the course of a prolonged administration of nootropes, as well as the possible mechanisms accounting for a difference in the action of GVS-111 and piracetam are discussed. PMID:12596524

  16. Neuroprotective effect of N-acetyl-aspartyl-glutamate in combination with mild hypothermia in the endothelin-1 rat model of focal cerebral ischaemia.

    PubMed

    Van Hemelrijck, An; Hachimi-Idrissi, Said; Sarre, Sophie; Ebinger, Guy; Michotte, Yvette

    2005-12-01

    Previously we showed that treatment with mild hypothermia (34 degrees C for 2 h) after a focal cerebral infarct was neuroprotective by reducing apoptosis in the penumbra (cortex), but not in the core (striatum) of the infarct. In this study we examined whether administration of N-acetyl-aspartyl-glutamate (NAAG) in combination with mild hypothermia could improve striatal neuroprotection in the endothelin-1 rat model. NAAG (10 mg/kg i.p.) was injected under normothermic (37 degrees C) or mild hypothermic conditions, either 40 min before or 20 min after the insult. NAAG reduced caspase 3 immunoreactivity in the striatum, irrespective of the time of administration and brain temperature. This neuroprotective effect could be explained, at least partially, by decreased nitric oxide synthase activity in the striatum and was blocked by the group II metabotropic glutamate receptor antagonist, LY341495. Hypothermia applied together with NAAG reduced both cortical and striatal caspase 3 immunoreactivity, as well as the overall ischaemic damage in these areas. However, no pronounced improvement was seen in total damaged brain volume. Extracellular glutamate levels did not correlate with the observed protection, whatever treatment protocol was applied. We conclude that treatment with NAAG causes the same degree of neuroprotection as treatment with hypothermia. Combination of the two treatments, although reducing apoptosis, does not considerably improve ischaemic damage. PMID:16135071

  17. Simultaneous assay of glucose, lactate, L-glutamate and hypoxanthine levels in a rat striatum using enzyme electrodes based on neutral red-doped silica nanoparticles.

    PubMed

    Zhang, Fen-Fen; Wan, Qiao; Li, Chen-Xin; Wang, Xiao-Li; Zhu, Zi-Qiang; Xian, Yue-Zhong; Jin, Li-Tong; Yamamoto, Katsunobu

    2004-10-01

    An electrochemical method suitable for the simultaneous measurement of cerebral glucose, lactate, L-glutamate and hypoxanthine concentrations from in vivo microdialysis sampling has been successfully performed for the first time using a neutral red-doped silica (NRDS) nanoparticle-derived enzyme sensor system. These uniform NRDS nanoparticles (about 50 +/- 3 nm) were prepared by a water-in-oil (W/O) microemulsion method, and characterized by a TEM technique. The neutral red-doped interior maintained its high electron-activity, while the exterior nano-silica surface prevented the mediator from leaching out into the aqueous solution, and showed high biocompability. These nanoparticles were then mixing with the glucose oxidase (GOD), lactate oxidase (LOD), L-glutamate oxidase (L-GLOD) or xanthine oxidase (XOD), and immobilized on four glassy carbon electrodes, respectively. A thin Nafion film was coated on the enzyme layer to prevent interference from molecules such as ascorbic acid and uric acid in the dialysate. The high sensitivity of the NRDS modified enzyme electrode system enables the simultaneous monitoring of trace levels of glucose, L-glutamate, lactate and hypoxanthine in diluted dialysate samples from a rat striatum. PMID:15517210

  18. Polyphenol-Rich Extract of Syzygium cumini Leaf Dually Improves Peripheral Insulin Sensitivity and Pancreatic Islet Function in Monosodium L-Glutamate-Induced Obese Rats.

    PubMed

    Sanches, Jonas R; França, Lucas M; Chagas, Vinicyus T; Gaspar, Renato S; Dos Santos, Kayque A; Gonçalves, Luciana M; Sloboda, Deborah M; Holloway, Alison C; Dutra, Richard P; Carneiro, Everardo M; Cappelli, Ana Paula G; Paes, Antonio Marcus de A

    2016-01-01

    Syzygium cumini (L.) Skeels (Myrtaceae) has been traditionally used to treat a number of illnesses. Ethnopharmacological studies have particularly addressed antidiabetic and metabolic-related effects of extracts prepared from its different parts, especially seed, and pulp-fruit, however. there is a lack of studies on phytochemical profile and biological properties of its leaf. As there is considerable interest in bioactive compounds to treat metabolic syndrome and its clustered risk factors, we sought to characterize the metabolic effects of hydroethanolic extract of S. cumini leaf (HESc) on lean and monosodium L-glutamate (MSG)-induced obese rats. HPLC-MS/MS characterization of the HESc polyphenolic profile, at 254 nm, identified 15 compounds pertaining to hydrolysable tannin and flavanol subclasses. At 60 days of age, both groups were randomly assigned to receive HESc (500 mg/kg) or vehicle for 30 days. At the end of treatment, obese+HESc exhibited significantly lower body weight gain, body mass index, and white adipose tissue mass, compared to obese rats receiving vehicle. Obese rats treated with HESc showed a twofold increase in lipolytic activity in the periepididymal fat pad, as well as, brought triglyceride levels in serum, liver and skeletal muscle back to levels close those found in lean animals. Furthermore, HESc also improved hyperinsulinemia and insulin resistance in obese+HESc rats, which resulted in partial reversal of glucose intolerance, as compared to obese rats. HESc had no effect in lean rats. Assessment of ex vivo glucose-stimulated insulin secretion showed HESc potentiated pancreatic function in islets isolated from both lean and obese rats treated with HESc. In addition, HESc (10-1000 μg/mL) increased glucose stimulated insulin secretion from both isolated rat islets and INS-1E β-cells. These data demonstrate that S. cumini leaf improved peripheral insulin sensitivity via stimulating/modulating β-cell insulin release, which was associated

  19. Polyphenol-Rich Extract of Syzygium cumini Leaf Dually Improves Peripheral Insulin Sensitivity and Pancreatic Islet Function in Monosodium L-Glutamate-Induced Obese Rats

    PubMed Central

    Sanches, Jonas R.; França, Lucas M.; Chagas, Vinicyus T.; Gaspar, Renato S.; dos Santos, Kayque A.; Gonçalves, Luciana M.; Sloboda, Deborah M.; Holloway, Alison C.; Dutra, Richard P.; Carneiro, Everardo M.; Cappelli, Ana Paula G.; Paes, Antonio Marcus de A.

    2016-01-01

    Syzygium cumini (L.) Skeels (Myrtaceae) has been traditionally used to treat a number of illnesses. Ethnopharmacological studies have particularly addressed antidiabetic and metabolic-related effects of extracts prepared from its different parts, especially seed, and pulp-fruit, however. there is a lack of studies on phytochemical profile and biological properties of its leaf. As there is considerable interest in bioactive compounds to treat metabolic syndrome and its clustered risk factors, we sought to characterize the metabolic effects of hydroethanolic extract of S. cumini leaf (HESc) on lean and monosodium L-glutamate (MSG)-induced obese rats. HPLC-MS/MS characterization of the HESc polyphenolic profile, at 254 nm, identified 15 compounds pertaining to hydrolysable tannin and flavanol subclasses. At 60 days of age, both groups were randomly assigned to receive HESc (500 mg/kg) or vehicle for 30 days. At the end of treatment, obese+HESc exhibited significantly lower body weight gain, body mass index, and white adipose tissue mass, compared to obese rats receiving vehicle. Obese rats treated with HESc showed a twofold increase in lipolytic activity in the periepididymal fat pad, as well as, brought triglyceride levels in serum, liver and skeletal muscle back to levels close those found in lean animals. Furthermore, HESc also improved hyperinsulinemia and insulin resistance in obese+HESc rats, which resulted in partial reversal of glucose intolerance, as compared to obese rats. HESc had no effect in lean rats. Assessment of ex vivo glucose-stimulated insulin secretion showed HESc potentiated pancreatic function in islets isolated from both lean and obese rats treated with HESc. In addition, HESc (10–1000 μg/mL) increased glucose stimulated insulin secretion from both isolated rat islets and INS-1E β-cells. These data demonstrate that S. cumini leaf improved peripheral insulin sensitivity via stimulating/modulating β-cell insulin release, which was associated

  20. P2X7 receptor activation downmodulates Na(+)-dependent high-affinity GABA and glutamate transport into rat brain cortex synaptosomes.

    PubMed

    Barros-Barbosa, A R; Lobo, M G; Ferreirinha, F; Correia-de-Sá, P; Cordeiro, J M

    2015-10-15

    Sodium-dependent high-affinity amino-acid transporters play crucial roles in terminating synaptic transmission in the central nervous system (CNS). However, there is lack of information about the mechanisms underlying the regulation of amino-acid transport by fast-acting neuromodulators, like ATP. Here, we investigated whether activation of the ATP-sensitive P2X7 receptor modulates Na(+)-dependent high-affinity γ-aminobutyric acid (GABA) and glutamate uptake into nerve terminals (synaptosomes) of the rat cerebral cortex. Radiolabeled neurotransmitter accumulation was evaluated by liquid scintillation spectrometry. The cell-permeant sodium-selective fluorescent indicator, SBFI-AM, was used to estimate Na(+) influx across plasma membrane. 2'(3')-O-(4-benzoylbenzoyl)ATP (BzATP, 3-300 μM), a prototypic P2X7 receptor agonist, concentration-dependently decreased [(3)H]GABA (14%) and [(14)C]glutamate (24%) uptake; BzATP decreased transport maximum velocity (Vmax) without affecting the Michaelis constant (Km) values. The selective P2X7 receptor antagonist, A-438079 (3 μM), prevented inhibition of [(3)H]GABA and [(14)C]glutamate uptake by BzATP (100 μM). The inhibitory effect of BzATP coincided with its ability to increase intracellular Na(+) and was mimicked by Na(+) ionophores, like gramicidin and monensin. Increases in intracellular Na(+) (with veratridine or ouabain) or substitution of extracellular Na(+) by N-methyl-D-glucamine (NMDG)(+) all decreased [(3)H]GABA and [(14)C]glutamate uptake and attenuated BzATP effects. Uptake inhibition by BzATP (100 μM) was also attenuated by calmidazolium, which selectively inhibits Na(+) currents through the P2X7 receptor pore. In conclusion, disruption of the Na(+) gradient by P2X7 receptor activation downmodulates high-affinity GABA and glutamate uptake into rat cortical synaptosomes. Interference with amino-acid transport efficacy may constitute a novel target for therapeutic management of cortical excitability. PMID

  1. Influence of exposure period on in vivo hippocampal glutamate and GABA release in rats chronically exposed to lead.

    PubMed

    Lasley, S M; Green, M C; Gilbert, M E

    1999-08-01

    Previous work has demonstrated that continual exposure to 0.2% lead (Pb) beginning at birth diminishes depolarization-induced hippocampal glutamate (GLU) and GABA release in vivo. The present study sought to extend these findings by examining Pb-induced changes as a function of exposure period. Rats were continually exposed to 0.2% Pb in the drinking water beginning at conception (Gestational-Life, GL) or two weeks after weaning (Wean-Life, WL), while exposure in a third group was begun at conception but terminated at weaning (Gestational-Wean, GW). Hippocampal transmitter release was induced in adult animals by perfusion of 150 mM K+ in the presence of Ca+2 (total release) through a microdialysis probe in one test session, followed by perfusion through a contralateral probe in the absence of Ca+2 (Ca+2-independent release) in the second session. Decreases in total GLU and GABA release were observed in the GL and WL groups compared to controls over the first 20-min after initiation of high K+, decrements that could be attributed to exposure-induced reductions in Ca+2-dependent release. The pattern of Pb-induced changes in the GL group is similar to that observed previously in a group continuously exposed from birth, indicating that gestational exposure did not further enhance the impact of Pb beginning at birth when exposure in both groups extends into adulthood. Similar responses were also found in the WL group, indicating that exposure during early development is not a requirement to induce changes in GLU and GABA release. Pb-induced decreases in response were also seen in the GW group: a decrease in Ca+2-dependent GLU release was observed, while decrements in total and Ca+2-dependent GABA release were similar to those in the GL and WL groups. Thus, exposure limited to early development is also sufficient to produce deficits in evoked transmitter release. In addition, the exposure-induced decreases in GLU responses correspond to Pb-induced impairments in long

  2. Rat hippocampal glutamate and GABA release exhibit biphasic effects as a function of chronic lead exposure level.

    PubMed

    Lasley, S M; Gilbert, M E

    2002-03-01

    Previous work has suggested that the lead (Pb) exposure-induced decrease in K(+)-evoked hippocampal glutamate (GLU) release is an important factor in the elevated threshold and diminished magnitude reported for hippocampal long-term potentiation (LTP) in exposed animals. In addition, complex dose-effect relationships between Pb exposure level and LTP have been reported. This investigation was conducted to determine the effects of Pb on hippocampal GLU and GABA release as a function of exposure level. Rats were continuously exposed to 0.1, 0.2, 0.5, or 1.0% Pb in the drinking water beginning at gestational day 15-16. Hippocampal transmitter release was induced in adult males by perfusion of 150 mM K(+) in the presence of Ca(+2) (total release) through a microdialysis probe in one test session, followed by perfusion through a contralateral probe in the absence of Ca(+2) (Ca(+2)-independent release) in the second session. Chronic exposure produced decreases in total K(+)-stimulated hippocampal GLU and GABA release at exposure levels of 0.1-0.5% Pb. Maximal effects were seen in the 0.2% group (blood Pb = 40 microg/100 ml), and changes in total release could be directly traced to alterations in the Ca(+2)-dependent component. However, these effects were less evident in the 0.5% group and were no longer present in the 1.0% Pb group, thus defining U-shaped dose-effect relationships. Moreover, in the absence of Ca(+2) in the dialysis perfusate, K(+)-induced release was elevated in the 2 highest exposure groups, suggesting a Pb(+2)-induced enhancement in evoked release. This pattern of results indicates the presence of 2 actions of Pb on in vivo transmitter release: a more potent suppression of stimulated release seen at lower exposure levels (27-62 microg/100 ml) combined with Ca+2-mimetic actions to independently induce exocytosis that is exhibited at higher exposure levels (> or =62 microg/100 ml). Furthermore, significant similarities in the dose-effect relationships

  3. Homeostatic effect of p-chloro-diphenyl diselenide on glucose metabolism and mitochondrial function alterations induced by monosodium glutamate administration to rats.

    PubMed

    Quines, Caroline B; Rosa, Suzan G; Chagas, Pietro M; da Rocha, Juliana T; Dobrachinski, Fernando; Carvalho, Nélson R; Soares, Félix A; da Luz, Sônia C Almeida; Nogueira, Cristina W

    2016-01-01

    The metabolic syndrome is a group of metabolic alterations considered a worldwide public health problem. Organic selenium compounds have been reported to have many different pharmacological actions, such as anti-hypercholesterolemic and anti-hyperglycemic. The aim of this study was to evaluate the effect of p-chloro-diphenyl diselenide (p-ClPhSe)2, an organic selenium compound, in a model of obesity induced by monosodium glutamate (MSG) administration in rats. The rats were treated during the first ten postnatal days with MSG and received (p-ClPhSe)2 (10 mg/kg, intragastrically) from 45th to 51 th postnatal day. Glucose, lipid and lactate levels were determined in plasma of rats. Glycogen levels and activities of tyrosine aminotransferase, hexokinase, citrate synthase and glucose-6-phosphatase (G-6-Pase) were determined in livers of rats. Renal G-6-Pase activity was also determined. The purine content [Adenosine triphosphate (ATP), adenosine diphosphate (ADP) and adenosine monophosphate] and mitochondrial functionality in the liver were also investigated. p-(ClPhSe)2 did not alter the reduction in growth performance and in the body weight caused by MSG but reduced epididymal fat deposition of rats. p-(ClPhSe)2 restored glycemia, triglycerides, cholesterol and lactate levels as well as the glucose metabolism altered in rats treated with MSG. p-(ClPhSe)2 restored hepatic mitochondrial dysfunction and the decrease in citrate synthase activity and ATP and ADP levels caused by MSG in rats. In summary, (p-ClPhSe)2 had homeostatic effects on glucose metabolism and mitochondrial function alterations induced by MSG administration to rats. PMID:26293481

  4. Neuronal activity mediated regulation of glutamate transporter GLT-1 surface diffusion in rat astrocytes in dissociated and slice cultures.

    PubMed

    Al Awabdh, Sana; Gupta-Agarwal, Swati; Sheehan, David F; Muir, James; Norkett, Rosalind; Twelvetrees, Alison E; Griffin, Lewis D; Kittler, Josef T

    2016-07-01

    The astrocytic GLT-1 (or EAAT2) is the major glutamate transporter for clearing synaptic glutamate. While the diffusion dynamics of neurotransmitter receptors at the neuronal surface are well understood, far less is known regarding the surface trafficking of transporters in subcellular domains of the astrocyte membrane. Here, we have used live-cell imaging to study the mechanisms regulating GLT-1 surface diffusion in astrocytes in dissociated and brain slice cultures. Using GFP-time lapse imaging, we show that GLT-1 forms stable clusters that are dispersed rapidly and reversibly upon glutamate treatment in a transporter activity-dependent manner. Fluorescence recovery after photobleaching and single particle tracking using quantum dots revealed that clustered GLT-1 is more stable than diffuse GLT-1 and that glutamate increases GLT-1 surface diffusion in the astrocyte membrane. Interestingly, the two main GLT-1 isoforms expressed in the brain, GLT-1a and GLT-1b, are both found to be stabilized opposed to synapses under basal conditions, with GLT-1b more so. GLT-1 surface mobility is increased in proximity to activated synapses and alterations of neuronal activity can bidirectionally modulate the dynamics of both GLT-1 isoforms. Altogether, these data reveal that astrocytic GLT-1 surface mobility, via its transport activity, is modulated during neuronal firing, which may be a key process for shaping glutamate clearance and glutamatergic synaptic transmission. GLIA 2016;64:1252-1264. PMID:27189737

  5. Neuronal activity mediated regulation of glutamate transporter GLT‐1 surface diffusion in rat astrocytes in dissociated and slice cultures

    PubMed Central

    Al Awabdh, Sana; Gupta‐Agarwal, Swati; Sheehan, David F.; Muir, James; Norkett, Rosalind; Twelvetrees, Alison E.; Griffin, Lewis D.

    2016-01-01

    The astrocytic GLT‐1 (or EAAT2) is the major glutamate transporter for clearing synaptic glutamate. While the diffusion dynamics of neurotransmitter receptors at the neuronal surface are well understood, far less is known regarding the surface trafficking of transporters in subcellular domains of the astrocyte membrane. Here, we have used live‐cell imaging to study the mechanisms regulating GLT‐1 surface diffusion in astrocytes in dissociated and brain slice cultures. Using GFP‐time lapse imaging, we show that GLT‐1 forms stable clusters that are dispersed rapidly and reversibly upon glutamate treatment in a transporter activity‐dependent manner. Fluorescence recovery after photobleaching and single particle tracking using quantum dots revealed that clustered GLT‐1 is more stable than diffuse GLT‐1 and that glutamate increases GLT‐1 surface diffusion in the astrocyte membrane. Interestingly, the two main GLT‐1 isoforms expressed in the brain, GLT‐1a and GLT‐1b, are both found to be stabilized opposed to synapses under basal conditions, with GLT‐1b more so. GLT‐1 surface mobility is increased in proximity to activated synapses and alterations of neuronal activity can bidirectionally modulate the dynamics of both GLT‐1 isoforms. Altogether, these data reveal that astrocytic GLT‐1 surface mobility, via its transport activity, is modulated during neuronal firing, which may be a key process for shaping glutamate clearance and glutamatergic synaptic transmission. GLIA 2016;64:1252–1264 PMID:27189737

  6. The negative effects of alcohol hangover on high-anxiety phenotype rats are influenced by the glutamate receptors of the dorsal midbrain.

    PubMed

    Ezequiel Leite, L; Nobre, M J

    2012-06-28

    Alcoholism is a chronic disorder characterized by the appearance of a withdrawal syndrome following the abrupt cessation of alcohol intake that includes symptoms of physical and emotional disturbances, anxiety being the most prevalent symptom. In humans, it was shown that anxiety may increase the probability of relapse. In laboratory animals, however, the use of anxiety to predict alcohol preference has remained difficult. Excitatory amino acids as glutamate have been implicated in alcohol hangover and may be responsible for the seizures and anxiety observed during withdrawal. The dorsal periaqueductal gray (DPAG) is a midbrain region critical for the modulation/expression of anxiety- and fear-related behaviors and the propagation of seizures induced by alcohol withdrawal, the glutamate neurotransmission being one of the most affected. The present study was designed to evaluate whether low- (LA) and high-anxiety rats (HA), tested during the alcohol hangover phase, in which anxiety is the most prevalent symptom, are more sensitive to the reinforcing effects of alcohol when tested in a voluntary alcohol drinking procedure. Additionally, we were interested in investigating the main effects of reducing the excitatory tonus of the dorsal midbrain, after the blockade of the ionotropic glutamate receptors into the DPAG, on the voluntary alcohol intake of HA and LA motivated rats that were made previously experienced with the free operant response of alcohol drinking. For this purpose, we used local infusions of the N-metil D-Aspartato (NMDA) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-kainate receptors antagonist DL-2-Amino-7-phosphonoheptanoic acid - DL-AP7 (10 nmol/0.2 μl) and l-glutamic acid diethyl ester - GDEE (160 nmol/0.2 μl), respectively. Alcohol intoxication was produced by 10 daily bolus intraperitonial (IP) injections of alcohol (2.0 g/kg). Peak-blood alcohol levels were determined by gas-chromatography analysis in order to assess blood

  7. Activation of Group II Metabotropic Glutamate Receptors Induces Depotentiation in Amygdala Slices and Reduces Fear-Potentiated Startle in Rats

    ERIC Educational Resources Information Center

    Lin, Chia-Ho; Lee, Chia-Ching; Huang, Ya-Chun; Wang, Su-Jane; Gean, Po-Wu

    2005-01-01

    There is a close correlation between long-term potentiation (LTP) in the synapses of lateral amygdala (LA) and fear conditioning in animals. We predict that reversal of LTP (depotentiation) in this area of the brain may ameliorate conditioned fear. Activation of group II metabotropic glutamate receptors (mGluR II) with DCG-IV induces…

  8. Glutamate neurotoxicity in rat cerebellar granule cells involves cytochrome c release from mitochondria and mitochondrial shuttle impairment.

    PubMed

    Atlante, A; Gagliardi, S; Marra, E; Calissano, P; Passarella, S

    1999-07-01

    To gain some insight into the mechanism by which glutamate neurotoxicity takes place in cerebellar granule cells, two steps of glucose oxidation were investigated: the electron flow via respiratory chain from certain substrates to oxygen and the transfer of extramitochondrial reducing equivalents via the mitochondrial shuttles. However, cytochrome c release from intact mitochondria was found to occur in glutamate-treated cells as detected photometrically in the supernatant of the cell homogenate suspension. As a result of cytochrome c release, an increase of the oxidation of externally added NADH was found, probably occurring via the NADH-b5 oxidoreductase of the outer mitochondrial membrane. When the two mitochondrial shuttles glycerol 3-phosphate/dihydroxyacetone phosphate and malate/oxaloacetate, devoted to oxidizing externally added NADH, were reconstructed, both were found to be impaired under glutamate neurotoxicity. Consistent early activation in two NADH oxidizing mechanisms, i.e., lactate production and plasma membrane NADH oxidoreductase activity, was found in glutamate-treated cells. In spite of this, the increase in the cell NADH fluorescence was found to be time-dependent, an index of the progressive damage of the cell. PMID:10386976

  9. The Neuroprotective Effect of Dark Chocolate in Monosodium Glutamate-Induced Nontransgenic Alzheimer Disease Model Rats: Biochemical, Behavioral, and Histological Studies.

    PubMed

    Madhavadas, Sowmya; Kapgal, Vijaya Kumar; Kutty, Bindu M; Subramanian, Sarada

    2016-01-01

    The vulnerability to oxidative stress and cognitive decline continue to increase during both normal and pathological aging. Dietary changes and sedentary life style resulting in mid-life obesity and type 2 diabetes, if left uncorrected, further add to the risk of cognitive decline and Alzheimer disease (AD) in the later stages of life. Certain antioxidant agents such as dietary polyphenols, taken in adequate quantities, have been suggested to improve the cognitive processes. In this study, we examined the effect of oral administration of dark chocolate (DC) containing 70% cocoa solids and 4% total polyphenol content for three months at a dose of 500 mg/Kg body weight per day to 17-month-old monosodium glutamate treated obese Sprague-Dawley rats, earlier characterized as a nontransgenic AD (NTAD) rat model after reversal of obesity, diabetes, and consequent cognitive impairments. The results demonstrated that DC reduced the hyperglycemia, inhibited the cholinesterase activity in the hippocampal tissue homogenates, and improved the cognitive performance in spatial memory related Barnes maze task. Histological studies revealed an increase in cell volume in the DC treated rats in the CA3 region of the hippocampus. These findings demonstrated the benefits of DC in enhancing cognitive function and cholinergic activity in the hippocampus of the aged NTAD rats while correcting their metabolic disturbances. PMID:26673833

  10. Prenatal chronic mild stress induces depression-like behavior and sex-specific changes in regional glutamate receptor expression patterns in adult rats.

    PubMed

    Wang, Y; Ma, Y; Hu, J; Cheng, W; Jiang, H; Zhang, X; Li, M; Ren, J; Li, X

    2015-08-20

    Chronic stress during critical periods of human fetal brain development is associated with cognitive, behavioral, and mood disorders in later life. Altered glutamate receptor (GluR) expression has been implicated in the pathogenesis of stress-dependent disorders. To test whether prenatal chronic mild stress (PCMS) enhances offspring's vulnerability to stress-induced behavioral and neurobiological abnormalities and if this enhanced vulnerability is sex-dependent, we measured depression-like behavior in the forced swimming test (FST) and regional changes in GluR subunit expression in PCMS-exposed adult male and female rats. Both male and female PCMS-exposed rats exhibited stronger depression-like behavior than controls. Males and females exhibited unique regional changes in GluR expression in response to PCMS alone, FST alone (CON-FST), and PCMS with FST (PCMS-FST). In females, PCMS alone did not alter N-methyl-d-aspartate receptor (NMDAR) or metabotropic glutamate receptor (mGluR) expression, while in PCMS males, higher mGluR2/3, mGluR5, and NR1 expression levels were observed in the prefrontal cortex. In addition, PCMS altered the change in GluR expression induced by acute stress (the FST test), and this too was sex-specific. Male PCMS-FST rats expressed significantly lower mGluR5 levels in the hippocampus, lower mGluR5, NR1, postsynaptic density protein (PSD)95, and higher mGluR2/3 in the prefrontal cortex, and higher mGluR5 and PSD95 in the amygdala than male CON-FST rats. Female PCMS-FST rats expressed lower NR1 in the hippocampus, lower NR2B and PSD95 in the prefrontal cortex, lower mGluR2/3 in the amygdala, and higher PSD95 in the amygdala than female CON-FST rats. PCMS may increase the offspring's vulnerability to depression by altering sex-specific stress-induced changes in glutamatergic signaling. PMID:26071959

  11. Synaptic Glutamate Spillover Due to Impaired Glutamate Uptake Mediates Heroin Relapse

    PubMed Central

    Scofield, Michael D.; Boger, Heather; Hensley, Megan; Kalivas, Peter W.

    2014-01-01

    Reducing the enduring vulnerability to relapse is a therapeutic goal in treating drug addiction. Studies with animal models of drug addiction show a marked increase in extrasynaptic glutamate in the core subcompartment of the nucleus accumbens (NAcore) during reinstated drug seeking. However, the synaptic mechanisms linking drug-induced changes in extrasynaptic glutamate to relapse are poorly understood. Here, we discovered impaired glutamate elimination in rats extinguished from heroin self-administration that leads to spillover of synaptically released glutamate into the nonsynaptic extracellular space in NAcore and investigated whether restoration of glutamate transport prevented reinstated heroin seeking. Through multiple functional assays of glutamate uptake and analyzing NMDA receptor-mediated currents, we show that heroin self-administration produced long-lasting downregulation of glutamate uptake and surface expression of the transporter GLT-1. This downregulation was associated with spillover of synaptic glutamate to extrasynaptic NMDA receptors within the NAcore. Ceftriaxone restored glutamate uptake and prevented synaptic glutamate spillover and cue-induced heroin seeking. Ceftriaxone-induced inhibition of reinstated heroin seeking was blocked by morpholino-antisense targeting GLT-1 synthesis. These data reveal that the synaptic glutamate spillover in the NAcore results from reduced glutamate transport and is a critical pathophysiological mechanism underling reinstated drug seeking in rats extinguished from heroin self-administration. PMID:24741055

  12. Non-NMDA glutamate receptor occupancy and open probability at a rat cerebellar synapse with single and multiple release sites.

    PubMed Central

    Silver, R A; Cull-Candy, S G; Takahashi, T

    1996-01-01

    1. Excitatory postsynaptic currents (EPSCs) were recorded under whole-cell voltage clamp from granule cells in slices of rat cerebellum. EPSCs from individual mossy fibre inputs were identified by their all-or-none appearance in response to a graded stimulus. Excitatory synaptic transmission was investigated at room temperature (approximately 24 degrees C) and at near-physiological temperature (approximately 34 degrees C) by analysing current fluctuations in the peak and decay of the non-N-methyl-D-aspartate (non-NMDA) component of EPSCs. 2. In a subset of synapses the mean EPSC amplitude remained unchanged as the probability of transmitter release was substantially lowered by raising the extracellular [Mg2+] and lowering [Ca2+]. These synapses were considered to have only one functional release site. Single-site synapses had small EPSCs (139 +/- 16 pS, n = 5, at 24 degrees C) with a large coefficient of variation (c.v. = 0.23 +/- 0.02, n = 5) and an amplitude distribution that was well fitted by a Gaussian distribution in four out of five cases. The EPSC latency had a unimodal distribution and its standard deviation had a temperature dependence with a temperature coefficient (Q10; range, 24-35 degrees C) of 2.4 +/- 0.4 (n = 4). 3. Peak-scaled non-stationary fluctuation analysis of single-site EPSCs indicated that the mean conductance of the underlying non-NMDA channels was 12 +/- 2 pS (n = 4) at 35 degrees C. Upper and lower limits for mean channel open probability (Po), calculated from fluctuations in the EPSC peak amplitude, were 0.51 and 0.38, respectively. These estimates, together with the open probability of the channel when bound by transmitter, suggest that only about 50% of the non-NMDA channels were occupied following the release of a quantum of transmitter. 4. At some multi-site synapses EPSCs had a low c.v. (0.4 +/- 0.01, n = 5) at 34 degrees C and non-stationary fluctuation analysis gave a parabolic variance-mean current relationship. This suggests

  13. Permeation and block of rat GluR6 glutamate receptor channels by internal and external polyamines.

    PubMed Central

    Bähring, R; Bowie, D; Benveniste, M; Mayer, M L

    1997-01-01

    1. Polyamine block of rat GluR6(Q) glutamate receptor channels was studied in outside-out patches from transiently transfected HEK 293 cells. With symmetrical 150 mM Na+ and 30 microM internal spermine there was biphasic voltage dependence with 95% block at +40 mV but only 20% block at +140 mV. Dose-inhibition analysis for external spermine also revealed biphasic block; the Kd at +40 mV (54 microM) was lower than at +80 (167 microM) and -80 mV (78 microM). 2. For internal polyamines relief from block was most pronounced for spermine, weaker for N-(4-hydroxyphenylpropanoyl)-spermine (PPS), and virtually absent for philanthotoxin 343 (PhTX 343), suggesting that permeation of polyamines varies with cross-sectional width (spermine, 0.44 nm; PPS, 0.70 nm; PhTX 343, 0.75 nm). 3. With putrescine, spermidine, or spermine as sole external cations, inward currents at -120 mV confirmed permeation of polyamines. For bi-ionic conditions with 90 mM polyamine and 150 mM Na+i, reversal potentials were -12.4 mV for putrescine (permeability ratio relative to Na+, PPut/PNa = 0.42) and -32.7 mV for spermidine (PSpd/PNa = 0.07). Currents carried by spermine were too small to analyse accurately in the majority of patches. 4. Increasing [Na+]i from 44 to 330 mM had no effect on the potential for 50% block (V1/2) by 30 microM internal spermine; however, relief from block at positive membrane potentials increased with [Na+]i. In contrast, raising [Na+]o from 44 to 330 mM resulted in a depolarizing shift in V1/2, indicating a strong interaction between internal polyamines and external permeant ions. 5. The Woodhull infinite barrier model of ion channel block adequately described the action of spermine at membrane potentials insufficient to produce relief from block. For 30 microM internal spermine such analysis gave Kd(O) = 2.5 microM, z theta = 1.97; block by 30 microM external spermine was weaker and less voltage dependent (Kd(O) = 37.8 microM and z delta = 0.55); delta and theta are

  14. Differential long-term neuroadaptations of glutamate receptors in the basolateral and central amygdala after withdrawal from cocaine self-administration in rats.

    PubMed

    Lu, Lin; Dempsey, Jack; Shaham, Yavin; Hope, Bruce T

    2005-07-01

    Humans and laboratory animals remain highly vulnerable to relapse to cocaine-seeking after prolonged periods of withdrawal from the drug. It has been hypothesized that this persistent cocaine relapse vulnerability involves drug-induced alterations in glutamatergic synapses within the mesolimbic dopamine reward system. Previous studies have shown that cocaine self-administration induces long-lasting neuroadaptations in glutamate neurons of the ventral tegmental area and nucleus accumbens. Here, we determined the effect of cocaine self-administration and subsequent withdrawal on glutamate receptor expression in the amygdala, a component of the mesolimbic dopamine system that is involved in cocaine seeking and craving induced by drug-associated cues. Rats were trained for 10 days to self-administer intravenous cocaine (6 h/day) or saline (a control condition) and were killed after one or 30 withdrawal days. Basolateral and central amygdala tissues were assayed for protein expression of the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor subunits (GluR1 and GluR2) and the NMDA receptor subunits (NR1, NR2A and NR2B). In the basolateral amygdala, GluR1 but not GluR2 levels were increased on days 1 and 30, NR2A levels were increased on day 1, and NR2B levels were decreased on day 30 of withdrawal from cocaine. In the central amygdala, GluR2 but not GluR1 levels were increased on days 1 and 30, NR1 levels were increased on day 30 and NR2A or NR2B levels were not altered after withdrawal from cocaine. These results indicate that cocaine self-administration and subsequent withdrawal induces long-lasting and differential neuroadaptations in basolateral and central amygdala glutamate receptors. PMID:15953359

  15. Contrasting changes in extracellular dopamine and glutamate along the rostrocaudal axis of the anterior cingulate cortex of the rat following an acute d-amphetamine or dopamine challenge

    PubMed Central

    Ash, Elizabeth S.; Heal, David J.; Clare Stanford, S.

    2014-01-01

    There is evidence for functional specificity of subregions along the rostrocaudal axis of the anterior cingulate cortex (ACC). The subregion-specific distribution of dopaminergic afferents and glutamatergic efferents along the ACC make these obvious candidates for coding such regional responses. We investigated this possibility using microdialysis in freely-moving rats to compare changes in extracellular dopamine and glutamate in the rostral (‘rACC': Cg1 and Cg3 (prelimbic area)) and caudal (‘cACC’: Cg1 and Cg2) ACC induced by systemic or local administration of d-amphetamine. Systemic administration of d-amphetamine (3 mg/kg, i.p.) caused a transient increase in extracellular dopamine in the rACC, but an apparent increase in the cACC of the same animals was less clearly defined. Local infusion of d-amphetamine increased dopamine efflux in the rACC, only. Glutamate efflux in the rACC was increased by local infusion of dopamine (5–50 μM), which had negligible effect in the cACC, but only systemic administration of d-amphetamine increased glutamate efflux and only in the cACC. The asymmetry in the neurochemical responses within the rACC and cACC, to the same experimental challenges, could help explain why different subregions are recruited in the response to specific environmental and somatosensory stimuli and should be taken into account when studying the regulation of neurotransmission in the ACC. This article is part of the Special Issue entitled ‘CNS Stimulants’. PMID:24747182

  16. A patch clamp study of the effects of ciprofloxacin and biphenyl acetic acid on rat hippocampal neurone GABAA and ionotropic glutamate receptors.

    PubMed

    Halliwell, R F; Davey, P G; Lambert, J J

    1995-12-01

    The neurotoxic effects of 4-quinolones alone and in combination with certain non-steroidal anti-inflammatory drugs (NSAIDs) may be related to an interaction at GABAA and/or ionotropic glutamate receptors. In the present study, the effects of the fluoroquinolone, ciprofloxacin, alone and in combination with the NSAID, biphenyl acetic acid (BPAA), were examined on GABAA-, NMDA-, AMPA-, and kainate-evoked current responses recorded from cultured rat hippocampal neurones, using the whole cell patch clamp technique. GABA-evoked currents were reversibly inhibited by bicuculline (3 microM) and ciprofloxacin (100 microM) to 11 +/- 5 and 38 +/- 7% of control, respectively. BPAA (100 microM) had little affect on the GABA current (the response was 82 +/- 4% of control) but enhanced the inhibitory potency of ciprofloxacin by approx. 3000-fold. The antagonist effects of ciprofloxacin (30 microM) and ciprofloxacin (0.03 microM) together with BPAA (100 microM) on the GABA-evoked current were not voltage-dependent. Whole cell currents evoked by NMDA, AMPA or kainate were little influenced by ciprofloxacin (100 microM), BPAA (100 microM), or ciprofloxacin plus BPAA (both at 100 microM); the responses being > or = 90% of control in all cases. These data suggest that the proconvulsant effects of quinolones when combined with BPAA may be related to antagonism of central GABAA receptors but not to an interaction at ionotropic glutamate receptors. PMID:8788959

  17. Spontaneous L-glutamate release enhancement in rat substantia gelatinosa neurons by (-)-carvone and (+)-carvone which activate different types of TRP channel.

    PubMed

    Kang, Qin; Jiang, Chang-Yu; Fujita, Tsugumi; Kumamoto, Eiichi

    2015-04-10

    Transient receptor potential (TRP) channels in the spinal dorsal horn lamina II (substantia gelatinosa; SG), which are involved in the modulation of nociceptive transmission, have not yet been fully examined in property. Activation of the TRP channels by various plant-derived chemicals results in an increase in the spontaneous release of L-glutamate onto the SG neurons. We examined the effects of a monoterpene ketone (-)-carvone (contained in spearmint) and its stereoisomer (+)-carvone (in caraway) on glutamatergic spontaneous excitatory transmission in SG neurons of adult rat spinal cord slices by using the whole-cell patch-clamp technique. (-)-Carvone and (+)-carvone increased the frequency of spontaneous excitatory postsynaptic current (sEPSC) in a reversible and concentration-dependent manner with a small increase in its amplitude. Half-maximal effective concentrations of (-)-carvone and (+)-carvone in increasing sEPSC frequency were 0.70 mM and 0.72 mM, respectively. The (-)-carvone but not (+)-carvone activity was inhibited by a TRPV1 antagonist capsazepine. On the other hand, the (+)-carvone but not (-)-carvone activity was inhibited by a TRPA1 antagonist HC-030031. These results indicate that (-)-carvone and (+)-carvone activate TRPV1 and TRPA1 channels, respectively, resulting in an increase in spontaneous L-glutamate release onto SG neurons, with almost the same efficacy. Such a difference in TRP activation between the stereoisomers may serve to know the properties of TRP channels in the SG. PMID:25747716

  18. Central control of penile erection: a re-visitation of the role of oxytocin and its interaction with dopamine and glutamic acid in male rats.

    PubMed

    Melis, Maria Rosaria; Argiolas, Antonio

    2011-01-01

    Oxytocin is a potent inducer of penile erection when injected into the central nervous system. In male rats, the most sensitive brain area for the pro-erectile effect of oxytocin is the paraventricular nucleus of the hypothalamus. This nucleus and surrounding regions contain the cell bodies of all oxytocinergic neurons projecting to extra-hypothalamic brain areas and the spinal cord. This review shows that oxytocin induces penile erection also when injected in some of these areas (e.g., ventral tegmental area, ventral subiculum of the hippocampus, posteromedial cortical nucleus of the amygdala and thoraco-lumbar spinal cord). Microinjection studies combined with intra-cerebral microdialysis and double immuno-fluorescence studies suggest that oxytocin in these areas activates directly or indirectly (mainly through glutamic acid) mesolimbic dopaminergic neurons. Dopamine released in the nucleus accumbens in turn activates neural pathways leading to the activation of incerto-hypothalamic dopaminergic neurons in the paraventricular nucleus. This activates not only oxytocinergic neurons projecting to the spinal cord and mediating penile erection, but also those projecting to the above extra-hypothalamic areas, modulating directly or indirectly (through glutamic acid) the activity of mesolimbic dopaminergic neurons controlling motivation and reward. Together these neural pathways may constitute a complex hypothetical circuit, which plays a role not only in the consummatory phase of sexual activity (erectile function and copulation), but also in the motivational and rewarding aspects of the anticipatory phase of sexual behaviour. PMID:21050872

  19. Spinal astrocyte gap junction and glutamate transporter expression contributes to a rat model of bortezomib-induced peripheral neuropathy

    PubMed Central

    Robinson, Caleb R.; Dougherty, Patrick M.

    2014-01-01

    There is increasing evidence implicating astrocytes in multiple forms of chronic pain, as well as in the specific context of chemotherapy-induced peripheral neuropathy (CIPN). However, it is still unclear what the exact role of astrocytes may be in the context of CIPN. Findings in oxaliplatin and paclitaxel models have displayed altered expression of astrocytic gap junctions and glutamate transporters as means by which astrocytes may contribute to observed behavioral changes. The current study investigated whether these changes were also generalizable to the bortezomib CIPN. Changes in mechanical sensitivity were verified in bortezomib-treated animals, and these changes were prevented by co-treatment with a glial activation inhibitor (minocycline), a gap junction decoupler (carbenoxolone), and by a glutamate transporter upregulator (ceftriaxone). Immunohistochemistry data at day 30 in bortezomib-treated animals showed increases in expression of GFAP and connexin 43 but decrease in GLAST expression. These changes were prevented by co-treatment with minocycline. Follow-up Western blotting data showed a shift in connexin 43 from a non-phosphorylated state to a phosphorylated state, indicating increased trafficking of expressed connexin 43 to the cell membrane. These data suggest that increases in behavioral sensitivity to cutaneous stimuli may be tied to persistent synaptic glutamate resulting from increased calcium flow between spinal astrocytes. PMID:25446343

  20. Acute pancreatitis decreases the sensitivity of pancreas-projecting dorsal motor nucleus of the vagus neurones to group II metabotropic glutamate receptor agonists in rats

    PubMed Central

    Babic, Tanja; Travagli, R Alberto

    2014-01-01

    Recent studies have shown that pancreatic exocrine secretions (PES) are modulated by dorsal motor nucleus of the vagus (DMV) neurones, whose activity is finely tuned by GABAergic and glutamatergic synaptic inputs. Group II metabotropic glutamate receptors (mGluR) decrease synaptic transmission to pancreas-projecting DMV neurones and increase PES. In the present study, we used a combination of in vivo and in vitro approaches aimed at characterising the effects of caerulein-induced acute pancreatitis (AP) on the vagal neurocircuitry modulating pancreatic functions. In control rats, microinjection of bicuculline into the DMV increased PES, whereas microinjections of kynurenic acid had no effect. Conversely, in AP rats, microinjection of bicuculline had no effect, whereas kynurenic acid decreased PES. DMV microinjections of the group II mGluR agonist APDC and whole cell recordings of excitatory currents in identified pancreas-projecting DMV neurones showed a reduced functional response in AP rats compared to controls. Moreover, these changes persisted up to 3 weeks following the induction of AP. These data demonstrate that AP increases the excitatory input to pancreas-projecting DMV neurones by decreasing the response of excitatory synaptic terminals to group II mGluR agonist. PMID:24445314

  1. Development, validation, and application of a surrogate analyte method for determining N-acetyl-l-aspartyl-l-glutamic acid levels in rat brain, plasma, and cerebrospinal fluid.

    PubMed

    Kinoshita, Kohnosuke; Arai, Kotaro; Kawaura, Kazuaki; Hiyoshi, Tetsuaki; Yamaguchi, Jun-ichi

    2015-10-15

    A bioanalytical strategy for the simple and accurate determination of endogenous substances in a variety of biological matrices using liquid chromatography-tandem mass spectrometry is described. The robust method described here uses two stable isotope-labeled compounds as a surrogate analyte and an internal standard to construct calibration curves with authentic matrices that can be applied to determine N-acetyl-l-aspartyl-l-glutamic acid (NAAG) levels in rat brain, plasma, and cerebrospinal fluid (CSF) using a simple extraction and with a short analysis time of 4min. The validated lower limits of quantification were 1.00nmol/g for brain and 0.0100nmol/mL for plasma and CSF. Using this method, regional differences in NAAG levels in the brain as well as plasma and CSF levels that were much lower than those in the brain were successfully confirmed in treatment-naïve rats. Moreover, after the rats were treated with the intraventricular administration of a NAAG peptidase inhibitor, the NAAG levels increased rapidly and dramatically in the CSF and slightly in the plasma in a time-dependent manner, while the brain levels were not affected. Thus, the procedure described here was easily applied to the determination of NAAG in different matrices in the same manner as that used for xenobiotics, and this method would also be easily applicable to the accurate measurement of endogenous substances in a variety of biological matrices. PMID:26386976

  2. STEREOLOGICAL ESTIMATES OF THE BASAL FOREBRAIN CELL POPULATION IN THE RAT, INCLUDING NEURONS CONTAINING CHOLINE ACETYLTRANSFERASE (ChAT), GLUTAMIC ACID DECARBOXYLASE (GAD) OR PHOSPHATE-ACTIVATED GLUTAMINASE (PAG) AND COLOCALIZING VESICULAR GLUTAMATE TRANSPORTERS (VGluTs)

    PubMed Central

    GRITTI, I.; HENNY, P.; GALLONI, F.; MAINVILLE, L.; MARIOTTI, M.; JONES, B. E.

    2006-01-01

    The basal forebrain (BF) plays an important role in modulating cortical activity and influencing attention, learning and memory. These activities are fulfilled importantly yet not entirely by cholinergic neurons. Noncholinergic neurons also contribute and are comprised by GABAergic neurons and other possibly glutamatergic neurons. The aim of the present study was to estimate the total number of cells in the BF of the rat and the proportions of that total represented by cholinergic, GABAergic and glutamatergic neurons. For this purpose, cells were counted using unbiased stereological methods within the medial septum, diagonal band, magnocellular preoptic nucleus, substantia innominata and globus pallidus in sections stained for Nissl substance and/or the neurotransmitter enzymes, choline acetyltransferase (ChAT), glutamic acid decarboxylase (GAD) or phosphate-activated glutaminase (PAG). In Nissl-stained sections, the total number of neurons in the BF was estimated as ~355,000 and the numbers of ChAT-immuno-positive (+) as ~22,000, GAD+ ~119,000 and PAG+ ~316,000, corresponding to ~5%, ~35% and ~90% of the total. Thus, of the large population of BF neurons, only a small proportion has the capacity to synthesize acetylcholine (ACh), one third to synthesize GABA and the vast majority to synthesize glutamate (Glu). Moreover, through the presence of PAG, a proportion of ACh- and GABA-synthesizing neurons also have the capacity to synthesize Glu. In sections dual fluorescent immunostained for vesicular transporters, VGluT3 and not VGluT2 was present in the cell bodies of most PAG+ and ChAT+ and half the GAD+ cells. Given previous results showing that VGluT2 and not VGluT3 was present in BF axon terminals and not colocalized with VAChT or VGAT, we conclude that the BF cell population influences cortical and subcortical regions through neurons which release ACh, GABA or Glu from their terminals but which in part can also synthesize and release Glu from their soma or

  3. Distribution of the group II metabotropic glutamate receptors (mGluR2/3) in the enteric nervous system of the rat.

    PubMed

    Larzabal, A; Losada, J; Mateos, J M; Benítez, R; Garmilla, I J; Kuhn, R; Grandes, P; Sarría, R

    1999-12-01

    We used affinity purified antisera specific for group II metabotropic glutamate receptors in combination with a pre-embedding immunocytochemical method for light microscopy to investigate the localization of mGluR2/3 receptors in the enteric nervous system of the rat small intestine. In the submucosal plexuses of the jejunum and ileum, strongly mGluR2/3 immunoreactive cells were distributed between the circular muscular layer and the muscularis mucosa. In addition, oval or rounded immunostained ganglion cells appeared located in the myenteric plexuses of both intestinal regions. Nerve fibers intensely stained were observed extending between adjacent myenteric ganglia. The localization of mGluR2/3 receptors in enteric neurons might have functional implications in the physiology and pathology of the gut. PMID:10624799

  4. [Effect of long-term monosodium glutamate administration on structure and functional state of the stomach and body weight in rats].

    PubMed

    Falalieieva, T M; Kukhars'kyĭ, V M; Berehova, T V

    2010-01-01

    The influence of prolonged administration of monosodium glutamate (MSG) on basal gastric acid secretion, body weight and gastric mucosa in rats was studied. We found that 10-, 20-, 30-days feeding by MSG in doses 15 to 30 mg/kg (equivalent to I and 2 g/person) leads to erosive and ulcerative lesions of the gastric mucosa and an increased secretion of hydrochloric acid and an increased body weight. It is concluded that the stimulating effect of MSG on the basal secretion of hydrochloric acid in the stomach may be implicated in the pathogenesis of a number of acid-dependent diseases. An excessive consumption of MSG can cause a "Chinese Restaurant Syndrome" and gastritis, gastric and duodenal ulcers. Therefore, the maximum dose of MSG should be reconsidered taking into account its influence on the secretory capacity of the stomach. We also conclude that prolonged, excessive and systemic consumption of MSG causes obesity. PMID:20968043

  5. Diphenyl diselenide elicits antidepressant-like activity in rats exposed to monosodium glutamate: A contribution of serotonin uptake and Na(+), K(+)-ATPase activity.

    PubMed

    Quines, Caroline B; Rosa, Suzan G; Velasquez, Daniela; Da Rocha, Juliana T; Neto, José S S; Nogueira, Cristina W

    2016-03-15

    Depression is a disorder with symptoms manifested at the psychological, behavioral and physiological levels. Monosodium glutamate (MSG) is the most widely used additive in the food industry; however, some adverse effects induced by this additive have been demonstrated in experimental animals and humans, including functional and behavioral alterations. The aim of this study was to investigate the possible antidepressant-like effect of diphenyl diselenide (PhSe)2, an organoselenium compound with pharmacological properties already documented, in the depressive-like behavior induced by MSG in rats. Male and female newborn Wistar rats were divided in control and MSG groups, which received, respectively, a daily subcutaneous injection of saline (0.9%) or MSG (4g/kg/day) from the 1st to 5th postnatal day. At 60th day of life, animals received (PhSe)2 (10mg/kg, intragastrically) 25min before spontaneous locomotor and forced swimming tests (FST). The cerebral cortices of rats were removed to determine [(3)H] serotonin (5-HT) uptake and Na(+), K(+)-ATPase activity. A single administration of (PhSe)2 was effective against locomotor hyperactivity caused by MSG in rats. (PhSe)2 treatment protected against the increase in the immobility time and a decrease in the latency for the first episode of immobility in the FST induced by MSG. Furthermore, (PhSe)2 reduced the [(3)H] 5-HT uptake and restored Na(+), K(+)-ATPase activity altered by MSG. In the present study a single administration of (PhSe)2 elicited an antidepressant-like effect and decrease the synaptosomal [(3)H] 5-HT uptake and an increase in the Na(+), K(+)-ATPase activity in MSG-treated rats. PMID:26738966

  6. The anterior pretectal nucleus participates as a relay station in the glutamate-, but not morphine-induced antinociception from the dorsal raphe nucleus in rats.

    PubMed

    Prado, W A; Faganello, F A

    2000-11-01

    The anterior pretectal nucleus (APtN) and the dorsal raphe nucleus (DRN) are involved in descending pathways that control noxious inputs to the spinal cord and participate in the normal physiological response to noxious stimulation. Evidence has also been provided for the involvement of the APtN acting as a relay station through which the DRN partly modulates spinal nociceptive messages. In the present study, the effects of microinjecting glutamate or morphine into the DRN on the latency for the tail withdrawal reflex after noxious heating of the skin were examined in rats in which hyperbaric lidocaine (5%), naloxone (a non-selective opioid antagonist) or methiothepin (a non-selective 5-HT(1) antagonist) was previously microinjected into the APtN. Microinjection of glutamate (38 nmol/0.25 microl) into the DRN evoked strong but short-lasting antinociception that was fully inhibited by the previous administration of lidocaine (0.25 microl), naloxone (2.7 nmol/0.25 microl), or methiothepin (1 nmol/0.25 microl). A smaller dose of methiothepin (0.5 nmol/0.25 microl) significantly reduced the effect of glutamate. Microinjection of morphine (7.5 nmol/0.25 microl) into the DRN evoked strong and long-lasting antinociception that was not significantly changed by previous microinjection of lidocaine into the APtN. These results confirm that APtN integrity is at least in part necessary for the antinociceptive effects of stimulating the DRN, and that at least opioid and 5-HT1 mechanisms in the APtN participate as neuromodulators in the DRN-APtN connection. The results demonstrate that the antinociceptive effects of stimulating the DRN-APtN path depend on the activation of cell bodies in the DRN that can be excited by the local administration of glutamate, but not morphine. The study also further supports the notion that the DRN is involved in both descending and ascending pain inhibitory systems. PMID:11050372

  7. Glutamate (mGluR-5) gene expression in brain regions of streptozotocin induced diabetic rats as a function of age: role in regulation of calcium release from the pancreatic islets in vitro

    PubMed Central

    2009-01-01

    Metabotrophic glutamate receptors (mGluRs) modulate cellular activities involved in the processes of differentiation and degeneration. In this study, we have analysed the expression pattern of group-I metabotropic glutamate receptor (mGlu-5) in cerebral cortex, corpus striatum, brainstem and hippocampus of streptozotocin induced and insulin treated diabetic rats (D+I) as a function of age. Also, the functional role of glutamate receptors in intra cellular calcium release from the pancreatic islets was studied in vitro. The gene expression studies showed that mGlu-5 mRNA in the cerebral cortex increased siginficantly in 7 weeks old diabetic rats whereas decreased expression was observed in brainstem, corpus striatum and hippocampus when compared to control. 90 weeks old diabetic rats showed decreased expression in cerebral cortex, corpus striatum and hippocampus whereas in brainstem the expression increased significantly compared to their respective controls. In 7 weeks old D+I group, mGlu-5 mRNA expression was significantly decreased in cerebral cortex and corpus striatum whereas the expression increased significantly in brainstem and hippocampus. 90 weeks old D+I group showed an increased expression in cerebral cortex, while it was decreased significantly in corpus striatum, brainstem and hippocampus compared to their respective controls. In vitro studies showed that glutamate at lower concentration (10-7 M) stimulated calcium release from the pancreatic islets. Our results suggest that mGlu-5 receptors have differential expression in brain regions of diabetes and D+I groups as a function of age. This will have clinical significance in management of degeneration in brain function and memory enhancement through glutamate receptors. Also, the regulatory role of glutamate receptors in calcium release has immense therapeutic application in insulin secretion and function. PMID:19903331

  8. Selective blockade of mGlu5 metabotropic glutamate receptors is protective against hepatic mitochondrial dysfunction in 6-OHDA lesioned Parkinsonian rats.

    PubMed

    Ferrigno, Andrea; Vairetti, Mariapia; Ambrosi, Giulia; Rizzo, Vittoria; Richelmi, Plinio; Blandini, Fabio; Fuzzati-Armentero, Marie-Therese

    2015-06-01

    Non-motor symptoms including those involving the splanchnic district are present in Parkinson's disease (PD). The authors previously reported that PD-like rats, bearing a lesion of the nigrostriatal pathway induced by the injection of 6-hydroxydopamine (6-OHDA), have impaired hepatic mitochondrial function. Glutamate intervenes at multiple levels in PD and liver pathophysiologies. The metabotropic glutamate receptor 5 (mGluR5) is abundantly expressed in brain and liver and may represent a pharmacological target for PD therapy. This study investigated whether and how chronic treatment with 2-methyl-6-(phenylethynyl)-pyridine (MPEP), a well-characterized mGluR5 antagonist, may influence hepatic function with regard to neuronal cell loss in PD-like rats. Chronic treatment with MPEP was started immediately (Early) or 4 weeks after (Delayed) intrastriatal injection of 6-OHDA and lasted 4 weeks. Early MPEP treatment significantly prevented the decrease in adenosine triphosphate (ATP) production/content and counteracted increased reactive oxygen species (ROS) formation in isolated hepatic mitochondria of PD-like animals. Early MPEP administration also reduced the toxin-induced neurodegenerative process; improved survival of nigral dopaminergic neurons correlated with enhanced mitochondrial ATP content and production. ATP content/production, in turn, negatively correlated with ROS formation suggesting that the MPEP-dependent improvement in hepatic function positively influenced neuronal cell survival. Delayed MPEP treatment had no effect on hepatic mitochondrial function and neuronal cell loss. Antagonizing mGluR5 may synergistically act against neuronal cell loss and PD-related hepatic mitochondrial alterations and may represent an interesting alternative to non-dopaminergic therapeutic strategies for the treatment of PD. PMID:25904005

  9. Prenatal valproate treatment produces autistic-like behavior and increases metabotropic glutamate receptor 1A-immunoreactivity in the hippocampus of juvenile rats.

    PubMed

    Peralta, Francisco; Fuentealba, Constanza; Fiedler, Jenny; Aliaga, Esteban

    2016-09-01

    Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental disorder characterized by deficits in social communication and social interaction, and repetitive and stereotypical patterns of behavior. Previously, a common physiopathological pathway, involving the control of synaptic protein synthesis, was proposed as a convergence point in ASD. In particular, a role for local mRNA translation activated by class I metabotropic glutamate receptor type 5 (mGluR5) was suggested in genetic syndromes with autistic signs and in the prenatal exposition to the valproate model of autism. However, the role of the other members of class I metabotropic glutamate receptors, including mGluR1, has been poorly studied. The present study analyzed the immunoreactivity for mGluR1a in the hippocampus of rats prenatally treated with valproate. Pregnant dams (embryonic day 12.5) were injected with valproate (450 mg/kg) and subsequently, the behavior and mGluR1a were evaluated at postnatal day 30. Experimental rats exhibited social deficit, repetitive conduct and anxious behaviors compared with that of the control animals. Additionally, the present study observed an increased level of mGluR1a-immunoreactivity in the hilus of dentate gyrus and in the CA1 alveus region of the hippocampus. These results suggested an over‑functioning of mGluR1a signaling in the hippocampus, induced in the valproate model of autism, which may serve a role in cognitive and behavioral signs of ASD. PMID:27430241

  10. Sub-chronic concomitant ingestion of L-arginine and monosodium glutamate improves feed efficiency, lipid metabolism and antioxidant capacity in male Wistar rats.

    PubMed

    Egbuonu, Anthony C Cemaluk

    2012-03-15

    The use of L-arginine (ARG) is common in supplements, whereas, Monosodium Glutamate (MSG) is widely used as flavor enhancing food additive. Thus, ARG and MSG may be present together in human diets, warranting this study aimed at investigating the effect of concomitant ingestion of ARG and MSG on some biochemical indices in male rats. Twelve male albino rats were grouped into three (n = 4) and concomitantly exposed to 0:0, 20:5 and 60:15 mg kg(-1) of ARG:MSG. Exposure was peroral and every twenty four h for 28 days. ARG plus MSG treatment caused a significant (p < or = 0.05) increase in Feed Efficiency (FE) (Low dose: 5.23 +/- 22%; High dose: 5.60 +/- 11%), whereas, it decreased (p < or = 0.05) the serum Total Cholesterol (T-Chol) (low dose: 80.83 +/- 0.11 mg/100 mL, high dose: 92.55 +/- 0.14 mg/100 mL), triacylglycerol (TAG) (low dose: 179.91 +/- 0.09 mg/100 mL, high dose: 119.77 +/- 0.32 mg/100 mL) and malondialdehyde (MDA) (low dose: 5.00 +/- 0.07 mg/100 mL, high dose: 24.36 +/- 0.10 mg/100 mL) concentrations of the rats in a dose dependent manner. However, (at the high dose) the increase in Body Weight (BW) (0.08 +/- 0.07 kg), Feed Intake (FI) (0.40 +/- 0.03 kg) and Water Intake (WI) (0.65 +/- 0.18 L) induced by ARG plus MSG exposure was not significant (p < or = 0.05), suggesting non treatment related effect on these routine parameters. However, exposure to ARG plus MSG may significantly improve feed efficiency, lipid metabolism and antioxidant capacity in the male rats. PMID:24175428

  11. Elevated intracranial dopamine impairs the glutamate-nitric oxide-cyclic guanosine monophosphate pathway in cortical astrocytes in rats with minimal hepatic encephalopathy

    PubMed Central

    DING, SAIDAN; HUANG, WEILONG; YE, YIRU; YANG, JIANJING; HU, JIANGNAN; WANG, XIAOBIN; LIU, LEPING; LU, QIN; LIN, YUANSHAO

    2014-01-01

    In a previous study by our group memory impairment in rats with minimal hepatic encephalopathy (MHE) was associated with the inhibition of the glutamate-nitric oxide-cyclic guanosine monophosphate (Glu-NO-cGMP) pathway due to elevated dopamine (DA). However, the effects of DA on the Glu-NO-cGMP pathway localized in primary cortical astrocytes (PCAs) had not been elucidated in rats with MHE. In the present study, it was identified that when the levels of DA in the cerebral cortex of rats with MHE and high-dose DA (3 mg/kg)-treated rats were increased, the co-localization of N-methyl-d-aspartate receptors subunit 1 (NMDAR1), calmodulin (CaM), nitric oxide synthase (nNOS), soluble guanylyl cyclase (sGC) and cyclic guanine monophosphate (cGMP) with the glial fibrillary acidic protein (GFAP), a marker protein of astrocytes, all significantly decreased, in both the MHE and high-dose DA-treated rats (P<0.01). Furthermore, NMDA-induced augmentation of the expression of NMDAR1, CaM, nNOS, sGC and cGMP localized in PCAs was decreased in MHE and DA-treated rats, as compared with the controls. Chronic exposure of cultured cerebral cortex PCAs to DA treatment induced a dose-dependent decrease in the concentration of intracellular calcium, nitrites and nitrates, the formation of cGMP and the expression of NMDAR1, CaM, nNOS and sGC/cGMP. High doses of DA (50 μM) significantly reduced NMDA-induced augmentation of the formation of cGMP and the contents of NMDAR1, CaM, nNOS, sGC and cGMP (P<0.01). These results suggest that the suppression of DA on the Glu-NO-cGMP pathway localized in PCAs contributes to memory impairment in rats with MHE. PMID:25059564

  12. Effect of the umami peptides on the ligand binding and function of rat mGlu4a receptor might implicate this receptor in the monosodium glutamate taste transduction

    PubMed Central

    Monastyrskaia, Katherine; Lundstrom, Kenneth; Plahl, Doris; Acuna, Gonzalo; Schweitzer, Christophe; Malherbe, Pari; Mutel, Vincent

    1999-01-01

    The effect of several metabotropic ligands and di- or tripeptides were tested on the binding of [3H]-L(+)-2-amino-4-phosphonobutyric acid ([3H]-L-AP4) on rat mGlu4 receptor. For selected compounds, the functional activity was determined on this receptor using the guanosine-5′[γ-35S]-thiotriphosphate [γ-35S]-GTP binding assay.Using the scintillation proximity assay, [3H]-L-AP4 saturation analysis gave binding parameters KD and Bmax values of 150 nM and 9.3 pmoles mg−1 protein, respectively. The specific binding was inhibited concentration-dependently by several mGlu receptor ligands, and their rank order of affinity was established.Several peptides inhibited the [3H]-L-AP4 binding with the following rank order of potency: glutamate-glutamate>glutamate-glutamate-leucine=aspartate - glutamate>>glutamate - glutamate-aspartate>lactoyl-glutamate>>aspartate-aspartate. Aspartate-phenylalanine-methyl ester (aspartame) was inactive up to 1 mM and guanosine-5′-monophosphate and inosine-5′-monophosphate were inactive up to 100 μM.The [γ-35S]-GTP binding functional assay was used to determine the agonist activities of the different compounds. For the rat mGlu4 agonists, L-AP4 and L-glutamate, the correlation between their occupancy and activation of the receptor was close to one. The peptides, Glu-Glu, Asp-Glu and Glu-Glu-Asp failed to stimulate the [γ-35S]-GTP binding at receptor occupancy greater than 80% and Glu-Glu-Leu appeared to be a weak partial agonist. These peptides did not elicit a clear dose-dependent umami perception. However, Glu-lac showed a good correlation between its potency to stimulate the [γ-35S]-GTP binding and its affinity for displacement of [3H]-L-AP4 binding. These data are in agreement with the peptide taste assessment in human subjects, which showed that the acid derivatives of glutamate had characteristics similar to umami. PMID:10556940

  13. Developmental regulation of N-methyl-D-aspartate- and kainate-type glutamate receptor expression in the rat spinal cord

    NASA Technical Reports Server (NTRS)

    Stegenga, S. L.; Kalb, R. G.

    2001-01-01

    Spinal motor neurons undergo experience-dependent development during a critical period in early postnatal life. It has been suggested that the repertoire of glutamate receptor subunits differs between young and mature motor neurons and contributes to this activity-dependent development. In the present study we examined the expression patterns of N-methyl-D-aspartate- and kainate-type glutamate receptor subunits during the postnatal maturation of the spinal cord. Young motor neurons express much higher levels of the N-methyl-D-aspartate receptor subunit NR1 than do adult motor neurons. Although there are eight potential splice variants of NR1, only a subgroup is expressed by motor neurons. With respect to NR2 receptor subunits, young motor neurons express NR2A and C, while adult motor neurons express only NR2A. Young motor neurons express kainate receptor subunits GluR5, 6 and KA2 but we are unable to detect these or any other kainate receptor subunits in the adult spinal cord. Other spinal cord regions display a distinct pattern of developmental regulation of N-methyl-D-aspartate and kainate receptor subunit expression in comparison to motor neurons. Our findings indicate a precise spatio-temporal regulation of individual subunit expression in the developing spinal cord. Specific combinations of subunits in developing neurons influence their excitable properties and could participate in the emergence of adult neuronal form and function.

  14. Lycopene modulates cholinergic dysfunction, Bcl-2/Bax balance, and antioxidant enzymes gene transcripts in monosodium glutamate (E621) induced neurotoxicity in a rat model.

    PubMed

    Sadek, Kadry; Abouzed, Tarek; Nasr, Sherif

    2016-04-01

    The effect of monosodium glutamate (MSG) on brain tissue and the relative ability of lycopene to avert these neurotoxic effects were investigated. Thirty-two male Wistar rats were distributed into 4 groups: group I, untreated (placebo); group II, injected with MSG (5 mg·kg(-1)) s.c.; group III, gastrogavaged with lycopene (10 mg·kg(-1)) p.o.; and group IV received MSG with lycopene with the same mentioned doses for 30 days. The results showed that MSG induced elevation in lipid peroxidation marker and perturbation in the antioxidant homeostasis and increased the levels of brain and serum cholinesterase (ChE), total creatine phosphokinase (CPK), creatine phosphokinase isoenzymes BB (CPK-BB), and lactate dehydrogenase (LDH). Glutathione S-transferase (GST), superoxide dismutase (SOD), and catalase (CAT) activities and gene expression were increased and glutathione content was reduced in the MSG-challenged rats, and these effects were ameliorated by lycopene. Furthermore, MSG induced apoptosis in brain tissues reflected in upregulation of pro-apoptotic Bax while lycopene upregulated the anti-apoptotic Bcl-2. Our results indicate that lycopene appears to be highly effective in relieving the toxic effects of MSG by inhibiting lipid peroxidation and inducing modifications in the activity of cholinesterase and antioxidant pathways. Interestingly, lycopene protects brain tissue by inhibiting apoptosis signaling induced by MSG. PMID:26900785

  15. Hypoxic-ischemic injury in the neonatal rat brain: effects of pre- and post-treatment with the glutamate release inhibitor BW1003C87.

    PubMed

    Gilland, E; Puka-Sundvall, M; Andiné, P; Bona, E; Hagberg, H

    1994-11-18

    In a model of perinatal hypoxia-ischemia (HI) we examined the neuroprotective efficacy of pre- and post-treatment with the glutamate release inhibitor BW1003C87 [5-(2,3,5-trichlorophenyl)-2,4-diamino-pyrimidine). Ipsilateral brain damage developed in 99% of rat pups subjected to HI (unilateral common carotid artery ligation and 100 min of 7.7% oxygen exposure) with a 26 +/- 16% (mean +/- S.D.) weight deficit of the damaged hemisphere 2 weeks after the insult. Pre-treatment with BW1003C87 (10 mg/kg intraperitoneally) reduced the brain damage by 46% (P < 0.05). A higher dose (20 mg/kg) of pre-treatment was not tolerated. Administration of BW1003C87 did not affect the rectal temperature of the rats. Post-treatment with BW1003C87 (10-30 mg/kg) offered no neuroprotection in this model. In conclusion, there was a neuroprotective effect from pre- but not post-treatment with BW1003C87 in this model, supporting the concept that intra-ischemic excitatory amino acid release is important for development of brain damage. The lack of post-treatment effect indicates that BW1003C87 did not attenuate deleterious EAA cycling during reflow in the neonatal brain. PMID:7697873

  16. Involvement of subtype 1 metabotropic glutamate receptors in apoptosis and caspase-7 over-expression in spinal cord of neuropathic rats

    PubMed Central

    Siniscalco, Dario; Giordano, Catia; Fuccio, Carlo; Luongo, Livio; Ferraraccio, Franca; Rossi, Francesca; de Novellis, Vito; Roth, Kevin A.; Maione, Sabatino

    2008-01-01

    The effect of the non-selective, 1-aminoindan-1,5-dicarboxylic acid (AIDA), and selective (3,4-dihydro-2H-pyrano[2,3-b]quinolin-7-yl)-(cis-4- methoxycyclohexyl) methanone (JNJ16259685), metabotropic glutamate subtype 1 (mGlu1) receptor antagonists, on rat sciatic nerve chronic constrictive injury (CCI)- induced hyperalgesia, allodynia, spinal dorsal horn apoptosis, and gliosis was examined at 3 and 7 days post-injury. RT-PCR analysis showed increased expression of bax, apoptotic protease-activating factor-1 (apaf-1), nestin, GFAP, and caspase-7 mRNA in the dorsal horn spinal cord by 3 days post-CCI. At 7 days post-CCI, only over-expression of bcl-2, nestin and GFAP mRNA was observed. Administration of AIDA reduced thermal hyperalgesia and mechanical allodynia at 3 and 7 days post-CCI; administration of JNJ16259685 reduced thermal hyperalgesia at 3 and 7 days post-CCI, but not mechanical allodynia. AIDA decreased the mRNA levels of bax, apaf-1, GFAP and caspase-7 genes. JNJ16259685 increased the mRNA levels of bcl- 2 and GFAP gene, and decreased APAF-1 and caspases-7 genes. Inhibiting mGlu1 receptors also reduced TUNEL-positive profiles and immunohistochemical reactivity for caspase-7. We report here that despite inhibiting CCI-induced over-expression of pro-apoptotic genes in the spinal cord dorsal horn, the selective mGlu1 receptor antagonist JNJ16259685 exerted only a slight and transient allodynic effect. Moreover, JNJ16259685, but not the non-selective AIDA, increased astrogliosis which may account for its decreased analgesic efficacy. This study provides evidence that the contemporary and partial blockade of group I and likely ionotropic glutamate receptors may be a more suitable therapy than selective blockade of mGlu1 subtype receptors condition to decrease neuropathic pain symptoms. PMID:18325779

  17. EXPRESSION OF GROUP I METABOTROPIC GLUTAMATE RECEPTORS ON PHENOTYPICALLY DIFFERENT CELLS WITHIN THE NUCLEUS OF THE SOLITARY TRACT IN THE RAT

    PubMed Central

    AUSTGEN, J. R.; FONG, A. Y.; FOLEY, C. M.; MUELLER, P. J.; KLINE, D. D.; HEESCH, C. M.; HASSER, E. M.

    2010-01-01

    Group I metabotropic glutamate receptors (mGluRs) are G-coupled receptors that modulate synaptic activity. Previous studies have shown that Group I mGluRs are present in the nucleus of the solitary tract (NTS), in which many visceral afferents terminate. Microinjection of selective Group I mGluR agonists into the NTS results in a depressor response and decrease in sympathetic nerve activity. There is, however, little evidence detailing which phenotypes of neurons within the NTS express Group I mGluRs. In brainstem slices, we performed immunohistochemical localization of Group I mGluRs and either glutamic acid decarboxylase 67 kDa isoform (GAD67), neuronal nitric oxide synthase (nNOS) or tyrosine hydroxylase (TH). Fluoro-Gold (FG, 2%; 15 nl) was microinjected in the caudal ventrolateral medulla (CVLM) of the rat to retrogradely label NTS neurons that project to CVLM. Group I mGluRs were distributed throughout the rostral-caudal extent of the NTS and were found within most NTS subregions. The relative percentages of Group I mGluR expressing neurons colabeled with the different markers were FG (6.9±0.7) nNOS (5.6±0.9), TH (3.9±1.0), and GAD67 (3.1±1.4). The percentage of FG containing cells colabeled with Group I mGluR (13.6±2.0) was greater than the percent colabeled with GAD67 (3.1±0.5), nNOS (4.7±0.5), and TH (0.1±0.08). Cells triple labeled for FG, nNOS, and Group I mGluRs were identified in the NTS. Thus, these data provide an anatomical substrate by which Group I mGluRs could modulate activity of CVLM projecting neurons in the NTS. PMID:19013221

  18. An Analog of Thyrotropin-Releasing Hormone (TRH) is Neuroprotective Against Glutamate-Induced Toxicity In Fetal Rat Hippocampal Neurons In Vitro

    PubMed Central

    Veronesi, Michael C.; Yard, Michael; Jackson, James; Lahiri, Debomoy K.; Kubek, Michael J.

    2007-01-01

    TRH has been found to be efficacious in treating certain neurodegenerative disorders such as epilepsy, Alzheimer’s disease, neurotrauma and depression, however, its mechanism of action is poorly understood. Since Glutamate (Glu) toxicity has been implicated in these disorders, we utilized primary enriched cultures of rat fetal (E 17) hippocampal neurons to test the hypothesis that an analog of TRH, 3-Methyl-Histidine TRH (3Me-H TRH), given concurrently with Glu would protect such neurons against cell damage and cell death. Cell viability was assessed via Trypan Blue exclusion cell counts and neuronal damage was determined by assaying lactic acid dehydrogenase (LDH) released in the conditioned media. Fetal hippocampal neurons were cultured in neurobasal media for 7 days. On day 7, neurons (106/well) were treated with: control media, 10 μM 3Me-H TRH, 500 μM Glu, or 500 μM Glu with either 10, 1, 0.1, 0.01 or 0.001 μM 3Me-H TRH. Both media and neurons were harvested 16 hr after treatment. Prolonged exposure to 10 μM 3Me-H TRH was not toxic to the cells, whereas, neurons exposed to 500 μM Glu resulted in maximal cell death. Notably, 10, 1 and 0.1 μM 3Me-H TRH, when co-treated with 500 μM Glu protected fetal neurons against cell death in a concentration-dependent manner. These results provide support for an important neuroprotective effect of TRH/analogs against glutamate toxicity in primary hippocampal neuronal culture, and implicate a potentially beneficial role of TRH/analogs in neurodegenerative diseases. PMID:17125753

  19. Ginkgo biloba Extract (EGb 761®) Inhibits Glutamate-induced Up-regulation of Tissue Plasminogen Activator Through Inhibition of c-Fos Translocation in Rat Primary Cortical Neurons.

    PubMed

    Cho, Kyu Suk; Lee, Ian Myungwon; Sim, Seobo; Lee, Eun Joo; Gonzales, Edson Luck; Ryu, Jong Hoon; Cheong, Jae Hoon; Shin, Chan Young; Kwon, Kyoung Ja; Han, Seol-Heui

    2016-01-01

    EGb 761(®) , a standardized extract of Ginkgo biloba leaves, has antioxidant and antiinflammatory properties in experimental models of neurodegenerative disorders such as stroke and Alzheimer's disease. Tissue plasminogen activator (tPA) acts a neuromodulator and plays a crucial role in the manifestation of neurotoxicity leading to exaggerated neuronal cell death in neurological insult conditions. In this study, we investigated the effects of EGb 761 on the basal and glutamate-induced activity and expression of tPA in rat primary cortical neurons. Under basal condition, EGb 761 inhibited both secreted and cellular tPA activities, without altering tPA mRNA level, as modulated by the activation of p38. Compared with basal condition, EGb 761 inhibited the glutamate-induced up-regulation of tPA mRNA resulting in the normalization of overt tPA activity and expression. c-Fos is a component of AP-1, which plays a critical role in the modulation of tPA expression. Interestingly, EGb 761 inhibited c-Fos nuclear translocation without affecting c-Fos expression in glutamate-induced rat primary cortical neurons. These results demonstrated that EGb 761 can modulate tPA activity under basal and glutamate-stimulated conditions by both translational and transcriptional mechanisms. Thus, EGb 761 could be a potential and effective therapeutic strategy in tPA-excessive neurotoxic conditions. PMID:26478151

  20. Increased extracellular glutamate evoked by 1-methyl-4-phenylpyridinium [MPP(+)] in the rat striatum is not essential for dopaminergic neurotoxicity and is not derived from released glutathione.

    PubMed

    Foster, S B; Tang, H; Miller, K E; Dryhurst, G

    2005-01-01

    A number of studies have implicated the interactions of the excitatory amino acid L-glutamate (Glu) with its ionotropic and metabotropic receptors as important components of the mechanism underlying the dopaminergic neurotoxicity of 1-methyl-4-phenylpyridinium [MPP(+)]. Furthermore, microdialysis experiments have demonstrated that perfusion of relatively high concentrations of MPP(+) into the rat striatum evoke a delayed, massive release of Glu. Interestingly, perfusion of MPP(+) also mediates a similar release of glutathione (GSH). Together, these observations raise the possibility that the rise of extracellular Glu mediated by MPP(+) may be the result of hydrolysis of released GSH by gamma-glutamyl transpeptidase (gamma-GT). In the present investigation it is demonstrated that perfusions of solutions of 0.7 and 1.3 mM MPP(+) dissolved in artificial cerebrospinal fluid into the rat striatum evoke neurotoxic damage to dopaminergic terminals, assessed by both a two-day test/challenge procedure and tyrosine hydroxylase immunoreactivity, but without the release of Glu. Perfusions of 2.5 mM MPP(+) cause more extensive dopaminergic neurotoxicity and a dose-dependent release of Glu. However, neither this release of Glu nor MPP(+)-induced dopaminergic neurotoxicity are blocked by the irreversible gamma-GT inhibitor acivicin. Together, these observations indicate that a rise of extracellular levels of Glu is not essential for the dopaminergic neurotoxicity of MPP(+). Furthermore, the rise of extracellular Glu caused by perfusion of 2.5 mM MPP(+) is not the result of the gamma-GT-mediated hydrolysis of released GSH. It is possible that the rise of extracellular levels of Glu, L-aspartate, L-glycine and L-taurine evoked by perfusions of 2.5 mM MPP(+) into the rat striatum may reflect, at least in part, the release of these amino acids from astrocytes. PMID:16179262

  1. Peripheral and spinal antihyperalgesic activity of SIB-1757, a metabotropic glutamate receptor (mGLUR(5)) antagonist, in experimental neuropathic pain in rats.

    PubMed

    Dogrul, A; Ossipov, M H; Lai, J; Malan, T P; Porreca, F

    2000-10-01

    Recent studies suggest a role of Group 1 metabotropic glutamate receptors in mediating the development of spinal hypersensitivity in some pain states. Here, the possible role of mGluR(5) receptors in experimental neuropathic pain elicited by ligation of spinal nerves (L(5)/L(6) spinal nerve ligation, SNL) was explored with SIB-1757, a selective mGluR(5) antagonist. SNL-induced tactile allodynia was detected by decreased paw withdrawal thresholds to probing with von Frey filaments and thermal hyperalgesia by decreased paw withdrawal latencies to radiant heat applied to the plantar aspect of the hindpaw. SIB-1757 was given by either intrathecal (i.th.), subcutaneous (s.c.) or intraplantar (i.pl.) injection. In SNL rats, i.th. SIB-1757 produced a partial reversal of tactile allodynia with a shallow dose-response curve ranging over three-orders of magnitude; SIB-1757 was inactive against allodynia when given systemically. SIB-1757 produced full reversal of thermal hyperalgesia in SNL rats following administration either spinally or locally to the injured paw; administration to the contralateral paw had no effect. SIB-1757 did not produce antinociception in either the SNL or sham-operated rats by any route. These data suggest a significant modulation of thermal hyperalgesia by mGluR(5) antagonists, consistent with reports that this receptor may be associated with afferent C-fibers. The less impressive effect seen on tactile allodynia, likely to be mediated by large fiber input, suggests that the observed modulation may be related to blockade of mGluR(5)-mediated spinal sensitization. These results do not support the involvement of these receptors in modulation of acute nociception but suggest the possibility of a role for Group I mGluRs in the mediation of aspects of neuropathic pain which may be associated with C-fiber inputs. PMID:10998562

  2. Glutamate Transporter-Mediated Glutamate Secretion in the Mammalian Pineal Gland

    PubMed Central

    Kim, Mean-Hwan; Uehara, Shunsuke; Muroyama, Akiko; Hille, Bertil; Moriyama, Yoshinori; Koh, Duk-Su

    2008-01-01

    Glutamate transporters are expressed throughout the central nervous system where their major role is to clear released glutamate from presynaptic terminals. Here we report a novel function of the transporter in rat pinealocytes. This electrogenic transporter conducted inward current in response to L-glutamate and L- or D-aspartate and depolarized the membrane in patch clamp experiments. Ca2+ imaging demonstrated that the transporter-mediated depolarization induced a significant Ca2+ influx through voltage-gated Ca2+ channels. The Ca2+ rise finally evoked glutamate exocytosis as detected by carbon-fiber amperometry and by high-performance liquid chromatography. In pineal slices with densely packed pinealocytes, glutamate released from the cells effectively activated glutamate transporters in neighboring cells. The Ca2+ signal generated by KCl depolarization or acetylcholine propagated through several cell layers by virtue of the regenerative ‘glutamate-induced glutamate release’. Therefore we suggest that glutamate transporters mediate synchronized elevation of L-glutamate and thereby efficiently down-regulate melatonin secretion via previously identified inhibitory metabotropic glutamate receptors in the pineal gland. PMID:18945893

  3. Effects of sufentanil on the release and metabolism of dopamine and ascorbic acid and glutamate release in the striatum of freely moving rats.

    PubMed

    Serra, Pier Andrea; Susini, Giuseppe; Rocchitta, Gaia; Migheli, Rossana; Dessanti, Giuseppina; Miele, Egidio; Desole, Maria Speranza; Miele, Maddalena

    2003-06-19

    The effects of either intraperitoneally (i.p.) or intrastriatally administered sufentanil on the release and metabolism of dopamine (DA) in the rat striatum were evaluated using in vivo microdialysis. Dialysate concentrations of DA and its acidic metabolites dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) were increased following i.p. administration of either clinical anesthetic (20 microg/kg) or clinical analgesic (1 microg/kg) sufentanil doses. In addition, sufentanil also increased uric acid concentrations. In contrast, dialysate ascorbic acid and glutamate concentrations were unaffected. Intrastriatal infusion of sufentanil (250 nM) induced only a short lasting decrease in dialysate DA. Subcutaneous naloxone (1.0 mg/kg) abolished sufentanil-induced increases in dialysate DA, DOPAC+HVA and uric acid; however, naloxone (0.1 mM) failed to affect these increases when infused intrastriatally. These results demonstrate that sufentanil, at clinical doses, increases striatal DA release and oxidative metabolism of both DA and xanthine acting at extrastriatal sites with a mu-receptor-mediated mechanism. PMID:12781909

  4. Effects of prenatal exposure to 2,4-D/2,4,5-T mixture on postnatal changes in rat brain glutamate, GABA protein, and nucleic acid levels

    SciTech Connect

    Mohammad, F.K.; Omer, V.E.V.

    1988-02-01

    The opportunity of maternal exposure to various chemicals in the work place and the general environments have increased, and the fetus and neonate may be at greater risk than the adult. However, the embryotoxic and teratogenic effects of the chlorinated phenoxy herbicides 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), the main chemicals in Agent Orange, are well documented only in laboratory animals. The brain of the developing fetus is vulnerable to the toxic effects of the phenoxy herbicides which readily cross the placental barrier and distribute into fetal tissues, including brain. Although the neurochemical basis for the behavioral teratogenicity of the phenoxy herbicides is not know, it was recently reported that non-teratogenic doses of a 1:1 mixture of 2,4-D and 2,4,5-T delayed the ontogeny of dopamine and serotonin in the brain of the developing rate. This communication provides further descriptive information about the ontogeny of rat brain nucleic acid, protein, glutamate and ..gamma..-aminobutyrate (GABA) following in utero exposure to non-teratogenic levels of a 1:1 mixture of 2,4-D/2,4,5-T.

  5. Orally Active Metabotropic Glutamate Subtype 2 Receptor Positive Allosteric Modulators: Structure-Activity Relationships and Assessment in a Rat Model of Nicotine Dependence

    PubMed Central

    Sidique, Shyama; Dhanya, Raveendra-Panickar; Sheffler, Douglas J.; Nickols, Hilary Highfield; Yang, Li; Dahl, Russell; Mangravita-Novo, Arianna; Smith, Layton H.; D’Souza, Manoranjan S.; Semenova, Svetlana; Conn, P. Jeffrey; Markou, Athina; Cosford, Nicholas D. P.

    2012-01-01

    Compounds that modulate metabotropic glutamate subtype 2 (mGlu2) receptors have the potential to treat several disorders of the central nervous system (CNS) including drug dependence. Herein we describe the synthesis and structure-activity relationship (SAR) studies around a series of mGlu2 receptor positive allosteric modulators (PAMs). The effects of N-substitution (R1) and substitutions on the aryl ring (R2) were identified as key areas for SAR exploration (Figure 3). Investigation of the effects of varying substituents in both the isoindolinone (2) and benzisothiazolone (3) series led to compounds with improved in vitro potency and/or efficacy. In addition, several analogues exhibited promising pharmacokinetic (PK) properties. Furthermore, compound 2 was shown to dose-dependently decrease nicotine self-administration in rats following oral administration. Our data, showing for the first time efficacy of an mGlu2 receptor PAM in this in vivo model, suggest potential utility for the treatment of nicotine dependence in humans. PMID:23009245

  6. Dopamine D2 receptors are involved in the regulation of Fyn and metabotropic glutamate receptor 5 phosphorylation in the rat striatum in vivo.

    PubMed

    Mao, Li-Min; Wang, John Q

    2016-04-01

    Fyn, a major Src family kinase (SFK) member that is densely expressed in striatal neurons, is actively involved in the regulation of cellular and synaptic activities in local neurons. This SFK member is likely regulated by dopamine signaling through a receptor mechanism involving dopamine D2 receptors (D2Rs). This study characterizes the D2R-dependent regulation of Fyn in the rat striatum in vivo. Moreover, we explore whether D2Rs regulate metabotropic glutamate receptor 5 (mGluR5) in its tyrosine phosphorylation and whether the D2R-SFK pathway modulates trafficking of mGluR5. We found that blockade of D2Rs by systemic administration of a D2R antagonist, eticlopride, substantially increased SFK phosphorylation in the striatum. This increase was a transient and reversible event. The eticlopride-induced SFK phosphorylation occurred predominantly in immunopurified Fyn but not in another SFK member, Src. Eticlopride also elevated tyrosine phosphorylation of mGluR5. In parallel, eticlopride enhanced synaptic delivery of active Fyn and mGluR5. Pretreatment with an SFK inhibitor blocked the eticlopride-induced tyrosine phosphorylation and synaptic trafficking of mGluR5. These results indicate that D2Rs inhibit SFK (mainly Fyn) phosphorylation in the striatum. D2Rs also inhibit tyrosine phosphorylation and synaptic recruitment of mGluR5 through a signaling mechanism likely involving Fyn. PMID:26777117

  7. Effects of the metabotropic glutamate receptor 5 positive allosteric modulator CDPPB on rats tested with the paired associates learning task in touchscreen-equipped operant conditioning chambers.

    PubMed

    Lins, Brittney R; Howland, John G

    2016-03-15

    Effective treatments for the cognitive symptoms of schizophrenia are critically needed. Positive allosteric modulation (PAM) of metabotropic glutamate receptor subtype 5 (mGluR5) is one strategy currently under investigation to improve these symptoms. Examining cognition using touchscreen-equipped operant chambers may increase translation between preclinical and clinical research through analogous behavioral testing paradigms in rodents and humans. We used acute CDPPB (1-30mg/kg) treatment to examine the effects of mGluR5 PAM in the touchscreen paired associates learning (PAL) task using well-trained rats with and without co-administration of acute MK-801 (0.15mg/kg). CDPPB had no consistent effects on task performance when administered alone and failed to reverse the MK-801 induced impairments at any of the examined doses. Overall, the disruptive effects of MK-801 on PAL were consistent with previous research but increasing mGluR5 signaling is not beneficial in the PAL task. Future research should test whether administration of CDPPB during PAL acquisition increases performance. PMID:26721467

  8. Diffuse perineuronal nets and modified pyramidal cells immunoreactive for glutamate and the GABA(A) receptor alpha1 subunit form a unique entity in rat cerebral cortex.

    PubMed

    Wegner, Florian; Härtig, Wolfgang; Bringmann, Andreas; Grosche, Jens; Wohlfarth, Kai; Zuschratter, Werner; Brückner, Gert

    2003-12-01

    Perineuronal nets (PNs) consisting of polyanionic chondroitin sulfate proteoglycans (CSPG) and other extracellular matrix components create an exceptional microenvironment around certain types of neurons. In rat neocortex, three types of PNs can be distinguished after staining with Wisteria floribunda agglutinin (WFA) by their different morphological structure: lattice-like PNs associated with subpopulations of nonpyramidal neurons, weakly labeled PNs showing a pyramidal morphology, and diffuse PNs that possess a thick, strongly labeled matrix sheath located mainly in layer VIb above the white matter. The type of neuron surrounded by diffuse nets has not been described so far. This study is focused on the cytochemical and morphological characteristics of neurons associated with diffusely contoured PNs in rat parietal cortex using immunocytochemical staining, intracellular injection, and retrograde tracing methods. Cells surrounded by diffuse PNs were glutamate-immunoreactive in contrast to nonpyramidal, net-associated neurons that showed immunoreactivity for GABA, the calcium-binding protein parvalbumin and the potassium channel subunit Kv3.1b. Both groups of PN-ensheathed cells were mostly immunoreactive for the GABA(A) receptor alpha1 subunit. Lucifer Yellow-injected neurons surrounded by diffuse PNs displayed the morphological properties of modified pyramidal cells with intracortical main axons. Many neurons with diffuse PNs were retrogradely labeled over a long distance after Fluoro-Gold tracer injection in the parietal cortex, but remained unlabeled after intrathalamic injection. We conclude that neurons associated with diffuse PNs are a subpopulation of glutamatergic modified pyramidal cells that could act as excitatory long-range intracortically projecting neurons. PMID:14769362

  9. Involvement of non-NMDA glutamate receptors of the hypothalamic paraventricular nucleus in the cardiovascular response to the microinjection of noradrenaline into the dorsal periaqueductal gray area of rats.

    PubMed

    Pelosi, Gislaine Garcia; Busnardo, Cristiane; Tavares, Rodrigo Fiacadori; Corrêa, Fernando Morgan Aguiar

    2015-03-30

    The dorsal periaqueductal gray area (dPAG) is involved in cardiovascular modulation. In a previous study, we showed that noradrenaline (NA) microinjected into the dPAG caused a vasopressin-mediated pressor response, involving a relay in the hypothalamic paraventricular nucleus (PVN). In the present study, we evaluated the involvement of ionotropic glutamate receptors within the PVN in the cardiovascular response to NA microinjection into the dPAG of unanesthetized rats. Microinjection of the selective NMDA glutamate receptor antagonist LY235959 (2nmol/100nL) unilaterally into the PVN did not affect the cardiovascular response evoked by microinjection of NA (15nmol/50nL) into the dPAG. On the other hand, unilateral PVN pretreatment with the non-NMDA glutamate receptor antagonist NBQX (2nmol/100nL) significantly reduced the pressor and cardiac response caused by microinjection of NA into the dPAG. In addition, bilateral PVN pretreatment with NBQX (2nmol/100nL) blocked the cardiovascular response to NA injected into the dPAG. In conclusion, the present results suggest that bilateral PVN activation of non-NMDA glutamate receptors mediates the vasopressin-related cardiovascular response to the microinjection of NA into the dPAG. PMID:25617821

  10. Effect of Jian-Pi-Zhi-Dong Decoction on striatal glutamate and γ-aminobutyric acid levels detected using microdialysis in a rat model of Tourette syndrome

    PubMed Central

    Zhang, Wen; Wei, Li; Yu, Wenjing; Cui, Xia; Liu, Xiaofang; Wang, Qian; Wang, Sumei

    2016-01-01

    Background Jian-Pi-Zhi-Dong Decoction (JPZDD) is a dedicated treatment of Tourette syndrome (TS). The balance of neurotransmitters in the cortico-striato-pallido-thalamo-cortical network is crucial to the occurrence of TS and related to its severity. This study evaluated the effect of JPZDD on glutamate (Glu) and γ-aminobutyric acid (GABA) and their receptors in a TS rat model. Materials and methods Rats were divided into four groups (n=12 each). TS was induced in three of the groups by injecting them with 3,3′-iminodipropionitrile for 7 consecutive days. Two model groups were treated with tiapride (Tia) or JPZDD, while the control and the remaining model group were gavaged with saline. Behavior was assessed by stereotypic score and autonomic activity. Striatal Glu and GABA contents were detected using microdialysis. Expressions of N-methyl-D-aspartate receptor 1 and GABAA receptor (GABAAR) were observed using Western blot and real-time polymerase chain reaction. Results Tia and JPZDD groups had decreased stereotypy compared with model rats; however, the JPZDD group showed a larger decrease in stereotypy than the Tia group at a 4-week time point. In a spontaneous activity test, the total distance of the JPZDD and Tia groups was significantly decreased compared with the model group. The Glu levels of the model group were higher than the control group and decreased with Tia or JPZDD treatment. The GABA level was higher in the model group than the control group. Expressions of GABAAR protein in the model group were higher than in the control group. Treatment with Tia or JPZDD reduced the expression of GABAAR protein. In the case of the mRNA expression, only Tia reduced the expression of N-methyl-D-aspartate receptor 1, compared with the model group. Conclusion JPZDD could alleviate impairments in behavior and dysfunctional signaling by downregulating GABAAR in the striatum. We suggest that this acts to maintain the balance of Glu and GABA. PMID:27279743

  11. Low expression of Gria1 and Grin1 glutamate receptors in the nucleus accumbens of Spontaneously Hypertensive Rats (SHR).

    PubMed

    Diana, Mariana C; Santoro, Marcos L; Xavier, Gabriela; Santos, Camila Mauricio; Spindola, Leticia N; Moretti, Patrícia N; Ota, Vanessa K; Bressan, Rodrigo A; Abilio, Vanessa C; Belangero, Sintia I

    2015-10-30

    The Spontaneously Hypertensive Rat (SHR) strain is a classical animal model for the study of essential hypertension. Recently, our group suggested that this strain could be a useful animal model for schizophrenia, which is a severe mental illness with involvement of glutamatergic system. The aim of this study is to investigate glutamatergic receptors (Gria1 and Grin1) and glycine transporter (Glyt1) gene expression in the prefrontal cortex (PFC) and nucleus accumbens (NAcc) of SHR animals. The effects in gene expression of a chronic treatment with antipsychotic drugs (risperidone, haloperidol and clozapine) were also analyzed. Animals were treated daily for 30 days, and euthanized for brain tissue collection. The expression pattern was evaluated by Real Time Reverse-Transcriptase (RT) PCR technique. In comparison to control rats, SHR animals present a lower expression of both NMDA (Grin1) and AMPA (Gria1) gene receptors in the NAcc. Antipsychotic treatments were not able to change gene expressions in any of the regions evaluated. These findings provide evidence for the role of glutamatergic changes in schizophrenia-like phenotype of the SHR strain. PMID:26296755

  12. Biochemical Alterations during the Obese-Aging Process in Female and Male Monosodium Glutamate (MSG)-Treated Mice

    PubMed Central

    Hernández-Bautista, René J.; Alarcón-Aguilar, Francisco J.; Escobar-Villanueva, María Del C.; Almanza-Pérez, Julio C.; Merino-Aguilar, Héctor; Konigsberg Fainstein, Mina; López-Diazguerrero, Norma E.

    2014-01-01

    Obesity, from children to the elderly, has increased in the world at an alarming rate over the past three decades, implying long-term detrimental consequences for individual’s health. Obesity and aging are known to be risk factors for metabolic disorder development, insulin resistance and inflammation, but their relationship is not fully understood. Prevention and appropriate therapies for metabolic disorders and physical disabilities in older adults have become a major public health challenge. Hence, the aim of this study was to evaluate inflammation markers, biochemical parameters and glucose homeostasis during the obese-aging process, to understand the relationship between obesity and health span during the lifetime. In order to do this, the monosodium glutamate (MSG) obesity mice model was used, and data were evaluated at 4, 8, 12, 16 and 20 months in both female and male mice. Our results showed that obesity was a major factor contributing to premature alterations in MSG-treated mice metabolism; however, at older ages, obesity effects were attenuated and MSG-mice became more similar to normal mice. At a younger age (four months old), the Lee index, triglycerides, total cholesterol, TNF-α and transaminases levels increased; while adiponectin decreased and glucose tolerance and insulin sensitivity levels were remarkably altered. However, from 16 months old-on, the Lee index and TNF-α levels diminished significantly, while adiponectin increased, and glucose and insulin homeostasis was recovered. In summary, MSG-treated obese mice showed metabolic changes and differential susceptibility by gender throughout life and during the aging process. Understanding metabolic differences between genders during the lifespan will allow the discovery of specific preventive treatment strategies for chronic diseases and functional decline. PMID:24979131

  13. Biochemical alterations during the obese-aging process in female and male monosodium glutamate (MSG)-treated mice.

    PubMed

    Hernández-Bautista, René J; Alarcón-Aguilar, Francisco J; Del C Escobar-Villanueva, María; Almanza-Pérez, Julio C; Merino-Aguilar, Héctor; Fainstein, Mina Konigsberg; López-Diazguerrero, Norma E

    2014-01-01

    Obesity, from children to the elderly, has increased in the world at an alarming rate over the past three decades, implying long-term detrimental consequences for individual's health. Obesity and aging are known to be risk factors for metabolic disorder development, insulin resistance and inflammation, but their relationship is not fully understood. Prevention and appropriate therapies for metabolic disorders and physical disabilities in older adults have become a major public health challenge. Hence, the aim of this study was to evaluate inflammation markers, biochemical parameters and glucose homeostasis during the obese-aging process, to understand the relationship between obesity and health span during the lifetime. In order to do this, the monosodium glutamate (MSG) obesity mice model was used, and data were evaluated at 4, 8, 12, 16 and 20 months in both female and male mice. Our results showed that obesity was a major factor contributing to premature alterations in MSG-treated mice metabolism; however, at older ages, obesity effects were attenuated and MSG-mice became more similar to normal mice. At a younger age (four months old), the Lee index, triglycerides, total cholesterol, TNF-α and transaminases levels increased; while adiponectin decreased and glucose tolerance and insulin sensitivity levels were remarkably altered. However, from 16 months old-on, the Lee index and TNF-α levels diminished significantly, while adiponectin increased, and glucose and insulin homeostasis was recovered. In summary, MSG-treated obese mice showed metabolic changes and differential susceptibility by gender throughout life and during the aging process. Understanding metabolic differences between genders during the lifespan will allow the discovery of specific preventive treatment strategies for chronic diseases and functional decline. PMID:24979131

  14. Impaired adrenergic-mediated plasticity of prefrontal cortical glutamate synapses in rats with developmental disruption of the ventral hippocampus.

    PubMed

    Bhardwaj, Sanjeev K; Tse, Yiu Chung; Ryan, Richard; Wong, Tak Pan; Srivastava, Lalit K

    2014-12-01

    Neonatal ventral hippocampus (nVH) lesion in rats is a useful model to study developmental origins of adult cognitive deficits and certain features of schizophrenia. nVH lesion-induced reorganization of excitatory and inhibitory neurotransmissions within prefrontal cortical (PFC) circuits is widely believed to be responsible for many of the behavioral abnormalities in these animals. Here we provide evidence that development of an aberrant medial PFC (mPFC) α-1 adrenergic receptor (α-1AR) function following neonatal lesion markedly affects glutamatergic synaptic plasticity within PFC microcircuits and contributes to PFC-related behavior abnormalities. Using whole-cell patch-clamp recording, we report that norepinephrine-induced α-1AR-dependent long-term depression (LTD) in a subset of cortico-cortical glutamatergic inputs is strikingly diminished in mPFC slices from nVH-lesioned rats. The LTD impairment occurs in conjunction with completely blunted α-1AR signaling through extracellular signal-regulated kinase 1/2. These α-1AR abnormalities have functional significance in a mPFC-related function, that is, extinction of conditioned fear memory. Post-pubertal animals with nVH lesion show significant resistance to extinction of fear by repeated presentations of the conditioned tone stimulus. mPFC infusion of an α-1AR antagonist (benoxathian) or LTD blocking peptide (Tat-GluR23Y) impaired fear extinction in sham controls, but had no significant effect in the lesioned animals. The data suggest that impaired α-1 adrenergic regulation of cortical glutamatergic synaptic plasticity may be an important mechanism in cognitive dysfunctions reported in neurodevelopmental psychiatric disorders. PMID:24917197

  15. Activation of mGluR7s inhibits cocaine-induced reinstatement of drug-seeking behavior by a nucleus accumbens glutamate-mGluR2/3 mechanism in rats.

    PubMed

    Li, Xia; Li, Jie; Gardner, Eliot L; Xi, Zheng-Xiong

    2010-09-01

    The metabotropic glutamate receptor 7 (mGluR7) has been reported to be involved in cocaine and alcohol self-administration. However, the role of mGluR7 in relapse to drug seeking is unknown. Using a rat relapse model, we found that systemic administration of AMN082, a selective mGluR7 allosteric agonist, dose-dependently inhibits cocaine-induced reinstatement of drug-seeking behavior. Intracranial microinjections of AMN082 into the nucleus accumbens (NAc) or ventral pallidum, but not the dorsal striatum, also inhibited cocaine-primed reinstatement, an effect that was blocked by local co-administration of MMPIP, a selective mGluR7 antagonist. In vivo microdialysis demonstrated that cocaine priming significantly increased extracellular dopamine in the NAc, ventral pallidum and dorsal striatum, while increasing extracellular glutamate in the NAc only. AMN082 alone failed to alter extracellular dopamine, but produced a slow-onset long-lasting increase in extracellular glutamate in the NAc only. Pre-treatment with AMN082 dose-dependently blocked both cocaine-enhanced NAc glutamate and cocaine-induced reinstatement, an effect that was blocked by MMPIP or LY341497 (a selective mGluR2/3 antagonist). These data suggest that mGluR7 activation inhibits cocaine-induced reinstatement of drug-seeking behavior by a glutamate-mGluR2/3 mechanism in the NAc. The present findings support the potential use of mGluR7 agonists for the treatment of cocaine addiction. PMID:20534005

  16. Activation of group III metabotropic glutamate receptors inhibits basal and amphetamine-stimulated dopamine release in rat dorsal striatum: an in vivo microdialysis study.

    PubMed

    Mao, L; Lau, Y S; Wang, J Q

    2000-09-22

    Group III metabotropic glutamate (mGlu) receptors are negatively coupled to adenylate cyclase and are distributed pre-synaptically in the striatum. A behavioral study previously conducted in this laboratory shows that activation of this group of mGlu receptors attenuates acute amphetamine-stimulated motor activity. By administering a group III selective agonist or antagonist via the dialysis probe, the present study employed in vivo microdialysis to evaluate the capacity of the group III selective agents to alter extracellular levels of dopamine in the dorsal striatum of normal and amphetamine-treated rats. It was found that the group III agonist L-2-amino-4-phosphonobutyrate (L-AP4) dose-dependently (1, 10 and 100 microM) reduced basal levels of extracellular dopamine. In contrast, the group III antagonist alpha-methyl-4-phosphonophenylglycine (MPPG) dose-dependently (10, 50 and 250 microM) elevated the basal release of extracellular dopamine. This elevation was antagonized by co-perfusion of L-AP4. Perfusion of 5-microM amphetamine through the dialysis probe increased extracellular dopamine in the dorsal striatum. Co-perfusion of L-AP4 (100 microM) significantly reduced amphetamine-stimulated dopamine levels, whereas co-perfusion of L-AP4 (100 microM) and MPPG (100 microM) did not alter the capacity of amphetamine to elicit dopamine release. The data obtained from this study demonstrate the presence of a tonically active glutamatergic tone on group III mGlu receptors in the dorsal striatum to pre-synaptically regulate basal dopamine release in an inhibitory fashion. Moreover, activation of L-AP4-sensitive group III mGlu receptors can suppress the phasic release of dopamine induced by a dopamine stimulant amphetamine. PMID:10996594

  17. Distinct inhibition of acute cocaine-stimulated motor activity following microinjection of a group III metabotropic glutamate receptor agonist into the dorsal striatum of rats.

    PubMed

    Mao, L; Wang, J Q

    2000-09-01

    Group III metabotropic glutamate receptors (mGluRs) are negatively coupled to adenylate cyclase through G-proteins. Activation of this group of mGluRs shows an inhibition of dopaminergic transmission in the forebrain. To define the role of striatal group III mGluRs in the regulation of basal and dopamine-stimulated motor behavior, the recently developed agonist and antagonist relatively selective for group III mGluRs were utilized to pharmacologically enhance and reduce group III mGluR glutamatergic tone in the dorsal striatum of chronically cannulated rats. Bilateral injections of a group III agonist, L-2-amino-4-phosphonobutyrate (L-AP4), did not alter basal levels of motor activity at three doses surveyed (1, 10, and 100 nmol). Neither did intracaudate injection of a group III antagonist, alpha-methyl-4-phosphonophenylglycine (MPPG), at 10, 30, and 100 nmol. However, pretreatment with L-AP4 (10 and 100 nmol) dose dependently blocked hyperlocomotion induced by acute injection of cocaine (20 mg/kg, i.p.), amphetamine (2.5 mg/kg, i.p.), or apomorphine (1 mg/kg, s.c.). The behavioral activity induced by cocaine was much more sensitive to L-AP4 than that induced by amphetamine and apomorphine. At 100 nmol, L-AP4 completely blocked cocaine effect whereas amphetamine- and apomorphine-stimulated behaviors were blocked only by 28% and 31%, respectively. The blocking effect of L-AP4 on cocaine action was reversed by pretreatment with MPPG. MPPG itself did not modify behavioral responses to cocaine, amphetamine, or apomorphine. These data indicate that the glutamatergic tone on the group III mGluRs is not active in the regulation of basal and acute dopamine-stimulated motor activity. However, enhanced group III mGluR glutamatergic transmission by an exogenous ligand is capable of suppressing behavioral responses to acute exposure of dopamine stimulants. PMID:11113488

  18. NAAG peptidase inhibitor increases dialysate NAAG and reduces glutamate, aspartate and GABA levels in the dorsal hippocampus following fluid percussion injury in the rat.

    PubMed

    Zhong, Chunlong; Zhao, Xueren; Van, Ken C; Bzdega, Tomasz; Smyth, Aoife; Zhou, Jia; Kozikowski, Alan P; Jiang, Jiyao; O'Connor, William T; Berman, Robert F; Neale, Joseph H; Lyeth, Bruce G

    2006-05-01

    Traumatic brain injury (TBI) produces a rapid and excessive elevation in extracellular glutamate that induces excitotoxic brain cell death. The peptide neurotransmitter N-acetylaspartylglutamate (NAAG) is reported to suppress neurotransmitter release through selective activation of presynaptic group II metabotropic glutamate receptors. Therefore, strategies to elevate levels of NAAG following brain injury could reduce excessive glutamate release associated with TBI. We hypothesized that the NAAG peptidase inhibitor, ZJ-43 would elevate extracellular NAAG levels and reduce extracellular levels of amino acid neurotransmitters following TBI by a group II metabotropic glutamate receptor (mGluR)-mediated mechanism. Dialysate levels of NAAG, glutamate, aspartate and GABA from the dorsal hippocampus were elevated after TBI as measured by in vivo microdialysis. Dialysate levels of NAAG were higher and remained elevated in the ZJ-43 treated group (50 mg/kg, i.p.) compared with control. ZJ-43 treatment also reduced the rise of dialysate glutamate, aspartate, and GABA levels. Co-administration of the group II mGluR antagonist, LY341495 (1 mg/kg, i.p.) partially blocked the effects of ZJ-43 on dialysate glutamate and GABA, suggesting that NAAG effects are mediated through mGluR activation. The results are consistent with the hypothesis that inhibition of NAAG peptidase may reduce excitotoxic events associated with TBI. PMID:16606367

  19. Disorders of glutamate metabolism.

    PubMed

    Kelly, A; Stanley, C A

    2001-01-01

    The significant role the amino acid glutamate assumes in a number of fundamental metabolic pathways is becoming better understood. As a central junction for interchange of amino nitrogen, glutamate facilitates both amino acid synthesis and degradation. In the liver, glutamate is the terminus for release of ammonia from amino acids, and the intrahepatic concentration of glutamate modulates the rate of ammonia detoxification into urea. In pancreatic beta-cells, oxidation of glutamate mediates amino acid-stimulated insulin secretion. In the central nervous system, glutamate serves as an excitatory neurotransmittor. Glutamate is also the precursor of the inhibitory neurotransmittor GABA, as well as glutamine, a potential mediator of hyperammonemic neurotoxicity. The recent identification of a novel form of congenital hyperinsulinism associated with asymptomatic hyperammonemia assigns glutamate oxidation by glutamate dehydrogenase a more important role than previously recognized in beta-cell insulin secretion and hepatic and CNS ammonia detoxification. Disruptions of glutamate metabolism have been implicated in other clinical disorders, such as pyridoxine-dependent seizures, confirming the importance of intact glutamate metabolism. This article will review glutamate metabolism and clinical disorders associated with disrupted glutamate metabolism. PMID:11754524

  20. Paired-pulse facilitation of multivesicular release and intersynaptic spillover of glutamate at rat cerebellar granule cell–interneurone synapses

    PubMed Central

    Satake, Shin’Ichiro; Inoue, Tsuyoshi; Imoto, Keiji

    2012-01-01

    A simple form of presynaptic plasticity, paired-pulse facilitation (PPF), has been explained as a transient increase in the probability of vesicular release. Using the whole-cell patch-clamp technique to record synaptic activity in rat cerebellar slices, we found different forms of presynaptically originated short-term plasticity during glutamatergic excitatory neurotransmission from granule cells (GCs) to molecular-layer interneurones (INs). Paired-pulse activation of GC axons at short intervals (30–100 ms) elicited not only a facilitation in the peak amplitude (PPFamp), but also a prolongation in the decay-time constant (PPPdecay) of the EPSCs recorded from INs. The results of pharmacological tests and kinetics analyses suggest that the mechanisms underlying the respective types of short-term plasticity were different. PPFamp was elicited by a transient increase in the number of released vesicles. On the other hand, PPPdecay was caused not only by delayed release as has been reported but also by extrasynaptic spillover of the GC transmitter and the subsequent intersynaptic pooling. Both PPFamp and PPPdecay closely rely on repetitive-activation-induced multivesicular release. Using a dynamic clamp technique, we further examined the physiological significance of different presynaptic plasticity, and found that PPFamp and PPPdecay can differentially encode and process neuronal information by influencing the total synaptic charge transferred to postsynaptic INs to reflect activation frequency of the presynaptic GCs. PMID:22930264

  1. Astrocyte membrane properties are altered in a rat model of developmental cortical malformation but single-cell astrocytic glutamate uptake is robust.

    PubMed

    Hanson, Elizabeth; Danbolt, Niels Christian; Dulla, Chris G

    2016-05-01

    Developmental cortical malformations (DCMs) are linked with severe epilepsy and are caused by both genetic and environmental insults. DCMs include several neurological diseases, such as focal cortical dysplasia, polymicrogyria, schizencephaly, and others. Human studies have implicated astrocyte reactivity and dysfunction in the pathophysiology of DCMs, but their specific role is unknown. As astrocytes powerfully regulate glutamate neurotransmission, and glutamate levels are known to be increased in human epileptic foci, understanding the role of astrocytes in the pathological sequelae of DCMs is extremely important. Additionally, recent studies examining astrocyte glutamate uptake in DCMs have reported conflicting results, adding confusion to the field. In this study we utilized the freeze lesion (FL) model of DCM, which is known to induce reactive astrocytosis and cause significant changes in astrocyte morphology, proliferation, and distribution. Using whole-cell patch clamp recording from astrocytes, we recorded both UV-uncaging and synaptically evoked glutamate transporter currents (TCs), widely accepted assays of functional glutamate transport by astrocytes. With this approach, we set out to test the hypothesis that astrocyte membrane properties and glutamate transport were disrupted in this model of DCM. Though we found that the developmental maturation of astrocyte membrane resistance was disrupted by FL, glutamate uptake by individual astrocytes was robust throughout FL development. Interestingly, using an immunolabeling approach, we observed spatial and developmental differences in excitatory amino acid transporter (EAAT) expression in FL cortex. Spatially specific differences in EAAT2 (GLT-1) and EAAT1 (GLAST) expression suggest that the relative contribution of each EAAT to astrocytic glutamate uptake may be altered in FL cortex. Lastly, we carefully analyzed the amplitudes and onset times of both synaptically- and UV uncaging-evoked TCs. We found that in

  2. Activation of type 5 metabotropic glutamate receptor promotes the proliferation of rat retinal progenitor cell via activation of the PI-3-K and MAPK signaling pathways.

    PubMed

    Zhang, Z; Hu, F; Liu, Y; Ma, B; Chen, X; Zhu, K; Shi, Y; Wei, T; Xing, Y; Gao, Y; Lu, H; Liu, Y; Kang, Q

    2016-05-13

    The metabotropic glutamate receptor 5 (mGluR5) regulates neurogenesis in the brain, but the effect of mGluR5 on retinal progenitor cells (RPCs) remains unknown. In this study, we found that mGluR5 promoted the proliferation of rat RPCs with activation of the phosphatidylinositol-3-kinase (PI-3-K) and mitogen-activated protein kinase (MAPK) signaling pathways in vitro. The mGluR5 agonist (S)-3,5-dihydroxyphenylglycine hydrate (DHPG) increased the cellular viability in a concentration- and time-dependent manner, whereas the mGluR5 antagonist 6-methyl-2-(phenylethynyl)pyridine hydrochloride (MTEP) had the opposite effect, as shown by 3-((2-methyl-1,3-thiazol-4-yl)ethynyl)pyridine hydrochloride (MTT) assay. Treatment with DHPG (100μM) also promoted the proliferation of RPCs, as indicated by 5-Bromo-2-deoxyUridine (BrdU) staining and flow cytometry, and likewise, MTEP (100μM) and mGluR5 knockdown abolished the action of mGluR5 activity. Western blot demonstrated that the activation of mGluR5 enhanced the expression of Cyclin D1 and the phosphorylation level of PKC however, MTEP or mGluR5 knockdown also abrogated the effect of DHPG on RPCs. Furthermore, we found that activation of the extracellular signal-regulated protein kinase (ERK) and protein kinase B (AKT) signaling pathways was involved in the proliferation of RPC. After DHPG treatment, the levels of both p-ERK1/2 and p-AKT increased in a time-dependent manner. Then we used MTEP, mGluR5 knockdown, the ERK1/2 inhibitor U0126 and the AKT inhibitor LY294002 to pretreat the cells, and all of them clearly eliminated the influence of DHPG. These results demonstrated that mGluR5 regulates neurogenesis in RPCs through the MAPK and PI-3-K signaling pathways, and these findings may motivate a pharmacological study investigating a potential mechanism for the treatment of retinal diseases such as retinitis pigmentosa (RP) and age-related macular degeneration (AMD). PMID:26902516

  3. D1-like dopamine receptors selectively block P/Q-type calcium channels to reduce glutamate release onto cholinergic basal forebrain neurones of immature rats

    PubMed Central

    Momiyama, Toshihiko; Fukazawa, Yugo

    2007-01-01

    Whole-cell patch-clamp recordings of non-NMDA glutamatergic EPSCs were made from identified cholinergic neurones in slices of basal forebrain (BF) of young rats (P13–P18), to investigate the subtypes of calcium channels involved in dopamine D1-like receptor-mediated presynaptic inhibition of the EPSCs. The BF cholinergic neurones were pre-labelled by intracerebroventricular injection of a fluorescent marker, Cy3-192IgG. A D1-like receptor agonist, SKF 81297 (30 μm) suppressed the EPSCs reversibly by about 30%, and this inhibition was reproducible. Calcium channel subtypes involved in the glutamatergic transmission were elucidated using selective Ca2+ channel blockers. The N-type Ca2+ channel blocker ω-conotoxin (ω-CgTX, 3 μm) suppressed the EPSCs by 57.5%, whereas the P/Q-type channel selective blocker ω-agatoxin-TK (ω-Aga-TK, 200 nm) suppressed the EPSCs by 68.9%. Simultaneous application of both blockers suppressed the EPSCs by 96.1%. The R-type Ca2+ channel blocker SNX-482 (300 nm) suppressed the EPSCs by 18.4%, whereas nifedipine, the L-type Ca2+ channel blocker (10 μm), had little effect. In the presence of ω-Aga-TK, SKF 81297, a dopamine D1-like receptor agonist, had no effect on the EPSCs. On the other hand, SKF 81297 could still inhibit the EPSCs in the presence of either ω-CgTX, SNX-482 or nifedipine. SKF 81297 had no further effect on the EPSCs when external Ca2+ concentration was raised to 7.2 mm in the presence of ω-Aga-TK, but could still inhibit the EPSCs in high Ca2+ solution after ω-CgTX application. Forskolin (FK, 10 μm), an activator of adenylyl cyclase pathway, suppressed the EPSCs, and the FK-induced effect was mostly blocked in the presence of ω-Aga-TK but not that of ω-CgTX. These results suggest that D1-like receptor activation selectively blocks P/Q-type calcium channels to reduce glutamate release onto BF cholinergic neurones. PMID:17234695

  4. The effects of black garlic (Allium sativum L.) ethanol extract on the estimated total number of Purkinje cells and motor coordination of male adolescent Wistar rats treated with monosodium glutamate.

    PubMed

    Aminuddin, M; Partadiredja, G; Sari, D C R

    2015-03-01

    A number of studies have indicated that monosodium glutamate (MSG) might cause negative effects on the nervous system, including in the cerebellum. Garlic (Allium sativum) has long been known as a flavouring agent and a traditional remedy for various illnesses. The present study aimed at investigating the effects of garlic on the motor coordination and the number of Purkinje cells present in rats treated with MSG. A total of 25 male Wistar rats aged 4 to 5 weeks old were used in this study and were divided into five groups, namely a negative control (C-) group, which received 0.9 % NaCl solution, a positive control (C+) group, which received MSG, and three treated groups, which received 2 mg/g bw of MSG and 2.5 mg (T2.5), 5 mg (T5), or 10 mg (T10) of black garlic solution per oral administration (per 200 g bw), respectively. All treatments were carried out for 10 days. Upon the end of the treatment, the motor performance of all rats were tested using the rotarod apparatus. The rats were subsequently sacrificed, and the cerebella of the rats were processed for stereological analyses. It has been found that the number of Purkinje cells of the cerebella of all treated groups were significantly higher than that of the group treated with MSG only. No changes in motor coordination function were observed as a result of MSG treatment. PMID:24737450

  5. Developmental exposure to polychlorinated biphenyls or methylmercury, but not to its combination, impairs the glutamate-nitric oxide-cyclic GMP pathway and learning in 3-month-old rats.

    PubMed

    Piedrafita, B; Erceg, S; Cauli, O; Felipo, V

    2008-07-17

    Prenatal exposure to polychlorinated biphenyls (PCBs) or methylmercury (MeHg) contaminated food may affect brain development, leading to long-term alterations in cognitive function. Both types of contaminants, PCBs and MeHg, are often found together contaminating food, especially fish in some polluted areas. Exposure to combinations of neurotoxicants may exert different effects on the developing nervous system than exposure to individual contaminants. Developmental exposure (during pregnancy and lactation) to PCB126 or PCB153 impairs learning ability when the rats are 3 months old. Impairment of learning seems to be a consequence of impairment of the function of the glutamate-nitric oxide (NO)-cGMP pathway in brain in vivo. The aims of the present work were 1) to assess whether perinatal exposure to MeHg also affects the function of the glutamate-NO-cGMP pathway in brain in vivo analyzed by in vivo brain microdialysis and/or the ability to learn the Y maze task when the rats are 3 months old, and 2) to assess whether perinatal exposure to combinations of MeHg with PCB153 or PCB126 potentiates, decreases or does not modify the effects of the individual neurotoxicants. Perinatal exposure to PCB126, PCB153 or MeHg impaired the function of the glutamate-NO-cGMP pathway in cerebellum and learning ability. However, co-exposure to PCB126+MeHg or PCB153+MeHg inhibits the impairment of the pathway or learning ability. These results support that the function of this pathway modulates learning of the Y maze task. Moreover, they show that co-exposure to these PCBs and MeHg does not exacerbate, but reduces the effects on the ability to learn this task. PMID:18556134

  6. Chronic at-level thermal hyperalgesia following rat cervical contusion spinal cord injury is accompanied by neuronal and astrocyte activation and loss of the astrocyte glutamate transporter, GLT1, in superficial dorsal horn.

    PubMed

    Putatunda, Rajarshi; Hala, Tamara J; Chin, Jeannie; Lepore, Angelo C

    2014-09-18

    Neuropathic pain is a form of pathological nociception that occurs in a significant portion of traumatic spinal cord injury (SCI) patients, resulting in debilitating and often long-term physical and psychological burdens. While many peripheral and central mechanisms have been implicated in neuropathic pain, central sensitization of dorsal horn spinothalamic tract (STT) neurons is a major underlying substrate. Furthermore, dysregulation of extracellular glutamate homeostasis and chronic astrocyte activation play important underlying roles in persistent hyperexcitability of these superficial dorsal horn neurons. To date, central sensitization and astrocyte changes have not been characterized in cervical SCI-induced neuropathic pain models, despite the fact that a major portion of SCI patients suffer contusion trauma to cervical spinal cord. In this study, we have characterized 2 rat models of unilateral cervical contusion SCI that behaviorally result in chronic persistence of thermal hyperalgesia in the ipsilateral forepaw. In addition, we find that STT neurons are chronically activated in both models when compared to laminectomy-only uninjured rats. Finally, persistent astrocyte activation and significantly reduced expression of the major CNS glutamate transporter, GLT1, in superficial dorsal horn astrocytes are associated with both excitability changes in STT neurons and the neuropathic pain behavioral phenotype. In conclusion, we have characterized clinically-relevant rodent models of cervical contusion-induced neuropathic pain that result in chronic activation of both STT neurons and astrocytes, as well as compromise in astrocyte glutamate transporter expression. These models can be used as important tools to further study mechanisms underlying neuropathic pain post-SCI and to test potential therapeutic interventions. PMID:24833066

  7. Role of the glutamate dehydrogenase reaction in furnishing aspartate nitrogen for urea synthesis: studies in perfused rat liver with 15N.

    PubMed Central

    Nissim, Itzhak; Horyn, Oksana; Luhovyy, Bohdan; Lazarow, Adam; Daikhin, Yevgeny; Nissim, Ilana; Yudkoff, Marc

    2003-01-01

    The present study was designed to determine: (i) the role of the reductive amination of alpha-ketoglutarate via the glutamate dehydrogenase reaction in furnishing mitochondrial glutamate and its transamination into aspartate; (ii) the relative incorporation of perfusate 15NH4Cl, [2-15N]glutamine or [5-15N]glutamine into carbamoyl phosphate and aspartate-N and, thereby, [15N]urea isotopomers; and (iii) the extent to which perfusate [15N]aspartate is taken up by the liver and incorporated into [15N]urea. We used a liver-perfusion system containing a physiological mixture of amino acids and ammonia similar to concentrations in vivo, with 15N label only in glutamine, ammonia or aspartate. The results demonstrate that in perfusions with a physiological mixture of amino acids, approx. 45 and 30% of total urea-N output was derived from perfusate ammonia and glutamine-N respectively. Approximately two-thirds of the ammonia utilized for carbamoyl phosphate synthesis was derived from perfusate ammonia and one-third from glutamine. Perfusate [2-15N]glutamine, [5-15N]glutamine or [15N]aspartate provided 24, 10 and 10% respectively of the hepatic aspartate-N pool, whereas perfusate 15NH4Cl provided approx. 37% of aspartate-N utilized for urea synthesis, secondary to the net formation of [15N]glutamate via the glutamate dehydrogenase reaction. The results suggest that the mitochondrial glutamate formed via the reductive amination of alpha-ketoglutarate may have a key role in ammonia detoxification by the following processes: (i) furnishing aspartate-N for ureagenesis; (ii) serving as a scavenger for excess ammonia; and (iii) improving the availability of the mitochondrial [glutamate] for synthesis of N -acetylglutamate. In addition, the current findings suggest that the formation of aspartate via the mitochondrial aspartate aminotransferase reaction may play an important role in the synthesis of cytosolic argininosuccinate. PMID:12935293

  8. SLC1 Glutamate Transporters

    PubMed Central

    Grewer, Christof; Gameiro, Armanda; Rauen, Thomas

    2014-01-01

    The plasma membrane transporters for the neurotransmitter glutamate belong to the solute carrier 1 (SLC1) family. They are secondary active transporters, taking up glutamate into the cell against a substantial concentration gradient. The driving force for concentrative uptake is provided by the cotransport of Na+ ions and the countertransport of one K+ in a step independent of the glutamate translocation step. Due to eletrogenicity of transport, the transmembrane potential can also act as a driving force. Glutamate transporters are expressed in many tissues, but are of particular importance in the brain, where they contribute to the termination of excitatory neurotransmission. Glutamate transporters can also run in reverse, resulting in glutamate release from cells. Due to these important physiological functions, glutamate transporter expression and, therefore, the transport rate, are tightly regulated. This review summarizes recent literature on the functional and biophysical properties, structure-function relationships, regulation, physiological significance, and pharmacology of glutamate transporters. Particular emphasis is on the insight from rapid kinetic and electrophysiological studies, transcriptional regulation of transporter expression, and reverse transport and its importance for pathophysiological glutamate release under ischemic conditions. PMID:24240778

  9. Alcohol drinking increases the dopamine-stimulating effects of ethanol and reduces D2 auto-receptor and group II metabotropic glutamate receptor function within the posterior ventral tegmental area of alcohol preferring (P) rats.

    PubMed

    Ding, Zheng-Ming; Ingraham, Cynthia M; Rodd, Zachary A; McBride, William J

    2016-10-01

    Repeated local administration of ethanol (EtOH) sensitized the posterior ventral tegmental area (pVTA) to the local dopamine (DA)-stimulating effects of EtOH. Chronic alcohol drinking increased nucleus accumbens (NAC) DA transmission and pVTA glutamate transmission in alcohol-preferring (P) rats. The objectives of the present study were to determine the effects of chronic alcohol drinking by P rats on the (a) sensitivity and response of the pVTA DA neurons to the DA-stimulating actions of EtOH, and (b) negative feedback control of DA (via D2 auto-receptors) and glutamate (via group II mGlu auto-receptors) release in the pVTA. EtOH (50 or 150 mg%) or the D2/3 receptor antagonist sulpiride (100 or 200 μM) was microinjected into the pVTA while DA was sampled with microdialysis in the NAC shell (NACsh). The mGluR2/3 antagonist LY341495 (1 or 10 μM) was perfused through the pVTA via reverse microdialysis and local extracellular glutamate and DA levels were measured. EtOH produced a more robust increase of NACsh DA in the 'EtOH' than 'Water' groups (e.g., 150 mg% EtOH: to ∼ 210 vs 150% of baseline). In contrast, sulpiride increased DA release in the NACsh more in the 'Water' than 'EtOH' groups (e.g., 200 μM sulpiride: to ∼ 190-240 vs 150-160% of baseline). LY341495 (at 10 μM) increased extracellular glutamate and DA levels in the 'Water' (to ∼ 150-180% and 180-230% of baseline, respectively) but not the 'EtOH' groups. These results indicate that alcohol drinking enhanced the DA-stimulating effects of EtOH, and attenuated the functional activities of D2 auto-receptors and group II mGluRs within the pVTA. PMID:27260326

  10. LEUCINE-NITROGEN METABOLISM IN THE BRAIN OF CONSCIOUS RATS: ITS ROLE AS A NITROGEN CARRIER IN GLUTAMATE SYNTHESIS IN GLIAL AND NEURONAL METABOLIC COMPARTMENTS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The source of nitrogen (N) for the de novo synthesis of brain glutamate, glutamine, and gamma-aminobutyrate (GABA)remains controversial. Because leucine is readily transported into the brain and the brain contains high activities of branched-chain aminotransferase, we hypothesized that leucine is th...

  11. Cocaine-induced neuroadaptations in the dorsal striatum: glutamate dynamics and behavioral sensitization.

    PubMed

    Parikh, Vinay; Naughton, Sean X; Shi, Xiangdang; Kelley, Leslie K; Yegla, Brittney; Tallarida, Christopher S; Rawls, Scott M; Unterwald, Ellen M

    2014-09-01

    Recent evidence suggests that diminished ability to control cocaine seeking arises from perturbations in glutamate homeostasis in the nucleus accumbens. However, the neurochemical substrates underlying cocaine-induced neuroadaptations in the dorsal striatum and how these mechanisms link to behavioral plasticity is not clear. We employed glutamate-sensitive microelectrodes and amperometry to study the impact of repeated cocaine administration on glutamate dynamics in the dorsolateral striatum of awake freely-moving rats. Depolarization-evoked glutamate release was robustly increased in cocaine-pretreated rats challenged with cocaine. Moreover, the clearance of glutamate signals elicited either by terminal depolarization or blockade of non-neuronal glutamate transporters slowed down dramatically in cocaine-sensitized rats. Repeated cocaine exposure also reduced the neuronal tone of striatal glutamate. Ceftriaxone, a β-lactam antibiotic that activates the astrocytic glutamate transporter, attenuated the effects of repeated cocaine exposure on synaptic glutamate release and glutamate clearance kinetics. Finally, the antagonism of AMPA glutamate receptors in the dorsolateral striatum blocked the development of behavioral sensitization to repeated cocaine administration. Collectively, these data suggest that repeated cocaine exposure disrupts presynaptic glutamate transmission and transporter-mediated clearance mechanisms in the dorsal striatum. Moreover, such alterations produce an over activation of AMPA receptors in this brain region leading to the sensitized behavioral response to repeated cocaine. PMID:24911954

  12. Glutamate and Neurodegenerative Disease

    NASA Astrophysics Data System (ADS)

    Schaeffer, Eric; Duplantier, Allen

    As the main excitatory neurotransmitter in the mammalian central nervous system, glutamate is critically involved in most aspects of CNS function. Given this critical role, it is not surprising that glutamatergic dysfunction is associated with many CNS disorders. In this chapter, we review the literature that links aberrant glutamate neurotransmission with CNS pathology, with a focus on neurodegenerative diseases. The biology and pharmacology of the various glutamate receptor families are discussed, along with data which links these receptors with neurodegenerative conditions. In addition, we review progress that has been made in developing small molecule modulators of glutamate receptors and transporters, and describe how these compounds have helped us understand the complex pharmacology of glutamate in normal CNS function, as well as their potential for the treatment of neurodegenerative diseases.

  13. NMDA and non-NMDA glutamate receptors in the paraventricular nucleus of the hypothalamus modulate different stages of hemorrhage-evoked cardiovascular responses in rats.

    PubMed

    Busnardo, C; Crestani, C C; Fassini, A; Resstel, L B M; Corrêa, F M A

    2016-04-21

    Here we report the involvement of N-Methyl-d-Aspartate (NMDA) and non-NMDA glutamate receptors from the paraventricular nucleus of the hypothalamus (PVN) in the mediation of cardiovascular changes observed during hemorrhage and post-bleeding periods. In addition, the present study provides further evidence of the involvement of circulating vasopressin and cardiac sympathetic activity in cardiovascular responses to hemorrhage. Systemic treatment with the V1-vasopressin receptor antagonist dTyr(CH2)5(Me)AVP (50 μg/kg, i.v.) increased the latency to the onset of hypotension during hemorrhage and slowed post-bleeding recovery of blood pressure. Systemic treatment with the β1-adrenergic receptor antagonist atenolol (1 mg/kg, i.v.) also increased the latency to the onset of hypotension during hemorrhage. Moreover, atenolol reversed the hemorrhage-induced tachycardia into bradycardia. Bilateral microinjection of the selective NMDA glutamate receptor antagonist LY235959 (2 nmol/100 nL) into the PVN blocked the hypotensive response to hemorrhage and reduced the tachycardia during the post-hemorrhage period. Systemic treatment with dTyr(CH2)5(Me)AVP inhibited the effect of LY235959 on hemorrhage-induced hypotension, without affecting the post-bleeding tachycardia. PVN treatment with the selective non-NMDA receptor antagonist NBQX (2 nmol/100 nL) reduced the recovery of blood pressure to normal levels in the post-bleeding phase and reduced hemorrhage-induced tachycardia. Combined blockade of both NMDA and non-NMDA glutamate receptors in the PVN completely abolished the hypotensive response in the hemorrhage period and reduced the tachycardiac response in the post-hemorrhage period. These results indicate that local PVN glutamate neurotransmission is involved in the neural pathway mediating cardiovascular responses to hemorrhage, via an integrated control involving autonomic nervous system activity and vasopressin release into the circulation. PMID:26861418

  14. An investigation of interactions between hypocretin/orexin signaling and glutamate receptor surface expression in the rat nucleus accumbens under basal conditions and after cocaine exposure

    PubMed Central

    Plaza-Zabala, Ainhoa; Li, Xuan; Milovanovic, Mike; Loweth, Jessica A.; Maldonado, Rafael; Berrendero, Fernando; Wolf, Marina E.

    2013-01-01

    Hypocretin peptides are critical for the effects of cocaine on excitatory synaptic strength in the ventral tegmental area (VTA). However, little is known about their role in cocaine-induced synaptic plasticity in the nucleus accumbens (NAc). First, we tested whether hypocretin-1 by itself could acutely modulate glutamate receptor surface expression in the NAc, given that hypocretin-1 in the VTA reproduces cocaine’s effects on glutamate transmission. We found no effect of hypocretin-1 infusion on AMPA or NMDA receptor surface expression in the NAc, measured by biotinylation, either 30 min or 3 h after the infusion. Second, we were interested in whether changes in hypocretin receptor-2 (Hcrtr-2) expression contribute to cocaine-induced plasticity in the NAc. As a first step towards addressing this question, Hcrtr-2 surface expression was compared in the NAc after withdrawal from extended-access self-administration of saline (control) versus cocaine. We found that surface Hcrtr-2 levels remain unchanged following 14, 25 or 48 days of withdrawal from cocaine, a time period in which high conductance GluA2-lacking AMPA receptors progressively emerge in the NAc. Overall, our results fail to support a role for hypocretins in acute modulation of glutamate receptor levels in the NAc or a role for altered Hcrtr-2 expression in withdrawal-dependent synaptic adaptations in the NAc following cocaine self-administration. PMID:24262606

  15. Flavor Preferences Conditioned by Dietary Glutamate.

    PubMed

    Ackroff, Karen; Sclafani, Anthony

    2016-07-01

    Our understanding of the molecular basis of umami taste and its appetitive qualities has been greatly aided by studies in laboratory rodents. This review describes methods for testing responses to the prototypical umami substance monosodium glutamate (MSG) in rodents. Two techniques, forced exposure to MSG and 2-bottle choice tests with ascending concentrations, were used to evaluate the responses to the taste of umami itself, and 2 other methods used oral or postoral MSG to modify the responses to other flavors. Intake and preference for MSG are enhanced in mice by experience with MSG and with other nutrients with positive postoral effects. In addition, flavor preferences are enhanced in mice and rats by gastric or intestinal MSG infusions via an associative learning process. Even mice with an impaired or absent ability to taste MSG can learn to prefer a flavor added to an MSG solution, supporting the notion that glutamate acts postorally. The more complex flavor of dashi seasoning, which includes umami substances (inosinate, glutamate), is attractive to rodents, but dashi does not condition flavor preferences. Details of the postoral glutamate detection process and the nature of the signal involved in learned preferences are still uncertain but probably involve gastric or intestinal sensors or both and vagal transmission. Some findings suggest that postoral glutamate effects may enhance food preferences in humans, but this requires further study. PMID:27422522

  16. Serotonin impairs copulation and attenuates ejaculation-induced glutamate activity in the medial preoptic area.

    PubMed

    Dominguez, Juan M; Hull, Elaine M

    2010-08-01

    The medial preoptic area (MPOA) is critical for male sexual behavior. Glutamate is released in the MPOA of male rats during copulation, and increasing glutamate levels by reverse dialysis of glutamate uptake inhibitors facilitates mating. Conversely, increased release of serotonin (5-HT) inhibits sexual behavior. In both rats and men, selective serotonin reuptake inhibitors (SSRIs) impair erection, ejaculation, and libido. Here we reverse-dialyzed 5-HT through concentric microdialysis probes in the MPOA of male rats; concurrently we collected 2-min samples for analysis of glutamate and measured sexual behavior. Sexual activity, and especially ejaculation, increased levels of glutamate in the MPOA. However, reverse dialysis of 5-HT into the MPOA impaired ejaculatory ability and attenuated glutamate release. Implications of these results for impairment of sexual behavior that results from administration of SSRIs are discussed. PMID:20695654

  17. Rapid glutamate release in the mediobasal hypothalamus accompanies feeding and is exaggerated by an obesogenic food

    PubMed Central

    Guyenet, Stephan J.; Matsen, Miles E.; Morton, Gregory J.; Kaiyala, Karl J.; Schwartz, Michael W.

    2013-01-01

    The mediobasal hypothalamus (MBH) plays a central role in the regulation of food intake and energy balance. Although the excitatory neurotransmitter glutamate is implicated in energy balance regulation by the MBH, the hypothesis that feeding elicits local glutamate release remains untested. To test this hypothesis, we employed a glutamate biosensor that measures glutamate concentrations at 1-s intervals in conscious, freely behaving rats. Results indicate that feeding is associated with an increase of MBH glutamate concentration that occurs within 1–2 s of oral contact with a food pellet, and the glutamate response to a palatable high-fat pellet is greatly exaggerated relative to chow. In contrast, glutamate responses were not observed during water ingestion or other observed behaviors. These findings indicate that feeding is associated with rapid release of glutamate in the MBH, that this release is exaggerated with an obesogenic food, and that this response is likely stimulated by orosensory factors. PMID:24199157

  18. Glutamate release from platelets: exocytosis versus glutamate transporter reversal.

    PubMed

    Kasatkina, Ludmila A; Borisova, Tatiana A

    2013-11-01

    Platelets express neuronal and glial glutamate transporters EAAT 1-3 in the plasma membrane and vesicular glutamate transporters VGLUT 1,2 in the membrane of secretory granules. This study is focused on the assessment of non-exocytotic glutamate release, that is, the unstimulated release, heteroexchange and glutamate transporter reversal in platelets. Using the glutamate dehydrogenase assay, the absence of unstimulated release of endogenous glutamate from platelets was demonstrated, even after inhibition of glutamate transporters and cytoplasmic enzyme glutamine synthetase by dl-threo-β-benzyloxyaspartate and methionine sulfoximine, respectively. Depolarization of the plasma membrane by exposure to elevated [K(+)] did not induce the release of glutamate from platelets that was shown using the glutamate dehydrogenase assay and radiolabeled l-[(14)C]glutamate. Glutamate efflux by means of heteroexchange with transportable inhibitor of glutamate transporters dl-threo-β-hydroxyaspartate (dl-THA) was not observed. Furthermore, the protonophore cyanide-p-trifluoromethoxyphenyl-hydrazon (FCCP) and inhibitor of V-type H(+)-ATPase bafilomycin A1 also failed to stimulate the release of glutamate from platelets. However, exocytotic release of glutamate from secretory granules in response to thrombin stimulation was not prevented by elevated [K(+)], dl-THA, FCCP and bafilomycin A1. In contrast to nerve terminals, platelets cannot release glutamate in a non-exocytotic manner. Heteroexchange, transporter-mediated and unstimulated release of glutamate are not inherent to platelets. Therefore, platelets may be used as a peripheral marker/model for the analysis of glutamate uptake by brain nerve terminals only (direct function of transporters), whereas the mechanisms of glutamate release are different in platelets and nerve terminals. Glutamate is released by platelets exclusively by means of exocytosis. Also, reverse function of vesicular glutamate transporters of platelets is

  19. Evidence for Astrocytes as a Potential Source of the Glutamate Excess in Temporal Lobe Epilepsy

    PubMed Central

    Perez, Edgar L; Lauritzen, Fredrik; Wang, Yue; Lee, Tih-Shih W; Kang, Dewey; Zaveri, Hitten P; Chaudhry, Farrukh A; Ottersen, Ole P; Bergersen, Linda H; Eid, Tore

    2012-01-01

    Increased extracellular brain glutamate has been implicated in the pathophysiology of human refractory temporal lobe epilepsy (TLE), but the cause of the excessive glutamate is unknown. Prior studies by us and others have shown that the glutamate degrading enzyme glutamine synthetase (GS) is deficient in astrocytes in the epileptogenic hippocampal formation in a subset of patients with TLE. We have postulated that the loss of GS in TLE leads to increased glutamate in astrocytes with elevated concentrations of extracellular glutamate and recurrent seizures as the ultimate end-points. Here we test the hypothesis that the deficiency in GS leads to increased glutamate in astrocytes. Rats were chronically infused with methionine sulfoximine (MSO, n=4) into the hippocampal formation to induce GS-deficiency and recurrent seizures. A separate group of rats was infused with 0.9% NaCl (saline) as a control (n=6). At least 10 days after the start of infusion, once recurrent seizures were established in the MSO-treated rats, the concentration of glutamate was assessed in CA1 of the hippocampal formation by immunogold electron microscopy. The concentration of glutamate was 47% higher in astrocytes in the MSO-treated vs. saline-treated rats (p=0.02), and the ratio of glutamate in astrocytes relative to axon terminals was increased by 74% in the MSO-treated rats (p=0.003). These data support our hypothesis that a deficiency in GS leads to increased glutamate in astrocytes. We additionally propose that the GS-deficient astrocytes in the hippocampal formation in TLE lead to elevated extracellular brain glutamate either through decreased clearance of extracellular glutamate or excessive release of glutamate into the extracellular space from these cells, or a combination of the two. PMID:22659305

  20. On the defensive action of glutamate against the cytotoxicity and fibrogenicity of quartz dust.

    PubMed Central

    Morosova, K I; Aronova, G V; Katsnelson, B A; Velichkovski, B T; Genkin, A M; Elnichnykh, L N; Privalova, L I

    1982-01-01

    The cytotoxic action of quartz (DQ12) particles on cultures of rat peritoneal macrophages, as estimated by the inhibition of the TTC-reductase activity, is considerably reduced by preincubation with glutamic acid and by adding sodium glutamate (15 mg/ml) to the drinking water of the rats donating the macrophages. This increase in macrophage resistance under the influence of glutamate is the most probable cause of the delay in the development of silicotic fibrosis shown in several experiments on rats intratracheally injected with quartz and then treated by prolonged administration of glutamate. This effect is probably connected with the influence of glutamate on the stability of the macrophage membranes, which can in its turn be explained by different mechanisms, including the influence on the synthesis and phosphorylation of adenosine nucleotides. Such an influence was shown in rats receiving glutamate by the change of the ATP/ADP ratio in macrophages, but not in erythrocytes. The resistance of rat erythrocytes to the haemolytic action of quartz is also not influenced by the action of glutamate neither in vitro nor in vivo. Such differences in the influences of glutamate on two types of cells, equally susceptible to quartz cytotoxicity but considerably differing in the character of energy metabolism, is an indirect proof of the role of the latter in the realisation of the anticytotoxic, and thereby antifibrogenic, effect of glutamate. PMID:6124270

  1. Group III metabotropic glutamate receptors and D1-like and D2-like dopamine receptors interact in the rat nucleus accumbens to influence locomotor activity.

    PubMed

    David, Hélène N; Abraini, Jacques H

    2002-03-01

    Evidence for functional interactions between metabotropic glutamate (mGlu) receptors and dopamine (DA) neurotransmission is now clearly established. In the present study, we investigated interactions between group III mGlu receptors and D1- and D2-like receptors in the nucleus accumbens (NAcc). Administration, into the NAcc, of the selective group III mGlu receptor agonist, AP4, resulted in an increase in locomotor activity, which was blocked by pretreatment with the group III mGlu receptor antagonist, MPPG. In addition, pretreatment with AP4 further blocked the increase in motor activity induced by the D1-like receptor agonist, SKF 38393, but potentiated the locomotor responses induced by either the D2-like receptor agonist, quinpirole, or coinfusion of SKF 38393 and quinpirole. MPPG reversed the effects of AP4 on the motor responses induced by D1-like and/or D2-like receptor activation. These results confirm that glutamate transmission may control DA-dependent locomotor function through mGlu receptors and further indicate that group III mGlu receptors oppose the behavioural response produced by D1-like receptor activation and favour those produced by D2-like receptor activation. PMID:11906529

  2. Silicon Wafer-Based Platinum Microelectrode Array Biosensor for Near Real-Time Measurement of Glutamate in Vivo

    PubMed Central

    Wassum, Kate M.; Tolosa, Vanessa M.; Wang, Jianjun; Walker, Eric; Monbouquette, Harold G.; Maidment, Nigel T.

    2008-01-01

    Using Micro-Electro-Mechanical-Systems (MEMS) technologies, we have developed silicon wafer-based platinum microelectrode arrays (MEAs) modified with glutamate oxidase (GluOx) for electroenzymatic detection of glutamate in vivo. These MEAs were designed to have optimal spatial resolution for in vivo recordings. Selective detection of glutamate in the presence of the electroactive interferents, dopamine and ascorbic acid, was attained by deposition of polypyrrole and Nafion. The sensors responded to glutamate with a limit of detection under 1μM and a sub-1-second response time in solution. In addition to extensive in vitro characterization, the utility of these MEA glutamate biosensors was also established in vivo. In the anesthetized rat, these MEA glutamate biosensors were used for detection of cortically-evoked glutamate release in the ventral striatum. The MEA biosensors also were applied to the detection of stress-induced glutamate release in the dorsal striatum of the freely-moving rat. PMID:19543440

  3. Cystine/glutamate antiporter blockage induces myelin degeneration.

    PubMed

    Soria, Federico N; Zabala, Alazne; Pampliega, Olatz; Palomino, Aitor; Miguelez, Cristina; Ugedo, Luisa; Sato, Hideyo; Matute, Carlos; Domercq, María

    2016-08-01

    The cystine/glutamate antiporter is a membrane transport system responsible for the uptake of extracellular cystine and release of intracellular glutamate. It is the major source of cystine in most cells, and a key regulator of extrasynaptic glutamate in the CNS. Because cystine is the limiting factor in the biosynthesis of glutathione, and glutamate is the most abundant neurotransmitter, the cystine/glutamate antiporter is a central player both in antioxidant defense and glutamatergic signaling, two events critical to brain function. However, distribution of cystine/glutamate antiporter in CNS has not been well characterized. Here, we analyzed expression of the catalytic subunit of the cystine/glutamate antiporter, xCT, by immunohistochemistry in histological sections of the forebrain and spinal cord. We detected labeling in neurons, oligodendrocytes, microglia, and oligodendrocyte precursor cells, but not in GFAP(+) astrocytes. In addition, we examined xCT expression and function by qPCR and cystine uptake in primary rat cultures of CNS, detecting higher levels of antiporter expression in neurons and oligodendrocytes. Chronic inhibition of cystine/glutamate antiporter caused high toxicity to cultured oligodendrocytes. In accordance, chronic blockage of cystine/glutamate antiporter as well as glutathione depletion caused myelin disruption in organotypic cerebellar slices. Finally, mice chronically treated with sulfasalazine, a cystine/glutamate antiporter inhibitor, showed a reduction in the levels of myelin and an increase in the myelinated fiber g-ratio. Together, these results reveal that cystine/glutamate antiporter is expressed in oligodendrocytes, where it is a key factor to the maintenance of cell homeostasis. GLIA 2016. GLIA 2016;64:1381-1395. PMID:27247047

  4. Modulation of intestinal L-glutamate transport by luminal leptin.

    PubMed

    Fanjul, Carmen; Barrenetxe, Jaione; Lostao, María Pilar; Ducroc, Robert

    2015-06-01

    Leptin is secreted into the digestive tract and contributes to the absorption of dietary molecules by regulating transporters activity. Here, we studied the effect of luminal leptin on the intestinal transport of L-glutamate, an important component of human diet. We examined the effect of leptin on L-glutamate uptake in rat intestine in vitro measuring glutamate-induced short-circuit current (Isc) in Ussing chambers and L-[(3)H (U)]-glutamate uptake in jejunal everted rings. Glutamate-induced Isc was only observed in Na(+)-free conditions. This Isc was concentration (1-60 mmol L(-1)) and pH dependent. Luminal leptin increased glutamate Isc (∼100 %). Dose-response curve showed a biphasic pattern, with maximal stimulations observed at 10(-13) and 10(-10) mmol L(-1), that were sensitive to leptin receptor antagonist. In everted rings, two glutamate transport mechanisms were distinguished: a Na(+)-dependent, H(+)-independent, that was inhibited by leptin (∼20 %), and a Na(+)-independent but H(+)-dependent, that was enhanced by leptin (∼20 %), in line with data obtained in Ussing chambers. Altogether, these data reveal original non-monotonic effect of luminal leptin in the intestine and demonstrate a new role for this hormone in the modulation of L-glutamate transport, showing that luminal active gut peptides can influence absorption of amino acids. PMID:25935421

  5. Vitamin C neuroprotection against dose-dependent glutamate-induced neurodegeneration in the postnatal brain.

    PubMed

    Shah, Shahid Ali; Yoon, Gwang Ho; Kim, Hyun-Ok; Kim, Myeong Ok

    2015-05-01

    Glutamate-induced excitotoxicity due to over-activation of glutamate receptors and associated energy depletion (phosphorylation and activation of AMPK) results in neuronal cell death in various neurological disorders. Restoration of energy balance during an excitotoxic insult is critical for neuronal survival. Ascorbic acid (vitamin C), an essential nutrient with well-known antioxidant potential, protects the brain from oxidative damage in various models of neurodegeneration. In this study, we reported the therapeutic efficacy of vitamin C in response to glutamate-induced excitation, resulting in energy depletion and apoptosis in the hippocampus of the developing rat brain. A single subcutaneous injection of glutamate at two different concentrations (5 and 10 mg/kg) in postnatal day 7 rat pups increased brain glutamate levels and increased the protein expression of neuronal apoptotic markers. Both doses of glutamate upregulated the ratio of pro-apoptotic Bax to anti-apoptotic Bcl-2, cytochrome-c release, caspase-3 activation and the expression of PARP-1. However, co-treatment of vitamin C (250 mg/kg) with glutamate decreased brain glutamate levels and reversed the changes induced by glutamate in the developing hippocampus. Interestingly, only a high dose of glutamate caused the phosphorylation and activation of AMPK and induced neuronal cell death, whereas a low dose of glutamate failed to mediate these effects. Vitamin C supplementation reduced the glutamate-induced phosphorylation of AMPK and attenuated neuronal cell death, as assessed morphologically by Fluoro Jade B in the hippocampal CA1 region of the developing brain. Taken together, our results indicated that glutamate in both concentrations is toxic to the immature rat brain, whereas vitamin C is pharmacologically effective against glutamate-induced neurodegeneration. PMID:25701025

  6. Activation of Group I and Group II Metabotropic Glutamate Receptors Causes LTD and LTP of Electrical Synapses in the Rat Thalamic Reticular Nucleus.

    PubMed

    Wang, Zemin; Neely, Ryan; Landisman, Carole E

    2015-05-13

    Compared with the extensive characterization of chemical synaptic plasticity, electrical synaptic plasticity remains poorly understood. Electrical synapses are strong and prevalent among the GABAergic neurons of the rodent thalamic reticular nucleus. Using paired whole-cell recordings, we show that activation of Group I metabotropic glutamate receptors (mGluRs) induces long-term depression of electrical synapses. Conversely, activation of the Group II mGluR, mGluR3, induces long-term potentiation of electrical synapses. By testing downstream targets, we show that modifications induced by both mGluR groups converge on the same signaling cascade--adenylyl cyclase to cAMP to protein kinase A--but with opposing effects. Furthermore, the magnitude of modification is inversely correlated to baseline coupling strength. Thus, electrical synapses, like their chemical counterparts, undergo both strengthening and weakening forms of plasticity, which should play a significant role in thalamocortical function. PMID:25972185

  7. The effects of black garlic ethanol extract on the spatial memory and estimated total number of pyramidal cells of the hippocampus of monosodium glutamate-exposed adolescent male Wistar rats.

    PubMed

    Hermawati, Ery; Sari, Dwi Cahyani Ratna; Partadiredja, Ginus

    2015-09-01

    Monosodium glutamate (MSG) is believed to exert deleterious effects on various organs, including the hippocampus, likely via the oxidative stress pathway. Garlic (Alium sativum L.), which is considered to possess potent antioxidant activity, has been used as traditional remedy for various ailments since ancient times. We have investigated the effects of black garlic, a fermented form of garlic, on spatial memory and estimated the total number of pyramidal cells of the hippocampus in adolescent male Wistar rats treated with MSG. Twenty-five rats were divided into five groups: C- group, which received normal saline; C+ group, which was exposed to 2 mg/g body weight (bw) of MSG; three treatment groups (T2.5, T5, T10), which were treated with black garlic extract (2.5, 5, 10 mg/200 g bw, respectively) and MSG. The spatial memory test was carried out using the Morris water maze (MWM) procedure, and the total number of pyramidal cells of the hippocampus was estimated using the physical disector design. The groups treated with black garlic extract were found to have a shorter path length than the C- and C+ groups in the escape acquisition phase of the MWM test. The estimated total number of pyramidal cells in the CA1 region of the hippocampus was higher in all treated groups than that of the C+ group. Based on these results, we conclude that combined administration of black garlic and MSG may alter the spatial memory functioning and total number of pyramidal neurons of the CA1 region of the hippocampus of rats. PMID:25422084

  8. Activation of glial glutamate transporter via MAPK p38 prevents enhanced and long-lasting non-evoked resting pain after surgical incision in rats.

    PubMed

    Reichl, Sylvia; Segelcke, Daniel; Keller, Viktor; Jonas, Robin; Boecker, Armin; Wenk, Manuel; Evers, Dagmar; Zahn, Peter K; Pogatzki-Zahn, Esther M

    2016-06-01

    Pain after surgery has recently become a major issue not only due to lack of treatment success in the acute phase; even more alarming is the large number of patients developing prolonged pain after surgery. Because spinal glutamate as well as spinal glia plays a major role in acute incisional pain, we investigated the role of the spinal glial glutamate transporters (GT), GLAST, GLT-1, for acute and prolonged pain and hyperalgesia caused by an incision. Spinal administration of the GT-inhibitor DL-TBOA increased non-evoked pain but not evoked pain behavior (hyperalgesia) up to 2 weeks after incision. In accordance, spinal GLAST (and to a lesser degree GLT-1) were upregulated after incision for several days. Long-term incision induced GT upregulation was prevented by long-lasting p38-inhibitor administration but not by long-lasting ERK1/2-inhibition after incision. In accordance, daily treatment with the p38-inhibitor (but not the ERK1/2 inhibitor) prolonged non-evoked but not evoked pain behavior after incision. In electrophysiological experiments, spontaneous activity of high threshold (HT) (but not wide dynamic range (WDR)) neurons known to transmit incision induced non-evoked pain was increased after prolonged treatment with the p38-inhibitor. In conclusion, our findings indicate a new spinal pathway by which non-evoked pain behavior after incision is modulated. The pathway is modality (non-evoked pain) and neuron (HT) specific and disturbance contributes to prolonged long-term pain after surgical incision. This may have therapeutic implications for the treatment of acute and - even more relevant - for prevention of chronic pain after surgery in patients. PMID:26920805

  9. Astrocyte/neuron ratio and its importance on glutamate toxicity: an in vitro voltammetric study.

    PubMed

    Hacimuftuoglu, Ahmet; Tatar, Abdulgani; Cetin, Damla; Taspinar, Numan; Saruhan, Fatih; Okkay, Ufuk; Turkez, Hasan; Unal, Deniz; Stephens, Robert Louis; Suleyman, Halis

    2016-08-01

    The purpose of this study was to clarify the relationship between neuron cells and astrocyte cells in regulating glutamate toxicity on the 10th and 20th day in vitro. A mixed primary culture system from newborn rats that contain cerebral cortex neurons cells was employed to investigate the glutamate toxicity. All cultures were incubated with various glutamate concentrations, then viability tests and histological analyses were performed. The activities of glutamate transporters were determined by using in vitro voltammetry technique. Viable cell number was decreased significantly on the 10th day at 10(-7) M and at 10(-6) M glutamate applications, however, viable cell number was not decreased at 20th day. Astrocyte number was increased nearly six times on the 20th day as compared to the 10th day. The peak point of glutamate reuptake capacity was about 2 × 10(-4) M on the 10th day and 10(-3) M on the 20th day. According to our results, we suggested that astrocyte age was important to maintain neuronal survival against glutamate toxicity. Thus, we revealed activation or a trigger point of glutamate transporters on astrocytes due to time since more glutamate was taken up by astrocytes when glutamate transporters on the astrocyte were triggered with high exogenous glutamate concentrations. In conclusion, the present investigation is the first voltammetric study on the reuptake parameters of glutamate in vitro. PMID:26438331

  10. Amphetamine stimulates movement through thalamocortical glutamate release

    PubMed Central

    Mabrouk, Omar S; Semaan, Daniel Z; Mikelman, Sarah; Gnegy, Margaret E; Kennedy, Robert T

    2014-01-01

    The ventrolateral thalamus (VL) is a primary relay point between the basal ganglia and the primary motor cortex (M1). Using dual probe microdialysis and locomotor behavior monitoring, we investigated the contribution of VL input into M1 during amphetamine (AMPH)-stimulated monoamine release and hyperlocomotion in rats. Tetrodotoxin (TTX) (10 uM) perfusion into the VL significantly lowered hyperactivity induced by AMPH (1 mg/kg i.p.). This behavioral response corresponded to reduced cortical glutamate and monoamine release. To determine which glutamate receptors the thalamocortical projections acted upon, we perfused either the AMPA/kainate receptor antagonist NBQX (10 μM) or the NMDA receptor antagonist (MK-801) intracortically followed by systemic AMPH. The results show that AMPA/kainate, and to a lesser extent NMDA receptors, mediated the observed effects. Since glutamate-monoamine interactions could possibly occur through local or circuit-based mechanisms, we isolated and perfused M1 tissue ex vivo to determine the extent of local glutamate-dopamine interactions. Taken together, these results demonstrate that AMPH generates hyperlocomotive states via thalamocortical signaling and that cortical AMPA receptors are an important mediator of these effects. PMID:23889359

  11. Effect of insulin on the compartmentation of glutamate for protein synthesis

    SciTech Connect

    Brown, A.B.; Mohan, C.; Bessman, S.P.

    1986-03-05

    The effect of insulin on the formation of CO/sub 2/ and incorporation of 1-/sup 14/C glutamine and U-/sup 14/C acetate into protein was studied in isolated rat hepatocytes. Insulin caused an 18% increase in /sup 14/CO/sub 2/ production from U-/sup 14/C acetate in comparison to a 10% increase from 1-/sup 14/C glutamate. Insulin caused a greater increase in the incorporation of tracer acetate carbons into hepatocyte protein. Hydrolysis of labeled protein and subsequent determination of glutamate specific activity revealed that incorporation of acetate carbons into protein as glutamate was about 52% greater in the presence of insulin. These results demonstrate the existence of two compartments of glutamate for protein synthesis: (i) glutamate generated in the Krebs cycle through transamination of a-ketoglutarate; (ii) cytosolic glutamate. Insulin had a greater stimulatory effect on the incorporation of glutamate generated in the Krebs cycle.

  12. Temperature Differentially Facilitates Spontaneous but Not Evoked Glutamate Release from Cranial Visceral Primary Afferents

    PubMed Central

    Fawley, Jessica A.; Hofmann, Mackenzie E.; Largent-Milnes, Tally M.; Andresen, Michael C.

    2015-01-01

    Temperature is fundamentally important to all biological functions including synaptic glutamate release. Vagal afferents from the solitary tract (ST) synapse on second order neurons in the nucleus of the solitary tract, and glutamate release at this first central synapse controls autonomic reflex function. Expression of the temperature-sensitive Transient Receptor Potential Vanilloid Type 1 receptor separates ST afferents into C-fibers (TRPV1+) and A-fibers (TRPV1-). Action potential-evoked glutamate release is similar between C- and A-fiber afferents, but TRPV1 expression facilitates a second form of synaptic glutamate release in C-fibers by promoting substantially more spontaneous glutamate release. The influence of temperature on different forms of glutamate release is not well understood. Here we tested how temperature impacts the generation of evoked and spontaneous release of glutamate and its relation to TRPV1 expression. In horizontal brainstem slices of rats, activation of ST primary afferents generated synchronous evoked glutamate release (ST-eEPSCs) at constant latency whose amplitude reflects the probability of evoked glutamate release. The frequency of spontaneous EPSCs in these same neurons measured the probability of spontaneous glutamate release. We measured both forms of glutamate from each neuron during ramp changes in bath temperature of 4–5°C. Spontaneous glutamate release from TRPV1+ closely tracked with these thermal changes indicating changes in the probability of spontaneous glutamate release. In the same neurons, temperature changed axon conduction registered as latency shifts but ST-eEPSC amplitudes were constant and independent of TRPV1 expression. These data indicate that TRPV1-operated glutamate release is independent of action potential-evoked glutamate release in the same neurons. Together, these support the hypothesis that evoked and spontaneous glutamate release originate from two pools of vesicles that are independently

  13. Glutamate release from astrocytic gliosomes under physiological and pathological conditions.

    PubMed

    Milanese, Marco; Bonifacino, Tiziana; Zappettini, Simona; Usai, Cesare; Tacchetti, Carlo; Nobile, Mario; Bonanno, Giambattista

    2009-01-01

    Glial subcellular particles (gliosomes) have been purified from rat cerebral cortex or mouse spinal cord and investigated for their ability to release glutamate. Confocal microscopy showed that gliosomes are enriched with glia-specific proteins, such as GFAP and S-100 but not neuronal proteins, such as PSD-95, MAP-2, and beta-tubulin III. Furthermore, gliosomes exhibit labeling neither for integrin-alphaM nor for myelin basic protein, specific for microglia and oligodendrocytes, respectively. The gliosomal fraction contains proteins of the exocytotic machinery coexisting with GFAP. Consistent with ultrastructural analysis, several nonclustered vesicles are present in the gliosome cytoplasm. Finally, gliosomes represent functional organelles that actively export glutamate when subjected to releasing stimuli, such as ionomycin, high KCl, veratrine, 4-aminopyridine, AMPA, or ATP by mechanisms involving extracellular Ca2+, Ca2+ release from intracellular stores as well as reversal of glutamate transporters. In addition, gliosomes can release glutamate also by a mechanism involving heterologous transporter activation (heterotransporters) located on glutamate-releasing and glutamate transporter-expressing (homotransporters) gliosomes. This glutamate release involves reversal of glutamate transporters and anion channel opening, but not exocytosis. Both the exocytotic and the heterotransporter-mediated glutamate release were more abundant in gliosomes prepared from the spinal cord of transgenic mice, model of amyotrophic lateral sclerosis, than in controls; suggesting the involvement of astrocytic glutamate release in the excitotoxicity proposed as a cause of motor neuron degeneration. The results support the view that gliosomes may represent a viable preparation that allows to study mechanisms of astrocytic transmitter release and its regulation in healthy animals and in animal models of brain diseases. PMID:19607977

  14. Redistribution of Ionotropic Glutamate Receptors Detected by Laser Microdissection of the Rat Dentate Gyrus 48 h following LTP Induction In Vivo

    PubMed Central

    Kennard, Jeremy T. T.; Guévremont, Diane; Mason-Parker, Sara E.; Abraham, Wickliffe C.; Williams, Joanna M.

    2014-01-01

    The persistence and input specificity of long-term potentiation (LTP) make it attractive as a mechanism of information storage. In its initial phase, both in vivo and in vitro studies have shown that LTP is associated with increased membrane localization of AMPA receptor subunits, but the molecular basis of LTP maintenance over the long-term is still unclear. We have previously shown that expression of AMPA and NMDA receptor subunits is elevated in whole homogenates prepared from dentate gyrus 48 h after LTP induction in vivo. In the present study, we utilized laser microdissection (LMD) techniques to determine whether AMPA and NMDA receptor upregulation occurs specifically in the stimulated regions of the dentate gyrus dendritic arbor. Receptor proteins GluN1, GluA1 and GluA2, as well as postsynaptic density protein of 95 kDa and tubulin were detected by Western blot analysis in microdissected samples. Gradients of expression were observed for GluN1 and GluA2, decreasing from the inner to the outer zones of the molecular layer, and were independent of LTP. When induced at medial perforant path synapses, LTP was associated with an apparent specific redistribution of GluA1 and GluN1 to the middle molecular layer that contains these synapses. These data indicate that glutamate receptor proteins are delivered specifically to dendritic regions possessing LTP-expressing synapses, and that these changes are preserved for at least 48 h. PMID:24667777

  15. [Glutamate receptor-mediated retinal neuronal injury in experimental glaucoma].

    PubMed

    Wang, Zhong-Feng; Yang, Xiong-Li

    2016-08-25

    Glaucoma, the second leading cause of blindness, is a neurodegenerative disease characterized by optic nerve degeneration related to apoptotic death of retinal ganglion cells (RGCs). In the pathogenesis of RGC death following the onset of glaucoma, functional changes of glutamate receptors are commonly regarded as important risk factors. During the past several years, we have explored the mechanisms underlying RGC apoptosis and retinal Müller cell reactivation (gliosis) in a rat chronic ocular hypertension (COH) model. We demonstrated that elevated intraocular pressure in COH rats may induce changes of various signaling pathways, which are involved in RGC apoptosis by modulating glutamate NMDA and AMPA receptors. Moreover, we also demonstrated that over-activation of group I metabotropic glutamate receptors (mGluR I) by excessive extracellular glutamate in COH rats could contribute to Müller cell gliosis by suppressing Kir4.1 channels. In this review, incorporating our results, we discuss glutamate receptor- mediated RGC apoptosis and Müller cell gliosis in experimental glaucoma. PMID:27546508

  16. Design and Synthesis of Systemically Active Metabotropic Glutamate Subtype-2 and -3 (mGlu2/3) Receptor Positive Allosteric Modulators (PAMs): Pharmacological Characterization and Assessment in a Rat Model of Cocaine Dependence

    PubMed Central

    2015-01-01

    As part of our ongoing small-molecule metabotropic glutamate (mGlu) receptor positive allosteric modulator (PAM) research, we performed structure–activity relationship (SAR) studies around a series of group II mGlu PAMs. Initial analogues exhibited weak activity as mGlu2 receptor PAMs and no activity at mGlu3. Compound optimization led to the identification of potent mGlu2/3 selective PAMs with no in vitro activity at mGlu1,4–8 or 45 other CNS receptors. In vitro pharmacological characterization of representative compound 44 indicated agonist-PAM activity toward mGlu2 and PAM activity at mGlu3. The most potent mGlu2/3 PAMs were characterized in assays predictive of ADME/T and pharmacokinetic (PK) properties, allowing the discovery of systemically active mGlu2/3 PAMs. On the basis of its overall profile, compound 74 was selected for behavioral studies and was shown to dose-dependently decrease cocaine self-administration in rats after intraperitoneal administration. These mGlu2/3 receptor PAMs have significant potential as small molecule tools for investigating group II mGlu pharmacology. PMID:24735492

  17. The metabotropic glutamate receptor mGluR3 is critically required for hippocampal long-term depression and modulates long-term potentiation in the dentate gyrus of freely moving rats.

    PubMed

    Pöschel, Beatrice; Wroblewska, Barbara; Heinemann, Uwe; Manahan-Vaughan, Denise

    2005-09-01

    Group II metabotropic glutamate receptors (mGluRs) play an important role in the regulation of hippocampal synaptic plasticity in vivo: long-term potentiation (LTP) is inhibited and long-term depression (LTD) is enhanced by activation of these receptors. The contribution, in vivo, of the individual group II mGluR subtypes has not been characterized. We analysed the involvement of the subtype mGluR3 in LTD and LTP. Rats were implanted with electrodes to enable chronic measurement of evoked potentials from medial perforant path-dentate gyrus synapses. Neither the selective mGluR3 agonist, N-acetylaspartylglutamate (NAAG), nor the antagonist beta-NAAG, given intracerebrally, affected basal synaptic transmission. beta-NAAG significantly inhibited LTD expression. NAAG exhibited transient inhibitory effects on the intermediate phase of LTD. Whereas NAAG altered paired-pulse responses, beta-NAAG had no effect, suggesting that antagonism of mGluR3 prevents LTD via a postsynaptic mechanism, whereas agonist activation of mGluR3 modulates LTD at a presynaptic locus. NAAG impaired the expression of LTP, whereas beta-NAAG had no effect. NAAG effects on LTP were blocked by EGLU, a selective group II mGluR antagonist. Our data suggest an essential role for mGluR3 in LTD, and a modulatory role for mGluR3 in LTP, with effects being mediated by distinct pre- and post-synaptic loci. PMID:15635057

  18. Pharmacological characterization of the rat metabotropic glutamate receptor type 8a revealed strong similarities and slight differences with the type 4a receptor.

    PubMed

    De Colle, C; Bessis, A S; Bockaert, J; Acher, F; Pin, J P

    2000-04-01

    In the brain, group-III metabotropic glutamate (mGlu) receptors mGlu(4), mGlu(7) and mGlu(8) receptors play a critical role in controlling the release process at many glutamatergic synapses. The pharmacological profile of mGlu(4) receptor has been studied extensively, allowing us to propose a pharmacophore model for this receptor subtype. Surprisingly, the activity of only a few compounds have been reported on mGlu(7) and mGlu(8) receptors. In order to identify new possibilities for the design of selective compounds able to discriminate between the members of the group-III mGlu receptors, we have undertaken a complete pharmacological characterization of mGlu(8) receptor and compared it with that of mGlu(4) receptor, using the same expression system, and the same read out. The activities of 32 different molecules revealed that these two mGlu receptors subtypes share a similar pharmacological profile. Only small differences were noticed in addition to that previously reported with S-carboxyglutamate (S-Gla) being a partial agonist at mGlu(4) receptor and a full antagonist at mGlu(8) receptor. These include: a slightly higher relative potency of the agonists 1S,3R and 1S,3S-aminocyclopentane-1,3-dicarboxylic acid (ACPD), S-4-carboxyphenylglycine (S-4CPG) and S-4-carboxy-3-hydroxyphenylglycine (S-4C3HPG), and a slightly higher potency of the antagonists 2-aminobicyclo[3.1.0]hexane-2, 6-dicarboxylic acid (LY354740) and RS-alpha-methyl-4-phosphonophenylglycine (MPPG) on mGlu(8) receptor. When superimposed on the mGlu(4) receptor pharmacophore model, these molecules revealed three regions that may be different between the ligand binding sites of mGlu(8) and mGlu(4) receptors. PMID:10771029

  19. Protein kinase C -dependent regulation of synaptosomal glutamate uptake under conditions of hypergravity

    NASA Astrophysics Data System (ADS)

    Borisova, Tatiana; Krisanova, Natalia; Borisov, Arseniy; Sivko, Roman

    Glutamate is not only the main excitatory neurotransmitter in the mammalian CNS, but also a potent neurotoxin. Excessive concentration of ambient glutamate over activates glutamate receptors and causes neurotoxicity. Uptake of glutamate from the extracellular space into nerve cells was mediated by sodium-dependent glutamate transporters located in the plasma membrane. It was shown that the activity of glutamate transporters in rat brain nerve terminals was decreased after hypergravity (centrifugation of rats in special containers at 10 G for 1 hour). This decrease may result from the reduction in the number of glutamate transporters expressed in the plasma membrane of nerve terminals after hypergravity that was regulated by protein kinase C. The possibility of the involvement of protein kinase C in the regulation of the activity of glutamate transporters was assessed under conditions of hypergravity. The effect of protein kinase C inhibitor GF 109 203X on synaptosomal L-[14C]glutamate uptake was analysed. It was shown that the inhibitor decreased L-[14C]glutamate uptake by 15 % in control but did not influence it after hypergravity. In control, the initial velocity of L-[14C]glutamate uptake in the presence of the inhibitor decreased from 2.5 ± 0.2 nmol x min-1 x mg-1 of proteins to 2.17 ± 0.1 nmol x min-1 x mg-1 of proteins, whereas after hypergravity this value lowered from 2.05 ± 0.1 nmol x min-1 x mg-1 of proteins to 2.04 ± 0.1 nmol x min-1 x mg-1 of proteins. Thus, protein kinase C -dependent alteration in the cell surface expression of glutamate transporters may be one of the causes of a decrease in the activity of glutamate transporters after hypergravity.

  20. Behavioral and functional evidence of mGlu2/3 and mGlu5 metabotropic glutamate receptor dysregulation in cocaine-escalated rats: Factor in the transition to dependence

    PubMed Central

    Hao, Yue; Martin-Fardon, Rémi; Weiss, Friedbert

    2010-01-01

    Background Rats with extended daily cocaine access show escalating cocaine self-administration and behavioral signs of dependence. Regulation of glutamatergic transmission by metabotropic glutamate receptors (mGluR) has emerged as a mechanism in the addictive actions of drugs of abuse. We examined here whether neuroadaptive dysregulation of mGluR function is a factor in escalating cocaine self-administration. Methods Rats with 1 h daily cocaine access (short access, ShA) vs. 6 h access (long access, LgA) were tested for differences in the effects of the mGluR2/3 agonist LY379268 and the mGluR5 antagonist MTEP on cocaine-reinforced progressive-ratio (PR) responding and differences in expression levels and functional activity of mGluR2/3 and mGluR5. Results The LgA groups showed higher PR breakpoints than ShA groups. LY379268 (0-3 mg/kg, s.c.) dose-dependently lowered breakpoints in the LgA group but reduced breakpoints only at 3 mg/kg in the ShA group. Consistent with this behavioral effect, functional mGluR2/3 activity was significantly elevated following LgA cocaine exposure. MTEP (0-3 mg/kg, i.p.) reduced breakpoints in the ShA group only. LgA cocaine exposure was associated with decreased mGluR5 expression, accompanied by reduced functional mGluR5 activity in the nucleus accumbens. A downward trend developed in mGluR5 protein expression in the medial prefrontal cortex and hippocampus. Conclusion Functional upregulation of mGluR2/3 and downregulation of mGluR5 are likely factors in the transition to cocaine dependence. The differential behavioral effects of LY379268 and MTEP in rats with a history of long access to cocaine have implications for the treatment target potential of mGluR2/3 and mGluR5. PMID:20416862

  1. Beta-arrestin1 and 2 differently modulate metabotropic glutamate receptor 7 signaling in rat developmental sevoflurane-induced neuronal apoptosis.

    PubMed

    Wang, W-Y; Wu, X-M; Jia, L-J; Zhang, H-H; Cai, F; Mao, H; Xu, W-C; Chen, L; Zhang, J; Hu, S-F

    2016-01-28

    Beta-arrestins (β-arrs) are initially known as negative regulators of G protein-coupled receptors (GPCRs). Recently, there is increasing evidence suggesting that β-arrs also serve as scaffolds and adapters that mediate distinct intracellular signal transduction initiated by GPCR activation. In the previous study, we have shown that metabotropic glutamate receptor 7 (mGluR7) and extracellular signal-regulated kinase 1 and 2 (ERK1/2) signaling may be involved in the developmental sevoflurane neurotoxicity. In the present study, we showed that activation of mGluR7 with a group III mGluRs orthosteric agonist LAP4 or an atypical mGluR7 allosteric agonist N,N'-bis(diphenylmethyl)-1,2-ethanediamine dihydrochloride (AMN082) significantly attenuated sevoflurane-induced neuronal apoptosis. Interestingly, this neuroprotective role of LAP4 could be partially reduced by β-arr1 small interfering RNA (siRNA) or β-arr2 siRNA transfection. In contrast, β-arr2 siRNA transfection alone abolished the effects of AMN082 on sevoflurane neurotoxicity. In addition, administration of LAP4 or AMN082 significantly enhanced Phospho-ERK1/2 in sevoflurane neurotoxicity, which could be abrogated by β-arr2 siRNA transfection, but not by β-arr1 siRNA transfection. Increased β-arr2-dependent Phospho-ERK1/2 signaling alleviated sevoflurane neurotoxicity by inhibiting bad phosphorylation. We also found that the neuroprotective role of AMN082 was completely reversed by ERK1/2 inhibitor 1,4-diamino-2,3-dicyano-1,4-bis[2-aminophenylthio]butadiene (U0126). Alternatively, treatment with U0126 partially suppressed the neuroprotective of LAP4, suggesting that other mechanisms may be implicated in this process. Further investigation indicated that, in the scenario of sevoflurane neurotoxicity, application of LAP4 (but not AMN082) increased the interaction of β-arrs with transcriptional factors CREB binding protein (CBP) and p300. LAP4 also enhanced the β-arr1-dependent H3 and H4 acetylation in

  2. cAMP Response Element-binding Protein (CREB) and Nuclear Factor κB Mediate the Tamoxifen-induced Up-regulation of Glutamate Transporter 1 (GLT-1) in Rat Astrocytes*

    PubMed Central

    Karki, Pratap; Webb, Anton; Smith, Keisha; Lee, Kyuwon; Son, Deok-Soo; Aschner, Michael; Lee, Eunsook

    2013-01-01

    Tamoxifen (TX), a selective estrogen receptor modulator, exerts antagonistic effects on breast tissue and is used to treat breast cancer. Recent evidence also suggests that it may act as an agonist in brain tissue. We reported previously that TX enhanced the expression and function of glutamate transporter 1 (GLT-1) in rat astrocytes, an effect that was mediated by TGF-α. To gain further insight into the mechanisms that mediate TX-induced up-regulation of GLT-1 (EAAT2 in humans), we investigated its effect on GLT-1 at the transcriptional level. TX phosphorylated the cAMP response element-binding protein (CREB) and recruited CREB to the GLT-1 promoter consensus site. The effect of TX on astrocytic GLT-1 was attenuated by the inhibition of PKA, the upstream activator of the CREB pathway. In addition, the effect of TX on GLT-1 promoter activity was abolished by the inhibition of the NF-κB pathway. Furthermore, TX recruited the NF-κB subunits p65 and p50 to the NF-κB binding domain of the GLT-1 promoter. Mutation of NF-κB (triple, −583/-282/-251) or CRE (-308) sites on the GLT-1 promoter led to significant repression of the promoter activity, but neither mutant completely abolished the TX-induced GLT-1 promoter activity. Mutation of both the NF-κB (-583/-282/-251) and CRE (-308) sites led to a complete abrogation of the effect of TX on GLT-1 promoter activity. Taken together, our findings establish that TX regulates GLT-1 via the CREB and NF-κB pathways. PMID:23955341

  3. Role of N-methyl-D-aspartate and non-N-methyl-D-aspartate receptors in the cardiovascular effects of L-glutamate microinjection into the hypothalamic paraventricular nucleus of unanesthetized rats.

    PubMed

    Busnardo, Cristiane; Tavares, Rodrigo F; Corrêa, Fernando M A

    2009-07-01

    We report on the cardiovascular effects of L-glutamate (L-glu) microinjection into the hypothalamic paraventricular nucleus (PVN) as well as the mechanisms involved in their mediation. L-glu microinjection into the PVN caused dose-related pressor and tachycardiac responses in unanesthetized rats. These responses were blocked by intravenous (i.v.) pretreatment with the ganglion blocker pentolinium (PE; 5 mg/kg), suggesting sympathetic mediation. Responses to L-glu were not affected by local microinjection of the selective non-NMDA receptor antagonist NBQX (2 nmol) or by local microinjection of the selective NMDA receptor antagonist LY235959 (LY; 2 nmol). However, the tachycardiac response was changed to a bradycardiac response after treatment with LY235959, suggesting that NMDA receptors are involved in the L-glu heart rate response. Local pretreatment with LY235959 associated with systemic PE or dTyr(CH(2))(5)(Me)AVP (50 microg/kg) respectively potentiated or blocked the response to L-glu, suggesting that L-glu responses observed after LY235959 are vasopressin mediated. The increased pressor and bradycardiac responses observed after LY + PE was blocked by subsequent i.v. treatment with the V(1)-vasopressin receptor antagonist dTyr(CH(2))(5)(Me)AVP, suggesting vasopressin mediation. The pressor and bradycardiac response to L-glu microinjection into the PVN observed in animals pretreated with LY + PE was progressively inhibited and even blocked by additional pretreatment with increasing doses of NBQX (2, 10, and 20 nmol) microinjected into the PVN, suggesting its mediation by local non-NMDA receptors. In conclusion, results suggest the existence of two glutamatergic pressor pathways in the PVN: one sympathetic pathway that is mediated by NMDA receptors and a vasopressinergic pathway that is mediated by non-NMDA receptors. PMID:19229989

  4. Gamma-aminobutyric acid and glutamic acid levels in the auditory pathway of rats with chronic tinnitus: a direct determination using high resolution point-resolved proton magnetic resonance spectroscopy (1H-MRS)

    PubMed Central

    Brozoski, Thomas; Odintsov, Boris; Bauer, Carol

    2012-01-01

    Damage to the auditory system following high-level sound exposure reduces afferent input. Homeostatic mechanisms appear to compensate for the loss. Overcompensation may produce the sensation of sound without an objective physical correlate, i.e., tinnitus. Several potential compensatory neural processes have been identified, such as increased spontaneous activity. The cellular mechanisms enabling such compensatory processes may involve down-regulation of inhibitory neurotransmission mediated by γ-amino butyric acid (GABA), and/or up-regulation of excitatory neurotransmission, mediated by glutamic acid (Glu). Because central processing systems are integrated and well-regulated, compensatory changes in one system may produce reactive changes in others. Some or all may be relevant to tinnitus. To examine the roles of GABA and Glu in tinnitus, high resolution point-resolved proton magnetic resonance spectroscopy (1H-MRS) was used to quantify their levels in the dorsal cochlear nucleus (DCN), inferior colliculus (IC), medial geniculate body (MGB), and primary auditory cortex (A1) of rats. Chronic tinnitus was produced by a single high-level unilateral exposure to noise, and was measured using a psychophysical procedure sensitive to tinnitus. Decreased GABA levels were evident only in the MGB, with the greatest decrease, relative to unexposed controls, obtained in the contralateral MGB. Small GABA increases may have been present bilaterally in A1 and in the contralateral DCN. Although Glu levels showed considerable variation, Glu was moderately and bilaterally elevated both in the DCN and in A1. In the MGB Glu was increased ipsilaterally but decreased contralaterally. These bidirectional and region-specific alterations in GABA and Glu may reflect large-scale changes in inhibitory and excitatory equilibrium accompanying chronic tinnitus. The present results also suggest that targeting both neurotransmitter systems may be optimal in developing more effective therapeutics

  5. Impairment of Neuronal Glutamate Uptake and Modulation of the Glutamate Transporter GLT-1 Induced by Retinal Ischemia

    PubMed Central

    Varano, Giuseppe Pasquale; Milanese, Marco; Adornetto, Annagrazia; Nucci, Carlo; Bonanno, Giambattista; Morrone, Luigi Antonio; Corasaniti, Maria Tiziana; Bagetta, Giacinto

    2013-01-01

    Excitotoxicity has been implicated in the retinal neuronal loss in several ocular pathologies including glaucoma. Dysfunction of Excitatory Amino Acid Transporters is often a key component of the cascade leading to excitotoxic cell death. In the retina, glutamate transport is mainly operated by the glial glutamate transporter GLAST and the neuronal transporter GLT-1. In this study we evaluated the expression of GLAST and GLT-1 in a rat model of acute glaucoma based on the transient increase of intraocular pressure (IOP) and characterized by high glutamate levels during the reperfusion that follows the ischemic event associated with raised IOP. No changes were reported in GLAST expression while, at neuronal level, a reduction of glutamate uptake and of transporter reversal-mediated glutamate release was observed in isolated retinal synaptosomes. This was accompanied by modulation of GLT-1 expression leading to the reduction of the canonical 65 kDa form and upregulation of a GLT-1-related 38 kDa protein. These results support a role for neuronal transporters in glutamate accumulation observed in the retina following an ischemic event and suggest the presence of a GLT-1 neuronal new alternative splice variant, induced in response to the detrimental stimulus. PMID:23936321

  6. Metabotropic Glutamate Receptors

    PubMed Central

    Dillon, James; Franks, Christopher J.; Murray, Caitriona; Edwards, Richard J.; Calahorro, Fernando; Ishihara, Takeshi; Katsura, Isao; Holden-Dye, Lindy; O'Connor, Vincent

    2015-01-01

    Glutamatergic neurotransmission is evolutionarily conserved across animal phyla. A major class of glutamate receptors consists of the metabotropic glutamate receptors (mGluRs). In C. elegans, three mGluR genes, mgl-1, mgl-2, and mgl-3, are organized into three subgroups, similar to their mammalian counterparts. Cellular reporters identified expression of the mgls in the nervous system of C. elegans and overlapping expression in the pharyngeal microcircuit that controls pharyngeal muscle activity and feeding behavior. The overlapping expression of mgls within this circuit allowed the investigation of receptor signaling per se and in the context of receptor interactions within a neural network that regulates feeding. We utilized the pharmacological manipulation of neuronally regulated pumping of the pharyngeal muscle in the wild-type and mutants to investigate MGL function. This defined a net mgl-1-dependent inhibition of pharyngeal pumping that is modulated by mgl-3 excitation. Optogenetic activation of the pharyngeal glutamatergic inputs combined with electrophysiological recordings from the isolated pharyngeal preparations provided further evidence for a presynaptic mgl-1-dependent regulation of pharyngeal activity. Analysis of mgl-1, mgl-2, and mgl-3 mutant feeding behavior in the intact organism after acute food removal identified a significant role for mgl-1 in the regulation of an adaptive feeding response. Our data describe the molecular and cellular organization of mgl-1, mgl-2, and mgl-3. Pharmacological analysis identified that, in these paradigms, mgl-1 and mgl-3, but not mgl-2, can modulate the pharyngeal microcircuit. Behavioral analysis identified mgl-1 as a significant determinant of the glutamate-dependent modulation of feeding, further highlighting the significance of mGluRs in complex C. elegans behavior. PMID:25869139

  7. Ammonia Mediates Methamphetamine-Induced Increases in Glutamate and Excitotoxicity

    PubMed Central

    Halpin, Laura E; Northrop, Nicole A; Yamamoto, Bryan K

    2014-01-01

    Ammonia has been identified to have a significant role in the long-term damage to dopamine and serotonin terminals produced by methamphetamine (METH), but how ammonia contributes to this damage is unknown. Experiments were conducted to identify whether increases in brain ammonia affect METH-induced increases in glutamate and subsequent excitotoxicity. Increases in striatal glutamate were measured using in vivo microdialysis. To examine the role of ammonia in mediating changes in extracellular glutamate after METH exposure, lactulose was used to decrease plasma and brain ammonia. Lactulose is a non-absorbable disaccharide, which alters the intestinal lumen through multiple mechanisms that lead to the increased peripheral excretion of ammonia. METH caused a significant increase in extracellular glutamate that was prevented by lactulose. Lactulose had no effect on METH-induced hyperthermia. To determine if ammonia contributed to excitotoxicity, the effect of METH and lactulose treatment on calpain-mediated spectrin proteolysis was measured. METH significantly increased calpain-specific spectrin breakdown products, and this increase was prevented with lactulose treatment. To examine if ammonia-induced increases in extracellular glutamate were mediated by excitatory amino-acid transporters, the reverse dialysis of ammonia, the glutamate transporter inhibitor, DL-threo-β-benzyloxyaspartic acid (TBOA), or the combination of the two directly into the striatum of awake, freely moving rats was conducted. TBOA blocked the increases in extracellular glutamate produced by the reverse dialysis of ammonia. These findings demonstrate that ammonia mediates METH-induced increases in extracellular glutamate through an excitatory amino-acid transporter to cause excitotoxicity. PMID:24165886

  8. Short-term sleep deprivation disrupts the molecular composition of ionotropic glutamate receptors in entorhinal cortex and impairs the rat spatial reference memory.

    PubMed

    Xie, Meilan; Li, Chao; He, Chao; Yang, Li; Tan, Gang; Yan, Jie; Wang, Jiali; Hu, Zhian

    2016-03-01

    Numerous studies reported that sleep deprivation (SD) causes impairment in spatial cognitive performance. However, the molecular mechanisms affected by SD underlying this behavioral phenomenon remain elusive. Here, we focused on the entorhinal cortex (EC), the gateway of the hippocampus, and investigated how SD affected the subunit expression of AMPARs and NMDARs, the main ionotropic glutamategic receptors serving a pivotal role in spatial cognition. In EC, we found 4h SD remarkably reduced surface expression of GluA1, while there was an increase in the surface expression of GluA2 and GluA3. As for NMDARs, SD with short duration significantly reduced the surface expression levels of GluN1 and GluN2B without effect on the GluN2A. In parallel with the alterations in AMPARs and NMDARs, we found the 4h SD impaired rat spatial reference memory as assessed by Morris water maze task. Overall, these data indicate that brief SD differently affects the AMPAR and NMDAR subunit expressions in EC and might consequently disrupt the composition and functional properties of these receptors. PMID:26455878

  9. Caffeine promotes glutamate and histamine release in the posterior hypothalamus

    PubMed Central

    Kodama, Tohru; Siegel, Jerome M.

    2014-01-01

    Histamine neurons are active during waking and largely inactive during sleep, with minimal activity during rapid-eye movement (REM) sleep. Caffeine, the most widely used stimulant, causes a significant increase of sleep onset latency in rats and humans. We hypothesized that caffeine increases glutamate release in the posterior hypothalamus (PH) and produces increased activity of wake-active histamine neurons. Using in vivo microdialysis, we collected samples from the PH after caffeine administration in freely behaving rats. HPLC analysis and biosensor measurements showed a significant increase in glutamate levels beginning 30 min after caffeine administration. Glutamate levels remained elevated for at least 140 min. GABA levels did not significantly change over the same time period. Histamine level significantly increased beginning 30 min after caffeine administration and remained elevated for at least 140 min. Immunostaining showed a significantly elevated number of c-Fos-labeled histamine neurons in caffeine-treated rats compared with saline-treated animals. We conclude that increased glutamate levels in the PH activate histamine neurons and contribute to caffeine-induced waking and alertness. PMID:25031227

  10. Tea Polyphenols Protect Against Methylmercury-Induced Cell Injury in Rat Primary Cultured Astrocytes, Involvement of Oxidative Stress and Glutamate Uptake/Metabolism Disorders.

    PubMed

    Liu, Wei; Xu, Zhaofa; Yang, Tianyao; Deng, Yu; Xu, Bin; Feng, Shu

    2016-07-01

    Methylmercury (MeHg) is an extremely dangerous environmental contaminant, accumulating preferentially in CNS and causing a series of cytotoxic effects. However, the precise mechanisms are still incompletely understood. The current study explored the mechanisms that contribute to MeHg-induced cell injury focusing on the oxidative stress and Glu uptake/metabolism disorders in rat primary cultured astrocytes. Moreover, the neuroprotective effects of tea polyphenols (TP), a natural antioxidant, against MeHg cytotoxicity were also investigated. Astrocytes were exposed to 0, 2.5, 5, 10, and 20 μM MeHgCl for 6-30 h, or pretreated with 50, 100, 200, and 400 μM TP for 1-12 h; cell viability and LDH release were then determined. For further experiments, 50, 100, and 200 μM of TP pretreatment for 6 h followed by 10 μM MeHgCl for 24 h were performed for the examination of the responses of astrocytes, specifically addressing NPSH levels, ROS generation, ATPase activity, the expressions of Nrf2 pathway as well as Glu metabolism enzyme GS and Glu transporters (GLAST and GLT-1). Exposure of MeHg resulted in damages of astrocytes, which were shown by a loss of cell viability, and supported by high levels of LDH release, morphological changes, apoptosis rates, and NPSH depletion. In addition, astrocytes were sensitive to MeHg-mediated oxidative stress, a finding that is consistent with ROS overproduction; Nrf2 as well as its downstream genes HO-1 and γ-GCSh were markedly upregulated. Moreover, MeHg significantly inhibited GS activity, as well as expressions of GS, GLAST, and GLT-1. On the contrary, pretreatment with TP presented a concentration-dependent prevention against MeHg-mediated cytotoxic effects of astrocytes. In conclusion, the findings clearly indicated that MeHg aggravated oxidative stress and Glu uptake/metabolism dysfunction in astrocytes. TP possesses some abilities to prevent MeHg cytotoxicity through its antioxidative properties. PMID:25952541

  11. Pivotal Enzyme in Glutamate Metabolism of Poly-γ-Glutamate-Producing Microbes

    PubMed Central

    Ashiuchi, Makoto; Yamamoto, Takashi; Kamei, Tohru

    2013-01-01

    The extremely halophilic archaeon Natrialba aegyptiaca secretes the L-homo type of poly-γ-glutamate (PGA) as an extremolyte. We examined the enzymes involved in glutamate metabolism and verified the presence of L-glutamate dehydrogenases, L-aspartate aminotransferase, and L-glutamate synthase. However, neither glutamate racemase nor D-amino acid aminotransferase activity was detected, suggesting the absence of sources of D-glutamate. In contrast, D-glutamate-rich PGA producers mostly possess such intracellular sources of D-glutamate. The results of our present study indicate that the D-glutamate-anabolic enzyme “glutamate racemase” is pivotal in the biosynthesis of PGA. PMID:25371338

  12. Diffuse Brain Injury Elevates Tonic Glutamate Levels and Potassium-Evoked Glutamate Release in Discrete Brain Regions at Two Days Post-Injury: An Enzyme-Based Microelectrode Array Study

    PubMed Central

    Hinzman, Jason M.; Currier Thomas, Theresa; Burmeister, Jason J.; Quintero, Jorge E.; Huettl, Peter; Pomerleau, Francois; Gerhardt, Greg A.

    2010-01-01

    Abstract Traumatic brain injury (TBI) survivors often suffer from a wide range of post-traumatic deficits, including impairments in behavioral, cognitive, and motor function. Regulation of glutamate signaling is vital for proper neuronal excitation in the central nervous system. Without proper regulation, increases in extracellular glutamate can contribute to the pathophysiology and neurological dysfunction seen in TBI. In the present studies, enzyme-based microelectrode arrays (MEAs) that selectively measure extracellular glutamate at 2 Hz enabled the examination of tonic glutamate levels and potassium chloride (KCl)-evoked glutamate release in the prefrontal cortex, dentate gyrus, and striatum of adult male rats 2 days after mild or moderate midline fluid percussion brain injury. Moderate brain injury significantly increased tonic extracellular glutamate levels by 256% in the dentate gyrus and 178% in the dorsal striatum. In the dorsal striatum, mild brain injury significantly increased tonic glutamate levels by 200%. Tonic glutamate levels were significantly correlated with injury severity in the dentate gyrus and striatum. The amplitudes of KCl-evoked glutamate release were increased significantly only in the striatum after moderate injury, with a 249% increase seen in the dorsal striatum. Thus, with the MEAs, we measured discrete regional changes in both tonic and KCl-evoked glutamate signaling, which were dependent on injury severity. Future studies may reveal the specific mechanisms responsible for glutamate dysregulation in the post-traumatic period, and may provide novel therapeutic means to improve outcomes after TBI. PMID:20233041

  13. Phosphorylation and Assembly of Glutamate Receptors after Brain Ischemia

    PubMed Central

    Zhang, Fan; Guo, Ailan; Liu, Chunli; Comb, Micheal; Hu, Bingren

    2012-01-01

    Background and Purpose Over-assembly of synaptic glutamate receptors leads to excitotoxicity. The goal of this study is to investigate phosphorylation and assembly of AMPA and NMDA receptors after brain ischemia with reperfusion (I/R). Methods Rats were subjected to 15 min of global ischemia followed by 0.5, 4, and 24 h of reperfusion. Phosphotyrosine (Ptyr) peptides of glutamate receptors in synaptosomal fraction after I/R were identified and quantified by state-of-the-art immuno-affinity purification of Ptyr peptides followed by LC-MS/MS analysis (IAP-LC/MS/MS). Glutamate receptor phosphorylation and synaptic assembly after I/R were studied by biochemical methods. Results Numerous Ptyr sites of AMPA and NMDA were upregulated by about 2- to 37-fold after I/R. A core glutamate receptor kinase, Src kinase, was significantly activated. GluR2/3 and NR2A/B were rapidly clustered from extrasynaptic to synaptic membrane fractions after I/R. GluR2/3 was then translocated into the intracellular pool, whereas NR2A/B remained in the synaptic fraction for as long as 24 h. Consistently, trafficking-related phosphorylation of GluR2/3-S880 was significantly but transiently upregulated, whereas NR2A/B-Y1246 and -Y1472 were significantly and persistently upregulated after I/R. Conclusions Phosphorylation of glutamate receptors at synapses may lead to over-assembly of glutamate receptors, probably via activation of Src family kinases, after I/R. This study provides “global” proteomic information about glutamate receptor tyrosine phosphorylation after brain ischemia. PMID:23212166

  14. Detection of glutamate release from neurons by genetically encoded surface-displayed FRET nanosensors

    NASA Astrophysics Data System (ADS)

    Okumoto, Sakiko; Looger, Loren L.; Micheva, Kristina D.; Reimer, Richard J.; Smith, Stephen J.; Frommer, Wolf B.

    2005-06-01

    Glutamate is the predominant excitatory neurotransmitter in the mammalian brain. Once released, its rapid removal from the synaptic cleft is critical for preventing excitotoxicity and spillover to neighboring synapses. Despite consensus on the role of glutamate in normal and disease physiology, technical issues limit our understanding of its metabolism in intact cells. To monitor glutamate levels inside and at the surface of living cells, genetically encoded nanosensors were developed. The fluorescent indicator protein for glutamate (FLIPE) consists of the glutamate/aspartate binding protein ybeJ from Escherichia coli fused to two variants of the green fluorescent protein. Three sensors with lower affinities for glutamate were created by mutation of residues peristeric to the ybeJ binding pocket. In the presence of ligands, FLIPEs show a concentration-dependent decrease in FRET efficiency. When expressed on the surface of rat hippocampal neurons or PC12 cells, the sensors respond to extracellular glutamate with a reversible concentration-dependent decrease in FRET efficiency. Depolarization of neurons leads to a reduction in FRET efficiency corresponding to 300 nM glutamate at the cell surface. No change in FRET was observed when cells expressing sensors in the cytosol were superfused with up to 20 mM glutamate, consistent with a minimal contribution of glutamate uptake to cytosolic glutamate levels. The results demonstrate that FLIPE sensors can be used for real-time monitoring of glutamate metabolism in living cells, in tissues, or in intact organisms, providing tools for studying metabolism or for drug discovery. aspartate | hippocampal neuron | neurotransmitter | secretion | transport

  15. Magnesium Sulfate Protects Against the Bioenergetic Consequences of Chronic Glutamate Receptor Stimulation

    PubMed Central

    Clerc, Pascaline; Young, Christina A.; Bordt, Evan A.; Grigore, Alina M.; Fiskum, Gary; Polster, Brian M.

    2013-01-01

    Extracellular glutamate is elevated following brain ischemia or trauma and contributes to neuronal injury. We tested the hypothesis that magnesium sulfate (MgSO4, 3 mM) protects against metabolic failure caused by excitotoxic glutamate exposure. Rat cortical neuron preparations treated in medium already containing a physiological concentration of Mg2+ (1 mM) could be segregated based on their response to glutamate (100 µM). Type I preparations responded with a decrease or small transient increase in oxygen consumption rate (OCR). Type II neurons responded with >50% stimulation in OCR, indicating a robust response to increased energy demand without immediate toxicity. Pre-treatment with MgSO4 improved the initial bioenergetic response to glutamate and ameliorated subsequent loss of spare respiratory capacity, measured following addition of the uncoupler FCCP, in Type I but not Type II neurons. Spare respiratory capacity in Type I neurons was also improved by incubation with MgSO4 or NMDA receptor antagonist MK801 in the absence of glutamate treatment. This finding indicates that the major difference between Type I and Type II preparations is the amount of endogenous glutamate receptor activity. Incubation of Type II neurons with 5 µM glutamate prior to excitotoxic (100 µM) glutamate exposure recapitulated a Type I phenotype. MgSO4 protected against an excitotoxic glutamate-induced drop in neuronal ATP both with and without prior 5 µM glutamate exposure. Results indicate that MgSO4 protects against chronic moderate glutamate receptor stimulation and preserves cellular ATP following treatment with excitotoxic glutamate. PMID:24236167

  16. Single rodent mesohabenular axons release glutamate and GABA

    PubMed Central

    Root, David H.; Mejias-Aponte, Carlos; Zhang, Shiliang; Wang, Huiling; Hoffman, Alexander F.; Lupica, Carl R.; Morales, Marisela

    2016-01-01

    The lateral habenula (LHb) is involved in reward, aversion, addiction, and depression, through descending interactions with several brain structures, including the ventral tegmental area (VTA). VTA provides reciprocal inputs to LHb, but their actions are unclear. Here we show that the majority of rat and mouse VTA neurons innervating LHb co-express markers for both glutamate-signaling (vesicular glutamate transporter 2, VGluT2) and GABA-signaling (glutamate decarboxylase, GAD; and vesicular GABA transporter, VGaT). A single axon from these mesohabenular neurons co-expresses VGluT2-protein and VGaT-protein, and surprisingly establishes symmetric and asymmetric synapses on LHb neurons. In LHb slices, light activation of mesohabenular fibers expressing channelrhodopsin-2 (ChR2) driven by VGluT2 or VGaT promoters elicits release of both glutamate and GABA onto single LHb neurons. In vivo light-activation of mesohabenular terminals inhibits or excites LHb neurons. Our findings reveal an unanticipated type of VTA neuron that co-transmits glutamate and GABA, and provides the majority of mesohabenular inputs. PMID:25242304

  17. Glutamic acid as anticancer agent: An overview

    PubMed Central

    Dutta, Satyajit; Ray, Supratim; Nagarajan, K.

    2013-01-01

    The objective of the article is to highlight various roles of glutamic acid like endogenic anticancer agent, conjugates to anticancer agents, and derivatives of glutamic acid as possible anticancer agents. Besides these emphases are given especially for two endogenous derivatives of glutamic acid such as glutamine and glutamate. Glutamine is a derivative of glutamic acid and is formed in the body from glutamic acid and ammonia in an energy requiring reaction catalyzed by glutamine synthase. It also possesses anticancer activity. So the transportation and metabolism of glutamine are also discussed for better understanding the role of glutamic acid. Glutamates are the carboxylate anions and salts of glutamic acid. Here the roles of various enzymes required for the metabolism of glutamates are also discussed. PMID:24227952

  18. Computational Studies of Glutamate Transporters

    PubMed Central

    Setiadi, Jeffry; Heinzelmann, Germano; Kuyucak, Serdar

    2015-01-01

    Glutamate is the major excitatory neurotransmitter in the human brain whose binding to receptors on neurons excites them while excess glutamate are removed from synapses via transporter proteins. Determination of the crystal structures of bacterial aspartate transporters has paved the way for computational investigation of their function and dynamics at the molecular level. Here, we review molecular dynamics and free energy calculation methods used in these computational studies and discuss the recent applications to glutamate transporters. The focus of the review is on the insights gained on the transport mechanism through computational methods, which otherwise is not directly accessible by experimental probes. Recent efforts to model the mammalian glutamate and other amino acid transporters, whose crystal structures have not been solved yet, are included in the review. PMID:26569328

  19. Genotoxicity of monosodium glutamate.

    PubMed

    Ataseven, Nazmiye; Yüzbaşıoğlu, Deniz; Keskin, Ayten Çelebi; Ünal, Fatma

    2016-05-01

    Monosodium glutamate (MSG) is one of the most widely used flavor enhancers throughout the world. The aim of this study is to investigate the genotoxic potential of MSG by using chromosome aberrations (CAs), sister-chromatid exchanges (SCEs), cytokinesis-blocked micronucleus (CBMN), and random amplified polymorphic DNA-polimerase chain reaction (RAPD-PCR) in cultured human lymphocytes and alkaline comet assays in isolated human lymphocytes, which were incubated with six concentrations (250, 500, 1000, 2000, 4000 and 8000 μg/mL) of MSG. The result of this study indicated that MSG significantly and dose dependently increased the frequencies of CAs, SCE and MN in all treatments and times, compared with control. However, the replication (RI) and nuclear division indices (NDI) were not affected. In this paper, in vitro genotoxic effects of the MSG was also investigated on human peripheral lymphocytes by analysing the RAPD-PCR with arbitrary 10-mer primers. The changes occurring in RAPD profiles after MSG treatment include increase or decrease in band intensity and gain or loss of bands. In the comet assay, this additive caused DNA damage at all concentrations in isolated human lymphocytes after 1-h in vitro exposure. Our results demonstrate that MSG is genotoxic to the human peripheral blood lymphocytes in vitro. PMID:26929995

  20. Neuroprotective effects of bis(7)-tacrine against glutamate-induced retinal ganglion cells damage

    PubMed Central

    2010-01-01

    Background Glutamate-mediated excitotoxicity, primarily through N-methyl-D-aspartate (NMDA) receptors, may be an important cause of retinal ganglion cells (RGCs) death in glaucoma and several other retinal diseases. Bis(7)-tacrine is a noncompetitive NMDA receptors antagonist that can prevent glutamate-induced hippocampal neurons damage. We tested the effects of bis(7)-tacrine against glutamate-induced rat RGCs damage in vitro and in vivo. Results In cultured neonatal rats RGCs, the MTT assay showed that glutamate induced a concentration- and time-dependent toxicity. Bis(7)-tacrine and memantine prevented glutamate-induced cell death in a concentration-dependent manner with IC50 values of 0.028 μM and 0.834 μM, respectively. The anti-apoptosis effects of bis(7)-tacrine were confirmed by annexin V-FITC/PI staining. In vivo, TUNEL analysis and retrograde labeling analysis found that pretreatment with bis(7)-tacrine(0.2 mg/kg) induced a significant neuroprotective effect against glutamate-induced RGCs damage. Conclusions Our results showed that bis(7)-tacrine had neuroprotective effects against glutamate-induced RGCs damage in vitro and in vivo, possibly through the drug's anti-NMDA receptor effects. These findings make bis(7)-tacrine potentially useful for treating a variety of ischemic or traumatic retinopathies inclusive of glaucoma. PMID:20199668

  1. Researching glutamate - induced cytotoxicity in different cell lines: a comparative/collective analysis/study.

    PubMed

    Kritis, Aristeidis A; Stamoula, Eleni G; Paniskaki, Krystallenia A; Vavilis, Theofanis D

    2015-01-01

    Although glutamate is one of the most important excitatory neurotransmitters of the central nervous system, its excessive extracellular concentration leads to uncontrolled continuous depolarization of neurons, a toxic process called, excitotoxicity. In excitotoxicity glutamate triggers the rise of intracellular Ca(2+) levels, followed by up regulation of nNOS, dysfunction of mitochondria, ROS production, ER stress, and release of lysosomal enzymes. Excessive calcium concentration is the key mediator of glutamate toxicity through over activation of ionotropic and metabotropic receptors. In addition, glutamate accumulation can also inhibit cystine (CySS) uptake by reversing the action of the CySS/glutamate antiporter. Reversal of the antiporter action reinforces the aforementioned events by depleting neurons of cysteine and eventually glutathione's reducing potential. Various cell lines have been employed in the pursuit to understand the mechanism(s) by which excitotoxicity affects the cells leading them ultimately to their demise. In some cell lines glutamate toxicity is exerted mainly through over activation of NMDA, AMPA, or kainate receptors whereas in other cell lines lacking such receptors, the toxicity is due to glutamate induced oxidative stress. However, in the greatest majority of the cell lines ionotropic glutamate receptors are present, co-existing to CySS/glutamate antiporters and metabotropic glutamate receptors, supporting the assumption that excitotoxicity effect in these cells is accumulative. Different cell lines differ in their responses when exposed to glutamate. In this review article the responses of PC12, SH-SY5Y, HT-22, NT-2, OLCs, C6, primary rat cortical neurons, RGC-5, and SCN2.2 cell systems are systematically collected and analyzed. PMID:25852482

  2. Researching glutamate – induced cytotoxicity in different cell lines: a comparative/collective analysis/study

    PubMed Central

    Kritis, Aristeidis A.; Stamoula, Eleni G.; Paniskaki, Krystallenia A.; Vavilis, Theofanis D.

    2015-01-01

    Although glutamate is one of the most important excitatory neurotransmitters of the central nervous system, its excessive extracellular concentration leads to uncontrolled continuous depolarization of neurons, a toxic process called, excitotoxicity. In excitotoxicity glutamate triggers the rise of intracellular Ca2+ levels, followed by up regulation of nNOS, dysfunction of mitochondria, ROS production, ER stress, and release of lysosomal enzymes. Excessive calcium concentration is the key mediator of glutamate toxicity through over activation of ionotropic and metabotropic receptors. In addition, glutamate accumulation can also inhibit cystine (CySS) uptake by reversing the action of the CySS/glutamate antiporter. Reversal of the antiporter action reinforces the aforementioned events by depleting neurons of cysteine and eventually glutathione’s reducing potential. Various cell lines have been employed in the pursuit to understand the mechanism(s) by which excitotoxicity affects the cells leading them ultimately to their demise. In some cell lines glutamate toxicity is exerted mainly through over activation of NMDA, AMPA, or kainate receptors whereas in other cell lines lacking such receptors, the toxicity is due to glutamate induced oxidative stress. However, in the greatest majority of the cell lines ionotropic glutamate receptors are present, co-existing to CySS/glutamate antiporters and metabotropic glutamate receptors, supporting the assumption that excitotoxicity effect in these cells is accumulative. Different cell lines differ in their responses when exposed to glutamate. In this review article the responses of PC12, SH-SY5Y, HT-22, NT-2, OLCs, C6, primary rat cortical neurons, RGC-5, and SCN2.2 cell systems are systematically collected and analyzed. PMID:25852482

  3. Application of confocal microscopy on glutamate-induced intracellular calcium transient in neurons

    NASA Astrophysics Data System (ADS)

    Zhu, Geng; Zhou, Wei; Zhang, Yuan; Liu, Xiuli; Wu, Yuxiang; Luo, Qingming

    2006-02-01

    Intracellular calcium, as an important second messenger, plays a significant role in cell signaling transduction and metabolism. Glutamate can induce the intracellular calcium transient through triggering diverse signaling pathways. To test the effect of glutamate to neurons, we loaded Fluo-3/Am in cultured rat hippocampal neurons, and then acquired two-dimensional fluorescent image by confocal microscopy and the analyzed fluorescent intensity. In cultured neurons, we observed two types of neurons that have different morphology: bipolar-type and pyramidal-type. Inducing [Ca 2+] i transient by glutamate, we found the amplitude and time constant of the response curves of bipolar neurons are larger than those of pyramidal neurons. Further, we induced [Ca 2+] ii transient under different concentrations of glutamate. Two different types of kinetic of the [Ca 2+] i transient have been found, corresponded to the two kinds of neuron. The amplitude of [Ca 2+] i transient increased when applying higher concentration of glutamate in pyramidal neurons; while it decreased in bipolar ones. Responses of neurons bathing in calcium-free extracellular solution to glutamate were different from those bathing in normal solution. [Ca 2+] i transient of pyramidal neurons caused by any concentration were totally blocked; while [Ca 2+] i transient in bipolar neurons caused by high concentration of glutamate (500μM) were partly inhibited. All of the phenomena suggest that different types of cultured hippocampal neurons may have different mechanism of the response to glutamate.

  4. WAY208466 inhibits glutamate release at hippocampal nerve terminals.

    PubMed

    Wang, Hue Yu; Lu, Cheng Wei; Lin, Tzu Yu; Kuo, Jinn Rung; Wang, Su Jane

    2016-06-15

    Evidence suggests that the glutamatergic system plays a crucial role in the pathophysiology and treatment of depression. This study investigates the effect of WAY208466, a 5-HT6 receptor agonist exhibiting an antidepressant effect, on glutamate release from rat hippocampal nerve terminals (synaptosomes). WAY208466 inhibited the Ca(2+)-dependent release of glutamate that was evoked by exposing the synaptosomes to the potassium channel blocker 4-aminopyridine, and the selective 5-HT6 receptor antagonist SB258585 blocked this phenomenon. The WAY208466-mediated inhibition of glutamate release was associated with a reduction of 4-aminopyridine-induced increase in the cytosolic free Ca(2+) concentration ([Ca(2+)]C) mediated via Cav2.2 (N-type) and Cav2.1 (P/Q-type) channels. WAY208466 did not alter the resting synaptosomal membrane potential or 4-aminopyridine-mediated depolarization; thus, the inhibition of the Ca(2+) influx could not be attributed to the decrease in synaptosomal excitability caused by 5-HT6 receptor activation. Furthermore, the effect of WAY208466 on 4-aminopyridine-evoked glutamate release was prevented by a Gi/Go-protein inhibitor pertussis toxin, adenylate cyclase inhibitor SQ22536, and a protein kinase A inhibitor H89. These results suggest that WAY208466 acts at the 5-HT6 receptors present in the hippocampal nerve terminals to suppress the Gi/Go-protein-coupled adenylate cyclase/protein kinase A cascade, which subsequently reduces the Ca(2+) influx via N- and P/Q-type Ca(2+) channels to inhibit the evoked glutamate release. This finding implicated a potential therapeutic role of 5-HT6 receptor agonist in the treatment of depression and other neurological diseases associated with glutamate excitotoxicity. PMID:27068148

  5. Solubilization, partial purification, and reconstitution of glutamate- and N-methyl-D-aspartate-activated cation channels from brain synaptic membranes

    SciTech Connect

    Ly, A.M.; Michaelis, E.K. )

    1991-04-30

    L-Glutamate-activated cation channel proteins from rat brain synaptic membranes were solubilized, partially purified, and reconstituted into liposomes. Optimal conditions for solubilization and reconstitution included treatment of the membranes with nonionic detergents in the presence of neutral phospholipids plus glycerol. Quench-flow procedures were developed to characterize the rapid kinetics of ion flux induced by receptor agonists. ({sup 14}C)Methylamine, a cation that permeates through the open channel of both vertebrate and invertebrate glutamate receptors, was used to measure the activity of glutamate receptor-ion channel complexes in reconstituted liposomes. L-Glutamate caused an increase in the rate of ({sup 14}C)methylamine influx into liposomes reconstituted with either solubilized membrane proteins or partially purified glutamate-binding proteins. Of the major glutamate receptor agonists, only N-methyl-D-aspartate activated cation fluxes in liposomes reconstituted with glutamate-binding proteins. In liposomes reconstituted with glutamate-binding proteins, N-methyl-D-aspartate- or glutamate-induced influx of NA{sup +} led to a transient increase in the influx of the lipid-permeable anion probe S{sup 14}CN{sup {minus}}. These results indicate the functional reconstitution of N-methyl-D-aspartate-sensitive glutamate receptors and the role of the {approximately}69-kDa protein in the function of these ion channels.

  6. A high dietary intake of sodium glutamate as flavoring (ajinomoto) causes gross changes in retinal morphology and function.

    PubMed

    Ohguro, Hiroshi; Katsushima, Harumi; Maruyama, Ikuyo; Maeda, Tadao; Yanagihashi, Satsuki; Metoki, Tomomi; Nakazawa, Mitsuru

    2002-09-01

    The purpose of this study was to investigate the effects of glutamate accumulation in vitreous on retinal structure and function, due to a diet high in sodium glutamate. Three different diet groups were created, consisting of rats fed on a regular diet (diet A), a moderate excess of sodium glutamate diet (diet B) and a large excess of sodium glutamate diet (diet C). After 1, 3 and 6 months of the administration of these diets, amino acids concentrations in vitreous were analyzed. In addition, retinal morphology and function by electroretinogram (ERG) of three different diet groups were studied. Significant accumulation of glutamate in vitreous was observed in rats following addition of sodium glutamate to the diet as compared to levels with a regular diet. In the retinal morphology, thickness of retinal neuronal layers was remarkably thinner in rats fed on sodium glutamate diets than in those on a regular diet. TdT-dUTP terminal nick-end labelling (TUNEL) staining revealed significant accumulation of the positive staining cells within the retinal ganglion cell layers in retinas from diets B and C as compared with that from diet A. Similar to this, immunohistochemistry demonstrated increased expression of glial fibrillary acidic protein (GFAP) within the retinal inner layers from diets B and C as compared with diet A. Functionally, ERG responses were reduced in rats fed on a sodium glutamate diets as compared with those on a regular diet. The present study suggests that a diet with excess sodium glutamate over a period of several years may increase glutamate concentrations in vitreous and may cause retinal cell destruction. PMID:12384093

  7. The neuroactive peptide N-acetylaspartylglutamate is not an agonist at the metabotropic glutamate receptor subtype 3 of metabotropic glutamate receptor.

    PubMed

    Chopra, Maninder; Yao, Yi; Blake, Timothy J; Hampson, David R; Johnson, Edwin C

    2009-07-01

    The peptide N-acetylaspartylglutamate (NAAG) is present in high concentrations in the mammalian central nervous system. Various mechanisms have been proposed for its action, including selective activation of the metabotropic glutamate receptor (mGluR) subtype 3, its action at the N-methyl-D-aspartate receptor, or the production of glutamate by its hydrolysis catalyzed by an extracellular protease. To re-examine its agonist activity at mGluR3, we coexpressed human or rat mGluR3 with G protein inward rectifying channels in Xenopus laevis oocytes. High-performance liquid chromatography analysis of commercial sources of NAAG showed 0.38 to 0.48% glutamate contamination. Although both human and rat mGluR3 were highly sensitive to glutamate, with EC(50) values of 58 and 28 nM, respectively, purified NAAG (100 microM) had little activity (7.7% of full activation by glutamate). Only in the millimolar range did it show significant activity, possibly due to residual traces of glutamate remaining in the purified NAAG preparations. In contrast, the unpurified NAAG sample did produce a full agonist response with mGluR3 coexpressed with G alpha(15), with an EC(50) of 120 microM, as measured by a calcium release assay. This response can be explained by the 0.38 to 0.48% glutamate contamination. Our results suggest that NAAG may not have a direct agonist activity at the mGluR3 receptor. Thus, several in vivo and in vitro published results that did not address the issue of glutamate contamination of NAAG preparations may need to be re-evaluated. PMID:19389924

  8. Botulinum neurotoxin type A modulates vesicular release of glutamate from satellite glial cells

    PubMed Central

    da Silva, Larissa Bittencourt; Poulsen, Jeppe Nørgaard; Arendt-Nielsen, Lars; Gazerani, Parisa

    2015-01-01

    This study investigated the presence of cell membrane docking proteins synaptosomal-associated protein, 25 and 23 kD (SNAP-25 and SNAP-23) in satellite glial cells (SGCs) of rat trigeminal ganglion; whether cultured SGCs would release glutamate in a time- and calcium-dependent manner following calcium-ionophore ionomycin stimulation; and if botulinum neurotoxin type A (BoNTA), in a dose-dependent manner, could block or decrease vesicular release of glutamate. SGCs were isolated from the trigeminal ganglia (TG) of adult Wistar rats and cultured for 7 days. The presence of SNAPs in TG sections and isolated SGCs were investigated using immunohistochemistry and immunocytochemistry, respectively. SGCs were stimulated with ionomycin (5 μM for 4, 8, 12 and 30 min.) to release glutamate. SGCs were then pre-incubated with BoNTA (24 hrs with 0.1, 1, 10 and 100 pM) to investigate if BoNTA could potentially block ionomycin-stimulated glutamate release. Glutamate concentrations were measured by ELISA. SNAP-25 and SNAP-23 were present in SGCs in TG sections and in cultured SGCs. Ionomycin significantly increased glutamate release from cultured SGCs 30 min. following the treatment (P < 0.001). BoNTA (100 pM) significantly decreased glutamate release (P < 0.01). Results from this study demonstrated that SGCs, when stimulated with ionomycin, released glutamate that was inhibited by BoNTA, possibly through cleavage of SNAP-25 and/or SNAP-23. These novel findings demonstrate the existence of vesicular glutamate release from SGCs, which could potentially play a role in the trigeminal sensory transmission. In addition, interaction of BoNTA with non-neuronal cells at the level of TG suggests a potential analgesic mechanism of action of BoNTA. PMID:25754332

  9. Effects of Cymbopogon citratus and Ferula assa-foetida extracts on glutamate-induced neurotoxicity.

    PubMed

    Tayeboon, Ghazaleh S; Tavakoli, Fatemeh; Hassani, Shokoufeh; Khanavi, Mahnaz; Sabzevari, Omid; Ostad, S Nasser

    2013-10-01

    Many of CNS diseases can lead to a great quantity of release of glutamate and the extreme glutamate induces neuronal cell damage and death. Here, we wanted to investigate the effects of Cymbopogon citratus essential oil and Ferula assa-foetida extracts treatment on glutamate-induced cell damage in a primary culture of rat cerebellar granule neurons. Cerebellums were collected from 7-d rat brains and cerebellar granule neurons were obtained after 8-d culture. CGN cells were treated with C. citratus essential oil and F. assa-foetida extracts at concentration of 100 μg/ml before, after, and during exposure to 30 μM glutamate. The cellular viability was evaluated by 3-(4, 5-dimethytthiazol-2-yl)-2, 5-diphenyltetrazoliumbromide (MTT) staining. The flow cytometry assay was used to examine cell cycle and apoptosis. MTT assay showed a glutamate-induced reduction in cellular viability while treatment with C. citratus essential oil and F. assa-foetida extracts before, during, and after exposure to glutamate was increased. Flow cytometric analysis indicated that F. assa-foetida extracts treatment significantly (p < 0.001) attenuated glutamate-induced apoptotic/necrotic cell death and the necrotic rate was decreased by C. citratus essential oil treatment compared to glutamate group, significantly (p < 0.001). The results show that C. citratus essential oil and F. assa-foetida extracts display neuroprotective effects in glutamate-induced neurotoxicity. These extracts exert antiapoptotic activity in cerebellar granule neurons due to cell cycle arrest in G0G1 phase, which explain the beneficial effects of C. citratus essential oil and F. assa-foetida extracts as therapies for neurologic disorders. PMID:23949776

  10. Stimulation of peripheral cholinergic nerves by glutamate indicates a new peripheral glutamate receptor.

    PubMed

    Aas, P; Tansø, R; Fonnum, F

    1989-05-01

    The bronchial smooth muscle of the rat was examined for contractile responses to excitatory amino acids. The nerve-mediated contraction induced by electrical field stimulation was enhanced by exogenous L-glutamate (L-Glu). The apparent affinity (ED50) of L-Glu was 3.5 +/- 0.1 mM. Both tetrodotoxin and hemicholinium-3 completely abolished the electrical field-induced contraction and therefore the potentiation by L-Glu, which indicates that L-Glu has a prejunctional effect. Concentrations of L-Glu higher than 22 mM inhibited the electrical field-induced contractions and enhanced the tonus of the smooth muscle by postjunctional stimulation. The ED50 of exogenous ACh was not altered by L-Glu. High concentrations (62 mM) of L-Glu increased the intrinsic activity (alpha) of ACh, indicating a postjunctional potentiation of ACh-induced contractions. L-Glu did not inhibit the activity of acetylcholinesterase, therefore the postjunctional potentiation was not due to ACh accumulation. Inhibition of the electrical field-induced contraction was seen with high concentrations of D-Glu, L-aspartate (L-Asp), L-alpha-amino adipate and ibotenate. Neither glutamate diethyl ester nor 2-amino-5-phosphonovalerate had any inhibitory effects on the L-Glu- and L-Asp-induced alterations of the electrical field-stimulated contraction or on the L-Glu-enhanced tonus of the bronchial smooth muscle. Kainate, N-methyl-D-aspartate, quisqualate and N-acetyl-aspartyl-glutamate had only minor transient potentiating effects on the electrical field-induced contraction. The results provide evidence for a L-Glu receptor in rat bronchi that has a different specificity for glutamate agonists and antagonists than the L-Glu receptor described in the CNS. The receptor seems to be located prejunctionally and enhances nerve-mediated responses and thereby stimulates the bronchial smooth muscle to contract. The possible involvement of this type of receptor in the 'Chinese restaurant syndrome' is discussed. PMID

  11. Paraventricular Stimulation with Glutamate Elicits Bradycardia and Pituitary Responses

    NASA Technical Reports Server (NTRS)

    Darlington, Daniel N.; Miyamoto, Michael; Keil, Lanny C.; Dallman, Mary F.

    1989-01-01

    The excitatory neurotransmitter, L-glutamate (0.5 M, pH 7.4), or the organic acid, acetate (0.5 M, pH 7.4), was microinjected (50 nl over 2 min) directly into the paraventricular nuclei (PVN) of pentobarbital sodium-anesthetized rats while arterial blood pressure and heart rate and plasma adrenocorticotropic hormone (ACTH), vasopressin, and oxytocin were measured. Activation of PVN neurons with L-glutamate led to increases in plasma ACTH, vasopressin, and oxytocin and a profound bradycardia (-80 beats/min) with little change in arterial blood pressure. Microinjection of acetate had no effect on the above variables. The decrease in heart rate was shown to be dependent on the concentration of glutamate injected and the volume of injectate. The bradycardia was mediated through the autonomic nervous system because ganglionic blockade (pentolinium tartrate) eliminated the response; atropine and propranolol severely attenuated the bradycardia. The bradycardia was greatest when L-glutamate was microinjected into the caudal PVN. Injections into the rostral PVN or into nuclei surrounding the PVN led to small or nonsignificant decreases in heart rate. Focal electric stimulation (2-50 pA) of the PVN also led to decreases in heart rate and arterial blood pressure. These data suggest that activation of PVN neurons leads to the release of ACTH, vasopressin, and oxytocin from the pituitary and a bradycardia that is mediated by the autonomic nervous system.

  12. Glutamate receptors at atomic resolution

    SciTech Connect

    Mayer, Mark L.

    2010-12-03

    At synapses throughout the brain and spinal cord, the amino-acid glutamate is the major excitatory neurotransmitter. During evolution, a family of glutamate-receptor ion channels seems to have been assembled from a kit consisting of discrete ligand-binding, ion-channel, modulatory and cytoplasmic domains. Crystallographic studies that exploit this unique architecture have greatly aided structural analysis of the ligand-binding core, but the results also pose a formidable challenge, namely that of resolving the allosteric mechanisms by which individual domains communicate and function in an intact receptor.

  13. Glutamate in peripheral organs: Biology and pharmacology.

    PubMed

    Du, Jie; Li, Xiao-Hui; Li, Yuan-Jian

    2016-08-01

    Glutamate is a versatile molecule existing in both the central nervous system and peripheral organs. Previous studies have mainly focussed on the biological effect of glutamate in the brain. Recently, abundant evidence has demonstrated that glutamate also participates in the regulation of physiopathological functions in peripheral tissues, including the lung, kidney, liver, heart, stomach and immune system, where the glutamate/glutamate receptor/glutamate transporter system plays an important role in the pathogenesis of certain diseases, such as myocardial ischaemia/reperfusion injury and acute gastric mucosa injury. All these findings provide new insight into the biology and pharmacology of glutamate and suggest a potential therapeutic role of glutamate in non-neurological diseases. PMID:27164423

  14. Hyperammonaemia alters the mechanisms by which metabotropic glutamate receptors in nucleus accumbens modulate motor function.

    PubMed

    Cauli, Omar; Mlili, Nisrin; Rodrigo, Regina; Felipo, Vicente

    2007-10-01

    Activation of metabotropic glutamate receptors by injecting (S)3,5-dihydroxyphenylglycine (DHPG) in nucleus accumbens (NAcc) increases motor activity by different mechanisms in control rats and in rats with chronic liver failure due to portacaval shunt. In control rats DHPG increases extracellular dopamine in NAcc and induces locomotion by activating the 'normal' circuit: NAcc-->ventral pallidum-->medial-dorsal thalamus-->prefrontal cortex, which is not activated in portacaval shunt rats. In these rats, DHPG activates an 'alternative' circuit: NAcc-->substantia nigra pars reticulata-->ventro-medial thalamus-->prefrontal cortex, which is not activated in control rats. The reasons by which liver failure leads to activation of this 'alternative' circuit remain unclear. The aim of this work was to assess whether hyperammonaemia could be responsible for the alterations found in chronic liver failure. We injected DHPG in NAcc of control or hyperammonaemic rats and analysed, by in vivo brain microdialysis, the neurochemical responses of the 'normal' and 'alternative' circuits. In hyperammonaemic rats DHPG injection in NAcc activates both the 'normal' and 'alternative' circuits. In hyperammonaemia, activation of the 'alternative' circuit and increased motor response following metabotropic glutamate receptors activation in NAcc seem due to an increase in extracellular glutamate which activates AMPA receptors. PMID:17587309

  15. Glutamate metabolism of astrocytes during hyperbaric oxygen exposure and its effects on central nervous system oxygen toxicity.

    PubMed

    Chen, Yu-Liang; Li, Dan; Wang, Zhong-Zhuang; Xu, Wei-Gang; Li, Run-Ping; Zhang, Jun-Dong

    2016-01-20

    Hyperbaric oxygen (HBO) has been used widely in many underwater missions and clinical work. However, exposure to extremely high oxygen pressure may cause central nervous system oxygen toxicity (CNS-OT). The regulation of astrocyte glutamate metabolism is closely related to epilepsy. This study aimed to observe the effects of HBO exposure on glutamate metabolism in astrocytes and confirm the role of glutamate metabolism in CNS-OT. Anesthetized rats were exposed to 5 atmosphere absolute HBO for 80 min and microdialysis samples of brain interstitial fluid were continuously collected. Extracellular glutamate and glutamine concentrations were also detected. Freely moving rats were exposed to HBO of the same pressure for 20 min and glutamine synthetase (GS) activity in brain tissues was measured. Finally, we observed the effects of different doses of drugs related to glutamate metabolism on the latency of CNS-OT. Results showed that HBO exposure significantly increased glutamate content, whereas glutamine content was significantly reduced. Moreover, HBO exposure significantly reduced GS activity. Glutamate transporter-1 (GLT-1) selective antagonist ceftriaxone prolonged CNS-OT latency, whereas GLT-1 selective inhibitor dihydrokainate shortened CNS-OT latency. In summary, HBO exposure improved glutamate concentration and reduced glutamine concentration by inhibition of GS activity. GLT-1 activation also participated in the prevention of HBO-induced CNS-OT. Our research will provide a potential new target to terminate or attenuate CNS-OT. PMID:26619231

  16. Functional changes in glutamate transporters and astrocyte biophysical properties in a rodent model of focal cortical dysplasia

    PubMed Central

    Campbell, Susan L.; Hablitz, John J.; Olsen, Michelle L.

    2014-01-01

    Cortical dysplasia is associated with intractable epilepsy and developmental delay in young children. Recent work with the rat freeze-induced focal cortical dysplasia (FCD) model has demonstrated that hyperexcitability in the dysplastic cortex is due in part to higher levels of extracellular glutamate. Astrocyte glutamate transporters play a pivotal role in cortical maintaining extracellular glutamate concentrations. Here we examined the function of astrocytic glutamate transporters in a FCD model in rats. Neocortical freeze lesions were made in postnatal day (PN) 1 rat pups and whole cell electrophysiological recordings and biochemical studies were performed at PN 21–28. Synaptically evoked glutamate transporter currents in astrocytes showed a near 10-fold reduction in amplitude compared to sham operated controls. Astrocyte glutamate transporter currents from lesioned animals were also significantly reduced when challenged exogenously applied glutamate. Reduced astrocytic glutamate transport clearance contributed to increased NMDA receptor-mediated current decay kinetics in lesioned animals. The electrophysiological profile of astrocytes in the lesion group was also markedly changed compared to sham operated animals. Control astrocytes demonstrate large-amplitude linear leak currents in response to voltage-steps whereas astrocytes in lesioned animals demonstrated significantly smaller voltage-activated inward and outward currents. Significant decreases in astrocyte resting membrane potential and increases in input resistance were observed in lesioned animals. However, Western blotting, immunohistochemistry and quantitative PCR demonstrated no differences in the expression of the astrocytic glutamate transporter GLT-1 in lesioned animals relative to controls. These data suggest that, in the absence of changes in protein or mRNA expression levels, functional changes in astrocytic glutamate transporters contribute to neuronal hyperexcitability in the FCD model

  17. Transient extracellular glutamate events in the basolateral amygdala track reward seeking actions

    PubMed Central

    Wassum, KM; Tolosa, VM; Tseng, TC; Balleine, BW; Monbouquette, HG; Maidment, NT

    2012-01-01

    The ability to make rapid, informed decisions about whether or not to engage in a sequence of actions to earn reward is essential for survival. Modeling in rodents has demonstrated a critical role for the basolateral amygdala (BLA) in such reward-seeking actions, but the precise neurochemical underpinnings are not well understood. Taking advantage of recent advancements in biosensor technologies, we made spatially discrete near-real time extracellular recordings of the major excitatory transmitter, glutamate, in the BLA of rats performing a self-paced lever-pressing sequence task for sucrose reward. This allowed us to detect rapid transient fluctuations in extracellular BLA glutamate time-locked to action performance. These glutamate transients tended to precede lever pressing actions and were markedly increased in frequency when rats were engaged in such reward seeking actions. Based on muscimol and tetrodotoxin microinfusions these glutamate transients appeared to originate from the terminals of neurons with cell bodies in the orbital frontal cortex. Importantly, glutamate transient amplitude and frequency fluctuated with the value of the earned reward and positively predicted lever pressing rate. Such novel rapid glutamate recordings during instrumental performance identify a role for glutamatergic signaling within the BLA in instrumental reward-seeking actions. PMID:22357857

  18. 21 CFR 182.1045 - Glutamic acid.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Glutamic acid. 182.1045 Section 182.1045 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN....1045 Glutamic acid. (a) Product. Glutamic acid. (b) (c) Limitations, restrictions, or explanation....

  19. 21 CFR 182.1045 - Glutamic acid.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Glutamic acid. 182.1045 Section 182.1045 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN....1045 Glutamic acid. (a) Product. Glutamic acid. (b) (c) Limitations, restrictions, or explanation....

  20. 21 CFR 182.1045 - Glutamic acid.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Glutamic acid. 182.1045 Section 182.1045 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN....1045 Glutamic acid. (a) Product. Glutamic acid. (b) (c) Limitations, restrictions, or explanation....

  1. 21 CFR 182.1045 - Glutamic acid.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Glutamic acid. 182.1045 Section 182.1045 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN....1045 Glutamic acid. (a) Product. Glutamic acid. (b) (c) Limitations, restrictions, or explanation....

  2. 21 CFR 182.1045 - Glutamic acid.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Glutamic acid. 182.1045 Section 182.1045 Food and... GENERALLY RECOGNIZED AS SAFE Multiple Purpose GRAS Food Substances § 182.1045 Glutamic acid. (a) Product. Glutamic acid. (b) (c) Limitations, restrictions, or explanation. This substance is generally recognized...

  3. Modes of glutamate receptor gating

    PubMed Central

    Popescu, Gabriela K

    2012-01-01

    Abstract The time course of excitatory synaptic currents, the major means of fast communication between neurons of the central nervous system, is encoded in the dynamic behaviour of post-synaptic glutamate-activated channels. First-pass attempts to explain the glutamate-elicited currents with mathematical models produced reaction mechanisms that included only the most basic functionally defined states: resting vs. liganded, closed vs. open, responsive vs. desensitized. In contrast, single-molecule observations afforded by the patch-clamp technique revealed an unanticipated kinetic multiplicity of transitions: from microseconds-lasting flickers to minutes-long modes. How these kinetically defined events impact the shape of the synaptic response, how they relate to rearrangements in receptor structure, and whether and how they are physiologically controlled represent currently active research directions. Modal gating, which refers to the slowest, least frequently observed ion-channel transitions, has been demonstrated for representatives of all ion channel families. However, reaction schemes have been largely confined to the short- and medium-range time scales. For glutamate receptors as well, modal gating has only recently come under rigorous scrutiny. This article reviews the evidence for modal gating of glutamate receptors and the still developing hypotheses about the mechanism(s) by which modal shifts occur and the ways in which they may impact the time course of synaptic transmission. PMID:22106181

  4. Paracrine Neuroprotective Effects of Neural Stem Cells on Glutamate-Induced Cortical Neuronal Cell Excitotoxicity

    PubMed Central

    Geranmayeh, Mohammad Hossein; Baghbanzadeh, Ali; Barin, Abbas; Salar-Amoli, Jamileh; Dehghan, Mohammad Mehdi; Rahbarghazi, Reza; Azari, Hassan

    2015-01-01

    Purpose: Glutamate is a major excitatory neurotransmitter in mammalian central nervous system. Excessive glutamate releasing overactivates its receptors and changes calcium homeostasis that in turn leads to a cascade of intracellular events causing neuronal degeneration. In current study, we used neural stem cells conditioned medium (NSCs-CM) to investigate its neuroprotective effects on glutamate-treated primary cortical neurons. Methods: Embryonic rat primary cortical cultures were exposed to different concentrations of glutamate for 1 hour and then they incubated with NSCs-CM. Subsequently, the amount of cell survival in different glutamate excitotoxic groups were measured after 24 h of incubation by trypan blue exclusion assay and MTT assay. Hoechst and propidium iodide were used for determining apoptotic and necrotic cell death pathways proportion and then the effect of NSCs-CM was investigated on this proportion. Results: NSCs conditioned medium increased viability rate of the primary cortical neurons after glutamate-induced excitotoxicity. Also we found that NSCs-CM provides its neuroprotective effects mainly by decreasing apoptotic cell death rate rather than necrotic cell death rate. Conclusion: The current study shows that adult neural stem cells could exert paracrine neuroprotective effects on cortical neurons following a glutamate neurotoxic insult. PMID:26819924

  5. Secretory phospholipase A2-mediated neuronal cell death involves glutamate ionotropic receptors.

    PubMed

    Kolko, Miriam; de Turco, Elena B; Diemer, Nils Henrik; Bazan, Nicolas G

    2002-10-28

    To define the significance of glutamate ionotropic receptors in sPLA -mediated neuronal cell death we used the NMDA receptor antagonist MK-801 and the AMPA receptor antagonist PNQX. In primary neuronal cell cultures both MK-801 and PNQX inhibited sPLA - and glutamate-induced neuronal death. [ H]Arachidonic acid release induced by both sPLA and glutamate was partially blocked by MK-801, indicating that the glutamate-NMDA-cPLA pathway contributes to sPLA -induced arachidonic acid release. Systemic administration of MK-801 to rats that had sPLA injected into the right striatum significantly decreased neuronal cell death. We conclude that glutamatergic synaptic activity modulates sPLA -induced neuronal cell death. PMID:12395100

  6. [Cardioprotective properties of new glutamic acid derivative under stress conditions].

    PubMed

    Perfilova, V N; Sadikova, N V; Berestovitskaia, V M; Vasil'eva, O S

    2014-01-01

    The effect of new glutamic acid derivative on the cardiac ino- and chronotropic functions has been studied in experiments on rats exposed to 24-hour immobilization-and-pain stress. It is established that glutamic acid derivative RGPU-238 (glufimet) at a dose of 28.7 mg/kg increases the increment of myocardial contractility and relaxation rates and left ventricular pressure in stress-tested animals by 13 1,1, 72.4, and 118.6%, respectively, as compared to the control group during the test for adrenoreactivity. Compound RGPU-238 increases the increment of the maximum intensity of myocardium functioning by 196.5 % at 30 sec of isometric workload as compared to the control group. The cardioprotective effect of compound RGPU-238 is 1.5 - 2 times higher than that of the reference drug phenibut. PMID:25365864

  7. Glutamate and GABA in Vestibulo-Sympathetic Pathway Neurons

    PubMed Central

    Holstein, Gay R.; Friedrich, Victor L. Jr.; Martinelli, Giorgio P.

    2016-01-01

    The vestibulo-sympathetic reflex (VSR) actively modulates blood pressure during changes in posture. This reflex allows humans to stand up and quadrupeds to rear or climb without a precipitous decline in cerebral perfusion. The VSR pathway conveys signals from the vestibular end organs to the caudal vestibular nuclei. These cells, in turn, project to pre-sympathetic neurons in the rostral and caudal ventrolateral medulla (RVLM and CVLM, respectively). The present study assessed glutamate- and GABA-related immunofluorescence associated with central vestibular neurons of the VSR pathway in rats. Retrograde FluoroGold tract tracing was used to label vestibular neurons with projections to RVLM or CVLM, and sinusoidal galvanic vestibular stimulation (GVS) was employed to activate these pathways. Central vestibular neurons of the VSR were identified by co-localization of FluoroGold and cFos protein, which accumulates in some vestibular neurons following galvanic stimulation. Triple-label immunofluorescence was used to co-localize glutamate- or GABA- labeling in the identified VSR pathway neurons. Most activated projection neurons displayed intense glutamate immunofluorescence, suggestive of glutamatergic neurotransmission. To support this, anterograde tracer was injected into the caudal vestibular nuclei. Vestibular axons and terminals in RVLM and CVLM co-localized the anterograde tracer and vesicular glutamate transporter-2 signals. Other retrogradely-labeled cFos-positive neurons displayed intense GABA immunofluorescence. VSR pathway neurons of both phenotypes were present in the caudal medial and spinal vestibular nuclei, and projected to both RVLM and CVLM. As a group, however, triple-labeled vestibular cells with intense glutamate immunofluorescence were located more rostrally in the vestibular nuclei than the GABAergic neurons. Only the GABAergic VSR pathway neurons showed a target preference, projecting predominantly to CVLM. These data provide the first

  8. Glutamate and GABA in Vestibulo-Sympathetic Pathway Neurons.

    PubMed

    Holstein, Gay R; Friedrich, Victor L; Martinelli, Giorgio P

    2016-01-01

    The vestibulo-sympathetic reflex (VSR) actively modulates blood pressure during changes in posture. This reflex allows humans to stand up and quadrupeds to rear or climb without a precipitous decline in cerebral perfusion. The VSR pathway conveys signals from the vestibular end organs to the caudal vestibular nuclei. These cells, in turn, project to pre-sympathetic neurons in the rostral and caudal ventrolateral medulla (RVLM and CVLM, respectively). The present study assessed glutamate- and GABA-related immunofluorescence associated with central vestibular neurons of the VSR pathway in rats. Retrograde FluoroGold tract tracing was used to label vestibular neurons with projections to RVLM or CVLM, and sinusoidal galvanic vestibular stimulation (GVS) was employed to activate these pathways. Central vestibular neurons of the VSR were identified by co-localization of FluoroGold and cFos protein, which accumulates in some vestibular neurons following galvanic stimulation. Triple-label immunofluorescence was used to co-localize glutamate- or GABA- labeling in the identified VSR pathway neurons. Most activated projection neurons displayed intense glutamate immunofluorescence, suggestive of glutamatergic neurotransmission. To support this, anterograde tracer was injected into the caudal vestibular nuclei. Vestibular axons and terminals in RVLM and CVLM co-localized the anterograde tracer and vesicular glutamate transporter-2 signals. Other retrogradely-labeled cFos-positive neurons displayed intense GABA immunofluorescence. VSR pathway neurons of both phenotypes were present in the caudal medial and spinal vestibular nuclei, and projected to both RVLM and CVLM. As a group, however, triple-labeled vestibular cells with intense glutamate immunofluorescence were located more rostrally in the vestibular nuclei than the GABAergic neurons. Only the GABAergic VSR pathway neurons showed a target preference, projecting predominantly to CVLM. These data provide the first

  9. Fluorescence imaging of glutamate release in neurons

    SciTech Connect

    Wang, Ziqiang; Yeung, Edward S.

    1999-12-01

    A noninvasive detection scheme based on glutamate dehydrogenase (GDH) enzymatic assay combined with microscopy was developed to measure the glutamate release in cultured cells from the central nervous system (CNS). The enzyme reaction is very specific and sensitive. The detection limit with charge-coupled device (CCD) imaging is down to {mu}M levels of glutamate with reasonable response time ({approx}30 s). The standard glutamate test shows a linear response over 3 orders of magnitude, from {mu}M to 0.1 mM range. The in vitro monitoring of glutamate release from cultured neuron cells demonstrated excellent spatial and temporal resolution. (c) 1999 Society for Applied Spectroscopy.

  10. Alcohol-seeking behavior is associated with increased glutamate transmission in basolateral amygdala and nucleus accumbens as measured by glutamate-oxidase coated biosensors

    PubMed Central

    Gass, Justin T.; Sinclair, Courtney M.; Cleva, Richard M.; Widholm, John J.; Olive, M. Foster

    2010-01-01

    Relapse is one of the most problematic aspects in the treatment of alcoholism and is often triggered by alcohol-associated environmental cues. Evidence indicates that glutamate neurotransmission plays a critical role in cue-induced relapse-like behavior, as inhibition of glutamate neurotransmission can prevent reinstatement of alcohol-seeking behavior. However, few studies have examined specific changes in extracellular glutamate levels in discrete brain regions produced by exposure to alcohol-associated cues. The purpose of this study was to use glutamate oxidase (GluOx)-coated biosensors to monitor changes in extracellular glutamate in specific brain regions during cue-induced reinstatement of alcohol-seeking behavior. Male Wistar rats were implanted with indwelling jugular vein catheters and intracerebral guide cannula aimed at the basolateral amygdala (BLA) or nucleus accumbens (NAc) core, and then trained to self-administer alcohol intravenously. A separate group of animals was trained to self-administer food pellets. Each reinforcer was accompanied by the presentation of a light/tone stimulus. Following stabilization of responding for alcohol or food reinforcement and subsequent extinction training, animals were implanted with precalibrated biosensors and then underwent a 1 hr cue-induced reinstatement testing period. As determined by GluOx-coated biosensors, extracellular levels of glutamate were increased in the BLA and NAc core during cue-induced reinstatement of alcohol-seeking behavior. The cumulative change in extracellular glutamate in both regions was significantly greater for cue-induced reinstatement of alcohol-seeking behavior versus that of food-seeking behavior. These results indicate that increases in glutamate transmission in the BLA and NAc core may be a neurochemical substrate of cue-evoked alcohol-seeking behavior. PMID:21054692

  11. Systemic Pregabalin Attenuates Sensorimotor Responses and Medullary Glutamate Release in Inflammatory Tooth Pain Model

    PubMed Central

    Narita, Noriyuki; Kumar, Naresh; Cherkas, Pavel S.; Chiang, Chen Yu; Dostrovsky, Jonathan O.; Coderre, Terence J.; Sessle, Barry J.

    2012-01-01

    Our previous studies have demonstrated that application to the tooth pulp of the inflammatory irritant mustard oil (MO) induces medullary glutamate release and central sensitization in the rat medullary dorsal horn (MDH), as well as nociceptive sensorimotor responses in craniofacial muscles in rats. There is recent evidence that anticonvulsant drugs such as pregabalin that influence glutamatergic neurotransmission are effective in several pain states. The aim of this study was to examine whether systemic administration of pregabalin attenuated glutamate release in the medulla as well as these nociceptive effects reflected in increased electromyographic (EMG) activity induced by MO application to the tooth pulp. Male adult rats were anesthetized with isofluorane (1.0~1.2 %), and jaw and tongue muscle EMG activities were recorded by needle electrodes inserted bilaterally into masseter and anterior digastric muscles and into the genioglossus muscle, and also the medullary release of glutamate was assessed by in vivo microdialysis. Pregabalin or vehicle control (isotonic saline) was administered 30 min before the pulpal application of MO or vehicle control (mineral oil). Application of mineral oil to the maxillary first molar tooth pulp produced no change in baseline EMG activity and glutamate release. However, application of MO to the pulp significantly increased both the medullary release of glutamate and EMG activity in the jaw and tongue muscles for several minutes. In contrast, pre-medication with pregabalin, but not vehicle control, significantly and dose-dependently attenuated the medullary glutamate release and EMG activity in these muscles after MO application to the tooth pulp (ANOVA, p<0.05). These results suggest that pregabalin may attenuate the medullary release of glutamate and associated nociceptive sensorimotor responses in this acute inflammatory pulpal pain model, and that it may prove useful for the treatment of orofacial inflammatory pain states

  12. Systemic pregabalin attenuates sensorimotor responses and medullary glutamate release in inflammatory tooth pain model.

    PubMed

    Narita, N; Kumar, N; Cherkas, P S; Chiang, C Y; Dostrovsky, J O; Coderre, T J; Sessle, B J

    2012-08-30

    Our previous studies have demonstrated that application of inflammatory irritant mustard oil (MO) to the tooth pulp induces medullary glutamate release and central sensitization in the rat medullary dorsal horn (MDH), as well as nociceptive sensorimotor responses in craniofacial muscles in rats. There is recent evidence that anticonvulsant drugs such as pregabalin that influence glutamatergic neurotransmission are effective in several pain states. The aim of this study was to examine whether systemic administration of pregabalin attenuated glutamate release in the medulla as well as these nociceptive effects reflected in increased electromyographic (EMG) activity induced by MO application to the tooth pulp. Male adult rats were anesthetized with isofluorane (1.0-1.2%), and jaw and tongue muscle EMG activities were recorded by needle electrodes inserted bilaterally into masseter and anterior digastric muscles and into the genioglossus muscle, and also the medullary release of glutamate was assessed by in vivo microdialysis. Pregabalin or vehicle control (isotonic saline) was administered 30 min before the pulpal application of MO or vehicle control (mineral oil). Application of mineral oil to the maxillary first molar tooth pulp produced no change in baseline EMG activity and glutamate release. However, application of MO to the pulp significantly increased both the medullary release of glutamate and EMG activity in the jaw and tongue muscles for several minutes. In contrast, pre-medication with pregabalin, but not vehicle control, significantly and dose-dependently attenuated the medullary glutamate release and EMG activity in these muscles after MO application to the tooth pulp (analysis of variance (ANOVA), p<0.05). These results suggest that pregabalin may attenuate the medullary release of glutamate and associated nociceptive sensorimotor responses in this acute inflammatory pulpal pain model, and that it may prove useful for the treatment of orofacial

  13. Pre- and Postnatal Exposure to Moderate Levels of Ethanol Can Have Long-Lasting Effects on Hippocampal Glutamate Uptake in Adolescent Offspring

    PubMed Central

    de Souza, Daniela F.; Lopes, Fernanda M.; Leite, Marina C.; Gonçalves, Carlos-Alberto

    2015-01-01

    The developing brain is vulnerable to the effects of ethanol. Glutamate is the main mediator of excitatory signals in the brain and is probably involved in most aspects of normal brain function during development. The aim of this study was to investigate vulnerability to and the impact of ethanol toxicity on glutamate uptake signaling in adolescent rats after moderate pre and postnatal ethanol exposure. Pregnant female rats were divided into three groups and treated only with water (control), non-alcoholic beer (vehicle) or 10% (v/v) beer solution (moderate prenatal alcohol exposure—MPAE). Thirty days after birth, adolescent male offspring were submitted to hippocampal acute slice procedure. We assayed glutamate uptake and measured glutathione content and also quantified glial glutamate transporters (EAAT 1 and EAAT 2). The glutamate system vulnerability was tested with different acute ethanol doses in naïve rats and compared with the MPAE group. We also performed a (lipopolysaccharide-challenge (LPS-challenge) with all groups to test the glutamate uptake response after an insult. The MPAE group presented a decrease in glutamate uptake corroborating a decrease in glutathione (GSH) content. The reduction in GSH content suggests oxidative damage after acute ethanol exposure. The glial glutamate transporters were also altered after prenatal ethanol treatment, suggesting a disturbance in glutamate signaling. This study indicates that impairment of glutamate uptake can be dose-dependent and the glutamate system has a higher vulnerability to ethanol toxicity after moderate ethanol exposure In utero. The effects of pre- and postnatal ethanol exposure can have long-lasting impacts on the glutamate system in adolescence and potentially into adulthood. PMID:25978644

  14. Swim training of monosodium L-glutamate-obese mice improves the impaired insulin receptor tyrosine phosphorylation in pancreatic islets.

    PubMed

    Miranda, Rosiane Aparecida; Branco, Renato Chaves Souto; Gravena, Clarice; Barella, Luiz Felipe; da Silva Franco, Claudinéia Conationi; Andreazzi, Ana Eliza; de Oliveira, Júlio Cezar; Picinato, Maria Cecília; de Freitas Mathias, Paulo Cezar

    2013-06-01

    The goal of the present study was to investigate changes on glucose homoeostasis and of the insulin receptor (IR) and insulin receptor substrate-1 (IRS-1) signalling in pancreatic islets from MSG-obese mice submitted to or not submitted to swim training. Swim training of 90-day-old MSG mice was used to evaluate whether signalling pathways of the IR and IRS-1 in islets are involved with the insulin resistance and glucose intolerance observed in this obese animal model. The results showed that IR tyrosine phosphorylation (pIR) was reduced by 42 % in MSG-obese mice (MSG, 6.7 ± 0.2 arbitrary units (a.u.); control, 11.5 ± 0.4 a.u.); on the other hand, exercise training increased pIR by 76 % in MSG mice without affecting control mice (MSG, 11.8 ± 0.3; control, 12.8 ± 0.2 a.u.). Although the treatment with MSG increased IRS-1 tyrosine phosphorylation (pIRS-1) by 96 % (MSG, 17.02 ± 0.6; control, 8.7 ± 0.2 a.u.), exercise training also increased it in both groups (control, 13.6 ± 0.1; MSG, 22.2 ± 1.1 a.u.). Current research shows that the practice of swim training increases the tyrosine phosphorylation of IRS-1 which can modulate the effect caused by obesity in insulin receptors. PMID:22983867

  15. Nonvesicular Release of Glutamate by Glial xCT Transporters Suppresses Glutamate Receptor Clustering In Vivo

    PubMed Central

    Augustin, Hrvoje; Grosjean, Yael; Chen, Kaiyun; Sheng, Qi; Featherstone, David E.

    2008-01-01

    We hypothesized that cystine/glutamate transporters (xCTs) might be critical regulators of ambient extracellular glutamate levels in the nervous system and that misregulation of this glutamate pool might have important neurophysiological and/or behavioral consequences. To test this idea, we identified and functionally characterized a novel Drosophila xCT gene, which we subsequently named “genderblind” (gb). Genderblind is expressed in a previously overlooked subset of peripheral and central glia. Genetic elimination of gb causes a 50% reduction in extracellular glutamate concentration, demonstrating that xCT transporters are important regulators of extracellular glutamate. Consistent with previous studies showing that extracellular glutamate regulates postsynaptic glutamate receptor clustering, gb mutants show a large (200–300%) increase in the number of postsynaptic glutamate receptors. This increase in postsynaptic receptor abundance is not accompanied by other obvious synaptic changes and is completely rescued when synapses are cultured in wild-type levels of glutamate. Additional in situ pharmacology suggests that glutamate-mediated suppression of glutamate receptor clustering depends on receptor desensitization. Together, our results suggest that (1) xCT transporters are critical for regulation of ambient extracellular glutamate in vivo; (2) ambient extracellular glutamate maintains some receptors constitutively desensitized in vivo; and (3) constitutive desensitization of ionotropic glutamate receptors suppresses their ability to cluster at synapses. PMID:17202478

  16. Ligands for Ionotropic Glutamate Receptors

    NASA Astrophysics Data System (ADS)

    Swanson, Geoffrey T.; Sakai, Ryuichi

    Marine-derived small molecules and peptides have played a central role in elaborating pharmacological specificities and neuronal functions of mammalian ionotropic glutamate receptors (iGluRs), the primary mediators of excitatory syn-aptic transmission in the central nervous system (CNS). As well, the pathological sequelae elicited by one class of compounds (the kainoids) constitute a widely-used animal model for human mesial temporal lobe epilepsy (mTLE). New and existing molecules could prove useful as lead compounds for the development of therapeutics for neuropathologies that have aberrant glutamatergic signaling as a central component. In this chapter we discuss natural source origins and pharmacological activities of those marine compounds that target ionotropic glutamate receptors.

  17. Resveratrol Prevents Retinal Dysfunction by Regulating Glutamate Transporters, Glutamine Synthetase Expression and Activity in Diabetic Retina.

    PubMed

    Zeng, Kaihong; Yang, Na; Wang, Duozi; Li, Suping; Ming, Jian; Wang, Jing; Yu, Xuemei; Song, Yi; Zhou, Xue; Yang, Yongtao

    2016-05-01

    This study investigated the effects of resveratrol (RSV) on retinal functions, glutamate transporters (GLAST) and glutamine synthetase (GS) expression in diabetic rats retina, and on glutamate uptake, GS activity, GLAST and GS expression in high glucose-cultured Müller cells. The electroretinogram was used to evaluate retinal functions. Müller cells cultures were prepared from 5- to 7-day-old Sprague-Dawley rats. The expression of GLAST and GS was examined by qRT-PCR, ELISA and western-blotting. Glutamate uptake was measured as (3)H-glutamate contents of the lysates. GS activity was assessed by a spectrophotometric assay. 1- to 7-month RSV administrations (5 and 10 mg/kg/day) significantly alleviated hyperglycemia and weight loss in diabetic rats. RSV administrations also significantly attenuated diabetes-induced decreases in amplitude of a-wave in rod response, decreases in amplitude of a-, and b-wave in cone and rod response and decreases in amplitude of OP2 in oscillatory potentials. 1- to 7-month RSV treatments also significantly inhibited diabetes-induced delay in OP2 implicit times in scotopic 3.0 OPS test. The down-regulated mRNA and protein expression of GLAST and GS in diabetic rats retina was prevented by RSV administrations. In high glucose-treated cultures, Müller cells' glutamate uptake, GS activity, GLAST and GS expression were decreased significantly compared with normal control cultures. RSV (10, 20, and 30 mmol/l) significantly inhibited the HG-induced decreases in glutamate uptake, GS activity, GLAST and GS expression (at least P < 0.05). These beneficial results suggest that RSV may be considered as a therapeutic option to prevent from diabetic retinopathy. PMID:26677078

  18. Glutamate dysregulation in the trigeminal ganglion: a novel mechanism for peripheral sensitization of the craniofacial region.

    PubMed

    Laursen, J C; Cairns, B E; Dong, X D; Kumar, U; Somvanshi, R K; Arendt-Nielsen, L; Gazerani, P

    2014-01-01

    In the trigeminal ganglion (TG), satellite glial cells (SGCs) form a functional unit with neurons. It has been proposed that SGCs participate in regulating extracellular glutamate levels and that dysfunction of this SGC capacity can impact nociceptive transmission in craniofacial pain conditions. This study investigated whether SGCs release glutamate and whether elevation of TG glutamate concentration alters response properties of trigeminal afferent fibers. Immunohistochemistry was used to assess glutamate content and the expression of excitatory amino acid transporter (EAAT)1 and EAAT2 in TG sections. SGCs contained glutamate and expressed EAAT1 and EAAT2. Potassium chloride (10 mM) was used to evoke glutamate release from cultured rat SGCs treated with the EAAT1/2 inhibitor (3S)-3-[[3-[[4-(trifluoromethyl)ben zoyl]amino]phenyl]methoxy]-L-aspartic acid (TFB-TBOA) or control. Treatment with TFB-TBOA (1 and 10 μM) significantly reduced the glutamate concentration from 10.6 ± 1.1 to 5.8 ± 1.4 μM and 3.0 ± 0.8 μM, respectively (p<0.05). Electrophysiology experiments were conducted in anaesthetized rats to determine the effect of intraganglionic injections of glutamate on the response properties of ganglion neurons that innervated either the temporalis or masseter muscle. Intraganglionic injection of glutamate (500 mM, 3 μl) evoked afferent discharge and significantly reduced muscle afferent mechanical threshold. Glutamate-evoked discharge was attenuated bythe N-methyl-D-aspartate receptor antagonist 2-amino-5-phosphonovalerate (APV) and increased by TFB-TBOA, whereas mechanical sensitization was only sensitive to APV. Antidromic invasion of muscle afferent fibers by electrical stimulation of the caudal brainstem (10 Hz) or local anesthesia of the brainstem with lidocaine did not alter glutamate-induced mechanical sensitization. These findings provide a novel mechanism whereby dysfunctional trigeminal SGCs could contribute to cranial muscle tenderness in

  19. [PECULIARITIES OF THE CEREBROVASCULAR EFFECTS OF GLUTAMIC ACID].

    PubMed

    Gan'shina, T S; Kurza, E V; Kurdyumov, I N; Maslennikov, D V; Mirzoyan, R S

    2016-01-01

    Experiments on nonlinear rats subjected to global transient cerebral ischemia revealed the ability of glutamic acid to improve cerebral circulation. Consequently, the excitatory amino acid can produce adverse (neurotoxic) and positive (anti-ischemic) effects in cerebral ischemia. The cerebrovascular effect of glutamic acid in cerebral ischemia is attenuated on the background action of the MNDA receptor blocker MK-801 (0.5 mg/kg intravenously) and eliminated by bicuculline. When glutamic acid is combined with the non-competitive MNDA receptor antagonist MK-801, neither one nor another drug shows its vasodilator effect. The results are indicative of the interaction between excitatory and inhibitory systems on the level of cerebral vessels and once again confirm our previous conclusion about the decisive role of GABA(A) receptors in brain vessels in the implementation of anti-ischemic activity of endogenous compounds (melatonin) and well-known pharmacological substances (mexidol, afobazole), and new chemical compounds based on GABA-containing lipid derivatives. PMID:27455572

  20. Pyridoxine may protect the cerebellar granular cells against glutamate-induced toxicity.

    PubMed

    Büyükokuroglu, Mehmet Emin; Gepdiremen, Akcahan; Taştekin, Ayhan; Ors, Rahmi

    2007-09-01

    In the present study, the possible protective effect of the pyridoxine against glutamate-induced neurotoxicity in cerebellar granular cell culture of rat pups is investigated for its therapeutic potential. Glutamate (10(-7) M) was administered to cerebellar granular cell cultures that were prepared from one-day-old Sprague-Dawley rats. The neuroprotective effect of pyridoxine was examined. Pyridoxine at the doses of 10(-8), 10(-7), 10(-6), and 10(-5) M was introduced into the culture flasks before inclusion of glutamate. Pyridoxine at the doses of 10(-8) M and 10(-7) M significantly reduced glutamate cytotoxicity. A 10(-7) M dose of pyridoxine proved to be more effective than a 10(-8) M dose. The present study demonstrates that pyridoxine may protect glutamate-induced neurotoxicity. Neuroprotective effect of pyridoxine, at least in part, may result from its anti-glutamatergic activity. Pyridoxine merits further investigation as a therapeutic option in hypoxic-ischemic brain injury. PMID:18453318

  1. Striatal interaction among dopamine, glutamate and ascorbate.

    PubMed

    Morales, Ingrid; Fuentes, Angel; Ballaz, Santiago; Obeso, Jose A; Rodriguez, Manuel

    2012-12-01

    Despite evidence suggesting the interaction among glutamate (GLU), dopamine (DA) and ascorbic acid (AA) in the striatum, their actions are often studied separately. Microdialysis was used here to quantify the extracellular interaction among GLU-DA-AA in the striatum of rats, an interaction which was compared with those studied in the substantia nigra (SN). Perfusion of GLU by reverse microdialysis increased DA and decreased 3,4-dihydroxyphenylacetic acid (DOPAC) in the extracellular medium of the striatum, but increased both DA and DOPAC in the SN. The increase of extracellular DA-concentration induced by the local DA-perfusion decreased the extracellular level of GLU and glutamine, an effect that, as suggested by the GLU and glutamine increase observed after the haloperidol administration, probably involves the D2 dopamine receptor. Local administration of AA increased the extracellular DA, decreased DOPAC and had no effect on GLU and glutamine. Present data suggest that, in the striatum, GLU-release inhibits DA-uptake, DA-release inhibits GLU-release, and AA-release prevents DA-oxidation increasing its extracellular diffusion. These effects were different in the SN where GLU probably promoted the DA-release instead of inhibiting the DA-uptake as presumably occurred in the striatum. Present data denote a marked GLU-DA-AA interaction in the striatum, which might be relevant for the pharmacological control of basal ganglia disorders. PMID:22959966

  2. The glutamate homeostasis hypothesis of addiction.

    PubMed

    Kalivas, Peter W

    2009-08-01

    Addiction is associated with neuroplasticity in the corticostriatal brain circuitry that is important for guiding adaptive behaviour. The hierarchy of corticostriatal information processing that normally permits the prefrontal cortex to regulate reinforcement-seeking behaviours is impaired by chronic drug use. A failure of the prefrontal cortex to control drug-seeking behaviours can be linked to an enduring imbalance between synaptic and non-synaptic glutamate, termed glutamate homeostasis. The imbalance in glutamate homeostasis engenders changes in neuroplasticity that impair communication between the prefrontal cortex and the nucleus accumbens. Some of these pathological changes are amenable to new glutamate- and neuroplasticity-based pharmacotherapies for treating addiction. PMID:19571793

  3. In vitro evidence for the brain glutamate efflux hypothesis: brain endothelial cells cocultured with astrocytes display a polarized brain-to-blood transport of glutamate.

    PubMed

    Helms, Hans Christian; Madelung, Rasmus; Waagepetersen, Helle Sønderby; Nielsen, Carsten Uhd; Brodin, Birger

    2012-05-01

    The concentration of the excitotoxic amino acid, L-glutamate, in brain interstitial fluid is tightly regulated by uptake transporters and metabolism in astrocytes and neurons. The aim of this study was to investigate the possible role of the blood-brain barrier endothelium in brain L-glutamate homeostasis. Transendothelial transport- and accumulation studies of (3) H-L-glutamate, (3) H-L-aspartate, and (3) H-D-aspartate in an electrically tight bovine endothelial/rat astrocyte blood-brain barrier coculture model were performed. After 6 days in culture, the endothelium displayed transendothelial resistance values of 1014 ± 70 Ω cm(2) , and (14) C-D-mannitol permeability values of 0.88 ± 0.13 × 10(-6) cm s(-1) . Unidirectional flux studies showed that L-aspartate and L-glutamate, but not D-aspartate, displayed polarized transport in the brain-to-blood direction, however, all three amino acids accumulated in the cocultures when applied from the abluminal side. The transcellular transport kinetics were characterized with a K(m) of 69 ± 15 μM and a J(max) of 44 ± 3.1 pmol min(-1) cm(-2) for L-aspartate and a K(m) of 138 ± 49 μM and J(max) of 28 ± 3.1 pmol min(-1) cm(-2) for L-glutamate. The EAAT inhibitor, DL-threo-ß-Benzyloxyaspartate, inhibited transendothelial brain-to-blood fluxes of L-glutamate and L-aspartate. Expression of EAAT-1 (Slc1a3), -2 (Slc1a2), and -3 (Slc1a1) mRNA in the endothelial cells was confirmed by conventional PCR and localization of EAAT-1 and -3 in endothelial cells was shown with immunofluorescence. Overall, the findings suggest that the blood-brain barrier itself may participate in regulating brain L-glutamate concentrations. PMID:22392649

  4. Glutamate Increases In Vitro Survival and Proliferation and Attenuates Oxidative Stress-Induced Cell Death in Adult Spinal Cord-Derived Neural Stem/Progenitor Cells via Non-NMDA Ionotropic Glutamate Receptors.

    PubMed

    Hachem, Laureen D; Mothe, Andrea J; Tator, Charles H

    2016-08-15

    Traumatic spinal cord injury (SCI) leads to a cascade of secondary chemical insults, including oxidative stress and glutamate excitotoxicity, which damage host neurons and glia. Transplantation of exogenous neural stem/progenitor cells (NSPCs) has shown promise in enhancing regeneration after SCI, although survival of transplanted cells remains poor. Understanding the response of NSPCs to the chemical mediators of secondary injury is essential in finding therapies to enhance survival. We examined the in vitro effects of glutamate and glutamate receptor agonists on adult rat spinal cord-derived NSPCs. NSPCs isolated from the periventricular region of the adult rat spinal cord were exposed to various concentrations of glutamate for 96 h. We found that glutamate treatment (500 μM) for 96 h significantly increased live cell numbers, reduced cell death, and increased proliferation, but did not significantly alter cell phenotype. Concurrent glutamate treatment (500 μM) in the setting of H2O2 exposure (500 μM) for 10 h increased NSPC survival compared to H2O2 exposure alone. The effects of glutamate on NSPCs were blocked by the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate receptor antagonist GYKI-52466, but not by the N-methyl-D-aspartic acid receptor antagonist MK-801 or DL-AP5, or the mGluR3 antagonist LY-341495. Furthermore, treatment of NSPCs with AMPA, kainic acid, or the kainate receptor-specific agonist (RS)-2-amino-3-(3-hydroxy-5-tert-butylisoxazol-4-yl)propanoic acid mimicked the responses seen with glutamate both alone and in the setting of oxidative stress. These findings offer important insights into potential mechanisms to enhance NSPC survival and implicate a potential role for glutamate in promoting NSPC survival and proliferation after traumatic SCI. PMID:27316370

  5. Interaction of Peptide Transporter 1 With D-Glucose and L-Glutamic Acid; Possible Involvement of Taste Receptors.

    PubMed

    Arakawa, Hiroshi; Ohmachi, Taichi; Ichiba, Kiko; Kamioka, Hiroki; Tomono, Takumi; Kanagawa, Masahiko; Idota, Yoko; Hatano, Yasuko; Yano, Kentaro; Morimoto, Kaori; Ogihara, Takuo

    2016-01-01

    We investigated the influence of sweet and umami (savory) tastants on the intestinal absorption of cephalexin (CEX), a substrate of peptide transporter 1 (PEPT1, SLC15A1) in rats. After oral administration of glucose or mannitol to rats, CEX was administered together with a second dose of glucose or mannitol. Western blot analysis indicated that expression of PEPT1 in rat jejunum membrane was decreased by glucose, compared to mannitol. Furthermore, the maximum plasma concentration (Cmax) of orally administered CEX was reduced by glucose compared to mannitol. The effect of glucose was diminished by nifedipine, a L-type Ca(2+) channel blocker. We also found that Cmax of orally administered CEX was reduced by treatment with L-glutamic acid, compared to D-glutamic acid. Thus, excessive intake of glucose and L-glutamic acid may impair oral absorption of PEPT1 substrates. PMID:26852864

  6. N-acetyl-aspartyl-glutamate and inhibition of glutamate carboxypeptidases protects against soman-induced neuropathology.

    PubMed

    Guo, Huifu; Liu, Jiong; Van Shura, Kerry; Chen, HuaZhen; Flora, Michael N; Myers, Todd M; McDonough, John H; McCabe, Joseph T

    2015-05-01

    N-acetyl-aspartyl-glutamate (NAAG) is the most abundant neuropeptide in the mammalian brain. In a variety of animal models of brain injury, the administration of NAAG-related compounds, or inhibitors of glutamate carboxypeptidases (GCPs; the enzymes that hydrolyze NAAG), were shown to be neuroprotective. This study determined the impact of the administration of three NAAG-related compounds, NAAG, β-NAAG (a NAAG homologue resistant to degradation), and 2-phosphonomethyl pentanedioic acid (2-PMPA; an inhibitor of GCP enzymes), on the neuropathology that develops following exposure to the nerve agent, soman. When given 1 min after soman exposure, NAAG-related drug treatments did not alter the survival rate or body weight loss seen 24 h after rats were exposed to soman. Likewise, brain levels of both NAAG and its metabolite, N-acetyl-aspartate (NAA), were substantially decreased 24 h after soman, and in particularly vulnerable brain regions the drug treatments were unable to attenuate the reduction in NAA and NAAG levels. Histochemical study indicated there was a dramatic increase in Fluoro-Jade C (FJC) staining, indicative of neuron cell death, 24 h after soman exposure. However, in the amygdala and in the entorhinal and piriform limbic cortex, which sustained severe neuropathology following soman intoxication, single or combined injections of NAAG compounds and 2-PMPA significantly reduced the number of FJC-positive cells, and effect size estimates suggest that in some brain regions the treatments were effective. The findings suggest that NAAG neurotransmission in the central nervous system is significantly altered by soman exposure, and that the administration of NAAG-related compounds and 2-PMPA reduces neuron cell death in brain regions that sustain severe damage. PMID:25825357

  7. Novel potent selective phenylglycine antagonists of metabotropic glutamate receptors.

    PubMed

    Bedingfield, J S; Jane, D E; Kemp, M C; Toms, N J; Roberts, P J

    1996-08-01

    The metabotropic glutamate (mGlu) receptor antagonist properties of novel phenylglycine analogues were investigated in adult rat cortical slices (mGlu receptors negatively coupled to adenylyl cyclase), neonatal rat cortical slices and in cultured rat cerebellar granule cells (mGlu receptors coupled to phosphoinositide hydrolysis). (RS)-alpha-methyl-4-phosphonophenylglycine (MPPG), (RS)-alpha-methyl-4-sulphonophenylglycine (MSPG), (RS)-alpha-methyl-4-tetrazolylphenylglycine (MTPG), (RS)-alpha-methyl-3-carboxymethyl-4-hydroxyphenylglycine (M3CM4HPG) and (RS)-alpha-methyl-4-hydroxy-3-phosphonomethylphenylglycine (M4H3PMPG) were demonstrated to have potent and selective effects against 10 microM L-2-amino-4-phosphonobutyrate (L-AP4)- and 0.3 microM (2S,1'S,2'S)-2-(2-carboxycyclopropyl)glycine (L-CCG-1)-mediated inhibition of forskolin-stimulated cAMP accumulation in the adult rat cortex. In contrast, these compounds demonstrated either weak or no antagonism at mGlu receptors coupled to phosphoinositide hydrolysis in either neonatal rat cortex or in cultured cerebellar granule cells. These compounds thus appear to be useful discriminatory pharmacological tools for mGlu receptors and form the basis for the further development of novel antagonists. PMID:8864696

  8. Glutamate: Tastant and Neuromodulator in Taste Buds.

    PubMed

    Vandenbeuch, Aurelie; Kinnamon, Sue C

    2016-07-01

    In taste buds, glutamate plays a double role as a gustatory stimulus and neuromodulator. The detection of glutamate as a tastant involves several G protein-coupled receptors, including the heterodimer taste receptor type 1, member 1 and 3 as well as metabotropic glutamate receptors (mGluR1 and mGluR4). Both receptor types participate in the detection of glutamate as shown with knockout animals and selective antagonists. At the basal part of taste buds, ionotropic glutamate receptors [N-methyl-d-aspartate (NMDA) and non-NMDA] are expressed and participate in the modulation of the taste signal before its transmission to the brain. Evidence suggests that glutamate has an efferent function on taste cells and modulates the release of other neurotransmitters such as serotonin and ATP. This short article reviews the recent developments in the field with regard to glutamate receptors involved in both functions as well as the influence of glutamate on the taste signal. PMID:27422519

  9. Learned taste aversions induced by high doses of monosodium L-glutamate.

    PubMed

    Vogel, J R; Nathan, B A

    1975-01-01

    Learned taste aversions, as measured by increased time to complete 100 licks of a sweetened condensed milk solution, were demonstrated by laboratory rats 4 days after consumption of the milk solution paired with high oral doses of monosodium 1-glutamate (MSG). The hesitancy of the rats to consume milk on the test session cannot be simply attributed to direct action of the drug on motivation (e.g., hunger) or to drug debilitation. MSG has been reported to occasionally cause aversive effects in humans (Chinese restaurant syndrome), and the present experiments demonstrate that the effects of MSG are aversive to laboratory rats as well. PMID:1208638

  10. Glutamate Racemase Mutants of Bacillus anthracis

    PubMed Central

    Oh, So-Young; Richter, Stefan G.; Missiakas, Dominique M.

    2015-01-01

    ABSTRACT d-Glutamate is an essential component of bacterial peptidoglycan and a building block of the poly-γ-d-glutamic acid (PDGA) capsule of Bacillus anthracis, the causative agent of anthrax. Earlier work suggested that two glutamate racemases, encoded by racE1 and racE2, are each essential for growth of B. anthracis, supplying d-glutamic acid for the synthesis of peptidoglycan and PDGA capsule. Earlier work could not explain, however, why two enzymes that catalyze the same reaction may be needed for bacterial growth. Here, we report that deletion of racE1 or racE2 did not prevent growth of B. anthracis Sterne (pXO1+ pXO2−), the noncapsulating vaccine strain, or of B. anthracis Ames (pXO1+ pXO2+), a fully virulent, capsulating isolate. While mutants with deletions in racE1 and racE2 were not viable, racE2 deletion delayed vegetative growth of B. anthracis following spore germination and caused aberrant cell shapes, phenotypes that were partially restored by exogenous d-glutamate. Deletion of racE1 or racE2 from B. anthracis Ames did not affect the production or stereochemical composition of the PDGA capsule. A model is presented whereby B. anthracis, similar to Bacillus subtilis, utilizes two functionally redundant racemase enzymes to synthesize d-glutamic acid for peptidoglycan synthesis. IMPORTANCE Glutamate racemases, enzymes that convert l-glutamate to d-glutamate, are targeted for antibiotic development. Glutamate racemase inhibitors may be useful for the treatment of bacterial infections such as anthrax, where the causative agent, B. anthracis, requires d-glutamate for the synthesis of peptidoglycan and poly-γ-d-glutamic acid (PDGA) capsule. Here we show that B. anthracis possesses two glutamate racemase genes that can be deleted without abolishing either bacterial growth or PDGA synthesis. These data indicate that drug candidates must inhibit both glutamate racemases, RacE1 and RacE2, in order to block B. anthracis growth and achieve therapeutic

  11. Pre-ischemic treadmill training for prevention of ischemic brain injury via regulation of glutamate and its transporter GLT-1.

    PubMed

    Yang, Xiaojiao; He, Zhijie; Zhang, Qi; Wu, Yi; Hu, Yongshan; Wang, Xiaolou; Li, Mingfen; Wu, Zhiyuan; Guo, Zhenzhen; Guo, Jingchun; Jia, Jie

    2012-01-01

    Pre-ischemic treadmill training exerts cerebral protection in the prevention of cerebral ischemia by alleviating neurotoxicity induced by excessive glutamate release following ischemic stroke. However, the underlying mechanism of this process remains unclear. Cerebral ischemia-reperfusion injury was observed in a rat model after 2 weeks of pre-ischemic treadmill training. Cerebrospinal fluid was collected using the microdialysis sampling method, and the concentration of glutamate was determined every 40 min from the beginning of ischemia to 4 h after reperfusion with high-performance liquid chromatography (HPLC)-fluorescence detection. At 3, 12, 24, and 48 h after ischemia, the expression of the glutamate transporter-1 (GLT-1) protein in brain tissues was determined by Western blot respectively. The effect of pre-ischemic treadmill training on glutamate concentration and GLT-1 expression after cerebral ischemia in rats along with changes in neurobehavioral score and cerebral infarct volume after 24 h ischemia yields critical information necessary to understand the protection mechanism exhibited by pre-ischemic treadmill training. The results demonstrated that pre-ischemic treadmill training up-regulates GLT-1 expression, decreases extracellular glutamate concentration, reduces cerebral infarct volume, and improves neurobehavioral score. Pre-ischemic treadmill training is likely to induce neuroprotection after cerebral ischemia by regulating GLT-1 expression, which results in re-uptake of excessive glutamate. PMID:22949807

  12. Genetic labeling of both the axons of transduced, glutamatergic neurons in rat postrhinal cortex and their postsynaptic neurons in other neocortical areas by Herpes Simplex Virus vectors that coexpress an axon-targeted ß-galactosidase and wheat germ agglutinin from a vesicular glutamate transporter-1 promoter

    PubMed Central

    Zhang, Guo-rong; Cao, Haiyan; Li, Xu; Zhao, Hua; Geller, Alfred I.

    2010-01-01

    Neuronal circuits comprise the foundation for neuronal physiology and synaptic plasticity, and thus for consequent behaviors and learning, but our knowledge of neocortical circuits is incomplete. Mapping neocortical circuits is a challenging problem because these circuits contain large numbers of neurons, a high density of synapses, and numerous classes and subclasses of neurons that form many different types of synapses. Expression of specific genetic tracers in small numbers of specific subclasses of neocortical neurons has potential to map neocortical circuits. Suitable genetic tracers have been established in neurons in subcortical areas, but application to neocortical circuits has been limited. Enabling this approach, Herpes Simplex Virus (HSV-1) plasmid (amplicon) vectors can transduce small numbers of neurons in a specific neocortical area. Further, expression of a particular genetic tracer can be restricted to specific subclasses of neurons; in particular, the vesicular glutamate transporter-1 (VGLUT1) promoter supports expression in VGLUT1-containing glutamatergic neurons in rat postrhinal (POR) cortex. Here, we show that expression of an axon-targeted ß-galactosidase (ß-gal) from such vectors supports mapping specific commissural and associative projections of the transduced neurons in POR cortex. Further, coexpression of wheat germ agglutinin (WGA) and an axon-targeted ß-gal supports mapping both specific projections of the transduced neurons and identifying specific postsynaptic neurons for the transduced neurons. The neocortical circuit mapping capabilities developed here may support mapping specific neocortical circuits that have critical roles in cognitive learning. PMID:20849834

  13. Brainstem metabotropic glutamate receptors reduce food intake and activate dorsal pontine and medullar structures after peripheral bacterial lipopolysaccharide administration.

    PubMed

    Chaskiel, Léa; Paul, Flora; Gerstberger, Rüdiger; Hübschle, Thomas; Konsman, Jan Pieter

    2016-08-01

    During infection-induced inflammation food intake is reduced. Vagal and brainstem pathways are important both in feeding regulation and immune-to-brain communication. Glutamate is released by vagal afferent terminals in the nucleus of the solitary tract and by its neurons projecting to the parabrachial nuclei. We therefore studied the role of brainstem glutamate receptors in spontaneous food intake of healthy animals and during sickness-associated hypophagia after peripheral administration of bacterial lipopolysaccharides or interleukin-1beta. Brainstem group I and II metabotropic, but not ionotropic, glutamate receptor antagonism increased food intake both in saline- and lipopolysaccharide-treated rats. In these animals, expression of the cellular activation marker c-Fos in the lateral parabrachial nuclei and lipopolysaccharide-induced activation of the nucleus of the solitary tract rostral to the area postrema were suppressed. Group I metabotropic glutamate receptors did not colocalize with c-Fos or neurons regulating gastric function in these structures. Group I metabotropic glutamate receptors were, however, found on raphé magnus neurons that were part of the brainstem circuit innervating the stomach and on trigeminal and hypoglossal motor neurons. In conclusion, our findings show that brainstem metabotropic glutamate receptors reduce food intake and activate the lateral parabrachial nuclei as well as the rostral nucleus of the solitary tract after peripheral bacterial lipopolysaccharide administration. They also provide insight into potential group I metabotropic glutamate receptor-dependent brainstem circuits mediating these effects. PMID:27016016

  14. Autoradiographic characterization of L-(/sup 3/H)glutamate binding sites in the central nervous system

    SciTech Connect

    Greenamyre, J.T.

    1986-01-01

    A quantitative autoradiographic technique was developed to study L-(/sup 3/H(glutamate binding in sections of central nervous system tissue. This technique circumvented some problems associated with conventional receptor binding methodologies and allowed direct assessment of regional distribution, numbers and affinities of glutamate binding sites. The sensitivity and high degree of anatomical resolution attainable by autoradiography obviated the need for pooled samples of microdissected specimens. Under assay conditions, (/sup 4/H)glutamate bound rapidly and reversibly to sections of rat brain and was not metabolized appreciably. The distribution of glutamate binding sites corresponded to the projection areas of putative glutamatergic pathways. Thus, there was heavy glutamate binding in regions where there is evidence for glutamatergic innervation and little binding in nuclei which apparently do not receive glutamatergic input. Scatchard and Hill plots suggested that glutamate was interacting with a single population of sites; however, competition studies revealed binding site heterogeneity. Anatomical and pharmacological evidence suggested that the NMDA-, high affinity quisqualate-, and kainate-sensitive glutamate binding sites may correspond to physiologically-defined NMDA, quisqualate and kainate receptors.

  15. Glutamate-gated Chloride Channels*

    PubMed Central

    Wolstenholme, Adrian J.

    2012-01-01

    Glutamate-gated chloride channels (GluCls) are found only in protostome invertebrate phyla but are closely related to mammalian glycine receptors. They have a number of roles in these animals, controlling locomotion and feeding and mediating sensory inputs into behavior. In nematodes and arthropods, they are targeted by the macrocyclic lactone family of anthelmintics and pesticides, making the GluCls of considerable medical and economic importance. Recently, the three-dimensional structure of a GluCl was solved, the first for any eukaryotic ligand-gated anion channel, revealing a macrocyclic lactone-binding site between the channel domains of adjacent subunits. This minireview will highlight some unique features of the GluCls and illustrate their contribution to our knowledge of the entire Cys loop ligand-gated ion channel superfamily. PMID:23038250

  16. Different pools of glutamate receptors mediate sensitivity to ambient glutamate in the cochlear nucleus

    PubMed Central

    Yang, Yang

    2015-01-01

    Ambient glutamate plays an important role in pathological conditions, such as stroke, but its role during normal activity is not clear. In addition, it is not clear how ambient glutamate acts on glutamate receptors with varying affinities or subcellular localizations. To address this, we studied “endbulb of Held” synapses, which are formed by auditory nerve fibers onto bushy cells (BCs) in the anteroventral cochlear nucleus. When ambient glutamate was increased by applying the glutamate reuptake inhibitor TFB-TBOA, BCs depolarized as a result of activation of N-methyl-d-aspartate receptors (NMDARs) and group I metabotropic glutamate receptors (mGluRs). Application of antagonists against NMDARs (in 0 Mg2+) or mGluRs caused hyperpolarization, indicating that these receptors were bound by a tonic source of glutamate. AMPA receptors did not show these effects, consistent with their lower glutamate affinity. We also evaluated the subcellular localization of the receptors activated by ambient glutamate. The mGluRs were not activated by synaptic stimulation and thus appear to be exclusively extrasynaptic. By contrast, NMDARs in both synaptic and extrasynaptic compartments were activated by ambient glutamate, as shown using the use-dependent antagonist MK-801. Levels of ambient glutamate appeared to be regulated in a spike-independent manner, and glia likely play a major role. These low levels of ambient glutamate likely have functional consequences, as even low concentrations of TBOA caused significant increases in BC spiking following synaptic stimulation. These results indicate that normal resting potential appears to be poised in the region of maximal sensitivity to small changes in ambient glutamate. PMID:25855696

  17. Different pools of glutamate receptors mediate sensitivity to ambient glutamate in the cochlear nucleus.

    PubMed

    Yang, Yang; Xu-Friedman, Matthew A

    2015-06-01

    Ambient glutamate plays an important role in pathological conditions, such as stroke, but its role during normal activity is not clear. In addition, it is not clear how ambient glutamate acts on glutamate receptors with varying affinities or subcellular localizations. To address this, we studied "endbulb of Held" synapses, which are formed by auditory nerve fibers onto bushy cells (BCs) in the anteroventral cochlear nucleus. When ambient glutamate was increased by applying the glutamate reuptake inhibitor TFB-TBOA, BCs depolarized as a result of activation of N-methyl-D-aspartate receptors (NMDARs) and group I metabotropic glutamate receptors (mGluRs). Application of antagonists against NMDARs (in 0 Mg(2+)) or mGluRs caused hyperpolarization, indicating that these receptors were bound by a tonic source of glutamate. AMPA receptors did not show these effects, consistent with their lower glutamate affinity. We also evaluated the subcellular localization of the receptors activated by ambient glutamate. The mGluRs were not activated by synaptic stimulation and thus appear to be exclusively extrasynaptic. By contrast, NMDARs in both synaptic and extrasynaptic compartments were activated by ambient glutamate, as shown using the use-dependent antagonist MK-801. Levels of ambient glutamate appeared to be regulated in a spike-independent manner, and glia likely play a major role. These low levels of ambient glutamate likely have functional consequences, as even low concentrations of TBOA caused significant increases in BC spiking following synaptic stimulation. These results indicate that normal resting potential appears to be poised in the region of maximal sensitivity to small changes in ambient glutamate. PMID:25855696

  18. The glutamate aspartate transporter (GLAST) mediates L-glutamate-stimulated ascorbate-release via swelling-activated anion channels in cultured neonatal rodent astrocytes.

    PubMed

    Lane, Darius J R; Lawen, Alfons

    2013-03-01

    Vitamin C (ascorbate) plays important neuroprotective and neuromodulatory roles in the mammalian brain. Astrocytes are crucially involved in brain ascorbate homeostasis and may assist in regenerating extracellular ascorbate from its oxidised forms. Ascorbate accumulated by astrocytes can be released rapidly by a process that is stimulated by the excitatory amino acid, L-glutamate. This process is thought to be neuroprotective against excitotoxicity. Although of potential clinical interest, the mechanism of this stimulated ascorbate-release remains unknown. Here, we report that primary cultures of mouse and rat astrocytes release ascorbate following initial uptake of dehydroascorbate and accumulation of intracellular ascorbate. Ascorbate-release was not due to cellular lysis, as assessed by cellular release of the cytosolic enzyme lactate dehydrogenase, and was stimulated by L-glutamate and L-aspartate, but not the non-excitatory amino acid L-glutamine. This stimulation was due to glutamate-induced cellular swelling, as it was both attenuated by hypertonic and emulated by hypotonic media. Glutamate-stimulated ascorbate-release was also sensitive to inhibitors of volume-sensitive anion channels, suggesting that the latter may provide the conduit for ascorbate efflux. Glutamate-stimulated ascorbate-release was not recapitulated by selective agonists of either ionotropic or group I metabotropic glutamate receptors, but was completely blocked by either of two compounds, TFB-TBOA and UCPH-101, which non-selectively and selectively inhibit the glial Na(+)-dependent excitatory amino acid transporter, GLAST, respectively. These results suggest that an impairment of astrocytic ascorbate-release may exacerbate neuronal dysfunction in neurodegenerative disorders and acute brain injury in which excitotoxicity and/or GLAST deregulation have been implicated. PMID:22886112

  19. Regulation of brain glutamate metabolism by nitric oxide and S-nitrosylation

    PubMed Central

    Raju, Karthik; Doulias, Paschalis-Thomas; Evans, Perry; Krizman, Elizabeth N.; Jackson, Joshua G.; Horyn, Oksana; Daikhin, Yevgeny; Nissim, Ilana; Yudkoff, Marc; Nissim, Itzhak; Sharp, Kim A.; Robinson, Michael B.; Ischiropoulos, Harry

    2016-01-01

    Nitric oxide (NO) is a signaling intermediate during glutamatergic neurotransmission in the central nervous system (CNS). NO signaling is in part accomplished through cysteine S-nitrosylation, a posttranslational modification by which NO regulates protein function and signaling. In our investigation of the protein targets and functional impact of S-nitrosylation in the CNS under physiological conditions, we identified 269 S-nitrosocysteine residues in 136 proteins in the wild-type mouse brain. The number of sites was significantly reduced in the brains of mice lacking endothelial nitric oxide synthase (eNOS−/−) or neuronal nitric oxide synthase (nNOS−/−). In particular, nNOS−/− animals showed decreased S-nitrosylation of proteins that participate in the glutamate/glutamine cycle, a metabolic process by which synaptic glutamate is recycled or oxidized to provide energy. 15N-glutamine–based metabolomic profiling and enzymatic activity assays indicated that brain extracts from nNOS−/− mice converted less glutamate to glutamine and oxidized more glutamate than those from mice of the other genotypes. GLT1 [also known as EAAT2 (excitatory amino acid transporter 2)], a glutamate transporter in astrocytes, was S-nitrosylated at Cys373 and Cys561 in wild-type and eNOS−/− mice, but not in nNOS−/− mice. A form of rat GLT1 that could not be S-nitrosylated at the equivalent sites had increased glutamate uptake compared to wild-type GLT1 in cells exposed to an S-nitrosylating agent. Thus, NO modulates glutamatergic neurotransmission through the selective, nNOS-dependent S-nitrosylation of proteins that govern glutamate transport and metabolism. PMID:26152695

  20. Nitrogen-13 glutamate uptake and perfusion in Walker 256 carcinosarcoma before and after single-dose irradiation

    SciTech Connect

    Knapp, W.H.; Helus, F.; Layer, K.; Panzer, M.; Hoever, K.H.O.; Ostertag, H.

    1986-10-01

    Nitrogen-13 (13N) glutamate uptake was recorded in 18 anesthetized rats, both before and at least once after intervention. Each investigation was immediately followed by imaging of blood flow distribution using (11C)butanol. All animals had Walker 256 carcinosarcoma implants in one hind leg. Tumors were locally irradiated with a dose of 800 rad in 14 rats; in four rats, the vasoactive substance 5-hydroxytryptamine (5-HT) was administered. Prior to interventions, the (13N)glutamate tumor-to-muscle uptake showed a linear correlation with blood flow close to identity (y = 0.117 + 0.915x, r = 0.97). After irradiation, a discordant pattern was observed: blood flow tended to increase, while (13N)glutamate tumor-to-muscle uptake dropped from 4.30 +/- 0.66 (s.e.m.) to 3.06 +/- 0.36 (p less than 0.005) during 30 min and attained 4.04 +/- 0.67 2 days later. If (13N)glutamate tumor-to-muscle uptake was related to that of (11C) butanol in each individual animal, this index dropped from 0.93 +/- 0.03 (s.e.m.) to 0.62 +/- 0.04 (p less than 0.001) 30 min after irradiation and attained 0.90 +/- 0.09 after 2 days. In animals treated with 5-HT, (13N)glutamate and (11C)butanol showed a parallel drop from 6.60 +/- 0.84 to 2.10 +/- 0.60 (p less than 0.05) and from 6.8 +/- 0.78 to 2.08 +/- 0.74 (p less than 0.05), respectively. Thus, single-dose irradiation causes (13N)glutamate uptake to be uncoupled with respect to flow, while (13N)glutamate uptake in untreated tumors is flow-limited and responds together with flow on vasomotion.

  1. GLT-1 Transport Stoichiometry Is Constant at Low and High Glutamate Concentrations when Chloride Is Substituted by Gluconate

    PubMed Central

    Kabakov, Anatoli Y.; Rosenberg, Paul A.

    2015-01-01

    Glutamate is the major excitatory neurotransmitter, but prolonged exposure even at micromolar concentrations causes neuronal death. Extracellular glutamate is maintained at nanomolar level by glutamate transporters, which, however, may reverse transport and release glutamate. If and when the reverse occurs depends on glutamate transport stoichiometry (GTS). Previously we found that in the presence of chloride, the coupled GLT-1 glutamate transporter current and its relationship to radiolabeled glutamate flux significantly decreased when extracellular glutamate concentration increased above 0.2 mM, which implies a change in GTS. Such high concentrations are feasible near GLT-1 expressed close to synaptic release site during excitatory neurotransmission. The aim of this study was to determine GLT-1 GTS at both low (19–75 μM) and high (300–1200 μM) glutamate concentration ranges. GTS experiments were conducted in the absence of chloride to avoid contributions by the GLT-1 uncoupled chloride conductance. Mathematical analysis of the transporter thermodynamic equilibrium allowed us to derive equations revealing the number of a particular type of ion transported per elementary charge based on the measurements of the transporter reversal potential. We found that GLT-1a expressed in COS-7 cells co-transports 1.5 Na+, 0.5 Glu-, 0.5 H+ and counter-transports 0.6 K+ per elementary charge in both glutamate concentration ranges, and at both 37°C and 26°C temperatures. The thermodynamic parameter Q10 = 2.4 for GLT-1 turnover rate of 19 s-1 (37°C, -50 mV) remained constant in the 10 μM–10 mM glutamate concentration range. Importantly, the previously reported decrease in the current/flux ratio at high glutamate concentration was not seen in the absence of chloride in both COS-7 cells and cultured rat neurons. Therefore, only in the absence of chloride, GLT-1 GTS remains constant at all glutamate concentrations. Possible explanations for why apparent GTS might vary in

  2. Vesicular Glutamate Transport Promotes Dopamine Storage and Glutamate Corelease In Vivo

    PubMed Central

    Hnasko, Thomas S.; Chuhma, Nao; Zhang, Hui; Goh, Germaine Y.; Sulzer, David; Palmiter, Richard D.; Rayport, Stephen; Edwards, Robert H.

    2010-01-01

    SUMMARY Dopamine neurons in the ventral tegmental area (VTA) play an important role in the motivational systems underlying drug addiction, and recent work has suggested that they also release the excitatory neurotransmitter glutamate. To assess a physiological role for glutamate corelease, we disrupted the expression of vesicular glutamate transporter 2 selectively in dopamine neurons. The conditional knockout abolishes glutamate release from midbrain dopamine neurons in culture and severely reduces their excitatory synaptic output in mesoaccumbens slices. Baseline motor behavior is not affected, but stimulation of locomotor activity by cocaine is impaired, apparently through a selective reduction of dopamine stores in the projection of VTA neurons to ventral striatum. Glutamate co-entry promotes monoamine storage by increasing the pH gradient that drives vesicular monoamine transport. Remarkably, low concentrations of glutamate acidify synaptic vesicles more slowly but to a greater extent than equimolar Cl−, indicating a distinct, presynaptic mechanism to regulate quantal size. PMID:20223200

  3. Metabolic fate and function of dietary glutamate in the gut

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Glutamate is a major constituent of dietary protein and is also consumed in many prepared foods as an additive in the form of monosodium glutamate. Evidence from human and animal studies indicates that glutamate is a major oxidative fuel for the gut and that dietary glutamate is extensively metabol...

  4. Emerging aspects of dietary glutamate metabolism in the developing gut

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Glutamate is a major constituent of dietary protein and is also consumed in many prepared foods as a flavour additive in the form of monosodium glutamate (MSG). Evidence from human and animal studies indicates that glutamate is the major oxidative fuel for the gut and that dietary glutamate is exten...

  5. Role of Na,K-ATPase α1 and α2 Isoforms in the Support of Astrocyte Glutamate Uptake

    PubMed Central

    Illarionava, Nina B.; Brismar, Hjalmar; Aperia, Anita; Gunnarson, Eli

    2014-01-01

    Glutamate released during neuronal activity is cleared from the synaptic space via the astrocytic glutamate/Na+ co-transporters. This transport is driven by the transmembrane Na+ gradient mediated by Na,K-ATPase. Astrocytes express two isoforms of the catalytic Na,K-ATPase α subunits; the ubiquitously expressed α1 subunit and the α2 subunit that has a more specific expression profile. In the brain α2 is predominantly expressed in astrocytes. The isoforms differ with regard to Na+ affinity, which is lower for α2. The relative roles of the α1 and α2 isoforms in astrocytes are not well understood. Here we present evidence that the presence of the α2 isoform may contribute to a more efficient restoration of glutamate triggered increases in intracellular sodium concentration [Na+]i. Studies were performed on primary astrocytes derived from E17 rat striatum expressing Na,K-ATPase α1 and α2 and the glutamate/Na+ co-transporter GLAST. Selective inhibition of α2 resulted in a modest increase of [Na+]i accompanied by a disproportionately large decrease in uptake of aspartate, an indicator of glutamate uptake. To compare the capacity of α1 and α2 to handle increases in [Na+]i triggered by glutamate, primary astrocytes overexpressing either α1 or α2 were used. Exposure to glutamate 200 µM caused a significantly larger increase in [Na+]i in α1 than in α2 overexpressing cells, and as a consequence restoration of [Na+]i, after glutamate exposure was discontinued, took longer time in α1 than in α2 overexpressing cells. Both α1 and α2 interacted with astrocyte glutamate/Na+ co-transporters via the 1st intracellular loop. PMID:24901986

  6. Glutamate Receptor Stimulation Up-Regulates Glutamate Uptake in Human Müller Glia Cells.

    PubMed

    López-Colomé, Ana María; López, Edith; Mendez-Flores, Orquidia G; Ortega, Arturo

    2016-07-01

    Glutamate, the main excitatory amino acid in the vertebrate retina, is a well know activator of numerous signal transduction pathways, and has been critically involved in long-term synaptic changes acting through ionotropic and metabotropic glutamate receptors. However, recent findings underlining the importance of intensity and duration of glutamate stimuli for specific neuronal responses, including excitotoxicity, suggest a crucial role for Na(+)-dependent glutamate transporters, responsible for the removal of this neurotransmitter from the synaptic cleft, in the regulation of glutamate-induced signaling. Transporter proteins are expressed in neurons and glia cells, albeit most of glutamate uptake occurs in the glial compartment. Within the retina, Müller glia cells are in close proximity to glutamatergic synapses and participate in the recycling of glutamate through the glutamate/glutamine shuttle. In this context, we decided to investigate a plausible role of glutamate as a regulatory signal for its own transport in human retinal glia cells. To this end, we determined [(3)H]-D-aspartate uptake in cultures of spontaneously immortalized human Müller cells (MIO-M1) exposed to distinct glutamatergic ligands. A time and dose-dependent increase in the transporter activity was detected. This effect was dependent on the activation of the N-methyl D-aspartate subtype of glutamate receptors, due to a dual effect: an increase in affinity and an augmented expression of the transporter at the plasma membrane, as established via biotinylation experiments. Furthermore, a NMDA-dependent association of glutamate transporters with the cystoskeletal proteins ezrin and glial fibrillary acidic protein was also found. These results add a novel mediator of the glutamate transporter modulation and further strengthen the notion of the critical involvement of glia cells in synaptic function. PMID:27017513

  7. Glutamate Receptor Dynamics in Dendritic Microdomains

    PubMed Central

    Newpher, Thomas M.; Ehlers, Michael D.

    2008-01-01

    Among diverse factors regulating excitatory synaptic transmission, the abundance of postsynaptic glutamate receptors figures prominently in molecular memory and learning-related synaptic plasticity. To allow for both long-term maintenance of synaptic transmission and acute changes in synaptic strength, the relative rates of glutamate receptor insertion and removal must be tightly regulated. Interactions with scaffolding proteins control the targeting and signaling properties of glutamate receptors within the postsynaptic membrane. In addition, extrasynaptic receptor populations control the equilibrium of receptor exchange at synapses and activate distinct signaling pathways involved in plasticity. Here, we review recent findings that have shaped our current understanding of receptor mobility between synaptic and extrasynaptic compartments at glutamatergic synapses, focusing on AMPA and NMDA receptors. We also examine the cooperative relationship between intracellular trafficking and surface diffusion of glutamate receptors that underlies the expression of learning-related synaptic plasticity. PMID:18498731

  8. Mechanism for the activation of glutamate receptors

    Cancer.gov

    Scientists at the NIH have used a technique called cryo-electron microscopy to determine a molecular mechanism for the activation and desensitization of ionotropic glutamate receptors, a prominent class of neurotransmitter receptors in the brain and spina

  9. [Glutamate transporter dysfunction and major mental illnesses].

    PubMed

    Tanaka, Kohichi

    2016-01-01

    Glutamate is the main excitatory neurotransmitter in the central nervous system and plays an important role in most aspects of normal brain function. In spite of its importance as a neurotransmitter, excess glutamate is toxic to neurons. Clearance of extracellular glutamate is critical for maintenance of low extracellular glutamate concentration, and occurs in large part through the activity of GLT1 (EAAT2) and GLAST (EAAT1), which are primarily expressed by astrocytes. Rare variants and down-regulation of GLT1 and GLAST, in psychiatric disorders have been reported. In this review, we demonstrate that various kinds of GLT1 and/or GLAST knockout mice replicate many aspects of the behavioral abnormalities seen in major mental illnesses including schizophrenia, depression, obsessive -compulsive disorders, autism, epilepsy and addiction. PMID:26793898

  10. DNA nanopore translocation in glutamate solutions

    NASA Astrophysics Data System (ADS)

    Plesa, C.; van Loo, N.; Dekker, C.

    2015-08-01

    Nanopore experiments have traditionally been carried out with chloride-based solutions. Here we introduce silver/silver-glutamate-based electrochemistry as an alternative, and study the viscosity, conductivity, and nanopore translocation characteristics of potassium-, sodium-, and lithium-glutamate solutions. We show that it has a linear response at typical voltages and can be used to detect DNA translocations through a nanopore. The glutamate anion also acts as a redox-capable thickening agent, with high-viscosity solutions capable of slowing down the DNA translocation process by up to 11 times, with a corresponding 7 time reduction in signal. These results demonstrate that glutamate can replace chloride as the primary anion in nanopore resistive pulse sensing.

  11. Glutamic Acid Decarboxylation in Chlorella12

    PubMed Central

    Lane, T. R.; Stiller, Mary

    1970-01-01

    The decarboxylation of endogenous free glutamic acid by Chlorella pyrenoidosa, Marburg strain, was induced by a variety of metabolic poisons, by anaerobic conditions, and by freezing and thawing the cells. The rate of decarboxylation was proportional to the concentration of inhibitor present. Possible mechanisms which relate the effects of the various conditions on glutamate decarboxylation and oxygen consumption by Chlorella are discussed. Images PMID:5429350

  12. [Glutamate neurotransmission, stress and hormone secretion].

    PubMed

    Jezová, D; Juránková, E; Vigas, M

    1995-11-01

    Glutamate neurotransmission has been investigated in relation to several physiological processes (learning, memory) as well as to neurodegenerative and other disorders. Little attention has been paid to its involvement in neuroendocrine response during stress. Penetration of excitatory amino acids from blood to the brain is limited by the blood-brain barrier. As a consequence, several toxic effects but also bioavailability for therapeutic purposes are reduced. A free access to circulating glutamate is possible only in brain structures lacking the blood-brain barrier or under conditions of its increased permeability. Excitatory amino acids were shown to stimulate the pituitary hormone release, though the mechanism of their action is still not fully understood. Stress exposure in experimental animals induced specific changes in mRNA levels coding the glutamate receptor subunits in the hippocampus and hypothalamus. The results obtained with the use of glutamate receptor antagonists indicate that a number of specific receptor subtypes contribute to the stimulation of ACTH release during stress. The authors provided also data on the role of NMDA receptors in the control of catecholamine release, particularly in stress-induced secretion of epinephrine. These results were the first piece of evidence on the involvement of endogenous excitatory amino acids in neuroendocrine activation during stress. Neurotoxic effects of glutamate in animals are well described, especially after its administration in the neonatal period. In men, glutamate toxicity and its use as a food additive are a continuous subject of discussions. The authors found an increase in plasma cortisol and norepinephrine, but not epinephrine and prolactin, in response to the administration of a high dose of glutamate. It cannot be excluded that these effects might be induced even by lower doses in situations with increased vulnerability to glutamate action (age, individual variability). (Tab. 1, Fig. 6, Ref. 44

  13. Ionotropic Glutamate Receptors & CNS Disorders

    PubMed Central

    Bowie, Derek

    2008-01-01

    Disorders of the central nervous system (CNS) are complex disease states that represent a major challenge for modern medicine. Although etiology is often unknown, it is established that multiple factors such as defects in genetics and/or epigenetics, the environment as well as imbalance in neurotransmitter receptor systems are all at play in determining an individual’s susceptibility to disease. Gene therapy is currently not available and therefore, most conditions are treated with pharmacological agents that modify neurotransmitter receptor signaling. Here, I provide a review of ionotropic glutamate receptors (iGluRs) and the roles they fulfill in numerous CNS disorders. Specifically, I argue that our understanding of iGluRs has reached a critical turning point to permit, for the first time, a comprehensive re-evaluation of their role in the cause of disease. I illustrate this by highlighting how defects in AMPA receptor trafficking are important to Fragile X mental retardation and ectopic expression of kainate (KA) receptor synapses contributes to the pathology of temporal lobe epilepsy. Finally, I discuss how parallel advances in studies of other neurotransmitter systems may allow pharmacologists to work towards a cure for many CNS disorders rather than developing drugs to treat their symptoms. PMID:18537642

  14. Therapeutic Potential of Metabotropic Glutamate Receptor Modulators

    PubMed Central

    Hovelsø, N; Sotty, F; Montezinho, L.P; Pinheiro, P.S; Herrik, K.F; Mørk, A

    2012-01-01

    Glutamate is the main excitatory neurotransmitter in the central nervous system (CNS) and is a major player in complex brain functions. Glutamatergic transmission is primarily mediated by ionotropic glutamate receptors, which include NMDA, AMPA and kainate receptors. However, glutamate exerts modulatory actions through a family of metabotropic G-protein-coupled glutamate receptors (mGluRs). Dysfunctions of glutamatergic neurotransmission have been implicated in the etiology of several diseases. Therefore, pharmacological modulation of ionotropic glutamate receptors has been widely investigated as a potential therapeutic strategy for the treatment of several disorders associated with glutamatergic dysfunction. However, blockade of ionotropic glutamate receptors might be accompanied by severe side effects due to their vital role in many important physiological functions. A different strategy aimed at pharmacologically interfering with mGluR function has recently gained interest. Many subtype selective agonists and antagonists have been identified and widely used in preclinical studies as an attempt to elucidate the role of specific mGluRs subtypes in glutamatergic transmission. These studies have allowed linkage between specific subtypes and various physiological functions and more importantly to pathological states. This article reviews the currently available knowledge regarding the therapeutic potential of targeting mGluRs in the treatment of several CNS disorders, including schizophrenia, addiction, major depressive disorder and anxiety, Fragile X Syndrome, Parkinson’s disease, Alzheimer’s disease and pain. PMID:22942876

  15. Blockade of the locomotor stimulant effects of amphetamine by group I, group II, and group III metabotropic glutamate receptor ligands in the rat nucleus accumbens: possible interactions with dopamine receptors.

    PubMed

    David, H N; Abraini, J H

    2003-05-01

    Previous investigations have shown that mGlu receptors would be involved in the amphetamine-induced motor response. However, data are somewhat controversial across studies where methodological protocols vary. The aim of the present study was to determine the involvement of mGlu receptors in the NAcc in the locomotor-activating properties of amphetamine in rats well habituated to their experimental environment, a condition known to modulate the motor response to amphetamine. Focal infusion of the group I mGlu receptor antagonist S-4-CPG, which has no effect on basal motor activity, virtually suppressed the locomotor response to amphetamine, while infusion of the group II mGlu receptor antagonist LY 341495 or the group III mGlu receptor agonist AP4, at the minimal dose that produces locomotor activation, reduced it by approximately a half. These effects were blocked by the group I mGlu receptor agonist DHPG, the group II mGlu receptor agonist APDC, and the group III mGlu receptor antagonist MPPG, respectively. These data confirm that mGlu receptors in the NAcc contribute to the psychostimulant motor effect of amphetamine. Results are discussed from the view of recent neuropharmacological studies that have defined the effects of these mGlu receptor ligands on basal motor activity and DA receptor agonists-induced locomotor responses in rats exposed to similar experimental procedures (Eur J Neuroscience 13 (2001) 2157; Neuropharmacology 41 (2001) 454; Eur J Neuroscience 13 (2001) 869). It is suggested that the contribution of mGlu receptors to the amphetamine-induced motor response may result mainly from their functional, either direct or indirect, interactions with D1-like receptors in the NAcc. PMID:12681370

  16. Lack of effect of entorhinal kindling on L-(/sup 3/H)glutamic acid presynaptic uptake and postsynaptic binding in hippocampus

    SciTech Connect

    Slevin, J.T.; Ferrara, L.P.

    1985-07-01

    Sodium-independent L-(/sup 3/H)glutamic acid binding and sodium-dependent L-(/sup 3/H)glutamic acid high affinity uptake were measured in hippocampal membranes of rats administered electroshock seizures or kindled to class 5 seizures by entorhinal cortical stimulation. There were no differences in these glutamatergic synaptic markers among electroshocked, kindled, or surgical control animals. Entorhinal kindling is not a reflection of activity-regulated facilitation of perforant path glutamatergic neurotransmission.

  17. Structural mechanism of glutamate receptor activation and desensitization.

    PubMed

    Meyerson, Joel R; Kumar, Janesh; Chittori, Sagar; Rao, Prashant; Pierson, Jason; Bartesaghi, Alberto; Mayer, Mark L; Subramaniam, Sriram

    2014-10-16

    Ionotropic glutamate receptors are ligand-gated ion channels that mediate excitatory synaptic transmission in the vertebrate brain. To gain a better understanding of how structural changes gate ion flux across the membrane, we trapped rat AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) and kainate receptor subtypes in their major functional states and analysed the resulting structures using cryo-electron microscopy. We show that transition to the active state involves a 'corkscrew' motion of the receptor assembly, driven by closure of the ligand-binding domain. Desensitization is accompanied by disruption of the amino-terminal domain tetramer in AMPA, but not kainate, receptors with a two-fold to four-fold symmetry transition in the ligand-binding domains in both subtypes. The 7.6 Å structure of a desensitized kainate receptor shows how these changes accommodate channel closing. These findings integrate previous physiological, biochemical and structural analyses of glutamate receptors and provide a molecular explanation for key steps in receptor gating. PMID:25119039

  18. Hypothermia protects against oxygen-glucose deprivation-induced neuronal injury by down-regulating the reverse transport of glutamate by astrocytes as mediated by neurons.

    PubMed

    Wang, D; Zhao, Y; Zhang, Y; Zhang, T; Shang, X; Wang, J; Liu, Y; Kong, Q; Sun, B; Mu, L; Liu, X; Wang, G; Li, H

    2013-05-01

    Glutamate is the major mediator of excitotoxic neuronal death following cerebral ischemia. Under severe ischemic conditions, glutamate transporters can functionally reverse to release glutamate, thereby inducing further neuronal injury. Hypothermia has been shown to protect neurons from brain ischemia. However, the mechanism(s) involved remain unclear. Therefore, the aim of this study was to investigate the mechanism(s) mediating glutamate release during brain ischemia-reperfusion injury under hypothermic conditions. Neuron/astrocyte co-cultures were exposed to oxygen-glucose deprivation (OGD) at various temperatures for 2h, and cell viability was assayed 12h after reoxygenation. PI and MAP-2 staining demonstrated that hypothermia significantly decreased neuronal injury. Furthermore, [(3)H]-glutamate uptake assays showed that hypothermia protected rat primary cortical cultures against OGD reoxygenation-induced injury. Protein levels of the astrocytic glutamate transporter, GLT-1, which is primarily responsible for the clearance of extracellular glutamate, were also found to be reduced in a temperature-dependent manner. In contrast, expression of GLT-1 in astrocyte-enriched cultures was found to significantly increase following the addition of neuron-conditioned medium maintained at 37 °C, and to a lesser extent with neuron-conditioned medium at 33 °C. In conclusion, the neuroprotective effects of hypothermia against brain ischemia-reperfusion injury involve down-regulation of astrocytic GLT-1, which mediates the reverse transport of glutamate. Moreover, this process may be regulated by molecules secreted by stressed neurons. PMID:23402854

  19. The Degradation of 14C-Glutamic Acid by L-Glutamic Acid Decarboxylase.

    ERIC Educational Resources Information Center

    Dougherty, Charles M; Dayan, Jean

    1982-01-01

    Describes procedures and semi-micro reaction apparatus (carbon dioxide trap) to demonstrate how a particular enzyme (L-Glutamic acid decarboxylase) may be used to determine the site or sites of labeling in its substrate (carbon-14 labeled glutamic acid). Includes calculations, solutions, and reagents used. (Author/SK)

  20. Sodium-calcium exchanger modulates the L-glutamate Ca(i) (2+) signalling in type-1 cerebellar astrocytes.

    PubMed

    Rojas, Héctor; Colina, Claudia; Ramos, Magaly; Benaim, Gustavo; Jaffe, Erica; Caputo, Carlo; Di Polo, Reinaldo

    2013-01-01

    We have previously demonstrated that rat type-1 cerebellar astrocytes express a very active Na(+)/Ca(2+) exchanger which accounts for most of the total plasma membrane Ca(2+) fluxes and for the clearance of Ca (i) (2+) induced by physiological agonist. In this chapter, we have explored the mechanism by which the reverse Na(+)/Ca(2+) exchange is involved in agonist-induced Ca(2+) signalling in rat cerebellar astrocytes. Laser-scanning confocal microscopy experiments using immunofluorescence labelling of Na(+)/Ca(2+) exchanger and RyRs demonstrated that they are highly co-localized. The most important finding presented in this chapter is that L-glutamate activates the reverse mode of the Na(+)/Ca(2+) exchange by inducing a Na(+) entry through the electrogenic Na(+)-glutamate co-transporter and not through the ionophoric L-glutamate receptors as confirmed by pharmacological experiments with specific blockers of ionophoric L-glutamate receptors, electrogenic glutamate transporters and the Na/Ca exchange. PMID:23224886

  1. Glutamate receptor ligands as anxiolytics.

    PubMed

    Chojnacka-Wójcik, E; Kłodzinska, A; Pilc, A

    2001-08-01

    The glutamatergic system has received considerable attention over recent years as a potential target for anxiolytic drugs. In spite of the pronounced anxiolytic-like effects of competitive and non-competitive antagonists of NMDA receptors in animal models of anxiety, these substances can not be regarded as potential anxiolytic drugs, mainly due to their side-effect profiles (eg, ataxia, myorelaxation, impairment of learning and memory processes and psychotomimetic effects). Antagonists and partial agonists of the glycine, receptor inhibit function of the NMDA receptor complex and evoke in animals an anxiolytic-like response. Although data concerning anti-anxiety-like effects of glycine, receptor antagonists are not very promising, studies are underway to develop new, brain-penetrating agents devoid of side effects. Further developments are necessary to more fully elucidate the possible involvement of AMPA/kainate receptors in anxiety. The recent discovery of metabotropic glutamate receptors, which modulate the function of the glutamatergic system, offers new hope for discovery of a new generation of anxiolytics. MPEP, a highly selective, brain penetrable, noncompetitive mGlu5 receptor antagonist, evokes anxiolytic-like effects in several animal models of anxiety, remaining remarkably free of side effects. LY-354740, a selective brain-penetrable group II mGlu receptor agonist, evokes marked anxiolytic-like effects in animal models of anxiety. LY-354740 causes mild sedation in mice, does not disturb motor coordination and has no potential to cause dependence. Therefore mGlu receptor ligands may become the anxiolytics of the future, free from the side effects characteristic of benzodiazepines. PMID:11892923

  2. Glutamate infused posttraining into the hippocampus or caudate-putamen differentially strengthens place and response learning

    PubMed Central

    Packard, Mark G.

    1999-01-01

    A cross-maze task that can be acquired through either place or response learning was used to examine the hypothesis that posttraining neurochemical manipulation of the hippocampus or caudate-putamen can bias an animal toward the use of a specific memory system. Male Long-Evans rats received four trials per day for 7 days, a probe trial on day 8, further training on days 9–15, and an additional probe trial on day 16. Training occurred in a cross-maze task in which rats started from a consistent start-box (south), and obtained food from a consistent goal-arm (west). On days 4–6 of training, rats received posttraining intrahippocampal (1 μg/0.5 μl) or intracaudate (2 μg/0.5 μl) injections of either glutamate or saline (0.5 μl). On days 8 and 16, a probe trial was given in which rats were placed in a novel start-box (north). Rats selecting the west goal-arm were designated “place” learners, and those selecting the east goal-arm were designated “response” learners. Saline-treated rats predominantly displayed place learning on day 8 and response learning on day 16, indicating a shift in control of learned behavior with extended training. Rats receiving intrahippocampal injections of glutamate predominantly displayed place learning on days 8 and 16, indicating that manipulation of the hippocampus produced a blockade of the shift to response learning. Rats receiving intracaudate injections of glutamate displayed response learning on days 8 and 16, indicating an accelerated shift to response learning. The findings suggest that posttraining intracerebral glutamate infusions can (i) modulate the distinct memory processes mediated by the hippocampus and caudate-putamen and (ii) bias the brain toward the use of a specific memory system to control learned behavior and thereby influence the timing of the switch from the use of cognitive memory to habit learning to guide behavior. PMID:10536017

  3. The pathways of glutamate and glutamine oxidation by tumor cell mitochondria. Role of mitochondrial NAD(P)+-dependent malic enzyme.

    PubMed

    Moreadith, R W; Lehninger, A L

    1984-05-25

    Little evidence has been available on the oxidative pathways of glutamine and glutamate, the major respiratory substrates of cancer cells. Glutamate formed from glutamine by phosphate-dependent glutaminase undergoes quantitative transamination by aerobic tumor mitochondria to yield aspartate. However, when malate is also added there is a pronounced decrease in aspartate production and a large formation of citrate and alanine, in both state 3 and 4 conditions. In contrast, addition of malate to normal rat heart, liver, or kidney mitochondria oxidizing glutamate causes a marked increase in aspartate production. Further analysis showed that extramitochondrial malate is oxidized almost quantitatively to pyruvate + CO2 by NAD(P)+-linked malic enzyme, present in the mitochondria of all tumors tested, but absent in heart, liver, and kidney mitochondria. On the other hand intramitochondrial malate generated from glutamate is oxidized quantitatively to oxalacetate by mitochondrial malate dehydrogenase of tumors. Acetyl-CoA derived from extramitochondrial malate via pyruvate and oxalacetate derived from glutamate via intramitochondrial malate are quantitatively converted into citrate, which is extruded. No evidence was found that malic enzyme of tumor mitochondria converts glutamate-derived malate into pyruvate as postulated in other reports. Possible mechanisms for the integration of mitochondrial malic enzyme and malate dehydrogenase activities in tumors are discussed. PMID:6144677

  4. The Role of Glutamine Synthetase and Glutamate Dehydrogenase in Cerebral Ammonia Homeostasis

    PubMed Central

    Cooper, Arthur J. L.

    2012-01-01

    In the brain, glutamine synthetase (GS), which is located predominantly in astrocytes, is largely responsible for the removal of both blood-derived and metabolically generated ammonia. Thus, studies with [13N]ammonia have shown that about 25% of blood-derived ammonia is removed in a single pass through the rat brain and that this ammonia is incorporated primarily into glutamine (amide) in astrocytes. Major pathways for cerebral ammonia generation include the glutaminase reaction and the glutamate dehydrogenase (GDH) reaction. The equilibrium position of the GDH-catalyzed reaction in vitro favors reductive amination of α-ketoglutarate at pH 7.4. Nevertheless, only a small amount of label derived from [13N]ammonia in rat brain is incorporated into glutamate and the α-amine of glutamine in vivo. Most likely the cerebral GDH reaction is drawn normally in the direction of glutamate oxidation (ammonia production) by rapid removal of ammonia as glutamine. Linkage of glutamate/α-ketoglutarate-utilizing aminotransferases with the GDH reaction channels excess amino acid nitrogen toward ammonia for glutamine synthesis. At high ammonia levels and/or when GS is inhibited the GDH reaction coupled with glutamate/α-ketoglutarate-linked aminotransferases may, however, promote the flow of ammonia nitrogen toward synthesis of amino acids. Preliminary evidence suggests an important role for the purine nucleotide cycle (PNC) as an additional source of ammonia in neurons (Net reaction: L-Aspartate + GTP + H2O → Fumarate + GDP + Pi + NH3) and in the beat cycle of ependyma cilia. The link of the PNC to aminotransferases and GDH/GS and its role in cerebral nitrogen metabolism under both normal and pathological (e.g. hyperammonemic encephalopathy) conditions should be a productive area for future research. PMID:22618691

  5. 4-Hydroxynonenal, an aldehydic product of membrane lipid peroxidation, impairs glutamate transport and mitochondrial function in synaptosomes.

    PubMed

    Keller, J N; Mark, R J; Bruce, A J; Blanc, E; Rothstein, J D; Uchida, K; Waeg, G; Mattson, M P

    1997-10-01

    Removal of extracellular glutamate at synapses, by specific high-affinity glutamate transporters, is critical to prevent excitotoxic injury to neurons. Oxidative stress has been implicated in the pathogenesis of an array of prominent neurodegenerative conditions that involve degeneration of synapses and neurons in glutamatergic pathways including stroke, and Alzheimer's, Parkinson's and Huntington's diseases. Although cell culture data indicate that oxidative insults can impair key membrane regulatory systems including ion-motive ATPases and amino acid transport systems, the effects of oxidative stress on synapses, and the mechanisms that mediate such effects, are largely unknown. This study provides evidence that 4-hydroxynonenal, an aldehydic product of lipid peroxidation, mediates oxidation-induced impairment of glutamate transport and mitochondrial function in synapses. Exposure of rat cortical synaptosomes to 4-hydroxynonenal resulted in concentration- and time-dependent decreases in [3H]glutamate uptake, and mitochondrial function [assessed with the dye 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)]. Other related aldehydes including malondialdehyde and hexanal had little or no effect on glutamate uptake or mitochondrial function. Exposure of synaptosomes to insults known to induce lipid peroxidation (FeSO4 and amyloid beta-peptide) also impaired glutamate uptake and mitochondrial function. The antioxidants propyl gallate and glutathione prevented impairment of glutamate uptake and MTT reduction induced by FeSO4 and amyloid beta-peptide, but not that induced by 4-hydroxynonenal. Western blot analyses using an antibody to 4-hydroxynonenal-conjugated proteins showed that 4-hydroxynonenal bound to multiple cell proteins including GLT-1, a glial glutamate transporter present at high levels in synaptosomes. 4-Hydroxynonenal itself induced lipid peroxidation suggesting that, in addition to binding directly to membrane regulatory proteins, 4

  6. Glutamate Metabolism in Major Depressive Disorder

    PubMed Central

    Abdallah, Chadi G.; Jiang, Lihong; De Feyter, Henk M.; Fasula, Madonna; Krystal, John H.; Rothman, Douglas L.; Mason, Graeme F.; Sanacora, Gerard

    2015-01-01

    Objective Emerging evidence suggests abnormalities in amino acid neurotransmitter function and impaired energy metabolism contribute to the underlying pathophysiology of Major Depressive Disorder (MDD). To test whether impairments in energetics and glutamate neurotransmitter cycling are present in MDD we used in vivo 13C magnetic resonance spectroscopy (13C MRS) to measure these fluxes in individuals diagnosed with MDD relative to non-depressed subjects. Method 1H MRS and 13C MRS data were collected on 23 medication-free MDD and 17 healthy subjects. 1H MRS provided total glutamate and GABA concentrations, and 13C MRS, coupled with intravenous infusion of [1-13C]-glucose, provided measures of the neuronal tricarboxylic acid cycle (VTCAN) for mitochondrial energy production, GABA synthesis, and glutamate/glutamine cycling, from voxels placed in the occipital cortex. Results Our main finding was that mitochondrial energy production of glutamatergic neurons was reduced by 26% in MDD subjects (t = 2.57, p = 0.01). Paradoxically we found no difference in the rate of glutamate/glutamine cycle (Vcycle). We also found a significant correlation between glutamate concentrations and Vcycle considering the total sample. Conclusions We interpret the reduction in mitochondrial energy production as being due to either mitochondrial dysfunction or a reduction in proper neuronal input or synaptic strength. Future MRS studies could help distinguish these possibilities. PMID:25073688

  7. Single channel kinetics of a glutamate receptor.

    PubMed Central

    Kerry, C J; Kits, K S; Ramsey, R L; Sansom, M S; Usherwood, P N

    1987-01-01

    The glutamate receptor-channel of locust muscle membrane was studied using the patch-clamp technique. Muscles were pretreated with concanavalin A to block receptor-channel desensitization, thus facilitating analysis of receptor-channel gating kinetics. Single channel kinetics were analyzed to aid in identification of the molecular basis of channel gating. Channel dwell-time distributions and dwell-time autocorrelation functions were calculated from single channel data recorded in the precence of 10-4M glutamate. Analysis of the dwell time distributions in terms of mixtures of exponential functions revealed there to be at least three open states of the receptor-channel and at least four closed states. Autocorrelation function analysis showed there to be at least three pathways linking the open states with the closed. This results in a minimal scheme for gating of the glutamate receptor-channel, which is suggestive of allosteric models of receptor-channel gating. PMID:2436676

  8. Single Channel Kinetics of a Glutamate Receptor

    PubMed Central

    Kerry, Cathryn J.; Kits, Karel S.; Ramsey, Robert L.; Sansom, Mark S. P.; Usherwood, Peter N. R.

    1986-01-01

    The glutamate receptor-channel of locust muscle membrane was studied using the patch-clamp technique. Muscles were pretreated with concanavalin A to block receptor-channel desensitization, thus facilitating analysis of receptor-channel gating kinetics. Single channel kinetics were analyzed to aid in identification of the molecular basis of channel gating. Channel dwell-time distributions and dwell-time autocorrelation functions were calculated from single channel data recorded in the presence of 10-4 M glutamate. Analysis of the dwell time distributions in terms of mixtures of exponential functions revealed there to be at least three open states of the receptor-channel and at least four closed states. Autocorrelation function analysis showed there to be at least three pathways linking the open states with the closed. This results in a minimal scheme for gating of the glutamate receptor-channel, which is suggestive of allosteric models of receptor-channel gating. PMID:19431683

  9. Classical Conditioning of the Rabbit Eyelid Response Increases Glutamate Receptor Binding in Hippocampal Synaptic Membranes

    NASA Astrophysics Data System (ADS)

    Mamounas, Laura A.; Thompson, Richard F.; Lynch, Gary; Baudry, Michel

    1984-04-01

    Hippocampal pyramidal neurons exhibit a rapid within-trial increase in firing frequency during classical conditioning of the rabbit eyelid response. It has been proposed that the cellular mechanisms responsible for hippocampal long-term potentiation (LTP) may also mediate this learning-dependent increase in neuronal activity. The induction of LTP in rat hippocampal slices results in an increase in the number of [3H]glutamate-binding sites in the potentiated region. The present study investigates the kinetics of [3H]glutamate binding to hippocampal synaptic membranes after eyelid conditioning in the rabbit. We report that the regional distribution of [3H]glutamate binding across the layers of rabbit hippocampus is compatible with a dendritic localization. The pharmacological and ionic properties of the binding suggest that it is associated with an excitatory amino acid receptor. After eyelid conditioning, the maximal number of hippocampal [3H]glutamate-binding sites is increased in animals receiving paired presentations of the tone conditioned stimulus and corneal air-puff unconditioned stimulus relative to that found in naive or unpaired control animals. These results strengthen the hypothesis that an LTP-like mechanism underlies the increase in hippocampal firing frequency during rabbit eyelid conditioning.

  10. GLT-1: The elusive presynaptic glutamate transporter.

    PubMed

    Rimmele, Theresa S; Rosenberg, Paul A

    2016-09-01

    Historically, glutamate uptake in the CNS was mainly attributed to glial cells for three reasons: 1) none of the glutamate transporters were found to be located in presynaptic terminals of excitatory synapses; 2) the putative glial transporters, GLT-1 and GLAST are expressed at high levels in astrocytes; 3) studies of the constitutive GLT-1 knockout as well as pharmacological studies demonstrated that >90% of glutamate uptake into forebrain synaptosomes is mediated by the operation of GLT-1. Here we summarize the history leading up to the recognition of GLT-1a as a presynaptic glutamate transporter. A major issue now is understanding the physiological and pathophysiological significance of the expression of GLT-1 in presynaptic terminals. To elucidate the cell-type specific functions of GLT-1, a conditional knockout was generated with which to inactivate the GLT-1 gene in different cell types using Cre/lox technology. Astrocytic knockout led to an 80% reduction of GLT-1 expression, resulting in intractable seizures and early mortality as seen also in the constitutive knockout. Neuronal knockout was associated with no obvious phenotype. Surprisingly, synaptosomal uptake capacity (Vmax) was found to be significantly reduced, by 40%, in the neuronal knockout, indicating that the contribution of neuronal GLT-1 to synaptosomal uptake is disproportionate to its protein expression (5-10%). Conversely, the contribution of astrocytic GLT-1 to synaptosomal uptake was much lower than expected. In contrast, the loss of uptake into liposomes prepared from brain protein from astrocyte and neuronal knockouts was proportionate with the loss of GLT-1 protein, suggesting that a large portion of GLT-1 in astrocytic membranes in synaptosomal preparations is not functional, possibly because of a failure to reseal. These results suggest the need to reinterpret many previous studies using synaptosomal uptake to investigate glutamate transport itself as well as changes in glutamate

  11. The safety evaluation of monosodium glutamate.

    PubMed

    Walker, R; Lupien, J R

    2000-04-01

    L-Glutamic acid and its ammonium, calcium, monosodium and potassium salts were evaluated by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) in 1988. The Committee noted that intestinal and hepatic metabolism results in elevation of levels in systemic circulation only after extremely high doses given by gavage (>30mg/kg body weight). Ingestion of monosodium glutamate