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Sample records for afferent nerve terminals

  1. Pharmacology of airway afferent nerve activity

    PubMed Central

    Undem, Bradley J; Carr, Michael J

    2001-01-01

    Afferent nerves in the airways serve to regulate breathing pattern, cough, and airway autonomic neural tone. Pharmacologic agents that influence afferent nerve activity can be subclassified into compounds that modulate activity by indirect means (e.g. bronchial smooth muscle spasmogens) and those that act directly on the nerves. Directly acting agents affect afferent nerve activity by interacting with various ion channels and receptors within the membrane of the afferent terminals. Whether by direct or indirect means, most compounds that enter the airspace will modify afferent nerve activity, and through this action alter airway physiology. PMID:11686889

  2. Disappearance of afferent and efferent nerve terminals in the inner ear of the chick embryo after chronic treatment with beta-bungarotoxin

    PubMed Central

    1977-01-01

    Beta-Bungarotoxin(beta-BT) was applied to chick embryos at 3-day intervals beginning on the 4th day of incubation to see the effect of chronically and massively applied beta-BT, and to investigate the hair cell-nerve relationship in the developing inner ear by electron microscopy. On the 10th day of incubation, nerve terminals had achieved contact with differentiating hair cells, but the acoustico-vestibular ganglion cells of treated animals were decreased in number to one-third of those of the control. By the 14th day, most of the ganglion cells degenerated and disappeared, and only a few nerve terminals were seen in the neuroepithelium. At this time, most of the hair cells lacked synaptic contacts with nerve terminals; but their presynaptic specialization remained intact and they showed evidence of continuing differentiation. On the 17th day, the acoustico-vestibular ganglion cells were completely absent. All the hair cells were devoid of afferent and efferent innervation but were fully differentiated on the 21st day. Beta-BT was found to have a similar destructive effect on cultured spinal ganglion cells. The present study shows that beta-BT kills acoustico-vestibular and spinal nerve cells when applied chronically and massively during development. Furthermore, the differentiation of hair cells proceeds normally, and their presynaptic specializations are maintained when nerve terminals are absent during later developmental stages. PMID:856835

  3. Persistence of PAD and presynaptic inhibition of muscle spindle afferents after peripheral nerve crush.

    PubMed

    Enríquez-Denton, M; Manjarrez, E; Rudomin, P

    2004-11-19

    Two to twelve weeks after crushing a muscle nerve, still before the damaged afferents reinnervate the muscle receptors, conditioning stimulation of group I fibers from flexor muscles depolarizes the damaged afferents [M. Enriquez, I. Jimenez, P. Rudomin, Changes in PAD patterns of group I muscle afferents after a peripheral nerve crush. Exp. Brain Res., 107 (1996), 405-420]. It is not known, however, if this primary afferent depolarization (PAD) is indeed related to presynaptic inhibition. We now show in the cat that 2-12 weeks after crushing the medial gastrocnemius nerve (MG), conditioning stimulation of group I fibers from flexors increases the excitability of the intraspinal terminals of both the intact lateral gastrocnemius plus soleus (LGS) and of the previously damaged MG fibers ending in the motor pool, because of PAD. The PAD is associated with the depression of the pre- and postsynaptic components of the extracellular field potentials (EFPs) evoked in the motor pool by stimulation of either the intact LGS or of the previously damaged MG nerves. These observations indicate, in contrast to what has been reported for crushed cutaneous afferents [K.W. Horch, J.W. Lisney, Changes in primary afferent depolarization of sensory neurones during peripheral nerve regeneration in the cat, J. Physiol., 313 (1981), 287-299], that shortly after damaging their peripheral axons, the synaptic efficacy of group I spindle afferents remains under central control. Presynaptic inhibitory mechanisms could be utilized to adjust the central actions of muscle afferents not fully recovered from peripheral lesions.

  4. Peripheral innervation patterns of vestibular nerve afferents in the bullfrog utriculus

    NASA Technical Reports Server (NTRS)

    Baird, Richard A.; Schuff, N. R.

    1994-01-01

    Vestibular nerve afferents innervating the bullfrog utriculus differ in their response dynamics and sensitivity to natural stimulation. They also supply hair cells that differ markedly in hair bundle morphology. To examine the peripheral innervation patterns of individual utricular afferents more closely, afferent fibers were labeled by the extracellular injection of horseradish peroxidase (HRP) into the vestibular nerve after sectioning the vestibular nerve medial to Scarpa's ganglion to allow the degeneration of sympathetic and efferent fibers. The peripheral arborizations of individual afferents were then correlated with the diameters of their parent axons, the regions of the macula they innervate, and the number and type of hair cells they supply. The utriculus is divided by the striola, a narrow zone of distinctive morphology, into media and lateral parts. Utiricular afferents were classified as striolar or extrastriolar according to the epithelial entrance of their parent axons and the location of their terminal fields. In general, striolar afferents had thicker parent axons, fewer subepithelial bifurcations, larger terminal fields, and more synaptic endings than afferents in extrstriolar regions. Afferents in a juxtastriolar zone, immediately adjacent to the medial striola, had innervation patterns transitional between those in the striola and more peripheral parts of the medial extrastriola. moast afferents innervated only a single macular zone. The terminal fields of striolar afferents, with the notable exception of a few afferents with thin parent axons, were generally confined to one side of the striola. Hair cells in the bullfrog utriculus have perviously been classified into four types based on hair bundle morphology. Afferents in the extrastriolar and juxtastriolar zones largely or exclusively innervated Type B hair cells, the predominant hair cell type in the utricular macula. Striolar afferents supplied a mixture of four hair cell types, but largely

  5. Central distribution of nociceptive intradental afferent nerve fibers in the rat.

    PubMed

    Bombardi, C; Chiocchetti, R; Brunetti, O; Grandis, A; Lucchi, M L; Bortolami, R

    2006-08-01

    The central distribution of intradental afferent nerve fibers was investigated by combining electron microscopic observations with a selective method for inducing degeneration of the A delta- and C-type afferent fibers. Degenerating terminals were found on the proprioceptive mesencephalic trigeminal neurons and on dendrites in the neuropil of the trigeminal motor nucleus after application of capsaicin to the rat's lower incisor tooth pulp. The results give anatomical evidence of new sites of central projection of intradental A delta- and C-type fibers whereby the nociceptive information from the tooth pulp can affect jaw muscle activity.

  6. Influences of neck afferents on sympathetic and respiratory nerve activity.

    PubMed

    Bolton, P S; Kerman, I A; Woodring, S F; Yates, B J

    1998-11-15

    It is well established that the vestibular system influences the sympathetic nervous system and the respiratory system; presumably, vestibulosympathetic and vestibulorespiratory responses participate in maintaining stable blood pressure and blood oxygenation during movement and changes in posture. Many brainstem neurons that generate vestibulospinal reflexes integrate signals from the labyrinth and neck muscles to distinguish between head movements on a stable body and whole body movements. In the present study, responses were recorded from the splanchnic (sympathetic), hypoglossal (inspiratory) and abdominal (expiratory) nerves during stimulation of the C2 dorsal root ganglion or C2 or C3 nerve branches innervating dorsal neck muscles. Stimulation of neck afferents using low current intensities, in many cases less than twice the threshold for producing an afferent volley recordable from the cord dorsum, elicited changes in sympathetic and respiratory nerve activity. These data suggest that head rotation on a stable body would elicit both cervical and vestibular inputs to respiratory motoneurons and sympathetic preganglionic neurons. The effects of cervical afferent stimulation on abdominal, splanchnic and hypoglossal nerve activity were not abolished by transection of the brainstem caudal to the vestibular nuclei; thus, pathways in addition to those involving the vestibular nuclei are involved in relaying cervical inputs to sympathetic preganglionic neurons and respiratory motoneurons. Transection of the C1-3 dorsal roots enhanced responses of the splanchnic and abdominal nerves to pitch head rotations on a fixed body but diminished responses of the hypoglossal nerve. Thus, neck and vestibular afferent influences on activity of respiratory pump muscles and sympathetic outflow appear to be antagonistic, so that responses will occur during whole body movements but not head movements on a stationary trunk. In contrast, neck and vestibular influences on tongue

  7. Mechano- and thermosensitivity of regenerating cutaneous afferent nerve fibers.

    PubMed

    Jänig, Wilfrid; Grossmann, Lydia; Gorodetskaya, Natalia

    2009-06-01

    Crush lesion of a skin nerve is followed by sprouting of myelinated (A) and unmyelinated (C) afferent fibers into the distal nerve stump. Here, we investigate quantitatively both ongoing activity and activity evoked by mechanical or thermal stimulation of the nerve in 43 A- and 135 C-fibers after crush lesion of the sural nerve using neurophysiological recordings in anesthetized rats. The discharge patterns in the injured afferent nerve fibers and in intact (control) afferent nerve fibers were compared. (1) Almost all (98%) A-fibers were mechanosensitive, some of them exhibited additionally weak cold/heat sensitivity; 7% had ongoing activity. (2) Three patterns of physiologically evoked activity were present in the lesioned C-fibers: (a) C-fibers with type 1 cold sensitivity (low cold threshold, inhibition on heating, high level of ongoing and cold-evoked activity; 23%): almost all of them were mechanoinsensitive and 40% of them were additionally heat-sensitive; (b) C-fibers with type 2 cold sensitivity (high cold threshold, low level of ongoing and cold-evoked activity; 23%). All of them were excited by mechanical and/or heat stimuli; (c) cold-insensitive C-fibers (54%), which were heat- and/or mechanosensitive. (3) The proportions of C-fibers exhibiting these three patterns of discharge to physiological stimuli were almost identical in the population of injured C-fibers and in a population of 91 intact cutaneous C-fibers. 4. Ongoing activity was present in 56% of the lesioned C-fibers. Incidence and rate of ongoing activity were the same in the populations of lesioned and intact type 1 cold-sensitive C-fibers. The incidence (but not rate) of ongoing activity was significantly higher in lesioned type 2 cold-sensitive and cold insensitive C-fibers than in the corresponding populations of intact C-fibers (42/93 fibers vs. 11/72 fibers).

  8. Vagal afferent activation decreases brown adipose tissue (BAT) sympathetic nerve activity and BAT thermogenesis

    PubMed Central

    Madden, Christopher J.; Santos da Conceicao, Ellen Paula; Morrison, Shaun F.

    2017-01-01

    ABSTRACT In urethane/α-chloralose anesthetized rats, electrical stimulation of cervical vagal afferent fibers inhibited the increases in brown adipose tissue sympathetic nerve activity and brown adipose tissue thermogenesis evoked by cold exposure, by nanoinjection of the GABAA receptor antagonist, bicuculline, in the dorsomedial hypothalamus, and by nanoinjection of N-methyl-D-aspartate in the rostral raphe pallidus. Vagus nerve stimulation-evoked inhibition of brown adipose tissue sympathetic nerve activity was prevented by blockade of ionotropic glutamate receptors in the termination site of vagal afferents in the nucleus of the solitary tract, and by nanoinjection of GABAA receptor antagonists in the rostral raphe pallidus. In conclusion, the brown adipose tissue sympathoinhibitory effect of cervical afferent vagal nerve stimulation is mediated by glutamatergic activation of second-order sensory neurons in the nucleus of the solitary tract and by a GABAergic inhibition of brown adipose tissue sympathetic premotor neurons in the rostral raphe pallidus, but does not require GABAergic inhibition of the brown adipose tissue sympathoexcitatory neurons in the dorsomedial hypothalamus. PMID:28349097

  9. Projection of forelimb nerve afferents to external cuneate nucleus of the rat as revealed by intraneural injection of a neurotoxic lectin, Ricinus communis agglutinin.

    PubMed

    Cha, S W; Tan, C K

    1996-01-01

    This study seeks to extend the observations of previous studies of projection of primary afferent fibres from the forelimb nerves and muscles to the external cuneate nucleus (ECN) of mammals using a neurotoxic lectin, Ricinus communis agglutinin (RCA) to achieve chemical ganglionectomy of the dorsal root ganglia. Following intraneural injection of RCA into the three main forelimb nerves, namely the radial, ulnar and median nerves, terminal degeneration of the primary afferent fibres in the ECN was studied under the light microscope by means of the Fink-Heimer method. The results show that the primary afferent fibres from these three nerves project to the medial part of the ECN. The field of terminal degeneration take a crescentic form. The projection from the median nerve was most dorsally located whereas that from the radial nerve was the most ventral with extensive overlaps between them. Of the three nerves, the projection from the radial nerve was the most dense. Rostrocaudally, the three nerves also show extensive overlaps. The rostrocaudal extent of maximum terminal degeneration was greatest for the radial nerve and least for the median nerve. Analysis of variance showed that these differences were statistically significant. This suggests that the radial nerve has the most extensive projection to the ECN and the median nerve the least.

  10. Differential presynaptic control of the synaptic effectiveness of cutaneous afferents evidenced by effects produced by acute nerve section

    PubMed Central

    Rudomin, P; Jiménez, I; Chávez, D

    2013-01-01

    In the anaesthetized cat, the acute section of the saphenous (Saph) and/or the superficial peroneal (SP) nerves was found to produce a long-lasting increase of the field potentials generated in the dorsal horn by stimulation of the medial branch of the sural (mSU) nerve. This facilitation was associated with changes in the level of the tonic primary afferent depolarization (PAD) of the mSU intraspinal terminals. The mSU afferent fibres projecting into Rexed's laminae III–IV were subjected to a tonic PAD that was reduced by the acute section of the SP and/or the Saph nerves. The mSU afferents projecting deeper into the dorsal horn (Rexed's laminae V–VI) were instead subjected to a tonic PAD that was increased after Saph and SP acute nerve section. A differential control of the synaptic effectiveness of the low-threshold cutaneous afferents according to their sites of termination within the dorsal horn is envisaged as a mechanism that allows selective processing of sensory information in response to tactile and nociceptive stimulation or during the execution of different motor tasks. PMID:23478136

  11. Differential presynaptic control of the synaptic effectiveness of cutaneous afferents evidenced by effects produced by acute nerve section.

    PubMed

    Rudomin, P; Jiménez, I; Chávez, D

    2013-05-15

    In the anaesthetized cat, the acute section of the saphenous (Saph) and/or the superficial peroneal (SP) nerves was found to produce a long-lasting increase of the field potentials generated in the dorsal horn by stimulation of the medial branch of the sural (mSU) nerve. This facilitation was associated with changes in the level of the tonic primary afferent depolarization (PAD) of the mSU intraspinal terminals. The mSU afferent fibres projecting into Rexed's laminae III-IV were subjected to a tonic PAD that was reduced by the acute section of the SP and/or the Saph nerves. The mSU afferents projecting deeper into the dorsal horn (Rexed's laminae V-VI) were instead subjected to a tonic PAD that was increased after Saph and SP acute nerve section. A differential control of the synaptic effectiveness of the low-threshold cutaneous afferents according to their sites of termination within the dorsal horn is envisaged as a mechanism that allows selective processing of sensory information in response to tactile and nociceptive stimulation or during the execution of different motor tasks.

  12. Targeting primary afferent nerves for novel antitussive therapy.

    PubMed

    Undem, Bradley J; Carr, Michael J

    2010-01-01

    The best available data support the hypothesis that there are at least two types of vagal nerves responsible for initiating coughing reflexes. One type of nerve conducts action potentials in the A-range and is characterized by rapidly adapting responses to mechanical probing or acidification of the large airway epithelium. Stimulation of these nerves can evoke cough in unconscious experimental animals and humans. These nerves are important in immediate cough evoked by aspiration and as such perform a critical role in airway defense. The other type of primary afferent nerve involved in cough is the vagal C-fiber. Inhalation of selective C-fiber stimulants leads to cough only in conscious animals. In clinical studies, inhalation of a low concentration of a C-fiber stimulant causes an irritating, itchy urge-to-cough sensation that mimics the urge-to-cough sensations associated with respiratory tract infection, post-infection, gastroesophageal reflux disorders, and inflammatory airway diseases. Here we discuss the recent advances in sensory neurobiology that allow for the targeting of vagal C-fibers for novel antitussive therapy. No attempts are made to be all-inclusive with respect to the numerous possible molecular targets being considered to accomplish this goal. Rather, two general strategies are discussed: decreasing generator potential amplitude and decreasing the efficiency by which a generator potential evokes action-potential discharge. For the first category we focus on two targets, transient receptor potential vanilloid 1 and transient receptor potential A1. For the latter category we focus on recent advances in voltage-gated sodium (Na(V)) channel biology.

  13. Ectopic activity in cutaneous regenerating afferent nerve fibers following nerve lesion in the rat.

    PubMed

    Gorodetskaya, Natalia; Constantin, Cristina; Jänig, Wilfrid

    2003-11-01

    Spontaneous activity, and mechanical and thermal sensitivity were investigated in regenerating afferent nerve fibers within 4-21 days post sural nerve lesion (crush or transection and resuturing) in anaesthetized rats. About 33-40% of the myelinated (A) and 22-27% of the unmyelinated (C) fibers excited by electrical nerve stimulation exhibited at least one of these ectopic discharge properties. In total 177 A- and 169 C-fibers with ectopic activity were analysed. Most A-fibers (161/177) were mechanosensitive. Spontaneous activity (median 1 imp/s) was present in 23/177 and thermosensitivity in 14/177 A-fibers (13 of them being activated by heat stimuli). Almost all A-fibers (159/177) exhibited only one type of ectopic discharge property. Most C-fibers (94/169) were thermosensitive responding either to cold (n = 45) or to heat stimuli (n = 33) or to both (n = 16). Eighty-four of 169 C-fibers were spontaneously active (median 0.3 imp/s) and 75/169 C-fibers were mechanosensitive. Both the proportion and the discharge rate of spontaneously active C-fibers were significantly higher after crush than after section and resuturing of the nerve. About 60% of the C-fibers (101/169) had only one ectopic discharge property and 40% two or three. In conclusion, regenerating cutaneous afferent A- and C-fibers may develop mechano- and/or thermosensitivity as well as spontaneous activity. We suggest that spontaneous and evoked ectopic activity in regenerating cutaneous afferents are a function of the intrinsic functional properties of these neurons and of the interaction between the regenerating nerve fibers and non-neural cells during Wallerian degeneration in the nerve distal to the nerve lesion.

  14. A novel method of selective ablation of afferent renal nerves by periaxonal application of capsaicin.

    PubMed

    Foss, Jason D; Wainford, Richard D; Engeland, William C; Fink, Gregory D; Osborn, John W

    2015-01-15

    Renal denervation has been shown to lower arterial pressure in some hypertensive patients, yet it remains unclear whether this is due to ablation of afferent or efferent renal nerves. To investigate the role of afferent renal nerves in arterial pressure regulation, previous studies have used methods that disrupt both renal and nonrenal afferent signaling. The present study was conducted to develop and validate a technique for selective ablation of afferent renal nerves that does not disrupt other afferent pathways. To do this, we adapted a technique for sensory denervation of the adrenal gland by topical application of capsaicin and tested the hypothesis that exposure of the renal nerves to capsaicin (renal-CAP) causes ablation of afferent but not efferent renal nerves. Renal-CAP had no effect on renal content of the efferent nerve markers tyrosine hydroxylase and norepinephrine; however, the afferent nerve marker, calcitonin gene-related peptide was largely depleted from the kidney 10 days after intervention, but returned to roughly half of control levels by 7 wk postintervention. Moreover, renal-CAP abolished the cardiovascular responses to acute pharmacological stimulation of afferent renal nerves. Renal-CAP rats showed normal weight gain, as well as cardiovascular and fluid balance regulation during dietary sodium loading. To some extent, renal-CAP did blunt the bradycardic response and increase the dipsogenic response to increased salt intake. Lastly, renal-CAP significantly attenuated the development of deoxycorticosterone acetate-salt hypertension. These results demonstrate that renal-CAP effectively causes selective ablation of afferent renal nerves in rats.

  15. The role of the renal afferent and efferent nerve fibers in heart failure

    PubMed Central

    Booth, Lindsea C.; May, Clive N.; Yao, Song T.

    2015-01-01

    Renal nerves contain afferent, sensory and efferent, sympathetic nerve fibers. In heart failure (HF) there is an increase in renal sympathetic nerve activity (RSNA), which can lead to renal vasoconstriction, increased renin release and sodium retention. These changes are thought to contribute to renal dysfunction, which is predictive of poor outcome in patients with HF. In contrast, the role of the renal afferent nerves remains largely unexplored in HF. This is somewhat surprising as there are multiple triggers in HF that have the potential to increase afferent nerve activity, including increased venous pressure and reduced kidney perfusion. Some of the few studies investigating renal afferents in HF have suggested that at least the sympatho-inhibitory reno-renal reflex is blunted. In experimentally induced HF, renal denervation, both surgical and catheter-based, has been associated with some improvements in renal and cardiac function. It remains unknown whether the effects are due to removal of the efferent renal nerve fibers or afferent renal nerve fibers, or a combination of both. Here, we review the effects of HF on renal efferent and afferent nerve function and critically assess the latest evidence supporting renal denervation as a potential treatment in HF. PMID:26483699

  16. The role of the renal afferent and efferent nerve fibers in heart failure.

    PubMed

    Booth, Lindsea C; May, Clive N; Yao, Song T

    2015-01-01

    Renal nerves contain afferent, sensory and efferent, sympathetic nerve fibers. In heart failure (HF) there is an increase in renal sympathetic nerve activity (RSNA), which can lead to renal vasoconstriction, increased renin release and sodium retention. These changes are thought to contribute to renal dysfunction, which is predictive of poor outcome in patients with HF. In contrast, the role of the renal afferent nerves remains largely unexplored in HF. This is somewhat surprising as there are multiple triggers in HF that have the potential to increase afferent nerve activity, including increased venous pressure and reduced kidney perfusion. Some of the few studies investigating renal afferents in HF have suggested that at least the sympatho-inhibitory reno-renal reflex is blunted. In experimentally induced HF, renal denervation, both surgical and catheter-based, has been associated with some improvements in renal and cardiac function. It remains unknown whether the effects are due to removal of the efferent renal nerve fibers or afferent renal nerve fibers, or a combination of both. Here, we review the effects of HF on renal efferent and afferent nerve function and critically assess the latest evidence supporting renal denervation as a potential treatment in HF.

  17. Sensitizing effects of lafutidine on CGRP-containing afferent nerves in the rat stomach

    PubMed Central

    Nishihara, Katsushi; Nozawa, Yoshihisa; Nakano, Motoko; Ajioka, Hirofusa; Matsuura, Naosuke

    2002-01-01

    Capsaicin sensitive afferent nerves play an important role in gastric mucosal defensive mechanisms. Capsaicin stimulates afferent nerves and enhances the release of calcitonin gene-related peptide (CGRP), which seems to be the predominant neurotransmitter of spinal afferents in the rat stomach, exerting many pharmacological effects by a direct mechanism or indirectly through second messengers such as nitric oxide (NO). Lafutidine is a new type of anti-ulcer drug, possessing both an antisecretory effect, exerted via histamine H2 receptor blockade, and gastroprotective activities. Studies with certain antagonists or chemical deafferentation techniques suggest the gastroprotective actions of lafutidine to be mediated by capsaicin sensitive afferent nerves, but this is an assumption based on indirect techniques. In order to explain the direct relation of lafutidine to afferent nerves, we conducted the following studies. We determined CGRP and NO release from rat stomach and specific [3H]-resiniferatoxin (RTX) binding to gastric vanilloid receptor subtype 1 (VR1), which binds capsaicin, using EIA, a microdialysis system and a radioreceptor assay, respectively. Lafutidine enhanced both CGRP and NO release from the rat stomach induced by a submaximal dose of capsaicin, but had no effect on specific [3H]-RTX and capsaicin binding to VR1. In conclusion, our findings demonstrate that lafutidine modulates the activity of capsaicin sensitive afferent nerves in the rat stomach, which may be a key mechanism involved in its gastroprotective action. PMID:11906962

  18. Effect of extracellular calcium on excitability of guinea pig airway vagal afferent nerves.

    PubMed

    Undem, Bradley J; Oh, Eun Joo; Lancaster, Eric; Weinreich, Daniel

    2003-03-01

    The effect of reducing extracellular calcium concentration ([Ca(2+)](o)) on vagal afferent excitability was analyzed in a guinea pig isolated vagally innervated trachea-bronchus preparation. Afferent fibers were characterized as either having low-threshold, rapidly adapting mechanosensors (Adelta fibers) or nociceptive-like phenotypes (Adelta and C fibers). The nociceptors were derived from neurons within the jugular ganglia, whereas the low-threshold mechanosensors were derived from neurons within the nodose ganglia. Reducing [Ca(2+)](o) did not affect the excitability of the low-threshold mechanosensors in the airway. By contrast, reducing [Ca(2+)](o) selectively increased the excitability of airway nociceptors as manifested by a substantive increase in action potential discharge in response to mechanical stimulation, and in a subset of fibers, by overtly evoking action potential discharge. This increase in the excitability of nociceptors was not mimicked by a combination of omega-conotoxin and nifedipine or tetraethylammonium. Whole cell patch recordings from airway-labeled and unlabeled neurons in the vagal jugular ganglia support the hypothesis that [Ca(2+)](o) inhibits a nonselective cation conductance in vagal nociceptors that may serve to regulate excitability of the nerve terminals within the airways.

  19. Changes in PAD patterns of group I muscle afferents after a peripheral nerve crush.

    PubMed

    Enríquez, M; Jiménez, I; Rudomin, P

    1996-01-01

    In the anesthetized cat we have analyzed the changes in primary afferent depolarization (PAD) evoked in single muscle spindle and tendon organ afferents at different times after their axons were crushed in the periphery and allowed to regenerate. Medial gastrocnemius (MG) afferents were depolarized by stimulation of group I fibers in the posterior biceps and semitendinosus nerve (PBSt), as soon as 2 weeks after crushing their axons in the periphery, in some cases before they could be activated by physiological stimulation of muscle receptors. Two to twelve weeks after crushing the MG nerve, stimulation of the PBSt produced PAD in all MG fibers reconnected with presumed muscle spindles and tendon organs. The mean amplitude of the PAD elicited in afferent fibers reconnected with muscle spindles was increased relative to values obtained from Ia fibers in intact (control) preparations, but remained essentially the same in fibers reconnected with tendon organs. Quite unexpectedly, we found that, between 2 and 12 weeks after crushing the MG nerve, stimulation of the bulbar reticular formation (RF) produced PAD in most afferent fibers reconnected with muscle spindle afferents. The mean amplitude of the PAD elicited in these fibers was significantly increased relative to the PAD elicited in muscle spindle afferents from intact preparations (from 0.08 +/- 0.4 to 0.47 +/- 0.34 mV). A substantial recovery was observed between 6 months and 2.5 years after the peripheral nerve injury. Stimulation of the sural (SU) nerve produced practically no PAD in muscle spindles from intact preparations, and this remained so in those afferents reconnected with muscle spindles impaled 2-12 weeks after the nerve crush. The mean amplitude of the PAD produced in afferent fibers reconnected with tendon organs by stimulation of the PBSt nerve and of the bulbar RF remained essentially the same as the PAD elicited in intact afferents. However, SU nerve stimulation produced a larger PAD in afferents

  20. Novel Afferent Terminal Structure in the Crista Ampullaris of the Goldfish, Carassius auratus

    NASA Technical Reports Server (NTRS)

    Lanford, Pamela J.; Popper, Arthur N.

    1996-01-01

    Using transmission electron microscopy, we have identified a new type of afferent terminal structure in the crista ampullaris of the goldfish Carassius auratus. In addition to the bouton-type afferent terminals previously described in the ear of this species, the crista also contained enlarged afferent terminals that enveloped a portion of the basolateral hair cell membrane. The hair cell membrane was evaginated and protruded into the afferent terminal in a glove-and-finger configuration. The membranes of the two cells were regularly aligned in the protruded region of the contact and had a distinct symmetrical electron density. The electron-dense profiles of these contacts were easily identified and were present in every crista sampled. In some cases, efferent terminals synapsed onto the afferents at a point where the hair cell protruded into the terminal. The ultrastructural similarities of the goldfish crista afferents to calyx afferents found in amniotes (birds, reptiles, and mammals) are discussed. The results of the study support the hypothesis that structural variation in the vertebrate inner ear may have evolved much earlier in evolution than previously supposed.

  1. NERVE GROWTH FACTOR MAINTAINS POTASSIUM CONDUCTANCE AFTER NERVE INJURY IN ADULT CUTANEOUS AFFERENT DORSAL ROOT GANGLION NEURONS

    PubMed Central

    EVERILL, B.; KOCSIS, J. D.

    2008-01-01

    Whole-cell patch-clamp techniques were used to study the effects of nerve growth factor on voltage-dependent potassium conductance in normal and axotomized identified large cutaneous afferent dorsal root ganglion neurons (48–50 μm diameter) many of which probably give rise to myelinated Aβ fibers. K-currents were isolated by blocking Na- and Ca-currents with appropriate ion replacement and channel blockers. Separation of current components was achieved on the basis of response to variation in conditioning voltage. Cutaneous afferents were labeled by the retrograde marker hydroxy-stilbamide (FluoroGold) which was injected into the skin of the foot. The sciatic nerve was either ligated or crushed with fine forceps five to seven days later. Neurons were dissociated 14–17 days after injury. The cut ends of the sciatic nerves were positioned into polyethylene tubes, which were connected to mini-osmotic pumps filled with either nerve growth factor or sterile saline. Control neurons displayed a prominent sustained K-current and the transient potassium currents “A” and “D”. Nerve ligation, which blocks target reconnection resulted in near 50% reduction of total outward current; isolated sustained K-current and transient A-current were reduced by a comparable amount. Nerve crush, which allows regeneration to peripheral targets and exposure of the regenerating nerve to the distal nerve segment, resulted in a small reduction in sustained K-current but no reduction in transient A-current compared to controls. Levels of transient A-current and sustained K-current were maintained at control levels after nerve growth factor treatment. These results indicate that the large reduction in transient A-current, and in sustained K-current, observed in cutaneous afferent cell bodies after nerve ligation is prevented by application of nerve growth factor. PMID:11008179

  2. Permanent reorganization of Ia afferent synapses on motoneurons after peripheral nerve injuries

    PubMed Central

    Alvarez, Francisco J.; Bullinger, Katie L.; Titus, Haley E.; Nardelli, Paul; Cope, Timothy C.

    2010-01-01

    After peripheral nerve injuries to a motor nerve the axons of motoneurons and proprioceptors are disconnected from the periphery and monosynaptic connections from group I afferents and motoneurons become diminished in the spinal cord. Following successful reinnervation in the periphery, motor strength, proprioceptive sensory encoding, and Ia afferent synaptic transmission on motoneurons partially recover. Muscle stretch reflexes, however, never recover and motor behaviors remain uncoordinated. In this review, we summarize recent findings that suggest that lingering motor dysfunction might be in part related to decreased connectivity of Ia afferents centrally. First, sensory afferent synapses retract from lamina IX causing a permanent relocation of the inputs to more distal locations and significant disconnection from motoneurons. Second, peripheral reconnection between proprioceptive afferents and muscle spindles is imperfect. As a result, a proportion of sensory afferents that retain central connections with motoneurons might not reconnect appropriately in the periphery. A hypothetical model is proposed in which the combined effect of peripheral and central reconnection deficits might explain the failure of muscle stretch to initiate or modulate firing of many homonymous motoneurons. PMID:20536938

  3. Electrophysiology of corneal cold receptor nerve terminals.

    PubMed

    Carr, Richard W; Brock, James A

    2002-01-01

    The mechanisms of sensory transduction in the fine nerve terminals of free nerve endings supplied by Adelta and C sensory axons are largely a matter of speculation. This is because the nerve terminals are small and inaccessible, particularly in intact tissues like skin. However, some of the difficulties associated with investigating the physiology of fine nerve terminals have recently been overcome using an in vitro preparation of the guinea-pig cornea that allows nerve terminal impulses (NTIs) to be recorded extracellularly from single polymodal and cold receptor nerve terminals. For cold receptors, the rate of spontaneously occurring NTIs is increased during cooling and decreased during heating. In addition, heating and cooling differentially modulate the shape of the recorded NTI. At the same temperature, NTIs are larger in amplitude and faster in time course during heating than those during cooling. The differential effect of heating and cooling on NTI shape is not considered to result simply from the temperature dependence of voltage-activated conductance kinetics or activity dependent changes in membrane excitability. Instead, changes in NTI shape may reflect changes in nerve terminal membrane potential that underlie the process of thermal transduction.

  4. The renal nerves in chronic heart failure: efferent and afferent mechanisms.

    PubMed

    Schiller, Alicia M; Pellegrino, Peter R; Zucker, Irving H

    2015-01-01

    The function of the renal nerves has been an area of scientific and medical interest for many years. The recent advent of a minimally invasive catheter-based method of renal denervation has renewed excitement in understanding the afferent and efferent actions of the renal nerves in multiple diseases. While hypertension has been the focus of much this work, less attention has been given to the role of the renal nerves in the development of chronic heart failure (CHF). Recent studies from our laboratory and those of others implicate an essential role for the renal nerves in the development and progression of CHF. Using a rabbit tachycardia model of CHF and surgical unilateral renal denervation, we provide evidence for both renal efferent and afferent mechanisms in the pathogenesis of CHF. Renal denervation prevented the decrease in renal blood flow observed in CHF while also preventing increases in Angiotensin-II receptor protein in the microvasculature of the renal cortex. Renal denervation in CHF also reduced physiological markers of autonomic dysfunction including an improvement in arterial baroreflex function, heart rate variability, and decreased resting cardiac sympathetic tone. Taken together, the renal sympathetic nerves are necessary in the pathogenesis of CHF via both efferent and afferent mechanisms. Additional investigation is warranted to fully understand the role of these nerves and their role as a therapeutic target in CHF.

  5. The renal nerves in chronic heart failure: efferent and afferent mechanisms

    PubMed Central

    Schiller, Alicia M.; Pellegrino, Peter R.; Zucker, Irving H.

    2015-01-01

    The function of the renal nerves has been an area of scientific and medical interest for many years. The recent advent of a minimally invasive catheter-based method of renal denervation has renewed excitement in understanding the afferent and efferent actions of the renal nerves in multiple diseases. While hypertension has been the focus of much this work, less attention has been given to the role of the renal nerves in the development of chronic heart failure (CHF). Recent studies from our laboratory and those of others implicate an essential role for the renal nerves in the development and progression of CHF. Using a rabbit tachycardia model of CHF and surgical unilateral renal denervation, we provide evidence for both renal efferent and afferent mechanisms in the pathogenesis of CHF. Renal denervation prevented the decrease in renal blood flow observed in CHF while also preventing increases in Angiotensin-II receptor protein in the microvasculature of the renal cortex. Renal denervation in CHF also reduced physiological markers of autonomic dysfunction including an improvement in arterial baroreflex function, heart rate variability, and decreased resting cardiac sympathetic tone. Taken together, the renal sympathetic nerves are necessary in the pathogenesis of CHF via both efferent and afferent mechanisms. Additional investigation is warranted to fully understand the role of these nerves and their role as a therapeutic target in CHF. PMID:26300788

  6. Frequency dependent changes in mechanosensitivity of rat knee joint afferents after antidromic saphenous nerve stimulation.

    PubMed

    Just, S; Heppelmann, B

    2002-01-01

    The aim of the present study was to examine the effect of electrical saphenous nerve stimulation (14 V, 1-10 Hz) on the mechanosensitivity of rat knee joint afferents. The responses to passive joint rotations at defined torque were recorded from slowly conducting knee joint afferent nerve fibres (0.6-20.0 m/s). After repeated nerve stimulation with 1 Hz, the mechanosensitivity of about 79% of the units was significantly affected. The effects were most prominent at a torque close to the mechanical threshold. In about 46% of the examined nerve fibres a significant increase was obtained, whereas about 33% reduced their mechanosensitivity. The sensitisation was prevented by an application of 5 microM phentolamine, an alpha-adrenergic receptor blocker, together with a neuropeptide Y receptor blocker. An inhibition of N-type Ca(2+) channels by an application of 1 microM omega-conotoxin GVIA caused comparable changes of the mechanosensitivity during the electrical stimulation. Electrical nerve stimulation with higher frequencies resulted in a further reduction of the mean response to joint rotations. After stimulation with 10 Hz, there was a nearly complete loss of mechanosensitivity.In conclusion, antidromic electrical nerve stimulation leads to a frequency dependent transient decrease of the mechanosensitivity. A sensitisation was only obtained at 1 Hz, but this effect may be based on the influence of sympathetic nerve fibres.

  7. Direct and Indirect Regulation of Spinal Cord Ia Afferent Terminal Formation by the γ-Protocadherins.

    PubMed

    Prasad, Tuhina; Weiner, Joshua A

    2011-01-01

    The Pcdh-γ gene cluster encodes 22 protocadherin adhesion molecules that interact as homophilic multimers and critically regulate synaptogenesis and apoptosis of interneurons in the developing spinal cord. Unlike interneurons, the two primary components of the monosynaptic stretch reflex circuit, dorsal root ganglion sensory neurons and ventral motor neurons (MNs), do not undergo excessive apoptosis in Pcdh-γ(del/del) null mutants, which die shortly after birth. However, as we show here, mutants exhibit severely disorganized Ia proprioceptive afferent terminals in the ventral horn. In contrast to the fine net-like pattern observed in wild-type mice, central Ia terminals in Pcdh-γ mutants appear clumped, and fill the space between individual MNs; quantitative analysis shows a ~2.5-fold increase in the area of terminals. Concomitant with this, there is a 70% loss of the collaterals that Ia afferents extend to ventral interneurons (vINs), many of which undergo apoptosis in the mutants. The Ia afferent phenotype is ameliorated, though not entirely rescued, when apoptosis is blocked in Pcdh-γ null mice by introduction of a Bax null allele. This indicates that loss of vINs, which act as collateral Ia afferent targets, contributes to the disorganization of terminals on motor pools. Restricted mutation of the Pcdh-γ cluster using conditional mutants and multiple Cre transgenic lines (Wnt1-Cre for sensory neurons; Pax2-Cre for vINs; Hb9-Cre for MNs) also revealed a direct requirement for the γ-Pcdhs in Ia neurons and vINs, but not in MNs themselves. Together, these genetic manipulations indicate that the γ-Pcdhs are required for the formation of the Ia afferent circuit in two ways: First, they control the survival of vINs that act as collateral Ia targets; and second, they provide a homophilic molecular cue between Ia afferents and target vINs.

  8. Transganglionic transport of choleragenoid by capsaicin-sensitive C-fibre afferents to the substantia gelatinosa of the spinal dorsal horn after peripheral nerve section.

    PubMed

    Sántha, P; Jancsó, G

    2003-01-01

    Choleratoxin B subunit-binding thick myelinated, A-fibre and unmyelinated, capsaicin-sensitive nociceptive C-fibre primary afferent fibres terminate in a strict topographic and somatotopic manner in the spinal cord dorsal horn. Injection of choleratoxin B subunit-horseradish peroxidase conjugate into injured but not intact peripheral nerves produced transganglionic labelling of primary afferents not only in the deeper layers (Rexed's laminae III-IV), but also in the substantia gelatinosa (Rexed's laminae II) of the spinal dorsal horn. This was interpreted in terms of a sprouting response of the Abeta-myelinated afferents and suggested a contribution to the pathogenesis of neuropathic pain [Nature 355 (1992) 75; J Comp Neurol 360 (1995) 121]. By utilising the selective neurotoxic effect of capsaicin, we examined the role of C-fibre sensory ganglion neurons in the mechanism of this phenomenon. Elimination of these particular, capsaicin-sensitive C-fibre afferents by prior intrathecal or systemic capsaicin treatment inhibited transganglionic labelling by the choleratoxin B subunit-horseradish peroxidase conjugate of the substantia gelatinosa evoked by chronic sciatic nerve section. More importantly, prior perineural capsaicin treatment of the transected nerve proximal to the anticipated site of injection of choleragenoid 12 hours later prevented the labelling of the substantia gelatinosa, but not that of the deeper layers. Electron microscopic examination of the dorsal roots revealed no significant difference in the proportion of labelled myelinated fibres relating to the intact (54.4+/-5.5%) and the transected (62.4+/-5.4%) sciatic nerves. In contrast, the proportion of labelled unmyelinated dorsal root axons relating to the transected, but not the intact nerves showed a significant, six-fold increase after sciatic nerve transection (intact: 4.9+/-1.3%; transected: 35+/-6.7%). These observations indicate that peripheral nerve lesion-induced transganglionic labelling

  9. Social stress in mice induces urinary bladder overactivity and increases TRPV1 channel-dependent afferent nerve activity.

    PubMed

    Mingin, Gerald C; Heppner, Thomas J; Tykocki, Nathan R; Erickson, Cuixia Shi; Vizzard, Margaret A; Nelson, Mark T

    2015-09-15

    Social stress has been implicated as a cause of urinary bladder hypertrophy and dysfunction in humans. Using a murine model of social stress, we and others have shown that social stress leads to bladder overactivity. Here, we show that social stress leads to bladder overactivity, increased bladder compliance, and increased afferent nerve activity. In the social stress paradigm, 6-wk-old male C57BL/6 mice were exposed for a total of 2 wk, via barrier cage, to a C57BL/6 retired breeder aggressor mouse. We performed conscious cystometry with and without intravesical infusion of the TRPV1 inhibitor capsazepine, and measured pressure-volume relationships and afferent nerve activity during bladder filling using an ex vivo bladder model. Stress leads to a decrease in intermicturition interval and void volume in vivo, which was restored by capsazepine. Ex vivo studies demonstrated that at low pressures, bladder compliance and afferent activity were elevated in stressed bladders compared with unstressed bladders. Capsazepine did not significantly change afferent activity in unstressed mice, but significantly decreased afferent activity at all pressures in stressed bladders. Immunohistochemistry revealed that TRPV1 colocalizes with CGRP to stain nerve fibers in unstressed bladders. Colocalization significantly increased along the same nerve fibers in the stressed bladders. Our results support the concept that social stress induces TRPV1-dependent afferent nerve activity, ultimately leading to the development of overactive bladder symptoms.

  10. Social stress in mice induces urinary bladder overactivity and increases TRPV1 channel-dependent afferent nerve activity

    PubMed Central

    Heppner, Thomas J.; Tykocki, Nathan R.; Erickson, Cuixia Shi; Vizzard, Margaret A.; Nelson, Mark T.

    2015-01-01

    Social stress has been implicated as a cause of urinary bladder hypertrophy and dysfunction in humans. Using a murine model of social stress, we and others have shown that social stress leads to bladder overactivity. Here, we show that social stress leads to bladder overactivity, increased bladder compliance, and increased afferent nerve activity. In the social stress paradigm, 6-wk-old male C57BL/6 mice were exposed for a total of 2 wk, via barrier cage, to a C57BL/6 retired breeder aggressor mouse. We performed conscious cystometry with and without intravesical infusion of the TRPV1 inhibitor capsazepine, and measured pressure-volume relationships and afferent nerve activity during bladder filling using an ex vivo bladder model. Stress leads to a decrease in intermicturition interval and void volume in vivo, which was restored by capsazepine. Ex vivo studies demonstrated that at low pressures, bladder compliance and afferent activity were elevated in stressed bladders compared with unstressed bladders. Capsazepine did not significantly change afferent activity in unstressed mice, but significantly decreased afferent activity at all pressures in stressed bladders. Immunohistochemistry revealed that TRPV1 colocalizes with CGRP to stain nerve fibers in unstressed bladders. Colocalization significantly increased along the same nerve fibers in the stressed bladders. Our results support the concept that social stress induces TRPV1-dependent afferent nerve activity, ultimately leading to the development of overactive bladder symptoms. PMID:26224686

  11. Intestinal Epithelial Stem/Progenitor Cells Are Controlled by Mucosal Afferent Nerves

    PubMed Central

    Lundgren, Ove; Jodal, Mats; Jansson, Madeleine; Ryberg, Anders T.; Svensson, Lennart

    2011-01-01

    Background The maintenance of the intestinal epithelium is of great importance for the survival of the organism. A possible nervous control of epithelial cell renewal was studied in rats and mice. Methods Mucosal afferent nerves were stimulated by exposing the intestinal mucosa to capsaicin (1.6 mM), which stimulates intestinal external axons. Epithelial cell renewal was investigated in the jejunum by measuring intestinal thymidine kinase (TK) activity, intestinal 3H-thymidine incorporation into DNA, and the number of crypt cells labeled with BrdU. The influence of the external gut innervation was minimized by severing the periarterial nerves. Principal Findings Luminal capsaicin increased all the studied variables, an effect nervously mediated to judge from inhibitory effects on TK activity or 3H-thymidine incorporation into DNA by exposing the mucosa to lidocaine (a local anesthetic) or by giving four different neurotransmitter receptor antagonists i.v. (muscarinic, nicotinic, neurokinin1 (NK1) or calcitonin gene related peptide (CGRP) receptors). After degeneration of the intestinal external nerves capsaicin did not increase TK activity, suggesting the involvement of an axon reflex. Intra-arterial infusion of Substance P (SP) or CGRP increased intestinal TK activity, a response abolished by muscarinic receptor blockade. Immunohistochemistry suggested presence of M3 and M5 muscarinic receptors on the intestinal stem/progenitor cells. We propose that the stem/progenitor cells are controlled by cholinergic nerves, which, in turn, are influenced by mucosal afferent neuron(s) releasing acetylcholine and/or SP and/or CGRP. In mice lacking the capsaicin receptor, thymidine incorporation into DNA and number of crypt cells labeled with BrdU was lower than in wild type animals suggesting that nerves are important also in the absence of luminal capsaicin, a conclusion also supported by the observation that atropine lowered thymidine incorporation into DNA by 60% in control

  12. Autoregulation of Neuromuscular Transmission by Nerve Terminals.

    DTIC Science & Technology

    1985-09-01

    release ACh synthesis by motor nerve terminals requires an adequate supply of its precusor, choline. We have found that diisopropyl1fluorophosphate (DFP...inhibits choline efflux from the isolated hemidiaphragm and futher suggest that, by limiting the availability of choline for ACh synthesis , DFP reduces the...the binding sites is compromised. The effect of choline in ACh synthesis and release has been investigated. We have shown previously that prevention

  13. Nerve injury induces a new profile of tactile and mechanical nociceptor input from undamaged peripheral afferents.

    PubMed

    Boada, M Danilo; Gutierrez, Silvia; Aschenbrenner, Carol A; Houle, Timothy T; Hayashida, Ken-Ichiro; Ririe, Douglas G; Eisenach, James C

    2015-01-01

    Chronic pain after nerve injury is often accompanied by hypersensitivity to mechanical stimuli, yet whether this reflects altered input, altered processing, or both remains unclear. Spinal nerve ligation or transection results in hypersensitivity to mechanical stimuli in skin innervated by adjacent dorsal root ganglia, but no previous study has quantified the changes in receptive field properties of these neurons in vivo. To address this, we recorded intracellularly from L4 dorsal root ganglion neurons of anesthetized young adult rats, 1 wk after L5 partial spinal nerve ligation (pSNL) or sham surgery. One week after pSNL, hindpaw mechanical withdrawal threshold in awake, freely behaving animals was decreased in the L4 distribution on the nerve-injured side compared with sham controls. Electrophysiology revealed that high-threshold mechanoreceptive cells of A-fiber conduction velocity in L4 were sensitized, with a seven-fold reduction in mechanical threshold, a seven-fold increase in receptive field area, and doubling of maximum instantaneous frequency in response to peripheral stimuli, accompanied by reductions in after-hyperpolarization amplitude and duration. Only a reduction in mechanical threshold (minimum von Frey hair producing neuronal activity) was observed in C-fiber conduction velocity high-threshold mechanoreceptive cells. In contrast, low-threshold mechanoreceptive cells were desensitized, with a 13-fold increase in mechanical threshold, a 60% reduction in receptive field area, and a 40% reduction in instantaneous frequency to stimulation. No spontaneous activity was observed in L4 ganglia, and the likelihood of recording from neurons without a mechanical receptive field was increased after pSNL. These data suggest massively altered input from undamaged sensory afferents innervating areas of hypersensitivity after nerve injury, with reduced tactile and increased nociceptive afferent response. These findings differ importantly from previous preclinical

  14. Nerve injury induces a new profile of tactile and mechanical nociceptor input from undamaged peripheral afferents

    PubMed Central

    Gutierrez, Silvia; Aschenbrenner, Carol A.; Houle, Timothy T.; Hayashida, Ken-ichiro; Ririe, Douglas G.; Eisenach, James C.

    2014-01-01

    Chronic pain after nerve injury is often accompanied by hypersensitivity to mechanical stimuli, yet whether this reflects altered input, altered processing, or both remains unclear. Spinal nerve ligation or transection results in hypersensitivity to mechanical stimuli in skin innervated by adjacent dorsal root ganglia, but no previous study has quantified the changes in receptive field properties of these neurons in vivo. To address this, we recorded intracellularly from L4 dorsal root ganglion neurons of anesthetized young adult rats, 1 wk after L5 partial spinal nerve ligation (pSNL) or sham surgery. One week after pSNL, hindpaw mechanical withdrawal threshold in awake, freely behaving animals was decreased in the L4 distribution on the nerve-injured side compared with sham controls. Electrophysiology revealed that high-threshold mechanoreceptive cells of A-fiber conduction velocity in L4 were sensitized, with a seven-fold reduction in mechanical threshold, a seven-fold increase in receptive field area, and doubling of maximum instantaneous frequency in response to peripheral stimuli, accompanied by reductions in after-hyperpolarization amplitude and duration. Only a reduction in mechanical threshold (minimum von Frey hair producing neuronal activity) was observed in C-fiber conduction velocity high-threshold mechanoreceptive cells. In contrast, low-threshold mechanoreceptive cells were desensitized, with a 13-fold increase in mechanical threshold, a 60% reduction in receptive field area, and a 40% reduction in instantaneous frequency to stimulation. No spontaneous activity was observed in L4 ganglia, and the likelihood of recording from neurons without a mechanical receptive field was increased after pSNL. These data suggest massively altered input from undamaged sensory afferents innervating areas of hypersensitivity after nerve injury, with reduced tactile and increased nociceptive afferent response. These findings differ importantly from previous preclinical

  15. Concurrent recordings of bladder afferents from multiple nerves using a microfabricated PDMS microchannel electrode array.

    PubMed

    Delivopoulos, Evangelos; Chew, Daniel J; Minev, Ivan R; Fawcett, James W; Lacour, Stéphanie P

    2012-07-21

    In this paper we present a compliant neural interface designed to record bladder afferent activity. We developed the implant's microfabrication process using multiple layers of silicone rubber and thin metal so that a gold microelectrode array is embedded within four parallel polydimethylsiloxane (PDMS) microchannels (5 mm long, 100 μm wide, 100 μm deep). Electrode impedance at 1 kHz was optimized using a reactive ion etching (RIE) step, which increased the porosity of the electrode surface. The electrodes did not deteriorate after a 3 month immersion in phosphate buffered saline (PBS) at 37 °C. Due to the unique microscopic topography of the metal film on PDMS, the electrodes are extremely compliant and can withstand handling during implantation (twisting and bending) without electrical failure. The device was transplanted acutely to anaesthetized rats, and strands of the dorsal branch of roots L6 and S1 were surgically teased and inserted in three microchannels under saline immersion to allow for simultaneous in vivo recordings in an acute setting. We utilized a tripole electrode configuration to maintain background noise low and improve the signal to noise ratio. The device could distinguish two types of afferent nerve activity related to increasing bladder filling and contraction. To our knowledge, this is the first report of multichannel recordings of bladder afferent activity.

  16. Electron microscopic observations of terminals of functionally identified afferent fibers in cat spinal cord.

    PubMed

    Egger, M D; Freeman, N C; Malamed, S; Masarachia, P; Proshansky, E

    1981-02-23

    Using the method of intra-axonal injection of horseradish peroxidase, functionally identified afferent fibers from three slowly adapting (Type I) receptors and one Pacinian corpuscle in the glabrous skin of the hind paw of the cat were stained. Electron microscopic observation of the terminals of these fibers revealed predominantly axodendritic asymmetric synapses containing round, clear vesicles. Multiple synapses on a single dendrite were observed, separated by as little as 900 mm from one another.

  17. Vagal nerve stimulation activates vagal afferent fibers that reduce cardiac efferent parasympathetic effects

    PubMed Central

    Yamakawa, Kentaro; Rajendran, Pradeep S.; Takamiya, Tatsuo; Yagishita, Daigo; So, Eileen L.; Mahajan, Aman; Shivkumar, Kalyanam

    2015-01-01

    Vagal nerve stimulation (VNS) has been shown to have antiarrhythmic effects, but many of these benefits were demonstrated in the setting of vagal nerve decentralization. The purpose of this study was to evaluate the role of afferent fiber activation during VNS on efferent control of cardiac hemodynamic and electrophysiological parameters. In 37 pigs a 56-electrode sock was placed over the ventricles to record local activation recovery intervals (ARIs), a surrogate of action potential duration. In 12 of 37 animals atropine was given systemically. Right and left VNS were performed under six conditions: both vagal trunks intact (n = 25), ipsilateral right (n = 11), ipsilateral left (n = 14), contralateral right (n = 7), contralateral left (n = 10), and bilateral (n = 25) vagal nerve transection (VNTx). Unilateral VNTx significantly affected heart rate, PR interval, Tau, and global ARIs. Right VNS after ipsilateral VNTx had augmented effects on hemodynamic parameters and increase in ARI, while subsequent bilateral VNTx did not significantly modify this effect (%change in ARI in intact condition 2.2 ± 0.9% vs. ipsilateral VNTx 5.3 ± 1.7% and bilateral VNTx 5.3 ± 0.8%, P < 0.05). Left VNS after left VNTx tended to increase its effects on hemodynamics and ARI response (P = 0.07), but only after bilateral VNTx did these changes reach significance (intact 1.1 ± 0.5% vs. ipsilateral VNTx 3.6 ± 0.7% and bilateral VNTx 6.6 ± 1.6%, P < 0.05 vs. intact). Contralateral VNTx did not modify VNS response. The effect of atropine on ventricular ARI was similar to bilateral VNTx. We found that VNS activates afferent fibers in the ipsilateral vagal nerve, which reflexively inhibit cardiac parasympathetic efferent electrophysiological and hemodynamic effects. PMID:26371172

  18. Expression and function of the ion channel TRPA1 in vagal afferent nerves innervating mouse lungs.

    PubMed

    Nassenstein, Christina; Kwong, Kevin; Taylor-Clark, Thomas; Kollarik, Marian; Macglashan, Donald M; Braun, Armin; Undem, Bradley J

    2008-03-15

    Transient receptor potential (TRP) A1 and TRPM8 are ion channels that have been localized to afferent nociceptive nerves. These TRP channels may be of particular relevance to respiratory nociceptors in that they can be activated by various inhaled irritants and/or cold air. We addressed the hypothesis that mouse vagal sensory nerves projecting to the airways express TRPA1 and TRPM8 and that they can be activated via these receptors. Single cell RT-PCR analysis revealed that TRPA1 mRNA, but not TRPM8, is uniformly expressed in lung-labelled TRPV1-expressing vagal sensory neurons. Neither TRPA1 nor TRPM8 mRNA was expressed in TRPV1-negative neurons. Capsaicin-sensitive, but not capsaicin-insensitive, lung-specific neurons responded to cinnamaldehyde, a TRPA1 agonist, with increases in intracellular calcium. Menthol, a TRPM8 agonist, was ineffective at increasing cellular calcium in lung-specific vagal sensory neurons. Cinnamaldehyde also induced TRPA1-like inward currents (as measured by means of whole cell patch clamp recordings) in capsaicin-sensitive neurons. In an ex vivo vagal innervated mouse lung preparation, cinnamaldehyde evoked action potential discharge in mouse vagal C-fibres with a peak frequency similar to that observed with capsaicin. Cinnamaldehyde inhalation in vivo mimicked capsaicin in eliciting strong central-reflex changes in breathing pattern. Taken together, our results support the hypothesis that TRPA1, but not TRPM8, is expressed in vagal sensory nerves innervating the airways. TRPA1 activation provides a mechanism by which certain environmental stimuli may elicit action potential discharge in airway afferent C-fibres and the consequent nocifensor reflexes.

  19. Differential role of afferent and efferent renal nerves in the maintenance of early- and late-phase Dahl S hypertension

    PubMed Central

    Foss, Jason D.; Fink, Gregory D.

    2015-01-01

    Clinical data suggest that renal denervation (RDNX) may be an effective treatment for human hypertension; however, it is unclear whether this therapeutic effect is due to ablation of afferent or efferent renal nerves. We have previously shown that RDNX lowers arterial pressure in hypertensive Dahl salt-sensitive (S) rats to a similar degree observed in clinical trials. In addition, we have recently developed a method for selective ablation of afferent renal nerves (renal-CAP). In the present study, we tested the hypothesis that the antihypertensive effect of RDNX in the Dahl S rat is due to ablation of afferent renal nerves by comparing the effect of complete RDNX to renal-CAP during two phases of hypertension in the Dahl S rat. In the early phase, rats underwent treatment after 3 wk of high-NaCl feeding when mean arterial pressure (MAP) was ∼140 mmHg. In the late phase, rats underwent treatment after 9 wk of high NaCl feeding, when MAP was ∼170 mmHg. RDNX reduced MAP ∼10 mmHg compared with sham surgery in both the early and late phase, whereas renal-CAP had no antihypertensive effect. These results suggest that, in the Dahl S rat, the antihypertensive effect of RDNX is not dependent on pretreatment arterial pressure, nor is it due to ablation of afferent renal nerves. PMID:26661098

  20. Efferents and afferents in an intact muscle nerve: background activity and effects of sural nerve stimulation in the cat.

    PubMed

    Bessou, P; Joffroy, M; Pagès, B

    1981-11-01

    1. The background activity was observed in gamma and alpha efferent fibres and in group I and II fibres innervating the muscle gastrocnemius lateralis or medialis. The reflex effects of ipsilateral and contralateral sural nerve stimulations on the muscle efferents were analysed together with their consequences upon the afferents of the same muscle. The observations were made in the decerebrated cat without opening the neural loops between the muscle and the spinal cord.2. The multi-unit discharges of each category of fibres were obtained, on line, by an original electronic device (Joffroy, 1975, 1980) that sorted the action potentials from the whole electrical activity of a small branch of gastrocnemius lateralis or medialis nerve according to the direction and velocity of propagation of the potentials.3. The small nerve may be regarded as a representative sample of different functional groups of fibres conducting faster than 12 m.sec(-1) and supplying gastrocnemius muscles.4. Some gamma efferents were always tonically firing except when a transient flaccid state developed. Usually the alpha efferents were silent, probably because the muscle was fixed close to the minimal physiological length.5. Separate and selective stimulations of Abeta, Adelta and C fibres of ipsilateral and contralateral sural nerve showed that each group could induce the excitation of gamma neurones. The reciprocal inhibition period of alpha efferents during a flexor reflex was only once accompanied by a small decrease in gamma-firing.6. The reflex increase of over-all frequency of gamma efferents resulted from an increased firing rate of tonic gamma neurones and from the recruitment of gamma neurones previously silent. When the gamma efferents in the small nerve naturally occurred in two subgroups, the slower-conducting subgroup (mainly composed of tonic gamma axons) was activated before the faster-conducting subgroup (mostly composed by gamma axons with no background discharge). Some rare

  1. [Pharmacotherapy for neuropathic pain caused by injury to the afferent nerve fibers].

    PubMed

    Weber, W E

    2001-04-28

    Phantom pain, a form of neuropathic pain, is caused by damage to somatosensible afferent nerve fibres in the peripheral or central nervous system. Often, the pain cannot be satisfactorily treated with nonsteroidal anti-inflammatory drugs. Dependent on the underlying mechanism the pain is treated with either antidepressants (for more or less continuous pain) or anti-epileptics (for paroxysmal pain). Of the antidepressants, the tricyclic antidepressants are the best studied and most prescribed. The activity of new drugs, such as the selective serotonin reuptake inhibitor paroxetine as well as venlafaxine, has yet to be clearly shown. Of the anti-epileptics, carbamazepine and phenytoin are the most prescribed. New drugs which provide greater pain relief than the placebo are oxcarbazepine, gabapentine and lamotrigine. Other effective drugs for phantom pain are: gamma-butyric acid agonists (baclofen), opiates (morphine preparations with a regulated release; phentanyl patch), the N-methyl-D-aspartate receptor antagonist amantadine, transdermally administered clonidine and locally applied lidocaine.

  2. Vagal and splanchnic afferent nerves are not essential for anorexia associated with abomasal parasitism in sheep.

    PubMed

    Fox, M T; Reynolds, G W; Scott, I; Simcock, D C; Simpson, H V

    2006-02-18

    Heavy burdens of the abomasal nematode, Ostertagia (Telodorsagia) circumcincta, in growing lambs result in a reduction in liveweight gain due largely to a drop in voluntary feed intake. The present study investigated: (1) the role of subdiaphragmatic vagal and non-vagal visceral afferent nerves in mediating a reduction in voluntary feed intake, using subdiaphragmatic vagal deafferentation (vagotomy) either alone or in combination with coeliac-superior mesenteric ganglionectomy (vagotomy and sympathectomy); and (2) the association between appetite, abomasal pH, selected blood values (amidated gastrin (G-17-amide), glycine-extended gastrin (G-17-Gly), pepsinogen and leptin) and worm burden, in sheep experimentally infected with 100,000 O. circumcincta infective larvae per os. Neither vagotomy alone nor vagotomy and sympathectomy in combination adversely affected the establishment or course of development of the parasite burden, when compared with a control group subject to sham surgery. Furthermore, neither surgical procedure prevented the drop in appetite seen 5-10 days post-infection, although combined vagotomy and sympathectomy did reduce voluntary feed intake prior to the start of the study. Ostertagia infection resulted in a significant increase in abomasal pH in all three groups, which was accompanied by an increase in blood G-17-amide and in G-17-Gly, the latter reported for the first time in parasitized ruminants. There were no significant differences in blood leptin, also reported for the first time in parasitized sheep, either between groups or in comparison with pre-infection levels, though weak negative correlations were established between blood leptin and appetite from day 5 to the end of the study in all three groups and a positive correlation with blood G-17-amide in the control group over the same period. These data suggest that neither intact subdiaphragmatic vagal afferent nerves or coeliac-superior mesenteric ganglion fibres, nor changes in

  3. Inhibition by efferent nerve fibres: action on hair cells and afferent synaptic transmission in the lateral line canal organ of the burbot Lota lota.

    PubMed Central

    Flock, A; Russell, I

    1976-01-01

    1. Intracellular recordings were made from morphologically identified hair cells in the lateral line canal organs of the burbot Lota lota. 2. I.p.s.p.s were recorded from hair cells when the efferent fibres were excited by electrical stimulation of the lateral line nerve. The i.p.s.p.s were abolished when the fish was injected with immobilizing concentration of Flaxedil which is known to block the efferent synapses. 3. The i.p.s.p.s are accompanied by a decrease in the resistance of the hair cell membrane and an increase in the intracellular receptor potential. 4. Spontaneous and mechanically evoked e.p.s.p.s which were recorded intracellularly from the post-synaptic afferent nerve terminals were reduced in amplitude for the duration of the i.p.s.p. Images A, B C PMID:948076

  4. An electron microscopic study of terminals of rapidly adapting mechanoreceptive afferent fibers in the cat spinal cord.

    PubMed

    Semba, K; Masarachia, P; Malamed, S; Jacquin, M; Harris, S; Yang, G; Egger, M D

    1985-02-08

    The intra-axonal horseradish peroxidase technique was used to examine the central terminals of 7 A beta primary afferent fibers from rapidly adapting (RA) mechanoreceptors in the glabrous skin of the cat's hindpaw. At the light microscopic level, labelled collaterals were seen to bear occasional boutonlike swellings, mostly (75-82%) of the en passant type. These swellings were distributed more or less uniformly from lamina III to a dorsal part of lamina VI in the dorsal horn, over a maximum longitudinal extent of about 4 mm. At the electron microscopic level, we observed that labelled boutons of RA afferent fibers were 1.0 to 3.3 micrometers in longest sectional dimension, and contained clear, round synaptic vesicles. They frequently formed asymmetric axospinous and axodendritic synapses and commonly appeared to receive contacts from unlabelled structures containing flattened or pleomorphic vesicles plus occasional large dense-cored vesicles. The examination of synaptic connectivity over the entire surface of individual boutons indicated that RA afferent boutons each made contacts with an average of one spine and one dendrite and, in addition, appeared to be postsynaptic to an average of two unlabelled vesicle-containing structures. This synaptic organization was, in general, more complex than that we had seen previously in Pacinian corpuscle (PC) and slowly adapting (SA) type I mechanoreceptive afferent fibers. Our findings indicate that RA, SA, and PC afferent terminals, while displaying some differential synaptic organizations, have many morphological and synaptological characteristics in common. These afferent terminals, in turn, seem to be generally distinguishable from the terminals of muscle spindle Ia afferents or unmyelinated primary afferents.

  5. Capsaicin-responsive corneal afferents do not contain TRPV1 at their central terminals in trigeminal nucleus caudalis in rats.

    PubMed

    Hegarty, Deborah M; Hermes, Sam M; Largent-Milnes, Tally M; Aicher, Sue A

    2014-11-01

    We examined the substrates for ocular nociception in adult male Sprague-Dawley rats. Capsaicin application to the ocular surface in awake rats evoked nocifensive responses and suppressed spontaneous grooming responses. Thus, peripheral capsaicin was able to activate the central pathways encoding ocular nociception. Our capsaicin stimulus evoked c-Fos expression in a select population of neurons within rostral trigeminal nucleus caudalis in anesthetized rats. These activated neurons also received direct contacts from corneal afferent fibers traced with cholera toxin B from the corneal surface. However, the central terminals of the corneal afferents that contacted capsaicin-activated trigeminal neurons did not contain TRPV1. To determine if TRPV1 expression had been altered by capsaicin stimulation, we examined TRPV1 content of corneal afferents in animals that did not receive capsaicin stimulation. These studies confirmed that while TRPV1 was present in 30% of CTb-labeled corneal afferent neurons within the trigeminal ganglion, TRPV1 was only detected in 2% of the central terminals of these corneal afferents within the trigeminal nucleus caudalis. Other TRP channels were also present in low proportions of central corneal afferent terminals in unstimulated animals (TRPM8, 2%; TRPA1, 10%). These findings indicate that a pathway from the cornea to rostral trigeminal nucleus caudalis is involved in corneal nociceptive transmission, but that central TRP channel expression is unrelated to the type of stimulus transduced by the peripheral nociceptive endings.

  6. Activation of afferent renal nerves modulates RVLM-projecting PVN neurons.

    PubMed

    Xu, Bo; Zheng, Hong; Liu, Xuefei; Patel, Kaushik P

    2015-05-01

    Renal denervation for the treatment of hypertension has proven to be successful; however, the underlying mechanism/s are not entirely clear. To determine if preautonomic neurons in the paraventricular nucleus (PVN) respond to afferent renal nerve (ARN) stimulation, extracellular single-unit recording was used to investigate the contribution of the rostral ventrolateral medulla (RVLM)-projecting PVN (PVN-RVLM) neurons to the response elicited during stimulation of ARN. In 109 spontaneously active neurons recorded in the PVN of anesthetized rats, 25 units were antidromically activated from the RVLM. Among these PVN-RVLM neurons, 84% (21/25) were activated by ARN stimulation. The baseline discharge rate was significantly higher in these neurons than those PVN-RVLM neurons not activated by ARN stimulation (16%, 4/25). The responsiveness of these neurons to baroreflex activation induced by phenylephrine and activation of cardiac sympathetic afferent reflex (CSAR) was also examined. Almost all of the PVN neurons that responded to ARN stimulation were sensitive to baroreflex (95%) and CSAR (100%). The discharge characteristics for nonevoked neurons (not activated by RVLM antidromic stimulation) showed that 23% of these PVN neurons responded to ARN stimulation. All the PVN neurons that responded to ARN stimulation were activated by N-methyl-D-aspartate, and these responses were attenuated by the glutamate receptor blocker AP5. These experiments demonstrated that sensory information originating in the kidney is integrated at the level of preautonomic neurons within the PVN, providing a novel mechanistic insight for use of renal denervation in the modulation of sympathetic outflow in disease states such as hypertension and heart failure.

  7. Interpretation of muscle spindle afferent nerve response to passive muscle stretch recorded with thin-film longitudinal intrafascicular electrodes.

    PubMed

    Djilas, Milan; Azevedo-Coste, Christine; Guiraud, David; Yoshida, Ken

    2009-10-01

    In this study, we explored the feasibility of estimating muscle length in passive conditions by interpreting nerve responses from muscle spindle afferents recorded with thin-film longitudinal intrafascicular electrodes. Afferent muscle spindle response to passive stretch was recorded in ten acute rabbit experiments. A newly proposed first-order model of muscle spindle response to passive sinusoidal muscle stretch manages to capture the relationship between afferent neural firing rate and muscle length. We demonstrate that the model can be used to track random motion trajectories with bandwidth from 0.1 to 1 Hz over a range of 4 mm with a muscle length estimation error of 0.3 mm (1.4 degrees of joint angle). When estimation is performed using four-channel ENG there is a 50% reduction in estimate variation, compared to using single-channel recordings.

  8. BDNF released during neuropathic pain potentiates NMDA receptors in primary afferent terminals

    PubMed Central

    Chen, Wenling; Walwyn, Wendy; Ennes, Helena S.; Kim, Hyeyoung; McRoberts, James A.; Marvizón, Juan Carlos G.

    2014-01-01

    NMDA receptors in primary afferent terminals can contribute to hyperalgesia by increasing neurotransmitter release. In rats and mice, we found that the ability of intrathecal NMDA to induce neurokinin 1 receptor (NK1R) internalization (a measure of substance P release) required a previous injection of BDNF. Selective knock-down of NMDA receptors in primary afferents decreased NMDA-induced NK1R internalization, confirming the presynaptic location of these receptors. The effect of BDNF was mediated by tropomyosin-related kinase B (trkB) receptors and not p75 neurotrophin receptors (p75NTR), because it was not produced by proBDNF and was inhibited by the trkB antagonist ANA-12 but not by the p75NTR inhibitor TAT-Pep5. These effects are probably mediated through the truncated form of the trkB receptor as there is little expression of full-length trkB in dorsal root ganglion (DRG) neurons. Src family kinase inhibitors blocked the effect of BDNF, suggesting that trkB receptors promote the activation of these NMDA receptors by Src family kinase phosphorylation. Western blots of cultured DRG neurons revealed that BDNF increased Tyr1472 phosphorylation of the NR2B subunit of the NMDA receptor, known to have a potentiating effect. Patch-clamp recordings showed that BDNF, but not proBDNF, increased NMDA receptor currents in cultured DRG neurons. NMDA-induced NK1R internalization was also enabled in a neuropathic pain model or by activating dorsal horn microglia with lipopolysaccharide. These effects were decreased by a BDNF scavenger, a trkB receptor antagonist and an Src family kinase inhibitor, indicating that BDNF released by microglia potentiates NMDA receptors in primary afferents during neuropathic pain. PMID:24611998

  9. Connections of the terminal nerve and the olfactory system in two galeomorph sharks: an experimental study using a carbocyanine dye.

    PubMed

    Yáñez, Julián; Folgueira, Mónica; Köhler, Elisabeth; Martínez, Cristina; Anadón, Ramón

    2011-11-01

    In elasmobranchs the terminal nerve courses separately from the olfactory nerve. This characteristic makes elasmobranchs excellent models to study the anatomy and function of these two systems. Here we study the neural connections of the terminal nerve and olfactory system in two sharks by experimental tracing methods using carbocyanine dyes. The main projections from the terminal nerve system (consisting of three ganglia in Scyliorhinus canicula) course ipsilaterally to the medial septal nucleus and bilaterally to the ventromedial telencephalic pallial region. Minor terminal nerve projections were also traced ipsilaterally to diencephalic and mesencephalic levels. With regard to the olfactory connections, our results show that in sharks, unlike ray-finned fishes, the primary olfactory projections are mainly restricted to the olfactory bulb. We also performed tracer application to the olfactory bulb in order to analyze the possible central neuroanatomical relationship between the projections of the terminal nerve and the olfactory bulb. In these experiments labeled neurons and fibers were observed from telencephalic to caudal mesencephalic regions. However, we observe almost no overlap between the two systems at central levels. The afferent and the putatively efferent connections of the dogfish olfactory bulb are compared with those previously reported in other elasmobranchs. The significance of the extratelencephalic secondary olfactory projections is also discussed in a comparative context.

  10. Origin and central projections of rat dorsal penile nerve: possible direct projection to autonomic and somatic neurons by primary afferents of nonmuscle origin.

    PubMed

    Núñez, R; Gross, G H; Sachs, B D

    1986-05-22

    Cell number, size, and somatotopic arrangement within the spinal ganglia of the cells of origin of the rat dorsal penile nerve (DPN), and their spinal cord projections, were studied by loading the proximal stump of the severed DPN with horseradish peroxidase (HRP). The DPN sensory cells were located entirely in the sixth lumbar (L6) dorsal root ganglia (DRG), in which a mean of 468 +/- 78 cells per side were observed, measuring 26.7 +/- 0.8 microns in their longest axis (range 10-65 microns) and distributed apparently randomly within the ganglia. Within the spinal cord, no retrograde label was found, i.e., no motoneurons were labeled, indicating that in the rat the DPN is formed exclusively of sensory nerve fibers. Although labeled fibers entered the cord only through L6, transganglionically transported HRP was evident in all spinal segments examined, i.e., T13-S2. Labeled fibers projected along the inner edge of the dorsal horn (medial pathway) throughout their extensive craniosacral distribution. However, laminar distribution varied with spinal segment. In the dorsal horn, terminals or preterminal axons were found in the dorsal horn marginal zone (lamina I), the substantia gelatinosa (lamina II), the nucleus proprius (laminae III and IV--the most consistent projection), Clarke's column (lamina VI), and the dorsal gray commissure. In the ventral horn, terminals were found in lamina VII and lamina IX. Label apposed to cell somas and dendrites in lamina VII may represent direct primary afferent projections onto sympathetic autonomic neurons. In lamina IX, labeled terminals delineated the somas and dendrites of cells that appeared to be motoneurons. This is the first description of an apparently monosynaptic contact onto motoneurons by a primary afferent of nonmuscle origin.

  11. Identification of different types of spinal afferent nerve endings that encode noxious and innocuous stimuli in the large intestine using a novel anterograde tracing technique.

    PubMed

    Spencer, Nick J; Kyloh, Melinda; Duffield, Michael

    2014-01-01

    In mammals, sensory stimuli in visceral organs, including those that underlie pain perception, are detected by spinal afferent neurons, whose cell bodies lie in dorsal root ganglia (DRG). One of the major challenges in visceral organs has been how to identify the different types of nerve endings of spinal afferents that transduce sensory stimuli into action potentials. The reason why spinal afferent nerve endings have been so challenging to identify is because no techniques have been available, until now, that can selectively label only spinal afferents, in high resolution. We have utilized an anterograde tracing technique, recently developed in our laboratory, which facilitates selective labeling of only spinal afferent axons and their nerve endings in visceral organs. Mice were anesthetized, lumbosacral DRGs surgically exposed, then injected with dextran-amine. Seven days post-surgery, the large intestine was removed. The characteristics of thirteen types of spinal afferent nerve endings were identified in detail. The greatest proportion of nerve endings was in submucosa (32%), circular muscle (25%) and myenteric ganglia (22%). Two morphologically distinct classes innervated myenteric ganglia. These were most commonly a novel class of intraganglionic varicose endings (IGVEs) and occasionally rectal intraganglionic laminar endings (rIGLEs). Three distinct classes of varicose nerve endings were found to innervate the submucosa and circular muscle, while one class innervated internodal strands, blood vessels, crypts of lieberkuhn, the mucosa and the longitudinal muscle. Distinct populations of sensory endings were CGRP-positive. We present the first complete characterization of the different types of spinal afferent nerve endings in a mammalian visceral organ. The findings reveal an unexpectedly complex array of different types of primary afferent endings that innervate specific layers of the large intestine. Some of the novel classes of nerve endings identified

  12. Characterization of muscle spindle afferents in the adult mouse using an in vitro muscle-nerve preparation.

    PubMed

    Wilkinson, Katherine A; Kloefkorn, Heidi E; Hochman, Shawn

    2012-01-01

    We utilized an in vitro adult mouse extensor digitorum longus (EDL) nerve-attached preparation to characterize the responses of muscle spindle afferents to ramp-and-hold stretch and sinusoidal vibratory stimuli. Responses were measured at both room (24°C) and muscle body temperature (34°C). Muscle spindle afferent static firing frequencies increased linearly in response to increasing stretch lengths to accurately encode the magnitude of muscle stretch (tested at 2.5%, 5% and 7.5% of resting length [Lo]). Peak firing frequency increased with ramp speeds (20% Lo/sec, 40% Lo/sec, and 60% Lo/sec). As a population, muscle spindle afferents could entrain 1:1 to sinusoidal vibrations throughout the frequency (10-100 Hz) and amplitude ranges tested (5-100 µm). Most units preferentially entrained to vibration frequencies close to their baseline steady-state firing frequencies. Cooling the muscle to 24°C decreased baseline firing frequency and units correspondingly entrained to slower frequency vibrations. The ramp component of stretch generated dynamic firing responses. These responses and related measures of dynamic sensitivity were not able to categorize units as primary (group Ia) or secondary (group II) even when tested with more extreme length changes (10% Lo). We conclude that the population of spindle afferents combines to encode stretch in a smoothly graded manner over the physiological range of lengths and speeds tested. Overall, spindle afferent response properties were comparable to those seen in other species, supporting subsequent use of the mouse genetic model system for studies on spindle function and dysfunction in an isolated muscle-nerve preparation.

  13. Excitability changes of terminal arborizations of single Ia and Ib afferent fibers produced by muscle and cutaneous conditioning volleys.

    PubMed

    Willis, W D; Núnez, R; Rudomín, P

    1976-11-01

    1. In cats anesthetized with sodium pentobarbital, recordings were made from dorsal root ganglion (DRG) cells having a peripheral process in the gastrocnemius-soleus (GS) nerve. The GS nerve was left in continuity with the muscle to allow identification of group Ia and Ib fibers by responses of the receptors to muscle stretch and contraction. The central processes of the DRG cells were activated antidromically by stimulation within the spinal cord so that changes in the excitability of the fibers could be examined following conditioning volleys in muscle and cutaneous nerves. 2. Recordings were made from 44 DRG cells. Of these, 15 were group Ia and 9 group Ib afferents of the GS nerve. 3. Of 15 Ia fibers, 12 were activated antidromically by stimulation in the motor nucleus, but no Ib fibers were discharged by such stimulation. Ib fibers could be antidromically activated by stimulation in the intermediate nucleus. 4. The central processes of the Ia DRG cells had slower conduction velocities than did the peripheral processes. 5. The thresholds to electrical stimulation of the peripheral processes of Ia and Ib fibers of the GS nerve showed considerable overlap. 6. All of the Ia DRG cells tested showed an increased excitability following conditioning volleys in the biceps-semitendinosus (BST) nerve. The increase in excitability was produced by the largest fibers of the BST nerve. 7. Stimulation of the sural (SU) or superficial peroneal (SP) cutaneous nerves also increased the excitability of some Ia fibers. However, other Ia fibers were unaffected, and in two cases the excitability was reduced. 8. The excitability of group Ib fibers was increased by conditioning volleys in the BST, SU, or SP nerves. 9. It is concluded that cutaneous volleys produce a mixture of primary afferent depolarization and primary afferent hyperpolarization in Ia fibers of anesthetized cats. Such converse actions probably cancel in excitability tests using population responses. 10. The

  14. Plasticity of urinary bladder reflexes evoked by stimulation of pudendal afferent nerves after chronic spinal cord injury in cats.

    PubMed

    Tai, Changfeng; Chen, Mang; Shen, Bing; Wang, Jicheng; Liu, Hailong; Roppolo, James R; de Groat, William C

    2011-03-01

    Bladder reflexes evoked by stimulation of pudendal afferent nerves (PudA-to-Bladder reflex) were studied in normal and chronic spinal cord injured (SCI) adult cats to examine the reflex plasticity. Physiological activation of pudendal afferent nerves by tactile stimulation of the perigenital skin elicits an inhibitory PudA-to-Bladder reflex in normal cats, but activates an excitatory reflex in chronic SCI cats. However, in both normal and chronic SCI cats electrical stimulation applied to the perigenital skin or directly to the pudendal nerve induces either inhibitory or excitatory PudA-to-Bladder reflexes depending on stimulation frequency. An inhibitory response occurs at 3-10 Hz stimulation, but becomes excitatory at 20-30 Hz. The inhibitory reflex activated by electrical stimulation significantly (P<0.05) increases the bladder capacity to about 180% of control capacity in normal and chronic SCI cats. The excitatory reflex significantly (P<0.05) reduces bladder capacity to about 40% of control capacity in chronic SCI cats, but does not change bladder capacity in normal cats. Electrical stimulation of pudendal afferent nerves during slow bladder filling elicits a large amplitude bladder contraction comparable to the contraction induced by distension alone. A bladder volume about 60% of bladder capacity was required to elicit this excitatory reflex in normal cats; however, in chronic SCI cats a volume less than 20% of bladder capacity was sufficient to unmask an excitatory response. This study revealed the co-existence of both inhibitory and excitatory PudA-to-Bladder reflex pathways in cats before and after chronic SCI. However our data combined with published electrophysiological data strongly indicates that the spinal circuitry for both the excitatory and inhibitory PudA-to-Bladder reflexes undergoes a marked reorganization after SCI.

  15. Effect of copper sulphate on the rate of afferent discharge in the gastric branch of the vagus nerve in the rat

    NASA Technical Reports Server (NTRS)

    Niijima, Akira; Jiang, Zheng-Yao; Daunton, Nancy G.; Fox, Robert A.

    1991-01-01

    The afferent nerve activity was recorded from a nerve filament isolated from the peripheral cut end of the gastric branch of the vagus nerve. The gastric perfusion of 4 ml of two different concentrations (0.04 percent and 0.08 percent) of CuSO4 solution provoked an increase in afferent activity. The stimulating effect of the 0.08 percent solution was stronger than that of the 0.04 percent solution, and lasted for a longer period of time. The observations suggest a possible mechanism by which CuSO4 elicits emesis.

  16. Reduction of food intake following X-ray irradiation of rats--involvement of visceral afferent nerves.

    PubMed

    Unno, Tatsuya; Hashimoto, Mitsuyasu; Arai, Shoichi; Kurosawa, Mieko

    2002-03-18

    Radiotherapy for malignant tumours often elicits anorexia or loss of appetite as an adverse effect. However, the mechanism for this is poorly understood. The present study was undertaken to investigate if visceral afferents are responsible for reduction of food intake following X-ray irradiation. Rats were exposed bilaterally to X-ray (10 MV) irradiation with total doses of 1.5, 3 and 6 Gy, using a high-energy electron linear accelerator at a dose rate of 4.9 Gy min(-1) X-ray irradiation of the whole body, abdomen or head with doses of 1.5, 3 and 6 Gy reduced food intake in a dose-dependent manner. The reduction of food intake after X-ray irradiation of the whole body or abdomen was significantly greater than when only the head was irradiated. Reduction of food intake was observed for the first 4 days after 6 Gy X-ray irradiation of the abdomen, while it was observed only on the first day after the same 6-Gy irradiation of the abdomen in animals whose small-diameter afferents were ablated by capsaicin pre-treatment. These results suggested that the abdominal afferent nerves at least contribute to the reduction of food intake observed on second to fourth days after 6-Gy abdominal irradiation. Taken together, the present evidence suggests that the reduction of food intake following X-ray irradiation of the whole body or the abdomen is partly mediated via abdominal afferent nerves. Moreover, the results of X-ray irradiation to the head suggest that X-ray irradiation directly influences the central nervous system to reduce food intake.

  17. Observation of apical part and nerve terminals of human vestibular hair cells.

    PubMed

    Morita, I; Komatsuzaki, A; Kanda, T; Tatsuoka, H; Chiba, T

    1995-01-01

    The human vestibular sensory epithelia of macula utriculi in 3 cases of acoustic neurinoma were examined by conventional and intermediate voltage electron microscopes. The apical part and the nerve terminals of hair cells were studied by means of a computer-aided three-dimensional (3-D) reconstruction technique. The sensory epithelia were fairly well preserved. Most type I and all type II hair cells appeared as those described in the other reports. However, some type I hair cells were incompletely surrounded by nerve calyces and received direct contacts from the efferent nerve endings. These type I hair cells were also innervated by a few neighbouring afferent nerve calyces. The stereocilia and the cuticular plate of type I hair cells differed from those of type II hair cells. The mean diameter of type I hair cell stereocilia was 488 +/- 59 nm and that of type II hair cells was 373 +/- 21 nm. The cuticular plate of type I hair cells resembled a cone and was about several times as thick as that of type II hair cells which was similar to a flat disc.

  18. Firing patterns and functional roles of different classes of spinal afferents in rectal nerves during colonic migrating motor complexes in mouse colon.

    PubMed

    Zagorodnyuk, Vladimir P; Kyloh, Melinda; Brookes, Simon J; Nicholas, Sarah J; Spencer, Nick J

    2012-08-01

    The functional role of the different classes of visceral afferents that innervate the large intestine is poorly understood. Recent evidence suggests that low-threshold, wide-dynamic-range rectal afferents play an important role in the detection and transmission of visceral pain induced by noxious colorectal distension in mice. However, it is not clear which classes of spinal afferents are activated during naturally occurring colonic motor patterns or during intense contractions of the gut smooth muscle. We developed an in vitro colorectum preparation to test how the major classes of rectal afferents are activated during spontaneous colonic migrating motor complex (CMMC) or pharmacologically induced contraction. During CMMCs, circular muscle contractions increased firing in low-threshold, wide-dynamic-range muscular afferents and muscular-mucosal afferents, which generated a mean firing rate of 1.53 ± 0.23 Hz (n = 8) under isotonic conditions and 2.52 ± 0.36 Hz (n = 17) under isometric conditions. These low-threshold rectal afferents were reliably activated by low levels of circumferential stretch induced by increases in length (1-2 mm) or load (1-3 g). In a small proportion of cases (5 of 34 units), some low-threshold muscular and muscular-mucosal afferents decreased their firing rate during the peak of the CMMC contractions. High-threshold afferents were never activated during spontaneous CMMC contractions or tonic contractions induced by bethanechol (100 μM). High-threshold rectal afferents were only activated by intense levels of circumferential stretch (10-20 g). These results show that, in the rectal nerves of mice, low-threshold, wide-dynamic-range muscular and muscular-mucosal afferents are excited during contraction of the circular muscle that occurs during spontaneous CMMCs. No activation of high-threshold rectal afferents was detected during CMMCs or intense contractile activity in naïve mouse colorectum.

  19. Reinnervation of renal afferent and efferent nerves at 5.5 and 11 months after catheter-based radiofrequency renal denervation in sheep.

    PubMed

    Booth, Lindsea C; Nishi, Erika E; Yao, Song T; Ramchandra, Rohit; Lambert, Gavin W; Schlaich, Markus P; May, Clive N

    2015-02-01

    Previous studies indicate that catheter-based renal denervation reduces blood pressure and renal norepinephrine spillover in human resistant hypertension. The effects of this procedure on afferent sensory and efferent sympathetic renal nerves, and the subsequent degree of reinnervation, have not been investigated. We therefore examined the level of functional and anatomic reinnervation at 5.5 and 11 months after renal denervation using the Symplicity Flex catheter. In normotensive anesthetized sheep (n=6), electric stimulation of intact renal nerves increased arterial pressure from 99±3 to 107±3 mm Hg (afferent response) and reduced renal blood flow from 198±16 to 85±20 mL/min (efferent response). In a further group (n=6), immediately after denervation, renal sympathetic nerve activity was absent and the responses to electric stimulation were abolished. At 11 months after denervation (n=5), renal sympathetic nerve activity and the responses to electric stimulation were at normal levels. Immunohistochemical staining for renal efferent (tyrosine hydroxylase) and renal afferent nerves (calcitonin gene-related peptide), as well as renal norepinephrine levels, was normal 11 months after denervation. Findings at 5.5 months after denervation were similar (n=5). In summary, catheter-based renal denervation effectively ablated the renal afferent and efferent nerves in normotensive sheep. By 11 months after denervation the functional afferent and efferent responses to electric stimulation were normal. Reinnervation at 11 months after denervation was supported by normal anatomic distribution of afferent and efferent renal nerves. In view of this evidence, the mechanisms underlying the prolonged hypotensive effect of catheter-based renal denervation in human resistant hypertension need to be reassessed.

  20. Variation in response dynamics of regular and irregular vestibular-nerve afferents during sinusoidal head rotations and currents in the chinchilla.

    PubMed

    Kim, Kyu-Sung; Minor, Lloyd B; Della Santina, Charles C; Lasker, David M

    2011-05-01

    In mammals, vestibular-nerve afferents that innervate only type I hair cells (calyx-only afferents) respond nearly in phase with head acceleration for high-frequency motion, whereas afferents that innervate both type I and type II (dimorphic) or only type II (bouton-only) hair cells respond more in phase with head velocity. Afferents that exhibit irregular background discharge rates have a larger phase lead re-head velocity than those that fire more regularly. The goal of this study was to investigate the cause of the variation in phase lead between regular and irregular afferents at high-frequency head rotations. Under the assumption that externally applied galvanic currents act directly on the nerve, we derived a transfer function describing the dynamics of a semicircular canal and its hair cells through comparison of responses to sinusoidally modulated head velocity and currents. Responses of all afferents were fit well with a transfer function with one zero (lead term). Best-fit lead terms describing responses to current for each group of afferents were similar to the lead term describing responses to head velocity for regular afferents (0.006 s + 1). This finding indicated that the pre-synaptic and synaptic inputs to regular afferents were likely to be pure velocity transducers. However, the variation in phase lead between regular and irregular afferents could not be explained solely by the ratio of type I to II hair cells (Baird et al 1988), suggesting that the variation was caused by a combination of pre- (type of hair cell) and post-synaptic properties.

  1. Cutaneous afferent C-fibers regenerating along the distal nerve stump after crush lesion show two types of cold sensitivity.

    PubMed

    Grossmann, Lydia; Gorodetskaya, Natalia; Teliban, Alina; Baron, Ralf; Jänig, Wilfrid

    2009-08-01

    Cutaneous C-fiber afferents show two distinct types of cold sensitivity corresponding to non-noxious and noxious cold sensations. Here, responses to cold stimulation of afferent fibers regenerating in the rat sural nerve were studied in vivo 7-14 days after nerve crush and compared with responses to mechanical and heat stimulation. The physiological stimuli were applied to the sural nerve at or distal to the lesion site. Ectopic activity was evoked in 43% of 98 A-fibers (all mechanosensitive; a few additionally weakly thermosensitive). Ectopic activity was evoked in 127 (49.2%) of 258 electrically identified C-fibers by the physiological stimuli. Eight C-fibers were spontaneously active only. Of the 127 C-fibers, 46% had one of two distinct response patterns to cooling: (1) type 1 cold-sensitive C-fibers (n=29) had a high rate of activity at 28 degrees C on the nerve surface and showed graded responses to cooling with maximal discharge rates of 11.5+/-1.1 imp/s. This activity was completely inhibited by heating, while 12/29 fibers were also excited at high threshold (median 48 degrees C) by heating. Only one type 1 cold-sensitive C-fiber was mechanosensitive. (2) Type 2 cold-sensitive C-fibers (n=29) were silent or showed a low rate of activity at 28 degrees C, had a high threshold (median 5 degrees C) and low maximal discharge rates (2.4+/-0.4 imp/s) to cooling. They were also heat-sensitive (n=25) and/or mechanosensitive (n=20). These C-fibers were, apart from their cold sensitivity, functionally indistinguishable from C-fibers with mechano- and/or heat sensitivity only. Thus regenerating cutaneous C-fibers show two types of cold sensitivity similar to those observed in intact skin: fibers of one group are predominantly sensitive to cooling, whereas the others are polymodal.

  2. De novo expression of Nav1.7 in injured putative proprioceptive afferents: Multiple tetrodotoxin-sensitive sodium channels are retained in the rat dorsal root after spinal nerve ligation.

    PubMed

    Fukuoka, T; Miyoshi, K; Noguchi, K

    2015-01-22

    Tetrodotoxin-sensitive (TTX-s) spontaneous activity is recorded from the dorsal roots after peripheral nerve injury. Primary sensory neurons in the dorsal root ganglion (DRG) express multiple TTX-s voltage-gated sodium channel α-subunits (Navs). Since Nav1.3 increases, whereas all other Navs decrease, in the DRG neurons after peripheral nerve lesion, Nav1.3 is proposed to be critical for the generation of these spontaneous discharges and the contributions of other Navs have been ignored. Here, we re-evaluate the changes in expression of three other TTX-s Navs, Nav1.1, Nav1.6 and Nav1.7, in the injured 5th lumbar (L5) primary afferent components following L5 spinal nerve ligation (SNL) using in situ hybridization histochemistry and immunohistochemistry. While the overall signal intensities for these Nav mRNAs decreased, many injured DRG neurons still expressed these transcripts at clearly detectable levels. All these Nav proteins accumulated at the proximal stump of the ligated L5 spinal nerve. The immunostaining patterns of Nav1.6 and Nav1.7 associated with the nodes of Ranvier were maintained in the ipsilateral L5 dorsal root. Interestingly, putative proprioceptive neurons characterized by α3 Na+/K+ ATPase-immunostaining specifically lacked Nav1.7 mRNA in naïve DRG but displayed de novo expression of this transcript following SNL. Nav1.7-immunoreactive fibers were significantly increased in the ipsilateral gracile nucleus where central axonal branches of the injured A-fiber afferents terminated. These data indicate that multiple TTX-s channel subunits could contribute to the generation and propagation of the spontaneous discharges in the injured primary afferents. Specifically, Nav1.7 may cause some functional changes in sensory processing in the gracile nucleus after peripheral nerve injury.

  3. Autoregulation of Neuromuscular Transmission by Nerve Terminals

    DTIC Science & Technology

    1985-12-01

    precursor control. In addition, the influence of acetyl - cholinesterase (AChE) inhibition on these mechanisms has been examined. Neuromuscular...In addition, this effort ir-1ided new experimentation to learn the fate of Ca2+ once it enters the termin~ l in response to depolarization. The...modu- lin, may play a role in the excitation-secretion coupling mechanism. In theory, Ca L +-calmodulin regulates ACh release by altering cAMP

  4. Multiple cytosolic calcium buffers in posterior pituitary nerve terminals.

    PubMed

    McMahon, Shane M; Chang, Che-Wei; Jackson, Meyer B

    2016-03-01

    Cytosolic Ca(2+) buffers bind to a large fraction of Ca(2+) as it enters a cell, shaping Ca(2+) signals both spatially and temporally. In this way, cytosolic Ca(2+) buffers regulate excitation-secretion coupling and short-term plasticity of release. The posterior pituitary is composed of peptidergic nerve terminals, which release oxytocin and vasopressin in response to Ca(2+) entry. Secretion of these hormones exhibits a complex dependence on the frequency and pattern of electrical activity, and the role of cytosolic Ca(2+) buffers in controlling pituitary Ca(2+) signaling is poorly understood. Here, cytosolic Ca(2+) buffers were studied with two-photon imaging in patch-clamped nerve terminals of the rat posterior pituitary. Fluorescence of the Ca(2+) indicator fluo-8 revealed stepwise increases in free Ca(2+) after a series of brief depolarizing pulses in rapid succession. These Ca(2+) increments grew larger as free Ca(2+) rose to saturate the cytosolic buffers and reduce the availability of Ca(2+) binding sites. These titration data revealed two endogenous buffers. All nerve terminals contained a buffer with a Kd of 1.5-4.7 µM, and approximately half contained an additional higher-affinity buffer with a Kd of 340 nM. Western blots identified calretinin and calbindin D28K in the posterior pituitary, and their in vitro binding properties correspond well with our fluorometric analysis. The high-affinity buffer washed out, but at a rate much slower than expected from diffusion; washout of the low-affinity buffer could not be detected. This work has revealed the functional impact of cytosolic Ca(2+) buffers in situ in nerve terminals at a new level of detail. The saturation of these cytosolic buffers will amplify Ca(2+) signals and may contribute to use-dependent facilitation of release. A difference in the buffer compositions of oxytocin and vasopressin nerve terminals could contribute to the differences in release plasticity of these two hormones.

  5. Ultrastructure of pacinian corpuscle primary afferent terminals in the cat spinal cord.

    PubMed

    Semba, K; Masarachia, P; Malamed, S; Jacquin, M; Harris, S; Egger, M D

    1984-06-04

    The glabrous skin of the hindlimb of the cat contains 3 types of low-threshold mechanoreceptors: Pacinian corpuscles (PC), and slowly and rapidly adapting receptors. In the present study, 12 primary afferent fibers transmitting impulses from PC were injected intra-axonally with horseradish peroxidase (HRP) in the spinal cord to examine the morphology of their terminals in the dorsal horn. At the light microscopic level, terminal arborizations were observed in laminae II-VI of the dorsal horn, extending up to 7 mm rostrocaudally in and near the seventh lumbar segment. Bouton-like swellings, predominantly (67%) of the en passant type, were distributed in two discrete clusters, one concentrated rostrally in Rexed's laminae III-IV, and the other concentrated caudally in lamina V. At the electron microscopic level, a combination of morphometric and serial reconstructive analyses with 3 fibers revealed the following. Boutons labelled with HRP invariably contained clear round vesicles, approximately 40 nm in diameter. Labelled bouton sections had longest dimensions of 1.84 +/- 0.63 micron. Their shapes varied from rounded to elongated forms with occasional scalloped appearances. A majority (73%) of the contacts associated with HRP-filled boutons were made with dendritic spines and shafts. Thick postsynaptic densities were usually associated with these synapses, although thinner densities were also observed. 24% of the contacts made by labelled boutons were synapse-like contacts with unlabelled vesicle-containing structures. The vesicles in the unlabelled structures were usually pleomorphic, but sometimes round. These contacts were identified as 'synapse-like' because labelling obscured possible landmarks necessary for definitive identification of synapses. However, in most of these contacts, there was an accumulation of vesicles near the cleft on the unlabelled side, suggesting that the labelled boutons were postsynaptic. Only 3% of the contacts made by labelled boutons

  6. Response properties of whisker-associated primary afferent neurons following infraorbital nerve transection with microsurgical repair in adult rats

    PubMed Central

    Xiao, Bo; Zanoun, Rami R.; Carvell, George E.; Washington, Kia M.

    2016-01-01

    The rodent whisker/trigeminal system, characterized by high spatial and temporal resolution, provides an experimental model for developing new therapies for improving sensory functions of damaged peripheral nerves. Here, we use controlled whisker stimulation and single-unit recordings of trigeminal ganglion cells to examine in detail the nature and time course of functional recovery of mechanoreceptive afferents following nerve transection with microsurgical repair of the infraorbital nerve (ION) branch of the trigeminal nerve in adult rats. Response measures include rapid vs. slow adaptation, firing rate, interspike intervals, latency, and angular (directional) tuning. Whisker-evoked responses, readily observable by 3 wk post-transection, recover progressively for at least the next 5 wk. All cells in transected animals, as in control cases, responded to deflections of single whiskers only, but topography within the ganglion was clearly disrupted. The time course and extent of recovery of quantitative response measures were receptor dependent. Cells displaying slowly adapting (SA) properties recovered more quickly than rapidly adapting (RA) populations, and for some response measures—notably evoked firing rates—closely approached or attained control levels by 8 wk post-transection. Angular tuning of RA cells was slightly better than control units, whereas SA tuning did not differ from control values. Nerve conduction times and refractory periods, examined separately using electrical stimulation of the ION, were slower than normal in all transected animals and poorly reflected recovery of whisker-evoked response latencies and interspike intervals. Results underscore the need for multiple therapeutic strategies that target different aspects of functional restitution following peripheral nerve injury. PMID:26792886

  7. Evoked Pain Analgesia in Chronic Pelvic Pain Patients using Respiratory-gated Auricular Vagal Afferent Nerve Stimulation

    PubMed Central

    Napadow, Vitaly; Edwards, Robert R; Cahalan, Christine M; Mensing, George; Greenbaum, Seth; Valovska, Assia; Li, Ang; Kim, Jieun; Maeda, Yumi; Park, Kyungmo; Wasan, Ajay D.

    2012-01-01

    Objective Previous Vagus Nerve Stimulation (VNS) studies have demonstrated anti-nociceptive effects, and recent non-invasive approaches; termed transcutaneous-VNS, or t-VNS, have utilized stimulation of the auricular branch of the vagus nerve in the ear. The dorsal medullary vagal system operates in tune with respiration, and we propose that supplying vagal afferent stimulation gated to the exhalation phase of respiration can optimize t-VNS. Design counterbalanced, crossover study. Patients patients with chronic pelvic pain (CPP) due to endometriosis in a specialty pain clinic. Interventions/Outcomes We evaluated evoked pain analgesia for Respiratory-gated Auricular Vagal Afferent Nerve Stimulation (RAVANS) compared with Non-Vagal Auricular Stimulation (NVAS). RAVANS and NVAS were evaluated in separate sessions spaced at least one week apart. Outcome measures included deep tissue pain intensity, temporal summation of pain, and anxiety ratings, which were assessed at baseline, during active stimulation, immediately following stimulation, and 15 minutes after stimulus cessation. Results RAVANS demonstrated a trend for reduced evoked pain intensity and temporal summation of mechanical pain, and significantly reduced anxiety in N=15 CPP patients, compared to NVAS, with moderate to large effect sizes (eta2>0.2). Conclusion Chronic pain disorders such as CPP are in great need of effective, non-pharmacological options for treatment. RAVANS produced promising anti-nociceptive effects for QST outcomes reflective of the noted hyperalgesia and central sensitization in this patient population. Future studies should evaluate longer-term application of RAVANS to examine its effects on both QST outcomes and clinical pain. PMID:22568773

  8. Spike sorting of muscle spindle afferent nerve activity recorded with thin-film intrafascicular electrodes.

    PubMed

    Djilas, Milan; Azevedo-Coste, Christine; Guiraud, David; Yoshida, Ken

    2010-01-01

    Afferent muscle spindle activity in response to passive muscle stretch was recorded in vivo using thin-film longitudinal intrafascicular electrodes. A neural spike detection and classification scheme was developed for the purpose of separating activity of primary and secondary muscle spindle afferents. The algorithm is based on the multiscale continuous wavelet transform using complex wavelets. The detection scheme outperforms the commonly used threshold detection, especially with recordings having low signal-to-noise ratio. Results of classification of units indicate that the developed classifier is able to isolate activity having linear relationship with muscle length, which is a step towards online model-based estimation of muscle length that can be used in a closed-loop functional electrical stimulation system with natural sensory feedback.

  9. Primary afferent terminals acting as excitatory interneurons contribute to spontaneous motor activities in the immature spinal cord.

    PubMed

    Bos, Rémi; Brocard, Frédéric; Vinay, Laurent

    2011-07-13

    Patterned, spontaneous activity plays a critical role in the development of neuronal networks. A robust spontaneous activity is observed in vitro in spinal cord preparations isolated from immature rats. The rhythmic ventral root discharges rely mainly on the depolarizing/excitatory action of GABA and glycine early during development, whereas at later stages glutamate drive is primarily responsible for the rhythmic activity and GABA/glycine are thought to play an inhibitory role. However, rhythmic discharges mediated by the activation of GABA(A) receptors are recorded from dorsal roots (DRs). In the present study, we used the in vitro spinal cord preparation of neonatal rats to identify the relationship between discharges that are conducted antidromically along DRs and the spontaneous activity recorded from lumbar motoneurons. We show that discharges in DRs precede those in ventral roots and that primary afferent depolarizations (PADs) start earlier than EPSPs in motoneurons. EPSP-triggered averaging revealed that the action potentials propagate not only antidromically in the DR but also centrally and trigger EPSPs in motoneurons. Potentiating GABAergic antidromic discharges by diazepam increased the EPSPs recorded from motoneurons; conversely, blocking DR bursts markedly reduced these EPSPs. High intracellular concentrations of chloride are maintained in primary afferent terminals by the sodium-potassium-chloride cotransporter NKCC1. Blocking these cotransporters by bumetanide decreased both dorsal and ventral root discharges. We conclude that primary afferent fibers act as excitatory interneurons and that GABA, through PADs reaching firing threshold, is still playing a key role in promoting spontaneous activity in neonates.

  10. Post-stimulation Inhibitory Effect on Reflex Bladder Activity Induced by Activation of Somatic Afferent Nerves in the Foot

    PubMed Central

    Chen, Guoqing; Larson, Jeffrey A.; Ogagan, P. Dafe; Shen, Bing; Wang, Jicheng; Roppolo, James R.; de Groat, William C.; Tai, Changfeng

    2011-01-01

    Purpose To determine if transcutaneous electrical stimulation of somatic afferent nerves in the foot of cats can induce a post-stimulation increase in bladder capacity. Materials and Methods In α-chloralose anesthetized cats (N=12) electrical stimulation (5 Hz) was applied to the skin of the hind foot for two periods of 30 minutes via dual pad electrodes attached on the plantar and dorsal surfaces (combination 1-2) or at two sites on the plantar surface (combination 1-3). The post-stimulation effect was examined by performing repeated CMGs following 30 minute stimulation. In the control group (N=12) the isovolumetric contractions were allowed to continue during each 30 minute period without stimulation. Results Stimulation inhibited isovolumetric rhythmic bladder contractions. The bladder capacity was not increased after the first 30 minute foot stimulation via electrode combination 1-2, but was significantly increased 47.5±2.9% after the second 30 minute stimulation via electrode combination 1-3. After inducing the post-stimulation effect, the foot stimulation applied during CMGs via electrode combinations 1-2 or 1-3 elicited a further increase in bladder capacity (23.26±17.64% and 20.07±18.59% respectively). Conclusions This study shows that the transcutaneous plantar electrical stimulation of somatic afferent nerves in the foot can induce a post-stimulation increase in bladder capacity, suggesting that an intermittent stimulation pattern rather than a continuous stimulation might be effective in clinical applications to treat overactive bladder symptoms. PMID:22099982

  11. Inputs from regularly and irregularly discharging vestibular nerve afferents to secondary neurons in squirrel monkey vestibular nuclei. III. Correlation with vestibulospinal and vestibuloocular output pathways

    NASA Technical Reports Server (NTRS)

    Boyle, R.; Goldberg, J. M.; Highstein, S. M.

    1992-01-01

    1. A previous study measured the relative contributions made by regularly and irregularly discharging afferents to the monosynaptic vestibular nerve (Vi) input of individual secondary neurons located in and around the superior vestibular nucleus of barbiturate-anesthetized squirrel monkeys. Here, the analysis is extended to more caudal regions of the vestibular nuclei, which are a major source of both vestibuloocular and vestibulospinal pathways. As in the previous study, antidromic stimulation techniques are used to classify secondary neurons as oculomotor or spinal projecting. In addition, spinal-projecting neurons are distinguished by their descending pathways, their termination levels in the spinal cord, and their collateral projections to the IIIrd nucleus. 2. Monosynaptic excitatory postsynaptic potentials (EPSPs) were recorded intracellularly from secondary neurons as shocks of increasing strength were applied to Vi. Shocks were normalized in terms of the threshold (T) required to evoke field potentials in the vestibular nuclei. As shown previously, the relative contribution of irregular afferents to the total monosynaptic Vi input of each secondary neuron can be expressed as a %I index, the ratio (x100) of the relative sizes of the EPSPs evoked by shocks of 4 x T and 16 x T. 3. Antidromic stimulation was used to type secondary neurons as 1) medial vestibulospinal tract (MVST) cells projecting to spinal segments C1 or C6; 2) lateral vestibulospinal tract (LVST) cells projecting to C1, C6; or L1; 3) vestibulooculo-collic (VOC) cells projecting both to the IIIrd nucleus and by way of the MVST to C1 or C6; and 4) vestibuloocular (VOR) neurons projecting to the IIIrd nucleus but not to the spinal cord. Most of the neurons were located in the lateral vestibular nucleus (LV), including its dorsal (dLV) and ventral (vLV) divisions, and adjacent parts of the medial (MV) and descending nuclei (DV). Cells receiving quite different proportions of their direct inputs

  12. Scaling factor relating conduction velocity and diameter for myelinated afferent nerve fibres in the cat hind limb.

    PubMed Central

    Boyd, I A; Kalu, K U

    1979-01-01

    1. Compound action potentials were recorded from certain muscle and cutaneous nerves in normal and chronically de-efferentated hind limbs of cats during stimulation of the appropriate dorsal spinal roots, 2. The peaks for groups I, II and III in the compound action potential were correlated with the corresponding peaks in the fibre-diameter histograms of the same de-efferentated nerve after processing it for light microscopy. 3. The scaling factor (ratio of conduction velocity in m/sec to total diameter in micrometer) was not constant for all sizes of fibre nor did it increase progressively with fibre size. Evidence is presented that a logarithmic relation between conduction velocity and fibre diameter is not appropriate. 4. In muscle nerves the scaling factor for fibres fixed by glutaraldehyde perfusion and embedded in Epon was 5.7 for group I afferent fibres and 4.6 for myelinated fibres in both group II and group III. 5. In cutaneous nerves the scaling factor was 5.6 for large fibres (group I or Abeta) and 4.6 for small fibres (group III or Adelta). 6. The scaling factor for group I fibres is the same as was found previously for alpha-efferent fibres, and that for groups II and III is the same as for gamma-efferent fibres (Boyd & Davey, 1968). 7. The possibility that there is a clear discontinuity in scaling factor between fibres in groups I and alpha, and those in other functional groups, is discussed. 8. It is concluded that there must be some structural feature of alpha and group I fibres which differs from that of smaller myelinated fibres. It is likely that a difference in the relative thickness of the myelin sheath is involved and possibly also in the conductances responsible for generating the action potential. Images Plate 1 PMID:458657

  13. The projection of jaw elevator muscle spindle afferents to fifth nerve motoneurones in the cat.

    PubMed Central

    Appenteng, K; O'Donovan, M J; Somjen, G; Stephens, J A; Taylor, A

    1978-01-01

    1. By spike-triggered averaging of intracellular synaptic noise it has been shown in pentobarbitone anaesthetized cats that jaw elevator muscle spindle afferents with their cell bodies in the mid-brain have a relatively weak monosynaptic projection to masseter and temporalis motoneurones. 2. Extending the spike-triggered averaging method to recording extracellular excitatory field potentials it has been shown that virtually all the spindles do project monosynaptically to the motoneurone pool. It is concluded that the general weakness of the projection is due to its restriction to a small proportion of the motoneurones, possibly those concerned most with tonic postural functions. 3. The shape of individual intracellular e.p.s.p.s together with the spatial distribution of extracellular excitatory potential fields provide some evidence for a dentrically weighted distribution of the synapses. 4. Evidence is presented that both primary- and secondary-type spindle afferents project monosynaptically, the secondary effects being some 71% of the strength of the primary ones. PMID:149860

  14. The projection of jaw elevator muscle spindle afferents to fifth nerve motoneurones in the cat.

    PubMed

    Appenteng, K; O'Donovan, M J; Somjen, G; Stephens, J A; Taylor, A

    1978-06-01

    1. By spike-triggered averaging of intracellular synaptic noise it has been shown in pentobarbitone anaesthetized cats that jaw elevator muscle spindle afferents with their cell bodies in the mid-brain have a relatively weak monosynaptic projection to masseter and temporalis motoneurones. 2. Extending the spike-triggered averaging method to recording extracellular excitatory field potentials it has been shown that virtually all the spindles do project monosynaptically to the motoneurone pool. It is concluded that the general weakness of the projection is due to its restriction to a small proportion of the motoneurones, possibly those concerned most with tonic postural functions. 3. The shape of individual intracellular e.p.s.p.s together with the spatial distribution of extracellular excitatory potential fields provide some evidence for a dentrically weighted distribution of the synapses. 4. Evidence is presented that both primary- and secondary-type spindle afferents project monosynaptically, the secondary effects being some 71% of the strength of the primary ones.

  15. Multiple cytosolic calcium buffers in posterior pituitary nerve terminals

    PubMed Central

    McMahon, Shane M.; Chang, Che-Wei

    2016-01-01

    Cytosolic Ca2+ buffers bind to a large fraction of Ca2+ as it enters a cell, shaping Ca2+ signals both spatially and temporally. In this way, cytosolic Ca2+ buffers regulate excitation-secretion coupling and short-term plasticity of release. The posterior pituitary is composed of peptidergic nerve terminals, which release oxytocin and vasopressin in response to Ca2+ entry. Secretion of these hormones exhibits a complex dependence on the frequency and pattern of electrical activity, and the role of cytosolic Ca2+ buffers in controlling pituitary Ca2+ signaling is poorly understood. Here, cytosolic Ca2+ buffers were studied with two-photon imaging in patch-clamped nerve terminals of the rat posterior pituitary. Fluorescence of the Ca2+ indicator fluo-8 revealed stepwise increases in free Ca2+ after a series of brief depolarizing pulses in rapid succession. These Ca2+ increments grew larger as free Ca2+ rose to saturate the cytosolic buffers and reduce the availability of Ca2+ binding sites. These titration data revealed two endogenous buffers. All nerve terminals contained a buffer with a Kd of 1.5–4.7 µM, and approximately half contained an additional higher-affinity buffer with a Kd of 340 nM. Western blots identified calretinin and calbindin D28K in the posterior pituitary, and their in vitro binding properties correspond well with our fluorometric analysis. The high-affinity buffer washed out, but at a rate much slower than expected from diffusion; washout of the low-affinity buffer could not be detected. This work has revealed the functional impact of cytosolic Ca2+ buffers in situ in nerve terminals at a new level of detail. The saturation of these cytosolic buffers will amplify Ca2+ signals and may contribute to use-dependent facilitation of release. A difference in the buffer compositions of oxytocin and vasopressin nerve terminals could contribute to the differences in release plasticity of these two hormones. PMID:26880753

  16. Abeta-afferents activate neurokinin-1 receptor in dorsal horn neurons after nerve injury.

    PubMed

    Zheng, Ji-Hong; Song, Xue-Jun

    2005-05-12

    We provide new evidence demonstrating that peripheral nerve injury produces profound alterations in synaptic input to dorsal horn neurons mediated by non-nociceptive sensory neurons, and activation of neurokinin-1 receptor may be involved in the enhanced synaptic response and thus contribute to the tactile allodynia. Our results show that Abeta-fiber-evoked field potential significantly increased in the first postoperative week and decreased thereafter while maximal mechanical allodynia was exhibited. The neurokinin-1 receptor antagonist L703,606 significantly reduced Abeta-fiber-evoked field potential in nerve-injured but not in sham-operated animals. The non-N-methyl-D-aspartate receptor antagonist CNQX inhibited Abeta-fiber-evoked field potential in both nerve-injured and sham-operated rats, while the N-methyl-D-aspartate receptor antagonist MK-801 did not affect Abeta-fiber-evoked field potential in either CCI or sham-operated animals.

  17. High sensitivity recording of afferent nerve activity using ultra-compliant microchannel electrodes: an acute in vivo validation

    NASA Astrophysics Data System (ADS)

    Minev, Ivan R.; Chew, Daniel J.; Delivopoulos, Evangelos; Fawcett, James W.; Lacour, Stéphanie P.

    2012-04-01

    Neuroprostheses interfaced with transected peripheral nerves are technological routes to control robotic limbs as well as convey sensory feedback to patients suffering from traumatic neural injuries or degenerative diseases. To maximize the wealth of data obtained in recordings, interfacing devices are required to have intrafascicular resolution and provide high signal-to-noise ratio (SNR) recordings. In this paper, we focus on a possible building block of a three-dimensional regenerative implant: a polydimethylsiloxane (PDMS) microchannel electrode capable of highly sensitive recordings in vivo. The PDMS 'micro-cuff' consists of a 3.5 mm long (100 µm × 70 µm cross section) microfluidic channel equipped with five evaporated Ti/Au/Ti electrodes of sub-100 nm thickness. Individual electrodes have average impedance of 640 ± 30 kΩ with a phase angle of -58 ± 1 degrees at 1 kHz and survive demanding mechanical handling such as twisting and bending. In proof-of-principle acute implantation experiments in rats, surgically teased afferent nerve strands from the L5 dorsal root were threaded through the microchannel. Tactile stimulation of the skin was reliably monitored with the three inner electrodes in the device, simultaneously recording signal amplitudes of up to 50 µV under saline immersion. The overall SNR was approximately 4. A small but consistent time lag between the signals arriving at the three electrodes was observed and yields a fibre conduction velocity of 30 m s-1. The fidelity of the recordings was verified by placing the same nerve strand in oil and recording activity with hook electrodes. Our results show that PDMS microchannel electrodes open a promising technological path to 3D regenerative interfaces.

  18. Role for NGF in augmented sympathetic nerve response to activation of mechanically and metabolically sensitive muscle afferents in rats with femoral artery occlusion.

    PubMed

    Lu, Jian; Xing, Jihong; Li, Jianhua

    2012-10-15

    Arterial blood pressure and heart rate responses to static contraction of the hindlimb muscles are greater in rats whose femoral arteries were previously ligated than in control rats. Also, the prior findings demonstrate that nerve growth factor (NGF) is increased in sensory neurons-dorsal root ganglion (DRG) neurons of occluded rats. However, the role for endogenous NGF in engagement of the augmented sympathetic and pressor responses to stimulation of mechanically and/or metabolically sensitive muscle afferent nerves during static contraction after femoral artery ligation has not been specifically determined. In the present study, both afferent nerves and either of them were activated by muscle contraction, passive tendon stretch, and arterial injection of lactic acid into the hindlimb muscles. Data showed that femoral occlusion-augmented blood pressure response to contraction was significantly attenuated by a prior administration of the NGF antibody (NGF-Ab) into the hindlimb muscles. The effects of NGF neutralization were not seen when the sympathetic nerve and pressor responses were evoked by stimulation of mechanically sensitive muscle afferent nerves with tendon stretch in occluded rats. In addition, chemically sensitive muscle afferent nerves were stimulated by lactic acid injected into arterial blood supply of the hindlimb muscles after the prior NGF-Ab, demonstrating that the reflex muscle responses to lactic acid were significantly attenuated. The results of this study further showed that NGF-Ab attenuated an increase in acid-sensing ion channel subtype 3 (ASIC3) of DRG in occluded rats. Moreover, immunohistochemistry was employed to examine the number of C-fiber and A-fiber DRG neurons. The data showed that distribution of DRG neurons with different thin fiber phenotypes was not notably altered when NGF was infused into the hindlimb muscles. However, NGF increased expression of ASIC3 in DRG neurons with C-fiber but not A-fiber. Overall, these data

  19. Reticulospinal actions on primary afferent depolarization of cutaneous and muscle afferents in the isolated frog neuraxis.

    PubMed

    González, H; Jiménez, I; Rudomin, P

    1993-01-01

    The effects of the brainstem reticular formation on the intraspinal excitability of low threshold cutaneous and muscle afferents were studied in the frog neuraxis isolated together with the right hindlimb nerves. Stimulation of low threshold fibers (less than two times threshold) in cutaneous nerves produced short latency, negative field potentials in the ipsilateral dorsal neuropil (200-400 microns depth) that reversed to positivity at deeper regions (500-700 microns). Stimulation of low threshold fibers (less than two times threshold) in muscle nerves produced, instead, negative response that acquired their maximum amplitude in the ventral neuropil (700-900 microns depth). These electrophysiological findings suggest, in agreement with observations in the cat, that low threshold cutaneous and muscle afferents end at different sites in the spinal cord. Intraspinal microstimulation applied within the dorsal neuropil produced antidromic responses in low threshold cutaneous afferents that were increased in size following stimulation of the dorsal or ventral roots, as well as of the brainstem reticular formation. This increase in excitability is interpreted as being due to primary afferent depolarization (PAD) of the intraspinal terminals of cutaneous fibers. Antidromic responses recorded in muscle nerves following intraspinal stimulation within the ventral neuropil were also increased following conditioning stimulation of adjacent dorsal or ventral roots. However, stimulation of the bulbar reticular formation produced practically no changes in the antidromic responses, but was able to inhibit the PAD of low threshold muscle afferents elicited by stimulation of the dorsal or ventral roots. It is suggested that the PAD of low threshold cutaneous and muscle afferents is mediated by independent sets of interneurons. Reticulospinal fibers would have excitatory connections with the interneurons mediating the PAD of cutaneous fibers and inhibitory connections with the

  20. Patterns of primary afferent depolarization of segmental and ascending intraspinal collaterals of single joint afferents in the cat.

    PubMed

    Rudomin, P; Lomelí, J

    2007-01-01

    We have examined in the anesthetized cat the threshold changes produced by sensory and supraspinal stimuli on intraspinal collaterals of single afferents from the posterior articular nerve (PAN). Forty-eight fibers were tested in the L3 segment, in or close to Clarke's column, and 70 fibers in the L6-L7 segments within the intermediate zone. Of these, 15 pairs of L3 and L6-L7 collaterals were from the same afferent. Antidromically activated fibers had conduction velocities between 23 and 74 m/s and peripheral thresholds between 1.1 and 4.7 times the threshold of the most excitable fibers (xT), most of them below 3 xT. PAN afferents were strongly depolarized by stimulation of muscle afferents and by cutaneous afferents, as well as by stimulation of the bulbar reticular formation and the midline raphe nuclei. Stimulation of muscle nerves (posterior biceps and semitendinosus, quadriceps) produced a larger PAD (primary afferent depolarization) in the L6-L7 than in the L3 terminations. Group II were more effective than group I muscle afferents. As with group I muscle afferents, the PAD elicited in PAN afferents by stimulation of muscle nerves could be inhibited by conditioning stimulation of cutaneous afferents. Stimulation of the cutaneous sural and superficial peroneal nerves increased the threshold of few terminations (i.e., produced primary afferent hyperpolarization, PAH) and reduced the threshold of many others, particularly of those tested in the L6-L7 segments. Yet, there was a substantial number of terminals where these conditioning stimuli had minor or no effects. Autogenetic stimulation of the PAN with trains of pulses increased the intraspinal threshold in 46% and reduced the threshold in 26% of fibers tested in the L6-L7 segments (no tests were made with trains of pulses on fibers ending in L3). These observations indicate that PAN afferents have a rather small autogenetic PAD, particularly if this is compared with the effects of heterogenetic stimulation

  1. Sympathetic preganglionic efferent and afferent neurons mediated by the greater splanchnic nerve in rabbit

    NASA Technical Reports Server (NTRS)

    Torigoe, Yasuhiro; Cernucan, Roxana D.; Nishimoto, Jo Ann S.; Blanks, Robert H. I.

    1985-01-01

    As a part of the study of the vestibular-autonomic pathways involved in motion sickness, the location and the morphology of preganglionic sympathetic neurons (PSNs) projecting via the greater splanchnic nerve were examined. Retrograde labeling of neurons was obtained by application of horseradish peroxidase to the cut end of the greater splanchnic nerve. Labeled PSNs were found, ipsilaterally, within the T1 to T11 spinal cord segments, with the highest density of neurons in T6. Most PSNs were located within the intermediolateral column, but a significant portion also occurred within the lateral funiculus, the intercalated region, and the central autonomic area; the proportion of labeling between the four regions depended on the spinal cord segment.

  2. Epinephrine- and norepinephrine-evoked potential changes of frog primary afferent terminals: pharmacological characterization of alpha and beta components.

    PubMed

    Wohlberg, C J; Hackman, J C; Ryan, G P; Davidoff, R A

    1985-02-18

    The effects of superfused epinephrine (E) and norepinephrine (NE) on the membrane potential of primary afferent fibers of the isolated frog spinal cord were studied by sucrose gap recordings from the dorsal root. In all preparations both E and NE, applied in concentrations ranging from 0.1 microM to 1.0 mM, produced a hyperpolarization of afferent terminals. In many instances this was followed by a slow depolarization and, in a small number of cords, a small depolarization preceded the increase in membrane potential. E- and NE-induced hyperpolarizations were blocked by the selective alpha 2-antagonists yohimbine and piperoxan, but not by the selective alpha 1-antagonists prazosin and corynanthine or by the beta-blockers propranolol and sotalol. The alpha 2-agonists clonidine, alpha-methylnorepinephrine and guanabenz also hyperpolarized terminals, causing a change in potential that was reduced by yohimbine and piperoxan. Taken together, these results suggest that alpha 2-receptors mediate the hyperpolarizing effects of E and NE. The beta-agonist isoproterenol evoked a slow depolarization similar to that produced by E and NE. The isoproterenol-depolarization was antagonized by propranolol. Sometimes, application of E and NE after superfusion with yohimbine produced only a depolarization of the dorsal root and this depolarization was sensitive to propranolol. It would appear therefore that the late depolarization seen after the application of E and NE is produced by activation of beta-receptors. In contrast, the alpha 1-agonist phenylephrine elicited a short latency, short duration depolarization similar to those seen preceding approximately 10% of the E- and NE-hyperpolarizations. Such short-latency depolarizations were blocked by prazosin and corynanthine. The major component of the response to both E and NE is indirectly mediated through a synaptic process: application of Mn2+, Mg2+, procaine or tetrodotoxin in concentrations sufficient to block synaptic

  3. Primary afferent response to signals in the intestinal lumen.

    PubMed

    Raybould, H

    2001-02-01

    The first recordings of vagal afferent nerve fibre activity were performed by Paintal in the early 1950s. In these experiments, he showed that phenyldiguanide (later recognized as a 5-HT3 receptor agonist) stimulated the firing of C-fibres innervating the intestine. In the following years, ample physiological and psychological studies have demonstrated the importance of afferent information arising from the gut in the regulation of gastrointestinal function and behaviour. Many stimuli are capable of eliciting these functional effects and of stimulating afferent fibre discharge, including mechanical, chemical, nutrient- and immune-derived stimuli. Studies in the last 10 years have begun to focus on the precise sensory transduction mechanisms by which these visceral primary afferent nerve terminals are activated and, like the contribution by Zhu et al. in this issue of The Journal of Physiology, are revealing some novel and exciting findings.

  4. Sensations evoked by microstimulation of single mechanoreceptive afferents innervating the human face and mouth.

    PubMed

    Trulsson, M; Essick, G K

    2010-04-01

    Intraneural microneurography and microstimulation were performed on single afferent axons in the inferior alveolar and lingual nerves innervating the face, teeth, labial, or oral mucosa. Using natural mechanical stimuli, 35 single mechanoreceptive afferents were characterized with respect to unit type [fast adapting type I (FA I), FA hair, slowly adapting type I and II (SA I and SA II), periodontal, and deep tongue units] as well as size and shape of the receptive field. All afferents were subsequently microstimulated with pulse trains at 30 Hz lasting 1.0 s. Afferents recordings whose were stable thereafter were also tested with single pulses and pulse trains at 5 and 60 Hz. The results revealed that electrical stimulation of single FA I, FA hair, and SA I afferents from the orofacial region can evoke a percept that is spatially matched to the afferent's receptive field and consistent with the afferent's response properties as observed on natural mechanical stimulation. Stimulation of FA afferents typically evoked sensations that were vibratory in nature; whereas those of SA I afferents were felt as constant pressure. These afferents terminate superficially in the orofacial tissues and seem to have a particularly powerful access to perceptual levels. In contrast, microstimulation of single periodontal, SA II, and deep tongue afferents failed to evoke a sensation that matched the receptive field of the afferent. These afferents terminate more deeply in the tissues, are often active in the absence of external stimulation, and probably access perceptual levels only when multiple afferents are stimulated. It is suggested that the spontaneously active afferents that monitor tension in collagen fibers (SA II and periodontal afferents) may have the role to register the mechanical state of the soft tissues, which has been hypothesized to help maintain the body's representation in the central somatosensory system.

  5. Palmitoylethanolamide inhibits glutamate release in rat cerebrocortical nerve terminals.

    PubMed

    Lin, Tzu-Yu; Lu, Cheng-Wei; Wu, Chia-Chan; Huang, Shu-Kuei; Wang, Su-Jane

    2015-03-11

    The effect of palmitoylethanolamide (PEA), an endogenous fatty acid amide displaying neuroprotective actions, on glutamate release from rat cerebrocortical nerve terminals (synaptosomes) was investigated. PEA inhibited the Ca²⁺-dependent release of glutamate, which was triggered by exposing synaptosomes to the potassium channel blocker 4-aminopyridine. This release inhibition was concentration dependent, associated with a reduction in cytosolic Ca²⁺ concentration, and not due to a change in synaptosomal membrane potential. The glutamate release-inhibiting effect of PEA was prevented by the Ca(v)2.1 (P/Q-type) channel blocker ω-agatoxin IVA or the protein kinase A inhibitor H89, not affected by the intracellular Ca²⁺ release inhibitors dantrolene and CGP37157, and partially antagonized by the cannabinoid CB1 receptor antagonist AM281. Based on these results, we suggest that PEA exerts its presynaptic inhibition, likely through a reduction in the Ca²⁺ influx mediated by Ca(v)2.1 (P/Q-type) channels, thereby inhibiting the release of glutamate from rat cortical nerve terminals. This release inhibition might be linked to the activation of presynaptic cannabinoid CB1 receptors and the suppression of the protein kinase A pathway.

  6. Dietary sodium modulates the interaction between efferent and afferent renal nerve activity by altering activation of α2-adrenoceptors on renal sensory nerves.

    PubMed

    Kopp, Ulla C; Cicha, Michael Z; Smith, Lori A; Ruohonen, Saku; Scheinin, Mika; Fritz, Nicolas; Hökfelt, Tomas

    2011-02-01

    Activation of efferent renal sympathetic nerve activity (ERSNA) increases afferent renal nerve activity (ARNA), which then reflexively decreases ERSNA via activation of the renorenal reflexes to maintain low ERSNA. The ERSNA-ARNA interaction is mediated by norepinephrine (NE) that increases and decreases ARNA by activation of renal α(1)-and α(2)-adrenoceptors (AR), respectively. The ERSNA-induced increases in ARNA are suppressed during a low-sodium (2,470 ± 770% s) and enhanced during a high-sodium diet (5,670 ± 1,260% s). We examined the role of α(2)-AR in modulating the responsiveness of renal sensory nerves during low- and high-sodium diets. Immunohistochemical analysis suggested the presence of α(2A)-AR and α(2C)-AR subtypes on renal sensory nerves. During the low-sodium diet, renal pelvic administration of the α(2)-AR antagonist rauwolscine or the AT1 receptor antagonist losartan alone failed to alter the ARNA responses to reflex increases in ERSNA. Likewise, renal pelvic release of substance P produced by 250 pM NE (from 8.0 ± 1.3 to 8.5 ± 1.6 pg/min) was not affected by rauwolscine or losartan alone. However, rauwolscine+losartan enhanced the ARNA responses to reflex increases in ERSNA (4,680 ± 1,240%·s), and renal pelvic release of substance P by 250 pM NE, from 8.3 ± 0.6 to 14.2 ± 0.8 pg/min. During a high-sodium diet, rauwolscine had no effect on the ARNA response to reflex increases in ERSNA or renal pelvic release of substance P produced by NE. Losartan was not examined because of low endogenous ANG II levels in renal pelvic tissue during a high-sodium diet. Increased activation of α(2)-AR contributes to the reduced interaction between ERSNA and ARNA during low-sodium intake, whereas no/minimal activation of α(2)-AR contributes to the enhanced ERSNA-ARNA interaction under conditions of high sodium intake.

  7. Dietary sodium modulates the interaction between efferent and afferent renal nerve activity by altering activation of α2-adrenoceptors on renal sensory nerves

    PubMed Central

    Cicha, Michael Z.; Smith, Lori A.; Ruohonen, Saku; Scheinin, Mika; Fritz, Nicolas; Hökfelt, Tomas

    2011-01-01

    Activation of efferent renal sympathetic nerve activity (ERSNA) increases afferent renal nerve activity (ARNA), which then reflexively decreases ERSNA via activation of the renorenal reflexes to maintain low ERSNA. The ERSNA-ARNA interaction is mediated by norepinephrine (NE) that increases and decreases ARNA by activation of renal α1-and α2-adrenoceptors (AR), respectively. The ERSNA-induced increases in ARNA are suppressed during a low-sodium (2,470 ± 770% s) and enhanced during a high-sodium diet (5,670 ± 1,260% s). We examined the role of α2-AR in modulating the responsiveness of renal sensory nerves during low- and high-sodium diets. Immunohistochemical analysis suggested the presence of α2A-AR and α2C-AR subtypes on renal sensory nerves. During the low-sodium diet, renal pelvic administration of the α2-AR antagonist rauwolscine or the AT1 receptor antagonist losartan alone failed to alter the ARNA responses to reflex increases in ERSNA. Likewise, renal pelvic release of substance P produced by 250 pM NE (from 8.0 ± 1.3 to 8.5 ± 1.6 pg/min) was not affected by rauwolscine or losartan alone. However, rauwolscine+losartan enhanced the ARNA responses to reflex increases in ERSNA (4,680 ± 1,240%·s), and renal pelvic release of substance P by 250 pM NE, from 8.3 ± 0.6 to 14.2 ± 0.8 pg/min. During a high-sodium diet, rauwolscine had no effect on the ARNA response to reflex increases in ERSNA or renal pelvic release of substance P produced by NE. Losartan was not examined because of low endogenous ANG II levels in renal pelvic tissue during a high-sodium diet. Increased activation of α2-AR contributes to the reduced interaction between ERSNA and ARNA during low-sodium intake, whereas no/minimal activation of α2-AR contributes to the enhanced ERSNA-ARNA interaction under conditions of high sodium intake. PMID:21106912

  8. Up-regulation of brain-derived neurotrophic factor is regulated by extracellular signal-regulated protein kinase 5 and by nerve growth factor retrograde signaling in colonic afferent neurons in colitis

    PubMed Central

    Yu, Sharon J; Grider, John R; Gulick, Melisa A; Xia, Chun-mei; Shen, Shanwei; Qiao, Li-Ya

    2012-01-01

    Brain-derived neurotrophic factor (BDNF) plays an essential role in sensory neuronal activation in response to visceral inflammation. Here we report that BDNF up-regulation in the primary afferent neurons in the dorsal root ganglia (DRG) in a rat model of colitis is mediated by the activation of endogenous extracellular signal-regulated protein kinases (ERK) 5 and by nerve growth factor (NGF) retrograde signaling. At 7 days of colitis, the expression level of BDNF is increased in conventional neuronal tracing dye Fast Blue labeled primary afferent neurons project to the distal colon. In these neurons, the phosphorylation (activation) level of ERK5 is also increased. In contrast, the level of phospho-ERK1/2 is not changed in the DRG during colitis. Prevention of the ERK5 activation in vivo with an intrathecal application of the MEK inhibitor PD98059 significantly attenuates the colitis-induced increases in BDNF expression in the DRG. Further studies show that BDNF up-regulation in the DRG is triggered by NGF retrograde signaling which also involves activation of the MEK/ERK pathways. Application of exogenous NGF exclusively to the compartment containing DRG nerve terminals in an ex vivo ganglia-nerve preparation has markedly increased the BDNF expression level in the DRG neuronal cell body that is placed in a different compartment; this BDNF elevation is attenuated by U0126, PD98059 and a specific ERK5 inhibitor BIX02188. These results demonstrate the mechanisms and pathways by which BDNF expression is elevated in primary sensory neurons following visceral inflammation that is mediated by increased activity of ERK5 and is likely to be triggered by the elevated NGF level in the inflamed viscera. PMID:22921460

  9. Involvement of peripheral ionotropic glutamate receptors in activation of cutaneous branches of spinal dorsal rami following antidromic electrical stimulation of adjacent afferent nerves in rats.

    PubMed

    Cao, Dong-Yuan; You, Hao-Jun; Zhao, Yan; Guo, Yuan; Wang, Hui-Sheng; Arendt-Nielsen, Lars; Wang, Hui-Ling; Zhang, Qi

    2007-04-02

    The aim of the present study was to investigate the role of peripheral ionotropic glutamate receptors in the process of signal transmission between adjacent different peripheral sensory nerves. The T9 and T10 cutaneous branches of spinal dorsal rami were dissociated and cut proximally in pentobarbital anesthetized rats. Eighty-seven single afferents from T10 nerve filaments were recorded and characterized by assessing their spontaneous activities. Following 30 s antidromic electrical stimulation (intensity: 1 mA; duration: 0.5 ms; frequency: 20 Hz) of T9 cutaneous branches, the spontaneous activities of Abeta, Adelta and C fibers of T10 nerve were significantly enhanced from 2.00+/-0.34, 2.42+/-0.33, and 2.19+/-0.32 impulses/min to 4.31+/-0.58, 5.22+/-0.55, and 5.27+/-0.69 impulses/min, respectively (n=29 for each type, P<0.05). These enhanced spontaneous discharges of T10 nerve were significantly blocked by local treatment of its receptive field with either N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 or non-NMDA receptor antagonist DNQX (0.1 mM, 10 microl for each drug) (P<0.05). These results suggest that peripheral ionotropic glutamate receptors are involved in the activation of peripheral nerves following the antidromic stimulation of adjacent afferents from different spinal segments. We further provide the direct evidence that neurotransmitters released from adjacent peripheral nerves may also contribute to the occurrence of allodynia as well as secondary hyperalgesia during the pathological nociception.

  10. Local cutaneous nerve terminal and mast cell responses to manual acupuncture in acupoint LI4 area of the rats.

    PubMed

    Wu, Mei-Ling; Xu, Dong-Sheng; Bai, Wan-Zhu; Cui, Jing-Jing; Shu, Hong-Ming; He, Wei; Wang, Xiao-Yu; Shi, Hong; Su, Yang-Shuai; Hu, Ling; Zhu, Bing; Jing, Xiang-Hong

    2015-10-01

    Previous studies have shown that the effects of manual acupuncture (MA) are contributed by collagen fibers and mast cells in local acupoints, at which acupuncture stimulation causes various afferent fiber groups to be excited. However what happens in local nerve fibers and mast cells after MA remains unclear. The aim of this study was to examine the response of cutaneous nerve fibers and mast cells to MA stimulation in acupoint Hegu (LI4). The contralateral LI4 of the same rat was used as a non-stimulated control. Immnohistochemistry analysis were carried out to observe the expression of histamine (HA), serotonin (5-HT) and nociceptive neuropeptides, calcitonin gene-related peptide (CGRP) and substance P (SP), in the LI4 area. Mast cells were labeled with anti-mast cell tryptase antibody and simultaneously with HA or 5-HT primary antibodies to observe their co-expression. Our results showed that SP and CGRP were expressed more highly on the cutaneous nerve fibers of LI4 after MA stimulation than that of the control. Mast cells aggregated in close proximity to the blood vessels in intra-epidermis and dermis and some of them with degranulation in the lower dermis and subcutaneous tissue of LI4. Both mast cells and their granules appeared with HA (+) and 5-HT (+) expression at stimulated L14 sites, while a few intact mast cells with a little expression of 5-HT and HA were distributed in areas of non-stimulated L14. The results indicated that local cutaneous nerve terminals and mast cells responded to MA with higher expression of SP and CGRP in nerve fibers, as well as with aggregation and degranulation of mast cells with HA and 5-HT granules at acupoint LI4. These neuroactive substances may convey signals to certain pathways that contribute to the effects of acupuncture.

  11. Unmyelinated visceral afferents exhibit frequency dependent action potential broadening while myelinated visceral afferents do not.

    PubMed

    Li, Bai-Yan; Feng, Bin; Tsu, Hwa Y; Schild, John H

    2007-06-21

    Sensory information arising from visceral organ systems is encoded into action potential trains that propagate along afferent fibers to target nuclei in the central nervous system. These information streams range from tight patterns of action potentials that are well synchronized with the sensory transduction event to irregular, patternless discharge with no clear correlation to the sensory input. In general terms these afferent pathways can be divided into unmyelinated and myelinated fiber types. Our laboratory has a long standing interest in the functional differences between these two types of afferents in terms of the preprocessing of sensory information into action potential trains (synchrony, frequency, duration, etc.), the reflexogenic consequences of this sensory input to the central nervous system and the ionic channels that give rise to the electrophysiological properties of these unique cell types. The aim of this study was to determine whether there were any functional differences in the somatic action potential characteristics of unmyelinated and myelinated vagal afferents in response to different rates of sensory nerve stimulation. Our results showed that activity and frequency-dependent widening of the somatic action potential was quite prominent in unmyelinated but not myelinated vagal afferents. Spike broadening often leads to increased influx of Ca(2+) ions that has been associated with a diverse range of modulatory mechanisms both at the cell body and central synaptic terminations (e.g. increased neurotransmitter release.) We conclude that our observations are indicative of fundamentally different mechanisms for neural integration of sensory information arising from unmyelinated and myelinated vagal afferents.

  12. How is the cytoplasmic calcium concentration controlled in nerve terminals?

    PubMed

    Blaustein, M P; McGraw, C F; Somlyo, A V; Schweitzer, E S

    1980-09-01

    1. The ability of intraterminal organelles to sequester calcium and buffer the cytoplasmic free Ca2+ concentration ([Ca2+]i) has been investigated in isolated mammalian presynaptic nerve terminals (synaptosomes). A combination of biochemical and morphological methods has been used. 2. When the plasmalemma of synaptosomes is disrupted by osmotic shock or saponin, Ca from the medium can be sequestered by two types of intraterminal organelles in the presence of ATP. 2. Typical mitochondrial poisons (e.g., oligomycin, azide and 2,4-dinitrophenol) block the Ca uptake into one type of organelle (mitochondria); the second type of organelle, which has a higher affinity for Ca (half-saturation congruent to 0.35 microM Ca2+) is spared by the mitochondrial poisons. 4. When the "leaky" synaptosomes are incubated in media containing oxalate, and then fixed and prepared for electron microscopy, electron-dense deposits are observed in the intraterminal mitochondria and smooth endoplasmic reticulum (SER). Mitochondrial poisons block the formation of the deposits in the mitochondria, but spare the SER. 5. X-ray microprobe analysis demonstrates that these deposits contain Ca. 6. Experiments with the Ca-sensitive metallochromic indicator, arsenazo III, demonstrate that the intraterminal organelles in the "leaky" synaptosomes can buffer Ca2+ in the medium to below 5 X 10(-7) M. With small (physiological) Ca loads, the Ca2+ is effectively buffered (to < 5 X 10(-7) M) even in the presence of mitochondrial poisons. 7. The data indicate that the SER in presynaptic terminals may play an important role in helping to buffer the Ca that normally enters during neuronal activity.

  13. Primary afferent depolarization and inhibory interactions in spinal cord of the stingray, Dasyatis sabina.

    PubMed

    Rudomín, P; Leonard, R B; Willis, W D

    1978-01-01

    1. Excitability changes in primary afferents and inhibitory interactions in evoked spinal cord activity were investigated in unanesthetized stingrays (Dasyatis subina) with high cervical spinal transections. 2. Primary afferent excitability increases following a conditioning stimulus to an adjacent segmental nerve were demonstrated with the Wall (31) technique. 3. Stimulation of A-alpha,beta and A-delta afferent fibers produced excitability increases in both A-alpha,beta and delta-fibers of the adjacent segment. 4. The excitability increase had a latency of about 10 ms, it peaked around 25 ms, and the change lasted more than 100 ms. 5. The central afferent volley in A-alpha,beta fibers and the N1- and late negative waves due to postsynaptic activity of dorsal horn interneurons were reduced by conditioning volleys in adjacent afferent nerves. The time course of the inhibition paralleled that of the excitability increases in afferent terminal arborizations, suggesting that the depression of postsynaptic activity is, at least in part, due to presynaptic inhibition. 6. Reduction of evoked discharges and excitatory postsynaptic potentials was observed in recordings from interneurons with a time course similar to that of the primary afferent depolarization (PAD). 7. Conditioning volleys in afferents of adjacent peripheral nerves produced facilitation or inhibition of segmental reflexes.

  14. The effects of inorganic particles of lunar soil simulant on brain nerve terminals

    NASA Astrophysics Data System (ADS)

    Borisova, Tatiana; Krisanova, Natalia; Sivko, Roman; Borisov, Arseniy

    2012-07-01

    The health effects from lunar soil exposure are almost completely unknown, whereas the observations suggest that it can be deleterious to human physiology. It is important that the components of lunar soil may be internalized with lipid fractions of the lung epithelium, which in turn may help ions to overcome the blood-brain barrier. The study focused on the effects of JSC-1a Lunar Soil Simulant (LSS) (Orbital Technologies Corporation, Madison, USA) on rat brain nerve terminals (synaptosomes). We revealed that brain nerve terminals were not indifferent to the exposure to LSS inorganic particles. Using Zetasizer Nanosystem (Malvern Instruments) with helium-neon laser for dynamic light scattering (DLS), the synaptosomal size before and after the addition of LSS was measured and the binding of LSS inorganic particles to nerve terminals was demonstrated. Using potential-sensitive fluorescent dye rhodamine 6G, we showed that LSS inorganic particles did not influence the potential of the plasma membrane of nerve terminals. Acidification of synaptic vesicles of nerve terminals did not change in the presence of LSS inorganic particles that was revealed with pH-sensitive fluorescent dye acridine orange. However, LSS inorganic particles influenced accumulation of glutamate, the main excitatory neurotransmitter in the CNS, by nerve terminals. Thus, we report that inorganic particles of LSS influence accumulation of glutamate in brain nerve terminals and this fact may have harmful consequences to human physiology, in particular glutamate homeostasis in the mammalian CNS.

  15. Structure/Function assessment of synapses at motor nerve terminals

    PubMed Central

    Johnstone, A. F. M.; Viele, K.; Cooper, R. L.

    2010-01-01

    The release of transmitter at neuromuscular junctions (NMJ) of the opener muscle in crayfish is quantal in nature. This NMJ offers the advantage of being able to record quantal events at specific visually identified release sites, thus allowing measurement of the physiological parameters of vesicle release and its response to be directly correlated with synaptic structure. These experiments take advantage of areas between the varicosities on the nerve terminal that we define as “stems”. Stems were chosen as the region to study because of their low synaptic output due to fewer synaptic sites. Through 3-D reconstruction from hundreds of serial sections, obtained by transmission electron microscopy (TEM), at a site in which focal macropatch recordings were obtained, the number of synapses and AZs are revealed. Thus, physiological profiles with various stimulation conditions can be assessed in regards to direct synaptic structure. Here we used the properties of the quantal shape to determine if distinct subsets of quantal signatures existed and if differences in the distributions are present depending on the frequency of stimulation. Such a quantal signature could come about by parameters of area, rise time, peak amplitude, latency and tau decay. In this study, it is shown that even at defined sites on the stem, with few active zones, synaptic transmission is still complex and the quantal responses appear to be variable even for a given synapse over time. In this study we could not identify a quantal signature for the conditions utilized. PMID:20730805

  16. Specific and potassium components in the depolarization of the la afferents in the spinal cord of the cat.

    PubMed

    Jiménez, I; Rudomin, P; Solodkin, M; Vyklicky, L

    1983-08-01

    In the cat spinal cord, primary afferent depolarization (PAD) of group Ia fibers of extensor muscles is produced by high-frequency stimulation (100 Hz) of group I muscle flexor afferents without significant increases in extracellular potassium. On the other hand, the PAD produced by stimulation of mixed and pure cutaneous nerves correlates well with increases in potassium ions. We conclude that the PAD produced by group I muscle afferents results from the activation of specific pathways making axo-axonic synapses with the Ia fiber terminals. The PAD of Ia fibers resulting from activation of cutaneous nerves involves instead unspecific accumulation of potassium ions.

  17. Differential central projections of vestibular afferents in pigeons

    NASA Technical Reports Server (NTRS)

    Dickman, J. D.; Fang, Q.

    1996-01-01

    The question of whether a differential distribution of vestibular afferent information to central nuclear neurons is present in pigeons was studied using neural tracer compounds. Discrete tracing of afferent fibers innervating the individual semicircular canal and otolith organs was produced by sectioning individual branches of the vestibular nerve that innervate the different receptor organs and applying crystals of horseradish peroxidase, or a horseradish peroxidase/cholera toxin mixture, or a biocytin compound for neuronal uptake and transport. Afferent fibers and their terminal distributions within the brainstem and cerebellum were visualized subsequently. Discrete areas in the pigeon central nervous system that receive primary vestibular input include the superior, dorsal lateral, ventral lateral, medial, descending, and tangential vestibular nuclei; the A and B groups; the intermediate, medial, and lateral cerebellar nuclei; and the nodulus, the uvula, and the paraflocculus. Generally, the vertical canal afferents projected heavily to medial regions in the superior and descending vestibular nuclei as well as the A group. Vertical canal projections to the medial and lateral vestibular nuclei were observed but were less prominent. Horizontal canal projections to the superior and descending vestibular nuclei were much more centrally located than those of the vertical canals. A more substantial projection to the medial and lateral vestibular nuclei was seen with horizontal canal afferents compared to vertical canal fibers. Afferents innervating the utricle and saccule terminated generally in the lateral regions of all vestibular nuclei in areas that were separate from the projections of the semicircular canals. In addition, utricular fibers projected to regions in the vestibular nuclei that overlapped with the horizontal semicircular canal terminal fields, whereas saccular afferents projected to regions that received vertical canal fiber terminations. Lagenar

  18. Effects of brevetoxin-B on motor nerve terminals of mouse skeletal muscle.

    PubMed Central

    Tsai, M. C.; Chen, M. L.

    1991-01-01

    1. The effects of brevetoxin-B, a red tide toxin, on motor nerve terminal activity were assessed on mouse triangularis sterni nerve-muscle preparations. The perineural waveforms were recorded with extracellular electrodes placed in the perineural sheaths of motor nerves. 2. At 0.11 microM, brevetoxin-B increased the components of waveforms associated with sodium and potassium currents while it decreased the calcium activated potassium current and the slow calcium current of the nerve terminal. The fast calcium current and slow potassium current were not affected. 3. At 1.11 microM, brevetoxin-B decreased all of the components of waveforms associated with sodium, potassium and calcium currents. 4. It is concluded that brevetoxin-B affects sodium, potassium as well as calcium currents in the nerve terminal. The effects may contribute to its pharmacological actions on synaptic transmission. PMID:1652340

  19. Primary afferent depolarization and flexion reflexes produced by radiant heat stimulation of the skin.

    PubMed

    Burke, R E; Rudomin, P; Vyklický, L; Zajac, F E

    1971-02-01

    1. The reflex effects of pulses of intense radiant heat applied to the skin of the central plantar pad have been studied in unanaesthetized (decerebrate) spinal cats.2. Pad heat pulses produced flexion of the ipsilateral hind limb and increased ipsilateral flexor monosynaptic reflexes, due to post-synaptic excitation of flexor alpha motoneurones. These effects were accompanied by reduction of extensor monosynaptic reflexes and post-synaptic inhibition of extensor motoneurones.3. Ipsilateral (and contralateral) pad heat pulses consistently evoked negative dorsal root potentials (DRPs) as well as increased excitability of both cutaneous and group Ib muscle afferent terminals. The excitability of group Ia afferents was sometimes also increased during pad heat pulses, but to a lesser extent.4. Pad heat pulses produced negative DRPs in preparations in which positive DRP components could be demonstrated following electrical stimulation of both skin and muscle nerves.5. The motor and primary afferent effects of heat pulses always accompanied one another, beginning after the pad surface temperature had reached rather high levels (usually 48-55 degrees C).6. Negative DRPs increased excitability of cutaneous and group Ib afferents, and motoneurone activation produced by pad heat pulses was essentially unmodified when conduction in large myelinated afferents from the central plantar pad was blocked by cooling the posterior tibial nerve trunk.7. It is concluded that adequate noxious activation of cutaneous afferents of small diameter produces primary afferent depolarization in a variety of large diameter afferent fibres, as well as post-synaptic effects in alpha motoneurones.

  20. Primary afferent depolarization and flexion reflexes produced by radiant heat stimulation of the skin

    PubMed Central

    Burke, R. E.; Rudomin, P.; Vyklický, L.; Zajac, F. E.

    1971-01-01

    1. The reflex effects of pulses of intense radiant heat applied to the skin of the central plantar pad have been studied in unanaesthetized (decerebrate) spinal cats. 2. Pad heat pulses produced flexion of the ipsilateral hind limb and increased ipsilateral flexor monosynaptic reflexes, due to post-synaptic excitation of flexor alpha motoneurones. These effects were accompanied by reduction of extensor monosynaptic reflexes and post-synaptic inhibition of extensor motoneurones. 3. Ipsilateral (and contralateral) pad heat pulses consistently evoked negative dorsal root potentials (DRPs) as well as increased excitability of both cutaneous and group Ib muscle afferent terminals. The excitability of group Ia afferents was sometimes also increased during pad heat pulses, but to a lesser extent. 4. Pad heat pulses produced negative DRPs in preparations in which positive DRP components could be demonstrated following electrical stimulation of both skin and muscle nerves. 5. The motor and primary afferent effects of heat pulses always accompanied one another, beginning after the pad surface temperature had reached rather high levels (usually 48-55° C). 6. Negative DRPs increased excitability of cutaneous and group Ib afferents, and motoneurone activation produced by pad heat pulses was essentially unmodified when conduction in large myelinated afferents from the central plantar pad was blocked by cooling the posterior tibial nerve trunk. 7. It is concluded that adequate noxious activation of cutaneous afferents of small diameter produces primary afferent depolarization in a variety of large diameter afferent fibres, as well as post-synaptic effects in alpha motoneurones. PMID:5575337

  1. The organization of primary afferent depolarization in the isolated spinal cord of the frog

    PubMed Central

    Carpenter, D. O.; Rudomin, P.

    1973-01-01

    1. The organization of primary afferent depolarization (PAD) produced by excitation of peripheral sensory and motor nerves was studied in the frog cord isolated with hind limb nerves. 2. Dorsal root potentials from sensory fibres (DR-DRPs) were evoked on stimulation of most sensory nerves, but were largest from cutaneous, joint and flexor muscle afferents. With single shock stimulation the largest cutaneous and joint afferent fibres gave DR-DRPs, but potentials from muscle nerves resulted from activation of sensory fibres with thresholds to electrical stimulation higher than 1·2-1·5 times the threshold of the most excitable fibres in the nerve. This suggests that PAD from muscle afferents is probably due to excitation of extrafusal receptors. 3. Dorsal root potentials produced by antidromic activation of motor fibres (VR-DRPs) were larger from extensor muscles and smaller or absent from flexor muscles. The VR-DRPs were produced by activation of the lowest threshold motor fibres. 4. Three types of interactions were found between test and conditioning DRPs from the same or different nerves. With maximal responses occlusion was usually pronounced. At submaximal levels linear summation occurred. Near threshold the conditioning stimulus frequently resulted in a large facilitation of the test DRP. All three types of interactions were found with two DR-DRPs, two VR-DRPs or one DR-DRP and one VR-DRP. 5. The excitability of sensory nerve terminals from most peripheral nerves was increased during the DR-DRP. The magnitude of the excitability increase varied roughly with the magnitude of the DR-DRP evoked by the conditioning stimulus. 6. There was a marked excitability increase of cutaneous and extensor muscle afferent terminals during the VR-DRP. Flexor muscle afferent terminals often showed no excitability changes to ventral root stimulation. In those experiments where afferent terminals from flexor muscles did show an excitability increase, the effects were smaller than

  2. Connexin36 identified at morphologically mixed chemical/electrical synapses on trigeminal motoneurons and at primary afferent terminals on spinal cord neurons in adult mouse and rat.

    PubMed

    Bautista, W; McCrea, D A; Nagy, J I

    2014-03-28

    Morphologically mixed chemical/electrical synapses at axon terminals, with the electrical component formed by gap junctions, is common in the CNS of lower vertebrates. In mammalian CNS, evidence for morphologically mixed synapses has been obtained in only a few locations. Here, we used immunofluorescence approaches to examine the localization of the neuronally expressed gap junction forming protein connexin36 (Cx36) in relation to the axon terminal marker vesicular glutamate transporter-1 (vglut1) in the spinal cord and the trigeminal motor nucleus (Mo5) of rat and mouse. In adult rodents, immunolabeling for Cx36 appeared exclusively as Cx36-puncta, and was widely distributed at all rostro-caudal levels in most spinal cord laminae and in the Mo5. A high proportion of Cx36-puncta was co-localized with vglut1, forming morphologically mixed synapses on motoneurons, in intermediate spinal cord lamina, and in regions of medial lamina VII, where vglut1-containing terminals associated with Cx36 converged on neurons adjacent to the central canal. Unilateral transection of lumbar dorsal roots reduced immunolabeling of both vglut1 and Cx36 in intermediate laminae and lamina IX. Further, vglut1-terminals displaying Cx36-puncta were contacted by terminals labeled for glutamic acid decarboxylase65, which is known to be contained in presynaptic terminals on large-diameter primary afferents. Developmentally, mixed synapses begin to emerge in the spinal cord only after the second to third postnatal week and thereafter increase to adult levels. Our findings demonstrate that axon terminals of primary afferent origin form morphologically mixed synapses containing Cx36 in broadly distributed areas of adult rodent spinal cord and Mo5.

  3. [Peculiarities of synaptic vesicle recycling in frog and mouse motor nerve terminals].

    PubMed

    Zefirov, A L; Zakharov, A V; Mukhamedzianov, R D; Petrov, A M

    2008-01-01

    Using electrophysiology and fluorescence microscopy (dye FM1-43), comparative study of neurotransmitter secretion, synaptic vesicle exo-endocytosis, and recycling has been carried out in frog and mouse motor nerve terminals during a long strong stimulation (3 min; 20 imp/s). The obtained data have revealed three synaptic vesicle pools and two recycling ways existing on motor nerve terminals. The strong stimulation induced consecutive depletion of readily releasable, mobilized, and reserve vesicle pools of frog nerve terminals. The exocytosis rate exceeded the endocytosis rate; predominant was the slow synaptic vesicle recycling that replenished the reserve pool. In mouse nerve endings, vesicles of the readily releasable and mobilized pools were only exocytosed, the pools being replenished by fast recycling. At the same time, exo- and endocytosis occurred nearly in parallel and vesicles of the reserve pool did not participate in the neurotransmitter secretion. In is suggested that evolution of motor nerve terminals was directed to a decrease of the vesicle pool size, economic spending, and effective reuse of synaptic vesicles. This is achieved by an increase of endocytosis and recycling rates. These features can provide a long maintenance of a quite level of neurotransmitter secretion in nerve terminals of homoiothermal animals to preserve reliability of synaptic transmission during the high-frequency activity.

  4. Presynaptic inhibition of muscle spindle and tendon organ afferents in the mammalian spinal cord.

    PubMed

    Rudomin, P

    1990-12-01

    More than 30 years ago, Frank and Fuortes proposed that the synaptic effectiveness of muscle spindle afferents associated with spinal motoneurones could be diminished by the activation of nerves from flexor muscles. Since that time, research has focused on disclosing the mode of operation and the spinal pathways involved in this presynaptic inhibitory control. Initially, it was assumed that the same last-order interneurones mediated presynaptic inhibition of both muscle spindle and tendon organ afferent fibres. More recent evidence indicates that the synaptic effectiveness of these two groups of afferents is controlled by separate sets of GABAergic interneurones synapsing directly with the intraspinal terminals of the afferent fibres. This unique arrangement allows for selective control of the information on muscle length or muscle tension, despite the convergence of muscle spindle and tendon organ afferents on second-order interneurones.

  5. An electron microscopic study of primary afferent terminals from slowly adapting type I receptors in the cat.

    PubMed

    Semba, K; Masarachia, P; Malamed, S; Jacquin, M; Harris, S; Yang, G; Egger, M D

    1983-12-20

    Primary afferent fibers transmitting impulses from slowly adapting (SA) Type I receptors in the glabrous skin of the hind paw of the cat were injected intraaxonally in the spinal cord with horseradish peroxidase (HRP). At the light microscopic level, terminal arborizations were observed in the medial dorsal horn extending up to 6 mm rostrocaudally in and near the seventh lumbar segment. Boutonlike swellings labelled with HRP were distributed in clusters in Rexed's laminae III-VI. There was a tendency for the most dorsal clusters from an individual fiber to be located rostrally and for the most ventral clusters to be located caudally. At the electron microscopic level, a combination of morphometric analysis and serial reconstruction revealed the following: (1) All the boutons labelled with HRP contained predominantly clear, round synaptic vesicles, 40-50 nm in diameter. (2) Labelled boutons (n = 75) had cross-sectional longest dimensions of 1.72 +/- 0.53 micron (Mean +/- S.D.), perimeters of 4.95 +/- 1.52 micron, and areas of 1.18 +/- 0.59 micron 2. Their shapes in section varied from rounded to elongated forms. (3) The sizes of labelled boutons decreased significantly and linearly with depth from lamina IV to VI. The shapes of the bouton cross sections also became rounder with depth in the dorsal horn. (4) About 72% of synaptic contacts associated with HRP-filled boutons were with dendritic spines and shafts; most of these synapses were of the asymmetric type. (5) The remainder (28%) of the appositions were synapselike contacts between labelled boutons and unlabelled structures containing flattened or pleomorphic vesicles, and occasional dense-cored vesicles. (6) We observed no unequivocal axosomatic contacts made by labelled boutons. (7) The lengths of synaptic appositions with dendritic spines (0.46 +/- 0.20 micron) or with dendritic shafts (0.51 +/- 0.18 micron) were significantly greater than the synapselike contacts with vesicle-containing unlabelled

  6. Localization of TRPV1 and P2X3 in unmyelinated and myelinated vagal afferents in the rat

    PubMed Central

    Hermes, Sam M.; Andresen, Michael C.; Aicher, Sue A.

    2016-01-01

    The vagus nerve is dominated by afferent fibers that convey sensory information from the viscera to the brain. Most vagal afferents are unmyelinated, slow-conducting C-fibers, while a smaller portion are myelinated, fast-conducting A-fibers. Vagal afferents terminate in the nucleus tractus solitarius (NTS) in the dorsal brainstem and regulate autonomic and respiratory reflexes, as well as ascending pathways throughout the brain. Vagal afferents form glutamatergic excitatory synapses with postsynaptic NTS neurons that are modulated by a variety of channels. The organization of vagal afferents with regard to fiber type and channels is not well understood. In the present study, we used tract tracing methods to identify distinct populations of vagal afferents to determine if key channels are selectively localized to specific groups of afferent fibers. Vagal afferents were labeled with isolectin B4 (IB4) or cholera toxin B (CTb) to detect unmyelinated and myelinated afferents, respectively. We find that TRPV1 channels are preferentially found in unmyelinated vagal afferents identified with IB4, with almost half of all IB4 fibers showing co-localization with TRPV1. These results agree with prior electrophysiological findings. In contrast, we found that the ATP-sensitive channel P2X3 is found in a subset of both myelinated and unmyelinated vagal afferent fibers. Specifically, 18% of IB4 and 23% of CTb afferents contained P2X3. The majority of CTb-ir vagal afferents contained neither channel. Since neither channel was found in all vagal afferents, there are likely further degrees of heterogeneity in the modulation of vagal afferent sensory input to the NTS beyond fiber type. PMID:26706222

  7. Interaction of nanoparticles of ferric oxide with brain nerve terminals and blood platelets

    NASA Astrophysics Data System (ADS)

    Borisova, Tatiana; Krisanova, Natalia; Sivko, Roman; Borisov, Arseniy

    2012-07-01

    Nanoparticles of ferric oxide are the components of Lunar and Martian soil simulants. The observations suggest that exposure to Lunar soli simulant can be deleterious to human physiology and the components of lunar soil may be internalized by lung epithelium and may overcome the blood-brain barrier. The study focused on the effects of nanoparticles of ferric oxide on the functional state of rat brain nerve terminals (synaptosomes) and rabbit blood platelets. Using photon correlation spectroscopy, we demonstrated the binding of nanoparticles of ferric oxide with nerve terminals and platelets. Nanoparticles did not depolarize the plasma membrane of nerve terminals and platelets that was shown by fluorimetry with potential-sensitive fluorescent dye rhodamine 6G. Using pH-sensitive fluorescent dye acridine orange, we revealed that the acidification of synaptic vesicles of nerve terminals and secretory granules of platelets did not change in the presence of nanoparticles. The initial velocity of uptake of excitatory neurotransmitter glutamate was not influenced by nanoparticles of ferric oxide, whereas glutamate binding to nerve terminals was altered. Thus, it was suggested that nanoparticles of ferric oxide might disturb glutamate transport in the mammalian CNS.

  8. Morphologic Characterization of Nerves in Whole-Mount Airway Biopsies

    PubMed Central

    Canning, Brendan J.; Merlo-Pich, Emilio; Woodcock, Ashley A.; Smith, Jaclyn A.

    2015-01-01

    Rationale: Neuroplasticity of bronchopulmonary afferent neurons that respond to mechanical and chemical stimuli may sensitize the cough reflex. Afferent drive in cough is carried by the vagus nerve, and vagal afferent nerve terminals have been well defined in animals. Yet, both unmyelinated C fibers and particularly the morphologically distinct, myelinated, nodose-derived mechanoreceptors described in animals are poorly characterized in humans. To date there are no distinctive molecular markers or detailed morphologies available for human bronchopulmonary afferent nerves. Objectives: Morphologic and neuromolecular characterization of the afferent nerves that are potentially involved in cough in humans. Methods: A whole-mount immunofluorescence approach, rarely used in human lung tissue, was used with antibodies specific to protein gene product 9.5 (PGP9.5) and, for the first time in human lung tissue, 200-kD neurofilament subunit. Measurements and Main Results: We have developed a robust technique to visualize fibers consistent with autonomic and C fibers and pulmonary neuroendocrine cells. A group of morphologically distinct, 200-kD neurofilament-immunopositive myelinated afferent fibers, a subpopulation of which did not express PGP9.5, was also identified. Conclusions: PGP9.5-immunonegative nerves are strikingly similar to myelinated airway afferents, the cough receptor, and smooth muscle–associated airway receptors described in rodents. These have never been described in humans. Full description of human airway nerves is critical to the translation of animal studies to the clinical setting. PMID:25906337

  9. Vagal afferents sense meal-associated gastrointestinal and pancreatic hormones: mechanism and physiological role.

    PubMed

    Iwasaki, Yusaku; Yada, Toshihiko

    2012-12-01

    Some gastrointestinal and pancreatic hormones are potently secreted by meal intake and reduce food intake, therefore these hormones play a role in the meal-evoked satiety peptides. Previous reports have demonstrated that peripheral administration of these gastrointestinal or pancreatic hormones decrease feeding and the anorectic effects are abolished by lesions of vagal afferent nerves using surgical or chemical protocols, indicative of the involvement of the vagal afferents. Vagal afferent nerves link between several peripheral organs and the nucleus tractus solitarius of the brainstem. The present review focuses on cholecystokinin, peptide YY(3-36), pancreatic polypeptide, and nesfatin-1 released from endocrine cells of the gut and pancreas. These hormonal peptides directly act on and increase cytosolic Ca(2+) in vagal afferent nodose ganglion neurons and finally suppress food intake via vagal afferents. Therefore, peripheral terminals of vagal afferents could sense gastrointestinal and pancreatic hormones and regulate food intake. Here, we review how the vagal afferent neurons sense a variety of gastrointestinal and pancreatic hormones and discuss its physiological significance in regulation of feeding.

  10. Molecular Machines Determining the Fate of Endocytosed Synaptic Vesicles in Nerve Terminals

    PubMed Central

    Fassio, Anna; Fadda, Manuela; Benfenati, Fabio

    2016-01-01

    The cycle of a synaptic vesicle (SV) within the nerve terminal is a step-by-step journey with the final goal of ensuring the proper synaptic strength under changing environmental conditions. The SV cycle is a precisely regulated membrane traffic event in cells and, because of this, a plethora of membrane-bound and cytosolic proteins are devoted to assist SVs in each step of the journey. The cycling fate of endocytosed SVs determines both the availability for subsequent rounds of release and the lifetime of SVs in the terminal and is therefore crucial for synaptic function and plasticity. Molecular players that determine the destiny of SVs in nerve terminals after a round of exo-endocytosis are largely unknown. Here we review the functional role in SV fate of phosphorylation/dephosphorylation of SV proteins and of small GTPases acting on membrane trafficking at the synapse, as they are emerging as key molecules in determining the recycling route of SVs within the nerve terminal. In particular, we focus on: (i) the cyclin-dependent kinase-5 (cdk5) and calcineurin (CN) control of the recycling pool of SVs; (ii) the role of small GTPases of the Rab and ADP-ribosylation factor (Arf) families in defining the route followed by SV in their nerve terminal cycle. These regulatory proteins together with their synaptic regulators and effectors, are molecular nanomachines mediating homeostatic responses in synaptic plasticity and potential targets of drugs modulating the efficiency of synaptic transmission. PMID:27242505

  11. Selective Deletion of Sodium Salt Taste during Development Leads to Expanded Terminal Fields of Gustatory Nerves in the Adult Mouse Nucleus of the Solitary Tract.

    PubMed

    Sun, Chengsan; Hummler, Edith; Hill, David L

    2017-01-18

    Neuronal activity plays a key role in the development of sensory circuits in the mammalian brain. In the gustatory system, experimental manipulations now exist, through genetic manipulations of specific taste transduction processes, to examine how specific taste qualities (i.e., basic tastes) impact the functional and structural development of gustatory circuits. Here, we used a mouse knock-out model in which the transduction component used to discriminate sodium salts from other taste stimuli was deleted in taste bud cells throughout development. We used this model to test the hypothesis that the lack of activity elicited by sodium salt taste impacts the terminal field organization of nerves that carry taste information from taste buds to the nucleus of the solitary tract (NST) in the medulla. The glossopharyngeal, chorda tympani, and greater superficial petrosal nerves were labeled to examine their terminal fields in adult control mice and in adult mice in which the α-subunit of the epithelial sodium channel was conditionally deleted in taste buds (αENaC knockout). The terminal fields of all three nerves in the NST were up to 2.7 times greater in αENaC knock-out mice compared with the respective field volumes in control mice. The shapes of the fields were similar between the two groups; however, the density and spread of labels were greater in αENaC knock-out mice. Overall, our results show that disruption of the afferent taste signal to sodium salts disrupts the normal age-dependent "pruning" of all terminal fields, which could lead to alterations in sensory coding and taste-related behaviors.

  12. Expanded Terminal Fields of Gustatory Nerves Accompany Embryonic BDNF Overexpression in Mouse Oral Epithelia

    PubMed Central

    Sun, Chengsan; Dayal, Arjun

    2015-01-01

    Brain-derived neurotrophic factor (BDNF) is expressed in gustatory epithelia and is required for gustatory neurons to locate and innervate their correct target during development. When BDNF is overexpressed throughout the lingual epithelium, beginning embryonically, chorda tympani fibers are misdirected and innervate inappropriate targets, leading to a loss of taste buds. The remaining taste buds are hyperinnervated, demonstrating a disruption of nerve/target matching in the tongue. We tested the hypothesis here that overexpression of BDNF peripherally leads to a disrupted terminal field organization of nerves that carry taste information to the brainstem. The chorda tympani, greater superficial petrosal, and glossopharyngeal nerves were labeled in adult wild-type (WT) mice and in adult mice in which BDNF was overexpressed (OE) to examine the volume and density of their central projections in the nucleus of the solitary tract. We found that the terminal fields of the chorda tympani and greater superficial petrosal nerves and overlapping fields that included these nerves in OE mice were at least 80% greater than the respective field volumes in WT mice. The shapes of terminal fields were similar between the two groups; however, the density and spread of labels were greater in OE mice. Unexpectedly, there were also group-related differences in chorda tympani nerve function, with OE mice showing a greater relative taste response to a concentration series of sucrose. Overall, our results show that disruption in peripheral innervation patterns of sensory neurons have significant effects on peripheral nerve function and central organization of their terminal fields. PMID:25568132

  13. Chorda Tympani Nerve Terminal Field Maturation and Maintenance Is Severely Altered Following Changes To Gustatory Nerve Input to the Nucleus of the Solitary Tract

    PubMed Central

    Dudgeon, Sara L.; Hill, David L.

    2011-01-01

    Neural competition among multiple inputs can affect the refinement and maintenance of terminal fields in sensory systems. In the rat gustatory system, the chorda tympani, greater superficial petrosal, and glossopharyngeal nerves have distinct but overlapping terminal fields in the first central relay, the nucleus of the solitary tract (NTS). This overlap is largest at early postnatal ages followed by a significant refinement and pruning of the fields over a three-week period, suggesting that competitive mechanisms underlie the pruning. Here, we manipulated the putative competitive interactions among the three nerves by sectioning the greater superficial petrosal and glossopharyngeal nerves at postnatal day 15 (P15), P25, or at adulthood, while leaving the chorda tympani nerve intact. The terminal field of the chorda tympani nerve was assessed 35 days following nerve sections, a period before the sectioned nerves functionally regenerated. Regardless of the age when the nerves were cut, the chorda tympani nerve terminal field expanded to a volume four times larger than sham controls. Terminal field density measurements revealed that the expanded terminal field was similar to P15 control rats. Thus, it appears that the chorda tympani nerve terminal field defaults to its early postnatal field size and shape when the nerves with overlapping fields are cut, and this anatomical plasticity is retained into adulthood. These findings not only demonstrate the dramatic and lifelong plasticity in the central gustatory system, but also suggest that corresponding changes in functional and taste-related behaviors will accompany injury-induced changes in brainstem circuits. PMID:21613473

  14. Ciguatoxin enhances quantal transmitter release from frog motor nerve terminals.

    PubMed Central

    Molgó, J.; Comella, J. X.; Legrand, A. M.

    1990-01-01

    1. Ciguatoxin (CTX), a marine toxin produced by the benthic dinoflagellate Gambierdiscus toxicus, is responsible for a complex endemic disease in man known as ciguatera fish poisoning. In the present study we have investigated the effects of purified CTX extracted for Gymnothorax javanicus moray-eel liver on frog isolated neuromuscular preparations with conventional electrophysiological techniques. 2. CTX (1-2.5 nM) applied to cutaneous pectoris nerve-muscle preparations induced, after a short delay, spontaneous fibrillations of the muscle fibres that could be suppressed with 1 microM tetrodotoxin (TTX) or by formamide to uncouple excitation-contraction. 3. In preparations treated with formamide, CTX (1-2.5 nM) caused either spontaneous or repetitive muscle action potentials (up to frequencies of 60-100 Hz) in response to a single nerve stimulus. Recordings performed at extrajunctional regions of the muscle membrane revealed that during the repetitive firing a prolongation of the repolarizing phase of the action potential occurred. At junctional sites the repetitive action potentials were triggered by repetitive endplate potentials (e.p.ps). 4. CTX (2.5 nM) caused a TTX-sensitive depolarization of the muscle membrane. 5. In junctions equilibrated in solutions containing high Mg2+ + low Ca2+, addition of CTX (1.5 nM) first induced an average increase of 239 +/- 36% in the mean quantal content of e.p.ps. Subsequently CTX reduced and finally blocked nerve-evoked transmitter release irreversibly. 6. CTX (1.5-2.5 nM) increased the frequency of miniature endplate potentials (m.e.p.ps) in junctions bathed either in normal Ringer, low Ca2(+)-high Mg2+ medium or in a nominally Ca2(+)-free solution containing EGTA.2+ Extensive washing with toxin-free solutions did not reverse the effect.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1972891

  15. Afferent Fiber Remodeling in the Somatosensory Thalamus of Mice as a Neural Basis of Somatotopic Reorganization in the Brain and Ectopic Mechanical Hypersensitivity after Peripheral Sensory Nerve Injury

    PubMed Central

    Yagasaki, Yuki; Katayama, Yoko

    2017-01-01

    Abstract Plastic changes in the CNS in response to peripheral sensory nerve injury are a series of complex processes, ranging from local circuit remodeling to somatotopic reorganization. However, the link between circuit remodeling and somatotopic reorganization remains unclear. We have previously reported that transection of the primary whisker sensory nerve causes the abnormal rewiring of lemniscal fibers (sensory afferents) on a neuron in the mouse whisker sensory thalamus (V2 VPM). In the present study, using transgenic mice whose lemniscal fibers originate from the whisker sensory principle trigeminal nucleus (PrV2) are specifically labeled, we identified that the transection induced retraction of PrV2-originating lemniscal fibers and invasion of those not originating from PrV2 in the V2 VPM. This anatomical remodeling with somatotopic reorganization was highly correlated with the rewiring of lemniscal fibers. Origins of the non-PrV2-origin lemniscal fibers in the V2 VPM included the mandibular subregion of trigeminal nuclei and the dorsal column nuclei (DCNs), which normally represent body parts other than whiskers. The transection also resulted in ectopic receptive fields of V2 VPM neurons and extraterritorial pain behavior on the uninjured mandibular region of the face. The anatomical remodeling, emergence of ectopic receptive fields, and extraterritorial pain behavior all concomitantly developed within a week and lasted more than three months after the transection. Our findings, thus, indicate a strong linkage between these plastic changes after peripheral sensory nerve injury, which may provide a neural circuit basis underlying large-scale reorganization of somatotopic representation and abnormal ectopic sensations.

  16. The somatostatin receptor 4 agonist J-2156 reduces mechanosensitivity of peripheral nerve afferents and spinal neurons in an inflammatory pain model.

    PubMed

    Schuelert, Niklas; Just, Stefan; Kuelzer, Raimund; Corradini, Laura; Gorham, Louise C J; Doods, Henri

    2015-01-05

    Somatostatin (SST) is a peptide hormone that regulates the endocrine system and affects neurotransmission via interaction with G protein-coupled SST receptors and inhibition of the release of different hormones. The aim of this study was to investigate whether the analgesic properties of the selective SSTR4 agonist J-2156 are mediated via peripheral and/or spinal receptors. Effect on mechanical hyperalgesia in the Complete Freund׳s Adjuvant (CFA) model was measured after intraperitoneal application of J-2156. Electrophysiological neuronal recordings were conducted 24 h after injection of CFA or vehicle into the paw of Wistar rats. Mechanosensitivity of peripheral afferents of the saphenous nerve as well as of spinal wide dynamic range (WDR) and nociceptive-specific (NS) neurons were measured after systemic or spinal application of J-2156. In CFA animals J-2156 dose dependently reduced hyperalgesia in behavioral studies. The minimal effective dose was 0.1 mg/kg. Mechanosensitivity of peripheral afferents and spinal neurons was significantly reduced by J-2156. NS neurons were dose dependently inhibited by J-2156 while in WDR neurons only the highest concentration of 100 µM had an effect. In sham controls, J-2156 had no effect on neuronal activity. We demonstrated that J-2156 dose-dependently reduces peripheral and spinal neuronal excitability in the CFA rat model without affecting physiological pain transmission. Given the high concentration of the compound required to inhibit spinal neurons, it is unlikely that the behavioral effect seen in CFA model is mediated centrally. Overall these data demonstrated that the analgesic effect of J-2156 is mediated mainly via peripheral SST4 receptors.

  17. Sodium channels in presynaptic nerve terminals. Regulation by neurotoxins

    PubMed Central

    1980-01-01

    Regulation of Na+ channels by neurotoxins has been studied in pinched- off nerve endings (synaptosomes) from rat brain. Activation of Na+ channels by the steroid batrachotoxin and by the alkaloid veratridine resulted in an increase in the rate of influx of 22Na into the synaptosomes. In the presence of 145 mM Na+, these agents also depolarized the synaptosomes, as indicated by increased fluorescence in the presence of a voltage-sensitive oxacarbocyanine dye [diO-C5(3)]. Polypeptide neurotoxins from the scorpion Leiurus quinquestriatus and from the sea anemone Anthopleura xanthogrammica potentiated the stimulatory effects of batrachotoxin and veratridine on the influx of 22Na into synaptosomes. Saxitoxin and tetrodotoxin blocked the stimulatory effects of batrachotoxin and veratridine, both in the presence and absence of the polypeptide toxins, but did not affect control 22Na influx or resting membrane potential. A three-state model for Na+ channel operation can account for the effects of these neurotoxins on Na+ channels as determined both by Na+ flux measurements in vitro and by electrophysiological experiments in intact nerve and muscle. PMID:6252277

  18. Autoregulation of neuromuscular transmission by nerve terminals. Annual report, 1 July 1983-1 July 1984

    SciTech Connect

    Bierkamper, G.G.

    1984-09-01

    The objective of this project is to investigate three mechanisms through which acetycholine (ACh) release may be modulated prejunctionally at the motor nerve terminal of skeletal muscle: (1) prejunctional cholinoceptor regulation of ACh release, (2) modulation of ACh release through preconditioning patterns of nerve stimulation, and (3) precursor control of ACh release. Neuromuscular transmission has been assessed in the vascular perfused rat phrenic nerve-diaphragm preparation (VPRH) by measuring the release of ACh directly by radioenzymatic assay or by chemiluminescence assay, and indirectly by intracellular recordings and by force of contradiction (FC) measurements. Additional experiments have been done on rat sciatic nerve in order to examine the axonal transport of nicotinic binding sites. The mouse hemidiahragm preparation has been used to study antidromic activity (backfiring) in the phrenic nerve in the presence of an anticholinesterase agent. The data resulting from the project support the concept that the nerve terminal possesses local mechanism for modulating ACh release. Attempts have been made to understand the normal function of these mechanisms and then to explore their activity under demanding physological conditions, drug exposure, and in the presence of acetylcholinesterase (AChE) inhibitors.

  19. Balance of calcineurin Aα and CDK5 activities sets release probability at nerve terminals

    PubMed Central

    Kim, Sung Hyun; Ryan, Timothy A.

    2013-01-01

    The control of neurotransmitter release at nerve terminals is of profound importance for neurological function and provides a powerful control system in neural networks. We show that the balance of enzymatic activities of the alpha isoform of the phosphatase calcineurin (CNAα) and the kinase CDK5 has a dramatic influence over single AP-driven exocytosis at nerve terminals. Acute or chronic loss of these enzymatic activities results in a 7-fold impact on single action potential-driven exocytosis. We demonstrate that this control is mediated almost entirely through Cav2.2 (N-type) voltage-gated calcium channels as blocking these channels with a peptide toxin eliminates modulation by these enzymes. We found that a fraction of nerve terminals are kept in a presynaptically silent state with no measurable Ca2+ influx driven by single AP stimuli due to the balance of CNAα and CDK5 activities as blockade of either CNAα or CDK5 activity changes the proportion of presynaptically silent nerve terminals. Thus CNAα and CDK5 enzymatic activities are key determinants of release probability. PMID:23699505

  20. Topographical organization of TRPV1-immunoreactive epithelium and CGRP-immunoreactive nerve terminals in rodent tongue.

    PubMed

    Kawashima, M; Imura, K; Sato, I

    2012-05-10

    Transient receptor potential vanilloid subfamily member 1 (TRPV1) is activated by capsaicin, acid, and heat and mediates pain through peripheral nerves. In the tongue, TRPV1 expression has been reported also in the epithelium. This indicates a possibility that sensation is first received by the epithelium. However, how nerves receive sensations from the epithelium remains unclear. To clarify the anatomical basis of this interaction, we performed immunohistochemical studies in the rodent tongue to detect TRPV1 and calcitonin gene-related peptide (CGRP), a neural marker. Strong expression of TRPV1 in the epithelium was observed and was restricted to the apex of the tongue. Double immunohistochemical staining revealed that CGRP-expressing nerve terminals were in close apposition to the strongly TRPV1-expressing epithelium of fungiform papilla in the apex of rodent tongues. These results suggest that the TRPV1-expressing epithelium monitors the oral environment and acquired information may then be conducted to the adjacent CGRP-expressing terminals.

  1. Patterns of connectivity of spinal interneurons with single muscle afferents.

    PubMed

    Quevedo, J; Eguibar, J R; Lomeli, J; Rudomin, P

    1997-07-01

    A technique was developed to measure, in the anesthetized and paralyzed cat under artificial ventilation, changes of excitability to intraspinal stimulation simultaneously in two different afferent fibers or in two collaterals of the same afferent fiber. Intraspinal stimulation reduced the threshold of single muscle afferent fibers ending in the intermediate nucleus. This effect was seen with strengths below those required to activate the afferent fiber tested (1.5-12 microA), occurred at a short latency (1.5-2.0 ms), reached a maximum between 15 and 30 ms, and lasted up to 100 ms. The effects produced by graded stimulation applied at the shortest conditioning-testing stimulus time intervals increased by fixed steps, suggesting recruitment of discrete elements, most likely of last-order interneurons mediating primary afferent depolarization (PAD). The short-latency increases in excitability produced by the weakest effective intraspinal stimuli were usually detected only in the collateral closest to the stimulating micropipette, indicating that the stimulated interneurons mediating PAD have spatially restricted actions. The short-latency PAD produced by intraspinal stimuli, as well as the PAD produced by stimulation of the posterior biceps and semitendinosus (PBSt) nerve or by stimulation of the bulbar reticular formation (RF), was depressed 19-30 min after the i.v. injection of 0.5 mg/kg of picrotoxin, suggesting that all these effects were mediated by GABAergic mechanisms. The PAD elicited by stimulation of muscle and/or cutaneous nerves was depressed following the i.v. injection of (-)-baclofen, whereas the PAD elicited in the same collateral by stimulation of the RF was baclofen-resistant. The short-latency PAD produced by intraspinal stimulation was not always depressed by i.v. injections of (-)-baclofen. Baclofen-sensitive and baclofen-resistant monosynaptic PADs could be produced in different collaterals of the same afferent fiber. The results suggest that

  2. The afferent activity of the superior laryngeal nerve, and respiratory reflexes specifically responding to intralaryngeal pressure changes in anesthetized Shiba goats.

    PubMed

    Sekizawa, S; Tsubone, H; Hishida, N; Kuwahara, M; Sugano, S

    1997-10-01

    This study was aimed at characterizing the superior laryngeal nerve (SLN) afferent activities under four different respiratory conditions, i.e., tracheostomy breathing (TB), upper airway breathing (UAB), tracheal occlusion (TO) and upper airway occlusion (UAO), and investigating respiratory changes in response to transmural pressures applied to the larynx in anesthetized Shiba goats. The activity recorded from the whole SLN increased at both inspiration and expiration during TB, UAB and TO, while an expiratory augmentation accompanied by an inspiratory inhibition was found during UAO. Based on recordings from 109 thin filament-preparations, 47 units were identified as 'drive' receptors, 31 as 'pressure' receptors (22 'positive' and 9 'negative' pressure receptors), and the rest 31 as 'non-modulated type' of receptors. The posterior cricoarytenoid (PCA) muscle activity showed a clear inspiratory modulation during UAB and was significantly enhanced by negative pressure applied to the isolated upper airway, where such an augmented activity was abolished by bilateral section of the SLN. No significant changes were found in the respiratory cycle during application of negative pressures to the larynx. The respiratory modulation of the SLN in Shiba goats was essentially identical to that reported for rabbits, rats and guinea pigs, but not in dogs. The reflex response of the upper airway muscles to the laryngeal pressure changes in Shiba goats were found to be less noticeable than in rabbits and dogs.

  3. Size-related differences in the branching pattern of the motor nerve terminals in triangularis sterni muscle of the mouse.

    PubMed

    Tomasi, J; Fenol, R; Santafe, M; Mayayo, E

    1989-01-01

    A light microscopy morphometric study was performed in singly innervated synaptic areas of the triangularis sterni muscle of the normal adult Swiss mouse. Investigating mechanisms of the motor nerve growth control, we tested the hypothesis that significant differences in the nerve terminal branching pattern can be detected between different populations of nerve endings classified according to their arborization complexity or size. The main observations of this morphometric study are first, that the mean segment length of the terminal arborization between branch points behaves as an independent variable from the remaining parameters; the mean value of this parameter did not change in nerve endings of differing size and complexity. Secondly, the increase in size of the nerve endings is accompanied by a significant reduction in the mean length of the distal free-end segments. Results are discussed in the context of the possible regulatory mechanisms governing nerve terminal growth and remodelling.

  4. Morphophysiology of synaptic transmission between type I hair cells and vestibular primary afferents. An intracellular study employing horseradish peroxidase in the lizard, Calotes versicolor.

    PubMed

    Schessel, D A; Ginzberg, R; Highstein, S M

    1991-03-22

    Intracellular records with glass microelectrodes filled with horseradish peroxidase (HRP) were taken from primary afferents of the horizontal semicircular canal in the lizard, Calotes versicolor. A coefficient of variation (CV) of the interspike intervals of spontaneous action potentials (APs) was calculated and correlated with the terminal morphologies of afferents within the canal crista. Irregular fibers with CV greater than 0.4 always correlated with a nerve chalice or calyx afferent terminal expansion surrounding one or more type I hair cells; more regular fibers with CV less than 0.4 always correlated with a dimorphic or bouton only terminal expansion of afferents. Afferents with a CV greater than 0.4 demonstrated miniature excitatory postsynaptic potentials (mEPSPs) that summated to initiate APs. APs were blocked by tetrodotoxin and mEPSP frequency was modulated by caloric stimulation. Cobalt application reversibly blocked mEPSPs. Electron microscopic examination of physiologically studied afferents with CV greater than 0.4 revealed synaptic profiles consisting of typical synaptic bodies and synaptic vesicles in the type I hair cell presynaptic to the nerve chalice. Examples of the interspike baseline in regular and irregular afferents suggest differential modes of impulse initiation in these two fiber types.

  5. Effects of PAD on conduction of action potentials within segmental and ascending branches of single muscle afferents in the cat spinal cord.

    PubMed

    Lomelí, J; Castillo, L; Linares, P; Rudomin, P

    2000-11-01

    In anesthetized and paralyzed cats under artificial respiration, we examined the extent to which primary afferent depolarization (PAD) might affect invasion of action potentials in intraspinal axonal and/or terminal branches of single muscle afferents. To this end, one stimulating micropipette was placed at the L6 spinal level within the intermediate or motor nucleus, and another one at the L3 level, in or close to Clarke's column. Antidromically conducted responses produced in single muscle afferents by stimulation at these two spinal levels were recorded from fine lateral gastrocnemius nerve filaments. In all fibers examined, stimulation of one branch, with strengths producing action potentials, increased the intraspinal threshold of the other branch when applied at short conditioning testing stimulus intervals (<1.5-2.0 ms), because of the refractoriness produced by the action potentials invading the tested branch. Similar increases in the intraspinal threshold were found in branches showing tonic PAD and also during the PAD evoked by stimulation of group I afferent fibers in muscle nerves. It is concluded that during tonic or evoked PAD, axonal branches in the dorsal columns and myelinated terminals of muscle afferents ending deep in the L6 and L3 segmental levels continue to be invaded by action potentials. These findings strengthen the view that presynaptic inhibition of muscle afferents produced by activation of GABAergic mechanisms is more likely to result from changes in the synaptic effectiveness of the afferent terminals than from conduction failure because of PAD.

  6. Cholinergic septal afferent terminals preferentially contact neuropeptide Y-containing interneurons compared to parvalbumin-containing interneurons in the rat dentate gyrus.

    PubMed

    Dougherty, K D; Milner, T A

    1999-11-15

    Septal cholinergic neurons may affect hippocampal memory encoding and retrieval by differentially targeting parvalbumin (PARV)-containing basket cells and neuropeptide Y (NPY) interneurons. Thus, the cellular associations of cholinergic efferents, identified by the low-affinity, p75 neurotrophin receptor (p75(NTR)), with interneurons containing either PARV or NPY in the hilus of the rat dentate gyrus were examined in single sections using dual labeling immunoelectron microscopy. Most profiles immunoreactive (IR) for PARV and NPY were perikaryal and dendritic and found within the infragranular and central hilar regions, respectively, whereas most profiles with p75(NTR)-labeling were unmyelinated axons and axon terminals. Although PARV-labeled profiles were more numerous, p75(NTR)-labeled axons and terminals contacted few PARV-IR profiles compared to NPY-labeled profiles (2% of 561 for PARV vs 12% of 433 for NPY). Moreover, structures targeted by p75(NTR)-IR axon terminals varied depending on the presence of PARV or NPY immunoreactivity. p75(NTR)-IR terminals primarily contacted PARV-IR dendrites (87%) compared to somata (13%); however, they contacted more NPY-IR somata (57%) than dendrites (43%). p75(NTR)-labeled terminals formed exclusively symmetric (inhibitory-type) synapses with PARV-IR somata and dendrites; however, they formed mostly symmetric but also asymmetric (excitatory-type) synapses with NPY-IR somata and dendrites. These results suggest that septal cholinergic efferents in the dentate gyrus: (1) preferentially innervate NPY-containing interneurons compared to PARV-containing basket cells; and (2) may provide a more powerful (i.e., somatic contacts), yet functionally diverse (i.e., asymmetric and symmetric synapses), modulation of NPY-containing interneurons. Moreover, they provide evidence that neurochemical subsets of hippocampal interneurons can be distinguished by afferent input.

  7. Nuclei-specific differences in nerve terminal distribution, morphology, and development in mouse visual thalamus

    PubMed Central

    2014-01-01

    Background Mouse visual thalamus has emerged as a powerful model for understanding the mechanisms underlying neural circuit formation and function. Three distinct nuclei within mouse thalamus receive retinal input, the dorsal lateral geniculate nucleus (dLGN), the ventral lateral geniculate nucleus (vLGN), and the intergeniculate nucleus (IGL). However, in each of these nuclei, retinal inputs are vastly outnumbered by nonretinal inputs that arise from cortical and subcortical sources. Although retinal and nonretinal terminals associated within dLGN circuitry have been well characterized, we know little about nerve terminal organization, distribution and development in other nuclei of mouse visual thalamus. Results Immunolabeling specific subsets of synapses with antibodies against vesicle-associated neurotransmitter transporters or neurotransmitter synthesizing enzymes revealed significant differences in the composition, distribution and morphology of nonretinal terminals in dLGN, vLGN and IGL. For example, inhibitory terminals are more densely packed in vLGN, and cortical terminals are more densely distributed in dLGN. Overall, synaptic terminal density appears least dense in IGL. Similar nuclei-specific differences were observed for retinal terminals using immunolabeling, genetic labeling, axonal tracing and serial block face scanning electron microscopy: retinal terminals are smaller, less morphologically complex, and more densely distributed in vLGN than in dLGN. Since glutamatergic terminal size often correlates with synaptic function, we used in vitro whole cell recordings and optic tract stimulation in acutely prepared thalamic slices to reveal that excitatory postsynaptic currents (EPSCs) are considerably smaller in vLGN and show distinct responses following paired stimuli. Finally, anterograde labeling of retinal terminals throughout early postnatal development revealed that anatomical differences in retinal nerve terminal structure are not observable as

  8. Effects of Latrodectus spider venoms on sensory and motor nerve terminals of muscle spindles.

    PubMed

    Queiroz, L S; Duchen, L W

    1982-08-23

    The effects of the venoms of the spiders Latrodectus mactans tredecimguttatus (black widow) and Latrodectus mactans hasselti (red back) on sensory nerve terminals in muscle spindles were studied in the mouse. A sublethal dose of venom was injected into tibialis anterior and extensor digitorum longus muscles of one leg. After survival from 30 minutes to 6 weeks muscles were examined in serial paraffin sections impregnated with silver or by electron microscopy. Sensory endings became swollen, some within 30 minutes, while over the next few hours there was progressive degeneration of annulospiral endings. By 24 hours every spindle identified by light or electron microscopy was devoid of sensory terminals. Degenerated nerve endings were taken up into the sarcoplasm of intrafusal muscle fibres. Regeneration of sensory axons began within 24 hours, new incomplete spirals were formed by 5 days and by 1 week annulospiral endings were almost all normal in appearance. Intrafusal motor terminals underwent similar acute degenerative and regenerative changes. These experiments show that intrafusal sensory and motor terminals are equally affected by Latrodectus venoms. Sensory nerve fibres possess a capacity for regeneration equal to that of motor fibres and reinnervate intrafusal muscle fibres close to their original sites of innervation.

  9. Control and Plasticity of the Presynaptic Action Potential Waveform at Small CNS Nerve Terminals

    PubMed Central

    Hoppa, Michael B.; Gouzer, Geraldine; Armbruster, Moritz; Ryan, Timothy A.

    2014-01-01

    SUMMARY The steep dependence of exocytosis on Ca2+ entry at nerve terminals implies that voltage control of both Ca2+ channel opening and the driving force for Ca2+ entry are powerful levers in sculpting synaptic efficacy. Using fast, genetically encoded voltage indicators in dissociated primary neurons, we show that at small nerve terminals K+ channels constrain the peak voltage of the presynaptic action potential (APSYN) to values much lower than those at cell somas. This key APSYN property additionally shows adaptive plasticity: manipulations that increase presynaptic Ca2+ channel abundance and release probability result in a commensurate lowering of the APSYN peak and narrowing of the waveform, while manipulations that decrease presynaptic Ca2+ channel abundance do the opposite. This modulation is eliminated upon blockade of Kv3.1 and Kv1 channels. Our studies thus reveal that adaptive plasticity in the APSYN waveform serves as an important regulator of synaptic function. PMID:25447742

  10. Neurotransmission in the carotid body: transmitters and modulators between glomus cells and petrosal ganglion nerve terminals.

    PubMed

    Iturriaga, Rodrigo; Alcayaga, Julio

    2004-12-01

    The carotid body (CB) is the main arterial chemoreceptor. The most accepted model of arterial chemoreception postulates that carotid body glomus (type I) cells are the primary receptors, which are synaptically connected to the nerve terminals of petrosal ganglion (PG) neurons. In response to natural stimuli, glomus cells are expected to release one (or more) transmitter(s) which, acting on the peripheral nerve terminals of processes from chemosensory petrosal neurons, increases the sensory discharge. Among several molecules present in glomus cells, acetylcholine and adenosine nucleotides and dopamine are considered as excitatory transmitter candidates. In this review, we will examine recent evidence supporting the notion that acetylcholine and adenosine 5'-triphosphate are the main excitatory transmitters in the cat and rat carotid bodies. On the other hand, dopamine may act as a modulator of the chemoreception process in the cat, but as an excitatory transmitter in the rabbit carotid body.

  11. Vitamin B2 inhibits glutamate release from rat cerebrocortical nerve terminals.

    PubMed

    Wang, Su-Jane; Wu, Wen-Mein; Yang, Feili-Lo; Hsu, Guoo-Shyng Wang; Huang, Chia-Yu

    2008-08-27

    We examined the effect of riboflavin, vitamin B2, on the release of endogenous glutamate from nerve terminals purified from rat cerebral cortex. The release of glutamate evoked by 4-aminopyridine was inhibited by riboflavin. Further experiments indicated that riboflavin-mediated inhibition of glutamate release (i) results from a reduction of vesicular exocytosis, not from an inhibition of nonvesicular release; (ii) is associated with a decrease in presynaptic N-type and P/Q-type voltage-dependent Ca channel activity. These findings are the first to suggest that, in rat cerebrocortical nerve terminals, riboflavin suppresses voltage-dependent Ca channel activity and in so doing inhibits evoked glutamate release. This finding may explain the neuroprotective effects of vitamin B2 against neurotoxicity.

  12. Functional recovery of anterior semicircular canal afferents following hair cell regeneration in birds

    NASA Technical Reports Server (NTRS)

    Boyle, Richard; Highstein, Stephen M.; Carey, John P.; Xu, Jinping

    2002-01-01

    Streptomycin sulfate (1.2 g/kg i.m.) was administered for 5 consecutive days to 5-7-day-old white Leghorn chicks; this causes damage to semicircular canal hair cells that ultimately regenerate to reform the sensory epithelium. During the recovery period, electrophysiological recordings were taken sequentially from anterior semicircular canal primary afferents using an indentation stimulus of the canal that has been shown to mimic rotational stimulation. Chicks were assigned to an early (14-18 days; n = 8), intermediate (28-34 days; n = 5), and late (38-58 days; n = 4) period based on days after treatment. Seven untreated chicks, 15-67 days old, provided control data. An absence of background and indent-induced discharge was the prominent feature of afferents in the early period: only "silent" afferents were encountered in 5/8 experiments. In several of these chicks, fascicles of afferent fibers were seen extending up to the epithelium that was void of hair cells, and intra- and extracellular biocytin labeling revealed afferent processes penetrating into the supporting cell layer of the crista. In 3/8 chicks 74 afferents could be characterized, and they significantly differed from controls (n = 130) by having a lower discharge rate and a negligible response to canal stimulation. In the intermediate period there was considerable variability in discharge properties of 121 afferents, but as a whole the number of "silent" fibers in the canal nerve diminished, the background rate increased, and a response to canal stimulation detected. Individually biocytin-labeled afferents had normal-appearing terminal specializations in the sensory epithelium by 28 days poststreptomycin. In the late period, afferents (n = 58) remained significantly different from controls in background discharge properties and response gain. The evidence suggests that a considerable amount of variability exists between chicks in the return of vestibular afferent function following ototoxic injury and

  13. Lacosamide diminishes dryness-induced hyperexcitability of corneal cold sensitive nerve terminals.

    PubMed

    Kovács, Illés; Dienes, Lóránt; Perényi, Kristóf; Quirce, Susana; Luna, Carolina; Mizerska, Kamila; Acosta, M Carmen; Belmonte, Carlos; Gallar, Juana

    2016-09-15

    Lacosamide is an anti-epileptic drug that is also used for the treatment of painful diabetic neuropathy acting through voltage-gated sodium channels. The aim of this work was to evaluate the effects of acute application of lacosamide on the electrical activity of corneal cold nerve terminals in lacrimo-deficient guinea pigs. Four weeks after unilateral surgical removal of the main lachrimal gland in guinea pigs, corneas were excised and superfused in vitro at 34°C for extracellular electrophysiological recording of nerve terminal impulse activity of cold thermosensitive nerve terminals. The characteristics of the spontaneous and the stimulus-evoked (cooling ramps from 34°C to 15°C) activity before and in presence of lacosamide 100µM and lidocaine 100µM were compared. Cold nerve terminals (n=34) recorded from dry eye corneas showed significantly enhanced spontaneous activity (8.0±1.1 vs. 5.2±0.7imp/s; P<0.05) and cold response (21.2±1.7 vs. 16.8±1.3imp/s; P<0.05) as well as reduced cold threshold (1.5±0.1 vs. 2.8±0.2 Δ°C; P<0.05) to cooling ramps compared to terminals (n=58) from control animals. Both lacosamide and lidocaine decreased spontaneous activity and peak response to cooling ramps significantly (P<0.05). Temperature threshold was increased by the addition of lidocaine (P<0.05) but not lacosamide (P>0.05) to the irrigation fluid. In summary, the application of lacosamide results in a significant decrease of the augmented spontaneous activity and responsiveness to cold of corneal sensory nerves from tear-deficient animals. Based on these promising results we speculate that lacosamide might be used to reduce the hyperexcitability of corneal cold receptors caused by prolonged ocular surface dryness due to hyposecretory or evaporative dry eye disease.

  14. Action potential propagation and propagation block by GABA in rat posterior pituitary nerve terminals.

    PubMed Central

    Jackson, M B; Zhang, S J

    1995-01-01

    1. A theoretical model was developed to investigate action potential propagation in posterior pituitary nerve terminals. This model was then used to evaluate the efficacy of depolarizing and shunting GABA responses on action potential propagation. 2. Experimental data obtained from the posterior pituitary with patch clamp techniques were used to derive empirical expressions for the voltage and time dependence of the nerve terminal Na+ and K+ channels. The essential structure employed here was based on anatomical and cable data from the posterior pituitary, and consisted of a long cylindrical axon (diameter, 0.5 mm) with a large spherical swelling (diameter, 4-21 mm) in the middle. 3. In the absence of an inhibitory conductance, simulated action potentials propagated with high fidelity through the nerve terminal. Swellings could block propagation, but only when sizes exceeded those observed in the posterior pituitary. Adding axonal branches reduced the critical size only slightly. These results suggested that action potentials invade the entire posterior pituitary nerve terminal in the absence of inhibition or depression. 4. The addition of inhibitory conductance to a swelling caused simulated action potentials to fail at the swelling. Depolarizing inhibitory conductances were 1.6 times more effective than shunting inhibitory conductances in blocking propagation. 5. Inhibitory conductances within the range of experimentally observed magnitudes and localized to swellings in the observed range of sizes were too weak to block simulated action potentials. However, twofold enhancement of GABA responses by neurosteroid resulted in currents strong enough to block propagation in realistic swelling sizes. 6. GABA could block simulated propagation without neurosteroid enhancement provided that GABA was present throughout a region in the order of a few hundred micrometres. For this widespread inhibition depolarizing conductance was 2.2 times more effective than shunting

  15. Presynaptic functional trkB receptors mediate the release of excitatory neurotransmitters from primary afferent terminals in lamina II (substantia gelatinosa) of postnatal rat spinal cord.

    PubMed

    Merighi, Adalberto; Bardoni, Rita; Salio, Chiara; Lossi, Laura; Ferrini, Francesco; Prandini, Massimiliano; Zonta, Micaela; Gustincich, Stefano; Carmignoto, Giorgio

    2008-03-01

    A subset of primary sensory neurons produces BDNF, which is implicated in control of nociceptive neurotransmission. We previously localized full-length trkB receptors on their terminals within lamina II. To functionally study these receptors, we here employed patch-clamp recordings, calcium imaging and immunocytochemistry on slices from 8-12 days post-natal rats. In this preparation, BDNF (100-500 ng/mL) enhances the release of sensory neurotransmitters (glutamate, substance P, CGRP) in lamina II by acting on trkB receptors expressed by primary afferent fibers of the peptidergic nociceptive type (PN-PAFs). Effect was blocked by trk antagonist K252a or anti-trkB antibody clone 47. A pre-synaptic mechanism was demonstrated after (i) patch-clamp recordings where the neurotrophin induced a significant increase in frequency, but not amplitude, of AMPA-mediated mEPSCs, (ii) real time calcium imaging, where sustained application of BDNF evoked an intense response in up to 57% lamina II neurons with a significant frequency rise. Antagonists of ionotropic glutamate receptors and NK(1) receptors completely inhibited the calcium response to BDNF. Reduction of CGRP (a specific marker of PN-PAFs) and substance P content in dorsal horn following BDNF preincubation, and analysis of the calcium response after depletion with capsaicin, confirmed that the neurotrophin presynaptically enhanced neurotransmitter release from PN-PAFs. This is the first demonstration that trkB receptors expressed by PN-PAF terminals in lamina II are functional during postnatal development. Implications of this finding are discussed considering that BDNF can be released by these same terminals and microglia, a fraction of which (as shown here) contains BDNF also in unactivated state.

  16. The unsilent majority-TRPV1 drives "spontaneous" transmission of unmyelinated primary afferents within cardiorespiratory NTS.

    PubMed

    Andresen, Michael C; Hofmann, Mackenzie E; Fawley, Jessica A

    2012-12-15

    Cranial primary afferent sensory neurons figure importantly in homeostatic control of visceral organ systems. Of the two broad classes of visceral afferents, the role of unmyelinated or C-type class remains poorly understood. This review contrasts key aspects of peripheral discharge properties of C-fiber afferents and their glutamate transmission mechanisms within the solitary tract nucleus (NTS). During normal prevailing conditions, most information arrives at the NTS through myelinated A-type nerves. However, most of visceral afferent axons (75-90%) in NTS are unmyelinated, C-type axons. Centrally, C-type solitary tract (ST) afferent terminals have presynaptic transient receptor potential vanilloid type 1 (TRPV1) receptors. Capsaicin activation of TRPV1 blocks phasic or synchronous release of glutamate but facilitates release of glutamate from a separate pool of vesicles. This TRPV1-operated pool of vesicles is active at normal temperatures and is responsible for actively driving a 10-fold higher release of glutamate at TRPV1 compared with TRPV1- terminals even in the absence of afferent action potentials. This novel TRPV1 mechanism is responsible for an additional asynchronous release of glutamate that is not present in myelinated terminals. The NTS is rich with presynaptic G protein-coupled receptors, and the implications of TRPV1-operated glutamate offer unique targets for signaling in C-type sensory afferent terminals from neuropeptides, inflammatory mediators, lipid metabolites, cytokines, and cannabinoids. From a homeostatic view, this combination could have broad implications for integration in chronic pathological disturbances in which the numeric dominance of C-type endings and TRPV1 would broadly disturb multisystem control mechanisms.

  17. The coexistence of multiple receptors in a single nerve terminal provides evidence for pre-synaptic integration.

    PubMed

    Ladera, Carolina; Godino, María Del Carmen; Martín, Ricardo; Luján, Rafael; Shigemoto, Ryuichi; Ciruela, Francisco; Torres, Magdalena; Sánchez-Prieto, José

    2007-12-01

    Excitatory synaptic transmission is inhibited by G protein coupled receptors, including the adenosine A(1), GABA(B), and metabotropic glutamate receptor 7. These receptors are present in nerve terminals where they reduce the release of glutamate through activating signaling pathways negatively coupled to Ca(2+) channels and adenylyl cyclase. However, it is not clear whether these receptors operate in distinct subpopulations of nerve terminals or if they are co-expressed in the same nerve terminals, despite the functional consequences that such distributions may have on synaptic transmission. Applying Ca(2+) imaging and immunocytochemistry, we show that these three G protein coupled receptors coexist in a subpopulation of cerebrocortical nerve terminals. The three receptors share an intracellular signaling pathway through which their inhibitory responses are integrated and coactivation of these receptors produced an integrated response. Indeed, this response was highly variable, from a synergistic response at subthreshold agonist concentrations to an occluded response at high agonist concentrations. The presence of multiple receptors in a nerve terminal could be responsible for the physiological effects of neurotransmitter spillover from neighboring synapses or alternatively, the co-release of transmitters by the same nerve terminal.

  18. Light microscopic image analysis system to quantify immunoreactive terminal area apposed to nerve cells

    NASA Technical Reports Server (NTRS)

    Wu, L. C.; D'Amelio, F.; Fox, R. A.; Polyakov, I.; Daunton, N. G.

    1997-01-01

    The present report describes a desktop computer-based method for the quantitative assessment of the area occupied by immunoreactive terminals in close apposition to nerve cells in relation to the perimeter of the cell soma. This method is based on Fast Fourier Transform (FFT) routines incorporated in NIH-Image public domain software. Pyramidal cells of layer V of the somatosensory cortex outlined by GABA immunolabeled terminals were chosen for our analysis. A Leitz Diaplan light microscope was employed for the visualization of the sections. A Sierra Scientific Model 4030 CCD camera was used to capture the images into a Macintosh Centris 650 computer. After preprocessing, filtering was performed on the power spectrum in the frequency domain produced by the FFT operation. An inverse FFT with filter procedure was employed to restore the images to the spatial domain. Pasting of the original image to the transformed one using a Boolean logic operation called 'AND'ing produced an image with the terminals enhanced. This procedure allowed the creation of a binary image using a well-defined threshold of 128. Thus, the terminal area appears in black against a white background. This methodology provides an objective means of measurement of area by counting the total number of pixels occupied by immunoreactive terminals in light microscopic sections in which the difficulties of labeling intensity, size, shape and numerical density of terminals are avoided.

  19. Repression of inactive motor nerve terminals in partially denervated rat muscle after regeneration of active motor axons.

    PubMed Central

    Ribchester, R R; Taxt, T

    1984-01-01

    The fourth deep lumbrical muscle in the hind foot of adult rats was partially denervated by crushing the sural nerve (s.n.). The denervated muscle fibres became completely reinnervated by sprouts from lateral plantar nerve (l.p.n.) motor axons. By about 20 days after the nerve crush, s.n. motor axons started to reinnervate the muscle. In control muscles, a small proportion of the muscle fibres--about 2.5% of the muscle per motor unit--was reinnervated by s.n. motor axons over the following 20 days. Hence the regenerating terminals were able to re-establish functional synapses, despite the fact that all the muscle fibres were functionally innervated by l.p.n. terminals. When nerve impulse conduction in the l.p.n. was blocked with tetrodotoxin for up to 2 weeks, starting from the time when s.n. axons returned to the muscle, s.n. motor axons retrieved a much larger proportion of the muscle fibres--about 6.5% of the muscle per motor unit. There was a concomitant decrease in the tension produced by the sprouted l.p.n. motor axons. Intracellular recordings showed that many muscle fibres became innervated exclusively by regenerated s.n. motor nerve terminals. Measurements of end-plate potentials suggested that l.p.n. sprouts and the original nerve terminals were eliminated non-selectively. These results suggest that regenerating, active motor nerve terminals have an additional competitive advantage in reinnervating innervated muscles, if the intact terminals are inactive. When the l.p.n. was cut, rather than blocked, extensive reinnervation by the s.n. occurred-about 30% of the muscle per motor unit. This suggests that the absence of an intact nerve terminal in the motor end-plate provides a stronger stimulus than inactivity for synapse formation by regenerating motor axons. PMID:6707966

  20. Remodelling of motor nerve terminals in demyelinating axons of periaxin null mutant mice

    PubMed Central

    Court, Felipe A; Brophy, Peter J; Ribchester, Richard R

    2015-01-01

    Myelin formation around axons increases nerve conduction velocity and regulates phenotypic characteristics of the myelinated axon. In the peripheral nervous system, demyelinating forms of hereditary Charcot-Marie-Tooth (CMT) diseases, due to Schwann-cell intrinsic molecular defects, leads to reduced nerve conduction velocity and changes in the axonal phenotype. Several mouse models of CMT diseases have been generated, allowing the study of consequences of demyelination in peripheral nerve fibres. Nevertheless, the effect of demyelination at the level of the neuromuscular synapse has been largely overlooked. Here we show that in the periaxin knock-out mice, a model of CMT condition, neuromuscular junctions develop profound morphological changes in pre-terminal region of motoraxons. These changes include extensive preterminal branches which originate in demyelinated regions of the nerve fibre and axonal swellings associated with residually-myelinated regions of the fibre. Using intracellular recording from muscle fibres we detected asynchronous failure of action potential transmission at high but not low stimulation frequencies, a phenomenon consistent with branch point failure. Taken together, our morphological and electrophysiological findings suggest that preterminal branching due to segmental demyelination near the neuromuscular synapse in periaxin KO mice may underlie phenotypic disabilities present in this mouse model of CMT disease. These results opens a new avenue of research in order to understand the cellular changes responsible for clinical disabilities in demyelinating conditions. PMID:18205176

  1. 5,6-EET Is Released upon Neuronal Activity and Induces Mechanical Pain Hypersensitivity via TRPA1 on Central Afferent Terminals

    PubMed Central

    Sisignano, Marco; Park, Chul-Kyu; Angioni, Carlo; Zhang, Dong Dong; von Hehn, Christian; Cobos, Enrique J.; Ghasemlou, Nader; Xu, Zhen-Zhong; Kumaran, Vigneswara; Lu, Ruirui; Grant, Andrew; Fischer, Michael J. M.; Schmidtko, Achim; Reeh, Peter; Ji, Ru-Rong; Woolf, Clifford J.; Geisslinger, Gerd; Scholich, Klaus; Brenneis, Christian

    2012-01-01

    Epoxyeicosatrienoic acids (EETs) are cytochrome P450-epoxygenase-derived metabolites of arachidonic acid that act as endogenous signaling molecules in multiple biological systems. Here we have investigated the specific contribution of 5,6-EET to transient receptor potential (TRP) channel activation in nociceptor neurons and its consequence for nociceptive processing. We found that, during capsaicin-induced nociception, 5,6-EET levels increased in dorsal root ganglia (DRGs) and the dorsal spinal cord, and 5,6-EET is released from activated sensory neurons in vitro. 5,6-EET potently induced a calcium flux (100 nm) in cultured DRG neurons that was completely abolished when TRPA1 was deleted or inhibited. In spinal cord slices, 5,6-EET dose dependently enhanced the frequency, but not the amplitude, of spontaneous EPSCs (sEPSCs) in lamina II neurons that also responded to mustard oil (allyl isothiocyanate), indicating a presynaptic action. Furthermore, 5,6-EET-induced enhancement of sEPSC frequency was abolished in TRPA1-null mice, suggesting that 5,6-EET presynaptically facilitated spinal cord synaptic transmission by TRPA1. Finally, in vivo intrathecal injection of 5,6-EET caused mechanical allodynia in wild-type but not TRPA1-null mice. We conclude that 5,6-EET is synthesized on the acute activation of nociceptors and can produce mechanical hypersensitivity via TRPA1 at central afferent terminals in the spinal cord. PMID:22553041

  2. Spike and Neuropeptide-Dependent Mechanisms Control GnRH Neuron Nerve Terminal Ca(2+) over Diverse Time Scales.

    PubMed

    Iremonger, Karl J; Porteous, Robert; Herbison, Allan E

    2017-03-22

    Fast cell-to-cell communication in the brain is achieved by action potential-dependent synaptic release of neurotransmitters. The fast kinetics of transmitter release are determined by transient Ca(2+) elevations in presynaptic nerve terminals. Neuromodulators have previously been shown to regulate transmitter release by inhibiting presynaptic Ca(2+) influx. Few studies to date have demonstrated the opposite, that is, neuromodulators directly driving presynaptic Ca(2+) rises and increases in nerve terminal excitability. Here we use GCaMP Ca(2+) imaging in brain slices from mice to address how nerve terminal Ca(2+) is controlled in gonadotropin-releasing hormone (GnRH) neurons via action potentials and neuromodulators. Single spikes and bursts of action potentials evoked fast, voltage-gated Ca(2+) channel-dependent Ca(2+) elevations. In contrast, brief exposure to the neuropeptide kisspeptin-evoked long-lasting Ca(2+) plateaus that persisted for tens of minutes. Neuropeptide-mediated Ca(2+) elevations were independent of action potentials, requiring Ca(2+) entry via voltage-gated Ca(2+) channels and transient receptor potential channels in addition to release from intracellular store mechanisms. Together, these data reveal that neuromodulators can exert powerful and long-lasting regulation of nerve terminal Ca(2+) independently from actions at the soma. Thus, GnRH nerve terminal function is controlled over disparate timescales via both classical spike-dependent and nonclassical neuropeptide-dependent mechanisms.SIGNIFICANCE STATEMENT Nerve terminals are highly specialized regions of a neuron where neurotransmitters and neurohormones are released. Many neuroendocrine neurons release neurohormones in long-duration bursts of secretion. To understand how this is achieved, we have performed live Ca(2+) imaging in the nerve terminals of gonadotropin-releasing hormone neurons. We find that bursts of action potentials and local neuropeptide signals are both capable of

  3. Different Mode of Afferents Determines the Frequency Range of High Frequency Activities in the Human Brain: Direct Electrocorticographic Comparison between Peripheral Nerve and Direct Cortical Stimulation

    PubMed Central

    Kobayashi, Katsuya; Matsumoto, Riki; Matsuhashi, Masao; Usami, Kiyohide; Shimotake, Akihiro; Kunieda, Takeharu; Kikuchi, Takayuki; Mikuni, Nobuhiro; Miyamoto, Susumu; Fukuyama, Hidenao; Takahashi, Ryosuke; Ikeda, Akio

    2015-01-01

    Physiological high frequency activities (HFA) are related to various brain functions. Factors, however, regulating its frequency have not been well elucidated in humans. To validate the hypothesis that different propagation modes (thalamo-cortical vs. cortico-coritcal projections), or different terminal layers (layer IV vs. layer II/III) affect its frequency, we, in the primary somatosensory cortex (SI), compared HFAs induced by median nerve stimulation with those induced by electrical stimulation of the cortex connecting to SI. We employed 6 patients who underwent chronic subdural electrode implantation for presurgical evaluation. We evaluated the HFA power values in reference to the baseline overriding N20 (earliest cortical response) and N80 (late response) of somatosensory evoked potentials (HFASEP(N20) and HFASEP(N80)) and compared those overriding N1 and N2 (first and second responses) of cortico-cortical evoked potentials (HFACCEP(N1) and HFACCEP(N2)). HFASEP(N20) showed the power peak in the frequency above 200 Hz, while HFACCEP(N1) had its power peak in the frequency below 200 Hz. Different propagation modes and/or different terminal layers seemed to determine HFA frequency. Since HFACCEP(N1) and HFA induced during various brain functions share a similar broadband profile of the power spectrum, cortico-coritcal horizontal propagation seems to represent common mode of neural transmission for processing these functions. PMID:26087042

  4. Different Mode of Afferents Determines the Frequency Range of High Frequency Activities in the Human Brain: Direct Electrocorticographic Comparison between Peripheral Nerve and Direct Cortical Stimulation.

    PubMed

    Kobayashi, Katsuya; Matsumoto, Riki; Matsuhashi, Masao; Usami, Kiyohide; Shimotake, Akihiro; Kunieda, Takeharu; Kikuchi, Takayuki; Mikuni, Nobuhiro; Miyamoto, Susumu; Fukuyama, Hidenao; Takahashi, Ryosuke; Ikeda, Akio

    2015-01-01

    Physiological high frequency activities (HFA) are related to various brain functions. Factors, however, regulating its frequency have not been well elucidated in humans. To validate the hypothesis that different propagation modes (thalamo-cortical vs. cortico-coritcal projections), or different terminal layers (layer IV vs. layer II/III) affect its frequency, we, in the primary somatosensory cortex (SI), compared HFAs induced by median nerve stimulation with those induced by electrical stimulation of the cortex connecting to SI. We employed 6 patients who underwent chronic subdural electrode implantation for presurgical evaluation. We evaluated the HFA power values in reference to the baseline overriding N20 (earliest cortical response) and N80 (late response) of somatosensory evoked potentials (HFA(SEP(N20)) and HFA(SEP(N80))) and compared those overriding N1 and N2 (first and second responses) of cortico-cortical evoked potentials (HFA(CCEP(N1)) and HFA(CCEP(N2))). HFA(SEP(N20)) showed the power peak in the frequency above 200 Hz, while HFA(CCEP(N1)) had its power peak in the frequency below 200 Hz. Different propagation modes and/or different terminal layers seemed to determine HFA frequency. Since HFA(CCEP(N1)) and HFA induced during various brain functions share a similar broadband profile of the power spectrum, cortico-coritcal horizontal propagation seems to represent common mode of neural transmission for processing these functions.

  5. Transfer characteristics of the hair cell's afferent synapse

    NASA Astrophysics Data System (ADS)

    Keen, Erica C.; Hudspeth, A. J.

    2006-04-01

    The sense of hearing depends on fast, finely graded neurotransmission at the ribbon synapses connecting hair cells to afferent nerve fibers. The processing that occurs at this first chemical synapse in the auditory pathway determines the quality and extent of the information conveyed to the central nervous system. Knowledge of the synapse's input-output function is therefore essential for understanding how auditory stimuli are encoded. To investigate the transfer function at the hair cell's synapse, we developed a preparation of the bullfrog's amphibian papilla. In the portion of this receptor organ representing stimuli of 400-800 Hz, each afferent nerve fiber forms several synaptic terminals onto one to three hair cells. By performing simultaneous voltage-clamp recordings from presynaptic hair cells and postsynaptic afferent fibers, we established that the rate of evoked vesicle release, as determined from the average postsynaptic current, depends linearly on the amplitude of the presynaptic Ca2+ current. This result implies that, for receptor potentials in the physiological range, the hair cell's synapse transmits information with high fidelity. auditory system | exocytosis | glutamate | ribbon synapse | synaptic vesicle

  6. Increase of transcription factor EB (TFEB) and lysosomes in rat DRG neurons and their transportation to the central nerve terminal in dorsal horn after nerve injury.

    PubMed

    Jung, J; Uesugi, N; Jeong, N Y; Park, B S; Konishi, H; Kiyama, H

    2016-01-28

    In the spinal dorsal horn (DH), nerve injury activates microglia and induces neuropathic pain. Several studies clarified an involvement of adenosine triphosphate (ATP) in the microglial activation. However, the origin of ATP together with the release mechanism is unclear. Recent in vitro study revealed that an ATP marker, quinacrine, in lysosomes was released from neurite terminal of dorsal root ganglion (DRG) neurons to extracellular space via lysosomal exocytosis. Here, we demonstrate a possibility that the lysosomal ingredient including ATP released from DRG neurons by lysosomal-exocytosis is an additional source of the glial activation in DH after nerve injury. After rat L5 spinal nerve ligation (SNL), mRNA for transcription factor EB (TFEB), a transcription factor controlling lysosomal activation and exocytosis, was induced in the DRG. Simultaneously both lysosomal protein, LAMP1- and vesicular nuclear transporter (VNUT)-positive vesicles were increased in L5 DRG neurons and ipsilateral DH. The quinacrine staining in DH was increased and co-localized with LAMP1 immunoreactivity after nerve injury. In DH, LAMP1-positive vesicles were also co-localized with a peripheral nerve marker, Isolectin B4 (IB4) lectin. Injection of the adenovirus encoding mCherry-LAMP1 into DRG showed that mCherry-positive lysosomes are transported to the central nerve terminal in DH. These findings suggest that activation of lysosome synthesis including ATP packaging in DRG, the central transportation of the lysosome, and subsequent its exocytosis from the central nerve terminal of DRG neurons in response to nerve injury could be a partial mechanism for activation of microglia in DH. This lysosome-mediated microglia activation mechanism may provide another clue to control nociception and pain.

  7. FMRFamide-related peptide expression in the vestibular-afferent neurons.

    PubMed

    Mercado, Francisco; López, Iván; Ortega, Aida; Almanza, Angélica; Soto, Enrique; Vega, Rosario

    2012-03-28

    Vestibular-afferent neurons innervate hair cells from the sensory epithelia of vestibular end-organs and their action-potential discharge dynamics are driven by linear and angular accelerations of the head. The electrical activity of the vestibular-afferent neurons depends on their intrinsic properties and on the synaptic input from hair cells and from the terminals of the efferent system. Here we report that vestibular-afferent neurons of the rat are immunoreactive to RFamide-related peptides, and that the stronger signal comes from calyx-shaped neuron dendrites, with no signal detected in hair cells or supporting cells. The whole-cell voltage clamp recording of isolated afferent neurons showed that they express robust acid-sensing ionic currents (ASICs). Extracellular multiunit recordings of the vestibular nerve in a preparation in vitro of the rat inner ear showed that the perfusion of FMRFamide (a snail ortholog of this family of neuropeptides) exerts an excitatory effect on the afferent-neurons spike-discharge rate. Because the FMRFamide cannot activate the ASIC but reduces its desensitization generating a more robust current, its effect indicates that the ASIC are tonically active in the vestibular-afferent neurons and modulated by RFamide-like peptides.

  8. Somatostatin inhibits activation of dorsal cutaneous primary afferents induced by antidromic stimulation of primary afferents from an adjacent thoracic segment in the rat.

    PubMed

    Guo, Yuan; Yao, Fan-Rong; Cao, Dong-Yuan; Pickar, Joel G; Zhang, Qi; Wang, Hui-Sheng; Zhao, Yan

    2008-09-10

    To investigate the effect of somatostatin on the cross-excitation between adjacent primary afferent terminals in the rats, we recorded single unit activity from distal cut ends of dorsal cutaneous branches of the T10 and T12 spinal nerves in response to antidromic stimulation of the distal cut end of the T11 dorsal root in the presence and absence of somatostatin and its receptor antagonist applied to the receptive field of the recorded nerve. Afferent fibers were classified based upon their conduction velocity. Mean mechanical thresholds decreased and spontaneous discharge rates increased significantly in C and Adelta but not Abeta fibers of the T10 and T12 spinal nerves in both male and female rats following antidromic electrical stimulation (ADES) of the dorsal root from adjacent spinal segment (DRASS) indicating cross-excitation of thin fiber afferents. The cross-excitation was not significantly different between male and female rats. Microinjection of somatostatin into the receptive field of recorded units inhibited the cross-excitation. This inhibitory effect, in turn, was reversed by the somatostation receptor antagonist cyclo-somatostatin (c-SOM). Application of c-SOM alone followed by ADES of DRASS significantly decreased the mechanical thresholds and increased the discharge rates of C and Adelta fibers, indicating that endogenous release of somatostatin plays a tonic inhibitory role on the cross-excitation between peripheral nerves. These results suggest that somatostatin could inhibit the cross-excitation involved in peripheral hyperalgesia and have a peripheral analgesic effect.

  9. Contribution of hind limb flexor muscle afferents to the timing of phase transitions in the cat step cycle.

    PubMed

    Hiebert, G W; Whelan, P J; Prochazka, A; Pearson, K G

    1996-03-01

    1. In this investigation, we tested the hypothesis that muscle spindle afferents signaling the length of hind-leg flexor muscles are involved in terminating extensor activity and initiating flexion during walking. The hip flexor muscle iliopsoas (IP) and the ankle flexors tibialis anterior (TA) and extensor digitorum longus (EDL) were stretched or vibrated at various phases of the step cycle in spontaneously walking decerebrate cats. Changes in electromyogram amplitude, duration, and timing were then examined. The effects of electrically stimulating group I and II afferents in the nerves to TA and EDL also were examined. 2. Stretch of the individual flexor muscles (IP, TA, or EDL) during the stance phase reduced the duration of extensor activity and promoted the onset of flexor burst activity. The contralateral step cycle also was affected by the stretch, the duration of flexor activity being shortened and extensor activity occurring earlier. Therefore, stretch of the flexor muscles during the stance phase reset the locomotor rhythm to flexion ipsilaterally and extension contralaterally. 3. Results of electrically stimulating the afferents from the TA and EDL muscles suggested that different groups of afferents were responsible for the resetting of the step cycle. Stimulation of the TA nerve reset the locomotor step cycle when the stimulus intensity was in the group II range (2-5 xT). By contrast, stimulation of the EDL nerve generated strong resetting of the step cycle in the range of 1.2-1.4 xT, where primarily the group Ia afferents from the muscle spindles would be activated. 4. Vibration of IP or EDL during stance reduced the duration of the extensor activity by similar amounts to that produced by muscle stretch or by electrical stimulation of EDL at group Ia strengths. This suggests that the group Ia afferents from IP and EDL are capable of resetting the locomotor pattern generator. Vibration of TA did not affect the locomotor rhythm. 5. Stretch of IP or

  10. Immunogold characteristics of VGLUT3-positive GABAergic nerve terminals suggest corelease of glutamate.

    PubMed

    Stensrud, Mats Julius; Sogn, Carl Johan; Gundersen, Vidar

    2015-12-15

    There is compelling evidence that glutamate can act as a cotransmitter in the mammalian brain. Interestingly, the third vesicular glutamate transporter (VGLUT3) is primarily found in neurons that were anticipated to be nonglutamatergic. Whereas the function of VGLUT3 in acetylcholinergic and serotoninergic neurons has been elucidated, the role of VGLUT3 in neurons releasing gamma-aminobutyric acid (GABA) is not settled. We have previously shown that VGLUT3 is found together with the vesicular GABA transporter (VIAAT) on synaptic vesicle membranes in the hippocampus. Now we provide novel electron microscopic data from the rat hippocampus suggesting that glutamate is enriched in inhibitory nerve terminals containing VGLUT3 compared to those lacking VGLUT3. The opposite was found for GABA; VGLUT3-positive inhibitory terminals contained lower density of GABA labeling compared to VGLUT3-negative inhibitory terminals. In addition, semiquantitative confocal immunofluorescence showed that N-methyl-D-aspartate (NMDA)-receptor labeling was present more frequently in VGLUT3-positive/VIAAT-positive synapses versus in VGLUT3-negative/VIAAT-positive synapses. Electron microscopic immunogold data further suggest that NMDA receptors are enriched in VGLUT3 containing inhibitory terminals. Our data reveal new chemical characteristics of a subset of GABAergic interneurons in the hippocampus. The analyses suggest that glutamate is coreleased with GABA from hippocampal basket cell-synapses to act on NMDA receptors.

  11. Neuronal porosome - The secretory portal at the nerve terminal: Its structure-function, composition, and reconstitution

    NASA Astrophysics Data System (ADS)

    Jena, Bhanu P.

    2014-09-01

    Cup-shaped secretory portals at the cell plasma membrane called porosomes mediate secretion from cells. Membrane bound secretory vesicles transiently dock and fuse at the cytosolic compartment of the porosome base to expel intravesicular contents to the outside during cell secretion. In the past decade, the structure, isolation, composition, and functional reconstitution of the neuronal porosome complex has been accomplished providing a molecular understanding of its structure-function. Neuronal porosomes are 15 nm cup-shaped lipoprotein structures composed of nearly 40 proteins; compared to the 120 nm nuclear pore complex comprised of over 500 protein molecules composed of 30 different proteins. Being a membrane-associated supramolecular complex has precluded determination of the atomic structure of the porosome. However recent studies using small-angle X-ray solution scattering (SAXS), provide at sub-nanometer resolution, the native 3D structure of the neuronal porosome complex associated with docked synaptic vesicle at the nerve terminal. Additionally, results from the SAXS study and earlier studies using atomic force microscopy, provide the possible molecular mechanism involved in porosome-mediated neurotransmitter release at the nerve terminal.

  12. Electrophysiological characterization of human rectal afferents

    PubMed Central

    Ng, Kheng-Seong; Brookes, Simon J.; Montes-Adrian, Noemi A.; Mahns, David A.

    2016-01-01

    It is presumed that extrinsic afferent nerves link the rectum to the central nervous system. However, the anatomical/functional existence of such nerves has never previously been demonstrated in humans. Therefore, we aimed to identify and make electrophysiological recordings in vitro from extrinsic afferents, comparing human rectum to colon. Sections of normal rectum and colon were procured from anterior resection and right hemicolectomy specimens, respectively. Sections were pinned and extrinsic nerves dissected. Extracellular visceral afferent nerve activity was recorded. Neuronal responses to chemical [capsaicin and “inflammatory soup” (IS)] and mechanical (Von Frey probing) stimuli were recorded and quantified as peak firing rate (range) in 1-s intervals. Twenty-eight separate nerve trunks from eight rectums were studied. Of these, spontaneous multiunit afferent activity was recorded in 24 nerves. Peak firing rates increased significantly following capsaicin [median 6 (range 3–25) spikes/s vs. 2 (1–4), P < 0.001] and IS [median 5 (range 2–18) spikes/s vs. 2 (1–4), P < 0.001]. Mechanosensitive “hot spots” were identified in 16 nerves [median threshold 2.0 g (range 1.4–6.0 g)]. In eight of these, the threshold decreased after IS [1.0 g (0.4–1.4 g)]. By comparison, spontaneous activity was recorded in only 3/30 nerves studied from 10 colons, and only one hot spot (threshold 60 g) was identified. This study confirms the anatomical/functional existence of extrinsic rectal afferent nerves and characterizes their chemo- and mechanosensitivity for the first time in humans. They have different electrophysiological properties to colonic afferents and warrant further investigation in disease states. PMID:27789454

  13. Parallel reflex pathways from flexor muscle afferents evoking resetting and flexion enhancement during fictive locomotion and scratch in the cat.

    PubMed

    Stecina, Katinka; Quevedo, Jorge; McCrea, David A

    2005-11-15

    Reflex actions of muscle afferents in hindlimb flexor nerves were examined on ipsilateral motoneurone activity recorded in peripheral nerves during midbrain stimulation-evoked fictive locomotion and during fictive scratch in decerebrate cats. Trains of stimuli (15-30 shocks at 200 Hz) were delivered during the flexion phase at intensities sufficient to activate both group I and II afferents (5 times threshold, T). In many preparations tibialis anterior (TA) nerve stimulation terminated ongoing flexion and reset the locomotor cycle to extension (19/31 experiments) while extensor digitorum longus (EDL) stimulation increased and prolonged the ongoing flexor phase activity (20/33 preparations). The effects of sartorius, iliopsoas and peroneus longus muscle afferent stimulation were qualitatively similar to those of EDL nerve. Resetting to extension was seen only with higher intensity stimulation (5T) while ongoing flexor activity was often enhanced at group I intensity (2T) stimulation. The effects of flexor nerve stimulation were qualitatively similar during fictive scratch. Reflex reversals were consistently observed in some fictive locomotor preparations. In those cases, EDL stimulation produced a resetting to extension and TA stimulation prolonged the ongoing flexion phase. Occasionally reflex reversals occurred spontaneously during only one of several stimulus presentations. The variable and opposite actions of flexor afferents on the locomotor step cycle indicate the existence of parallel spinal reflex pathways. A hypothetical organization of reflex pathways from flexor muscle afferents to the spinal pattern generator networks with competing actions of group I and group II afferents on the flexor and extensor portions of this central circuitry is proposed.

  14. Expression of 5-HT3 receptors by extrinsic duodenal afferents contribute to intestinal inhibition of gastric emptying.

    PubMed

    Raybould, Helen E; Glatzle, Jorg; Robin, Carla; Meyer, James H; Phan, Thomas; Wong, Helen; Sternini, Catia

    2003-03-01

    Intestinal perfusion with carbohydrates inhibits gastric emptying via vagal and spinal capsaicin-sensitive afferent pathways. The aim of the present study was to determine the role of 1) 5-hydroxytryptamine (5-HT)(3) receptors (5-HT(3)R) in mediating glucose-induced inhibition of gastric emptying and 2) 5-HT(3)R expression in vagal and spinal afferents in innervating the duodenum. In awake rats fitted with gastric and duodenal cannulas, perfusion of the duodenum with glucose (50 and 100 mg) inhibited gastric emptying. Intestinal perfusion of mannitol inhibited gastric emptying only at the highest concentration (990 mosm/kgH(2)O). Pretreatment with the 5-HT(3)R antagonist tropisetron abolished both glucose- and mannitol-induced inhibition of gastric emptying. Retrograde labeling of visceral afferents by injection of dextran-conjugated Texas Red into the duodenal wall was used to identify extrinsic primary afferents. Immunoreactivity for 5-HT(3)R, visualized with an antibody directed to the COOH terminus of the rat 5-HT(3)R, was found in >80% of duodenal vagal and spinal afferents. These results show that duodenal extrinsic afferents express 5-HT(3)R and that the receptor mediates specific glucose-induced inhibition of gastric emptying. These findings support the hypothesis that enterochromaffin cells in the intestinal mucosa release 5-HT in response to glucose, which activates 5-HT(3)R on afferent nerve terminals to evoke reflex changes in gastric motility. The primary glucose sensors of the intestine may be mucosal enterochromaffin cells.

  15. The effects of dietary protein restriction on chorda tympani nerve taste responses and terminal field organization.

    PubMed

    Thomas, J E; Hill, D L

    2008-11-19

    Prenatal dietary sodium restriction produces profound developmental effects on rat functional taste responses and formation of neural circuits in the brainstem. Converging evidence indicates that the underlying mechanisms for these effects are related to a compromised nutritional state and not to direct stimulus-receptor interactions. We explored whether early malnourishment produces similar functional and structural effects to those seen following dietary sodium restriction by using a protein deficient, sodium replete diet. To determine if early dietary protein-restriction affects the development of the peripheral gustatory system, multi-fiber neurophysiological recordings were made from the chorda tympani nerve and anterograde track tracing of the chorda tympani nerve into the nucleus of the solitary tract (NTS) was accomplished in rats fed a protein-restricted or a control diet (6% and 20%, respectively). The dietary regimens began on embryonic day 7 and continued until rats were used for neurophysiological recordings (postnatal days (P) 35-50) or for chorda tympani terminal field labeling (P40-50). Responses to a concentration series of NaCl, sodium acetate, KCl, and to 0.50 M sucrose, 0.03 M quinine-HCl, and 0.01 N HCl revealed attenuated responses (30-60%) to sodium-specific stimuli in rats fed the 6% protein diet compared with those fed the 20% protein diet. Responses to all other stimuli were similar between groups. Terminal field volumes were nearly twofold larger in protein-restricted rats compared with controls, with the differences located primarily in the dorsal-caudal zone of the terminal field. These results are similar to the results seen previously in rats fed a sodium-restricted diet throughout pre- and postnatal development, suggesting that dietary sodium- and protein-restriction share similar mechanisms in altering gustatory development.

  16. Distribution of glycine receptors on the surface of the mature calyx of Held nerve terminal

    PubMed Central

    Trojanova, Johana; Kulik, Akos; Janacek, Jiri; Kralikova, Michaela; Syka, Josef; Turecek, Rostislav

    2014-01-01

    The physiological functions of glycine receptors (GlyRs) depend on their subcellular locations. In axonal terminals of the central neurons, GlyRs trigger a slow facilitation of presynaptic transmitter release; however, their spatial relationship to the release sites is not known. In this study, we examined the distribution of GlyRs in the rat glutamatergic calyx of Held nerve terminal using high-resolution pre-embedding immunoelectron microscopy. We performed a quantitative analysis of GlyR-associated immunogold (IG) labeling in 3D reconstructed calyceal segments. A variable density of IG particles and their putative accumulations, inferred from the frequency distribution of inter-IG distances, indicated a non-uniform distribution of the receptors in the calyx. Subsequently, increased densities of IG particles were found in calyceal swellings, structures characterized by extensive exocytosis of glutamate. In swellings as well as in larger calyceal stalks, IG particles did not tend to accumulate near the glutamate releasing zones. On the other hand, GlyRs in swellings (but not in stalks) preferentially occupied membrane regions, unconnected to postsynaptic cells and presumably accessible by ambient glycine. Furthermore, the sites with increased GlyR concentrations were found in swellings tightly juxtaposed with GABA/glycinergic nerve endings. Thus, the results support the concept of an indirect mechanism underlying the modulatory effects of calyceal GlyRs, activated by glycine spillover. We also suggest the existence of an activity-dependent mechanism regulating the surface distribution of α homomeric GlyRs in axonal terminals of central neurons. PMID:25339867

  17. A role of amphiphysin in synaptic vesicle endocytosis suggested by its binding to dynamin in nerve terminals.

    PubMed Central

    David, C; McPherson, P S; Mundigl, O; de Camilli, P

    1996-01-01

    Amphiphysin, a major autoantigen in paraneoplastic Stiff-Man syndrome, is an SH3 domain-containing neuronal protein, concentrated in nerve terminals. Here, we demonstrate a specific, SH3 domain-mediated, interaction between amphiphysin and dynamin by gel overlay and affinity chromatography. In addition, we show that the two proteins are colocalized in nerve terminals and are coprecipitated from brain extracts consistent with their interactions in situ. We also report that a region of amphiphysin distinct from its SH3 domain mediates its binding to the alpha c subunit of AP2 adaptin, which is also concentrated in nerve terminals. These findings support a role of amphiphysin in synaptic vesicle endocytosis. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 PMID:8552632

  18. Action potential broadening and frequency-dependent facilitation of calcium signals in pituitary nerve terminals.

    PubMed

    Jackson, M B; Konnerth, A; Augustine, G J

    1991-01-15

    Hormone release from nerve terminals in the neurohypophysis is a sensitive function of action potential frequency. We have investigated the cellular mechanisms responsible for this frequency-dependent facilitation by combining patch clamp and fluorimetric Ca2+ measurements in single neurosecretory terminals in thin slices of the rat posterior pituitary. In these terminals both action potential-induced changes in the intracellular Ca2+ concentration ([Ca2+]i) and action potential duration were enhanced by high-frequency stimuli, all with a frequency dependence similar to that of hormone release. Furthermore, brief voltage clamp pulses inactivated a K+ current with a very similar frequency dependence. These results support a model for frequency-dependent facilitation in which the inactivation of a K+ current broadens action potentials, leading to an enhancement of [Ca2+]i signals. Further experiments tested for a causal relationship between action potential broadening and facilitation of [Ca2+]i changes. First, increasing the duration of depolarization, either by broadening action potentials with the K(+)-channel blocker tetraethylammonium or by applying longer depolarizing voltage clamp steps, increased [Ca2+]i changes. Second, eliminating frequency-dependent changes in duration, by voltage clamping the terminal with constant duration pulses, substantially reduced the frequency-dependent enhancement of [Ca2+]i changes. These results indicate that action potential broadening contributes to frequency-dependent facilitation of [Ca2+]i changes. However, the small residual frequency dependence of [Ca2+]i changes seen with constant duration stimulation suggests that a second process, distinct from action potential broadening, also contributes to facilitation. These two frequency-dependent mechanisms may also contribute to activity-dependent plasticity in synaptic terminals.

  19. Patch-clamp Capacitance Measurements and Ca2+ Imaging at Single Nerve Terminals in Retinal Slices

    PubMed Central

    Kim, Mean-Hwan; Vickers, Evan; von Gersdorff, Henrique

    2012-01-01

    embedded in agar (or placed onto a filter paper) and then sliced 20, 23, 18, 9. In this video, we employ the pre-embedding agar technique using goldfish retina. Some of the giant bipolar cell terminals in our slices of goldfish retina are axotomized (axon-cut) during the slicing procedure. This allows us to isolate single presynaptic nerve terminal inputs, because recording from axotomized terminals excludes the signals from the soma-dendritic compartment. Alternatively, one can also record from intact Mb bipolar cells, by recording from terminals attached to axons that have not been cut during the slicing procedure. Overall, use of this experimental protocol will aid in studies of retinal synaptic physiology, microcircuit functional analysis, and synaptic transmission at ribbon synapses. PMID:22297269

  20. Lunar and Martian soil stimulants have different effects on L-[14C]glutamate binding to brain nerve terminals

    NASA Astrophysics Data System (ADS)

    Borisova, Tatiana; Krisanova, Natalia; Nazarova, Anastasiya; Borysov, Arseniy; Chunihin, Olexander

    Nano-sized particles can be deleterious to human physiology because they may be internalized by lung epithelium and overcome the blood-brain barrier. The health effects from exposure to Lunar and Martian dust are almost completely unknown, whereas they can be deleterious to human physiology. The effects of Lunar and Martian Soil Simulants (Orbital Technologies Corporation, Madison, USA) on the conductance of planar lipid membrane, membrane potential, acidification of synaptic vesicles, glutamate uptake, and ambient level of glutamate in isolated rat brain nerve terminals (synaptosomes) were studied using photon correlation spectroscopy, Planar Lipid Bilayer technique, spectrofluorimetry, radiolabeled assay, respectively. Lunar and Martian Soil Simulants did not influence the conductance of planar lipid membrane. It was revealed that nerve terminals were not indifferent to the exposure to inorganic particles of Lunar and Martian Soil Simulants. Using Zetasizer Nanosystem (Malvern Instruments) with helium-neon laser for dynamic light scattering (DLS), the synaptosomal size before and after the addition of Lunar and Martian Soil Simulants was measured and the binding of Lunar and Martian Soil Simulants inorganic particles to nerve terminals was demonstrated. Using potential-sensitive fluorescent dye rhodamine 6G, we showed that Lunar and Martian Soil particles did not influence the potential of the plasma membrane of nerve terminals. Acidification of synaptic vesicles of nerve terminals was not changed in the presence of Lunar and Martian Soil particles that was revealed with pH-sensitive fluorescent dye acridine orange. Martian Soil Simulant particles did not change binding of L-[14C]glutamate to brain nerve terminals, in contrast, Lunar ones changed this parameter and this fact may have harmful consequences to human physiology, in particular, glutamate homeostasis in the mammalian CNS.

  1. Transients in global Ca2+ concentration induced by electrical activity in a giant nerve terminal

    PubMed Central

    Neher, Erwin; Taschenberger, Holger

    2013-01-01

    Giant nerve terminals offer a unique opportunity to learn about dynamic changes in intracellular global Ca2+ concentration ([Ca2+]i) because this quantity can be measured precisely with indicator dyes and the composition of the intra-terminal ionic milieu can be controlled. We review here recent literature on [Ca2+]i signalling in the calyx of Held and discuss what these measurements can tell us about endogenous Ca2+ buffers and Ca2+ extrusion mechanisms. We conclude that in spite of the favourable experimental conditions, some unresolved questions still remain regarding absolute values for the Ca2+-binding ratio, the affinity of the basic fixed buffer and the Ca2+ affinities of the major endogenous Ca2+ binding proteins. Uncertainties about some of these presynaptic properties, including the roles of Mg2+ and ATP (as a Mg2+ buffer), however, extend to the point that mechanisms controlling the decay of [Ca2+]i signals in unperturbed terminals may have to be reconsidered. PMID:23529127

  2. Sensory nerves in lung and airways.

    PubMed

    Lee, Lu-Yuan; Yu, Jerry

    2014-01-01

    Sensory nerves innervating the lung and airways play an important role in regulating various cardiopulmonary functions and maintaining homeostasis under both healthy and disease conditions. Their activities conducted by both vagal and sympathetic afferents are also responsible for eliciting important defense reflexes that protect the lung and body from potential health-hazardous effects of airborne particulates and chemical irritants. This article reviews the morphology, transduction properties, reflex functions, and respiratory sensations of these receptors, focusing primarily on recent findings derived from using new technologies such as neural immunochemistry, isolated airway-nerve preparation, cultured airway neurons, patch-clamp electrophysiology, transgenic mice, and other cellular and molecular approaches. Studies of the signal transduction of mechanosensitive afferents have revealed a new concept of sensory unit and cellular mechanism of activation, and identified additional types of sensory receptors in the lung. Chemosensitive properties of these lung afferents are further characterized by the expression of specific ligand-gated ion channels on nerve terminals, ganglion origin, and responses to the action of various inflammatory cells, mediators, and cytokines during acute and chronic airway inflammation and injuries. Increasing interest and extensive investigations have been focused on uncovering the mechanisms underlying hypersensitivity of these airway afferents, and their role in the manifestation of various symptoms under pathophysiological conditions. Several important and challenging questions regarding these sensory nerves are discussed. Searching for these answers will be a critical step in developing the translational research and effective treatments of airway diseases.

  3. Interaction of /sup 125/I-labeled botulinum neurotoxins with nerve terminals. II. Autoradiographic evidence for its uptake into motor nerves by acceptor-mediated endocytosis

    SciTech Connect

    Black, J.D.; Dolly, J.O.

    1986-01-01

    Using pharmacological and autoradiographic techniques it has been shown that botulinum neurotoxin (BoNT) is translocated across the motor nerve terminal membrane to reach a postulated intraterminal target. In the present study, the nature of this uptake process was investigated using electron microscopic autoradiography. It was found that internalization is acceptor-mediated and that binding to specific cell surface acceptors involves the heavier chain of the toxin. In addition, uptake was shown to be energy and temperature-dependent and to be accelerated by nerve stimulation, a treatment which also shortens the time course of the toxin-induced neuroparalysis. These results, together with the observation that silver grains were often associated with endocytic structures within the nerve terminal, suggested that acceptor-mediated endocytosis is responsible for toxin uptake. Possible recycling of BoNT acceptors (an important aspect of acceptor-mediated endocytosis of toxins) at motor nerve terminals was indicated by comparing the extent of labeling in the presence and absence of metabolic inhibitors. On the basis of these collective results, it is concluded that BoNT is internalized by acceptor-mediated endocytosis and, hence, the data support the proposal that this toxin inhibits release of acetylcholine by interaction with an intracellular target.

  4. Field potentials generated by group II muscle afferents in the lower-lumbar segments of the feline spinal cord

    PubMed Central

    Riddell, J S; Hadian, M

    2000-01-01

    The actions of group II muscle afferents projecting to the lower-lumbar (L6 and L7) segments of the cat spinal cord were investigated by recording the cord dorsum and focal synaptic field potentials evoked by electrical stimulation of hindlimb muscle nerves. Cord dorsum potentials recorded over the lower-lumbar segments were generally much smaller than those produced by group II afferents terminating within the midlumbar and sacral segments. Only group II afferents of tibialis posterior produced potentials with an amplitude (mean maximal amplitude 39 μV, n = 7) approaching that of potentials over other segments. Focal synaptic potentials (mean maximal amplitudes 135–200 μV) were evoked by group II afferents of the following muscle nerves, listed in order of effectiveness: quadriceps, tibialis posterior (throughout L6 and L7), gastrocnemius soleus, flexor digitorum longus, posterior biceps-semitendinosus and popliteus (mainly within L7). Field potentials were recorded in the dorsal horn (laminae IV–V) and also more ventrally in a region which included the lateral part of the intermediate zone (lateral to the large group I intermediate field potentials) and often extended into the ventral horn (laminae V–VII). The latencies of the group II potentials are considered compatible with the monosynaptic actions of the fastest conducting group II muscle afferents. The results are compared with morphological evidence on the pattern of termination of group II muscle afferents in the lower-lumbar segments and with previous descriptions of the actions of group II muscle afferents in midlumbar and sacral segments. PMID:10618155

  5. TRPA1 activation by lidocaine in nerve terminals results in glutamate release increase

    SciTech Connect

    Piao, L.-H.; Fujita, Tsugumi; Jiang, C.-Y.; Liu Tao; Yue, H.-Y.; Nakatsuka, Terumasa; Kumamoto, Eiichi

    2009-02-20

    We examined the effects of local anesthetics lidocaine and procaine on glutamatergic spontaneous excitatory transmission in substantia gelatinosa (SG) neurons in adult rat spinal cord slices with whole-cell patch-clamp techniques. Bath-applied lidocaine (1-5 mM) dose-dependently and reversibly increased the frequency but not the amplitude of spontaneous excitatory postsynaptic current (sEPSC) in SG neurons. Lidocaine activity was unaffected by the Na{sup +}-channel blocker, tetrodotoxin, and the TRPV1 antagonist, capsazepine, but was inhibited by the TRP antagonist, ruthenium red. In the same neuron, the TRPA1 agonist, allyl isothiocyanate, and lidocaine both increased sEPSC frequency. In contrast, procaine did not produce presynaptic enhancement. These results indicate that lidocaine activates TRPA1 in nerve terminals presynaptic to SG neurons to increase the spontaneous release of L-glutamate.

  6. TRPA1 activation by lidocaine in nerve terminals results in glutamate release increase.

    PubMed

    Piao, Lian-Hua; Fujita, Tsugumi; Jiang, Chang-Yu; Liu, Tao; Yue, Hai-Yuan; Nakatsuka, Terumasa; Kumamoto, Eiichi

    2009-02-20

    We examined the effects of local anesthetics lidocaine and procaine on glutamatergic spontaneous excitatory transmission in substantia gelatinosa (SG) neurons in adult rat spinal cord slices with whole-cell patch-clamp techniques. Bath-applied lidocaine (1-5 mM) dose-dependently and reversibly increased the frequency but not the amplitude of spontaneous excitatory postsynaptic current (sEPSC) in SG neurons. Lidocaine activity was unaffected by the Na(+)-channel blocker, tetrodotoxin, and the TRPV1 antagonist, capsazepine, but was inhibited by the TRP antagonist, ruthenium red. In the same neuron, the TRPA1 agonist, allyl isothiocyanate, and lidocaine both increased sEPSC frequency. In contrast, procaine did not produce presynaptic enhancement. These results indicate that lidocaine activates TRPA1 in nerve terminals presynaptic to SG neurons to increase the spontaneous release of L-glutamate.

  7. Flow Cytometric Analysis of Presynaptic Nerve Terminals Isolated from Rats Subjected to Hypergravity

    NASA Astrophysics Data System (ADS)

    Borisova, Tatiana

    2008-06-01

    Flow cytometric studies revealed an insignificant decrease in cell size heterogeneity and cytoplasmic granularity of rat brain nerve terminals (synaptosomes) isolated from animals subjected to centrifuge-induced hypergravity as compared to control ones. The analysis of plasma membrane potential using the potentiometric optical dye rhodamine 6G showed a decrease in fluorescence intensity by 10 % at steady state level in hypergravity synaptosomes. To monitor synaptic vesicle acidification we used pH-sensitive fluorescent dye acridine orange and demonstrated a lower fluorescence intensity level at steady state (10%) after hypergravity as compared to controls. Thus, exposure to hypergravity resulted in depolarization of the synaptosomal plasma membrane and diminution in synaptic vesicle acidification that may be a cause leading to altered synaptic neurotransmission.

  8. Collagen-derived matricryptins promote inhibitory nerve terminal formation in the developing neocortex

    PubMed Central

    Su, Jianmin; Chen, Jiang; Lippold, Kumiko; Monavarfeshani, Aboozar; Carrillo, Gabriela Lizana; Jenkins, Rachel

    2016-01-01

    Inhibitory synapses comprise only ∼20% of the total synapses in the mammalian brain but play essential roles in controlling neuronal activity. In fact, perturbing inhibitory synapses is associated with complex brain disorders, such as schizophrenia and epilepsy. Although many types of inhibitory synapses exist, these disorders have been strongly linked to defects in inhibitory synapses formed by Parvalbumin-expressing interneurons. Here, we discovered a novel role for an unconventional collagen—collagen XIX—in the formation of Parvalbumin+ inhibitory synapses. Loss of this collagen results not only in decreased inhibitory synapse number, but also in the acquisition of schizophrenia-related behaviors. Mechanistically, these studies reveal that a proteolytically released fragment of this collagen, termed a matricryptin, promotes the assembly of inhibitory nerve terminals through integrin receptors. Collectively, these studies not only identify roles for collagen-derived matricryptins in cortical circuit formation, but they also reveal a novel paracrine mechanism that regulates the assembly of these synapses. PMID:26975851

  9. A fast, transient K+ current in neurohypophysial nerve terminals of the rat.

    PubMed Central

    Thorn, P J; Wang, X M; Lemos, J R

    1991-01-01

    1. Nerve terminals of the rat posterior pituitary were acutely dissociated and identified using a combination of morphological and immunohistochemical techniques. Macroscopic terminal membrane currents and voltages were studied using the whole-cell patch clamp technique. 2. In physiological solutions, depolarizing voltage clamp steps, from a holding potential (-80 mV) similar to the normal terminal resting potential, elicited a fast, inward followed by a fast, transient, outward current. 3. The threshold of activation for the outward current was -60 mV. The outward current quickly reached a peak and then decayed more slowly. The decay was fitted by two exponentials with time constants of 21 +/- 2.9 and 143 +/- 36 ms. These decay constants did not show a dependence on voltage. The time to peak of the outward current decreased and the amplitude increased with increasingly depolarized potential steps. 4. The outward current was blocked by the substitution of K+ with Cs+ and its reversal potential was consistent with a potassium current. 5. The transient outward current showed steady-state inactivation at more depolarized (than -80 mV) holding potentials with 50% inactivation occurring at -47.9 mV. The time course of recovery from inactivation was complex with full recovery taking greater than 16 s. 6. 4-Aminopyridine (4-AP) blocked the transient outward current in a dose-dependent manner (approximately IC50 = 3 mM), while charybdotoxin (4 micrograms/ml) and tetraethylammonium (100 mM) had no effect on the current amplitude. 7. Lowering external [Ca2+] had no effect on the fast, transient outward current nor did the calcium channel blocker Cd2+ (2 mM). 8. The neurohypophysial outward current reported here corresponds most closely to IA, and not to the delayed rectifier or Ca2(+)-activated K+ currents. Neurohypophysial IA, however, appears to be different from the outward currents found in the cell bodies in the hypothalamus which project their axons to the posterior

  10. Influence of motor activities on the release of transmitter quanta from motor nerve terminals in mice.

    PubMed

    Taquahashi, Y; Yonezawa, K; Nishimura, M

    1999-05-01

    We investigated the effects of motor activities on transmitter release in mouse nerve-muscle preparations of the diaphragm muscle (DPH), extensor digitorum longus muscle (EDL), and soleus muscle (SOL). Mice were divided into a control group, a motor-restricted (RST) group, and a motor-compelled (CMP) group. The quantal content (m) of endplate potentials was measured intracellularly. In DPH the motor activity was unaffected. In the CMP group the m value of the EDL group increased with increases in the cooperativity of Ca2+ in transmitter release. Compared with the CMP group, the SOL of the RST group had a smaller m value with increases in the cooperativity of Ca2+ in transmitter release. These results suggest that motor activities can influence neuromuscular activity specific to different systems, however, the motor compulsion specifically activated the function of EDL and the motor restriction activated the function of SOL, and these effects might lead to altered activity of the release of transmitter quanta in motor nerve terminals of mice.

  11. Kv3 voltage-gated potassium channels regulate neurotransmitter release from mouse motor nerve terminals.

    PubMed

    Brooke, Ruth E; Moores, Thomas S; Morris, Neil P; Parson, Simon H; Deuchars, Jim

    2004-12-01

    Voltage-gated potassium (Kv) channels are critical to regulation of neurotransmitter release throughout the nervous system but the roles and identity of the subtypes involved remain unclear. Here we show that Kv3 channels regulate transmitter release at the mouse neuromuscular junction (NMJ). Light- and electron-microscopic immunohistochemistry revealed Kv3.3 and Kv3.4 subunits within all motor nerve terminals of muscles examined [transversus abdominus, lumbrical and flexor digitorum brevis (FDB)]. To determine the roles of these Kv3 subunits, intracellular recordings were made of end-plate potentials (EPPs) in FDB muscle fibres evoked by electrical stimulation of tibial nerve. Tetraethylammonium (TEA) applied at low concentrations (0.05-0.5 mM), which blocks only a few known potassium channels including Kv3 channels, did not affect muscle fibre resting potential but significantly increased the amplitude of all EPPs tested. Significantly, this effect of TEA was still observed in the presence of the large-conductance calcium-activated potassium channel blockers iberiotoxin (25-150 nM) and Penitrem A (100 nM), suggesting a selective action on Kv3 subunits. Consistent with this, 15-microM 4-aminopyridine, which blocks Kv3 but not large-conductance calcium-activated potassium channels, enhanced evoked EPP amplitude. Unexpectedly, blood-depressing substance-I, a toxin selective for Kv3.4 subunits, had no effect at 0.05-1 microM. The combined presynaptic localization of Kv3 subunits and pharmacological enhancement of EPP amplitude indicate that Kv3 channels regulate neurotransmitter release from presynaptic terminals at the NMJ.

  12. Visualization of Endosome Dynamics in Living Nerve Terminals with Four-dimensional Fluorescence Imaging

    PubMed Central

    Stewart, Richard S.; Kiss, Ilona M.; Wilkinson, Robert S.

    2014-01-01

    Four-dimensional (4D) light imaging has been used to study behavior of small structures within motor nerve terminals of the thin transversus abdominis muscle of the garter snake. Raw data comprises time-lapse sequences of 3D z-stacks. Each stack contains 4-20 images acquired with epifluorescence optics at focal planes separated by 400-1,500 nm. Steps in the acquisition of image stacks, such as adjustment of focus, switching of excitation wavelengths, and operation of the digital camera, are automated as much as possible to maximize image rate and minimize tissue damage from light exposure. After acquisition, a set of image stacks is deconvolved to improve spatial resolution, converted to the desired 3D format, and used to create a 4D "movie" that is suitable for variety of computer-based analyses, depending upon the experimental data sought. One application is study of the dynamic behavior of two classes of endosomes found in nerve terminals-macroendosomes (MEs) and acidic endosomes (AEs)-whose sizes (200-800 nm for both types) are at or near the diffraction limit. Access to 3D information at each time point provides several advantages over conventional time-lapse imaging. In particular, size and velocity of movement of structures can be quantified over time without loss of sharp focus. Examples of data from 4D imaging reveal that MEs approach the plasma membrane and disappear, suggesting that they are exocytosed rather than simply moving vertically away from a single plane of focus. Also revealed is putative fusion of MEs and AEs, by visualization of overlap between the two dye-containing structures as viewed in each three orthogonal projections. PMID:24799002

  13. Calmodulin increases transmitter release by mobilizing quanta at the frog motor nerve terminal.

    PubMed

    Brailoiu, Eugen; Miyamoto, Michael D; Dun, Nae J

    2002-11-01

    The role of calmodulin (CaM) in transmitter release was investigated using liposomes to deliver CaM and monoclonal antibodies against CaM (antiCaM) directly into the frog motor nerve terminal. Miniature endplate potentials (MEPPs) were recorded in a high K+ solution, and effects on transmitter release were monitored using estimates of the quantal release parameters m (number of quanta released), n (number of functional transmitter release sites), p (mean probability of release), and var(s) p (spatial variance in p). Administration of CaM, but not heat-inactivated CaM, encapsulated in liposomes (1000 units ml(-1)) produced an increase in m (25%) that was due to an increase in n. MEPP amplitude was not altered by CaM. Administration of antiCaM, but not heat-inactivated antiCaM, in liposomes (50 microl ml(-1)) produced a progressive decrease in m (40%) that was associated with decreases in n and p. MEPP amplitude was decreased (15%) after a 25 min lag time, suggesting a separation in time between the decreases in quantal release and quantal size. Bath application of the membrane-permeable CaM antagonist W7 (28 microM) produced a gradual decrease in m (25%) that was associated with a decrease in n. W7 also produced a decrease in MEPP amplitude that paralleled the decrease in m. The decreases in MEPP size and m produced by W7 were both reversed by addition of CaM. Our results suggest that CaM increases transmitter release by mobilizing synaptic vesicles at the frog motor nerve terminal.

  14. Role of endogenous hydrogen sulfide in nerve-evoked relaxation of pig terminal bronchioles.

    PubMed

    Fernandes, Vítor S; Recio, Paz; López-Oliva, Elvira; Martínez, María Pilar; Ribeiro, Ana Sofía; Barahona, María Victoria; Martínez, Ana Cristina; Benedito, Sara; Agis-Torres, Ángel; Cabañero, Alberto; Muñoz, Gemma M; García-Sacristán, Albino; Orensanz, Luis M; Hernández, Medardo

    2016-12-01

    Hydrogen sulfide (H2S) is a gasotransmitter employed for intra- and inter-cellular communication in almost all organ systems. This study investigates the role of endogenous H2S in nerve-evoked relaxation of pig terminal bronchioles with 260 μm medium internal lumen diameter. High expression of the H2S synthesis enzyme cystathionine γ-lyase (CSE) in the bronchiolar muscle layer and strong CSE-immunoreactivity within nerve fibers distributed along smooth muscle bundles were observed. Further, endogenous H2S generated in bronchiolar membranes was reduced by CSE inhibition. In contrast, cystathionine β-synthase expression, another H2S synthesis enzyme, however was not consistently detected in the bronchiolar smooth muscle layer. Electrical field stimulation (EFS) and the H2S donor P-(4-methoxyphenyl)-P-4-morpholinylphosphinodithioic acid (GYY4137) evoked smooth muscle relaxation. Inhibition of CSE, nitric oxide (NO) synthase, soluble guanylyl cyclase (sGC) and of ATP-dependent K(+), transient receptor potential A1 (TRPA1) and transient receptor potential vanilloid 1 (TRPV1) channels reduced the EFS relaxation but failed to modify the GYY4137 response. Raising extracellular K(+) concentration inhibited the GYY4137 relaxation. Large conductance Ca(2+)-activated K(+) channel blockade reduced both EFS and GYY4137 responses. GYY4137 inhibited the contractions induced by histamine and reduced to a lesser extent the histamine-induced increases in intracellular [Ca(2+)]. These results suggest that relaxation induced by EFS in the pig terminal bronchioles partly involves the H2S/CSE pathway. H2S response is produced via NO/sGC-independent mechanisms involving K(+) channels and intracellular Ca(2+) desensitization-dependent pathways. Thus, based on our current results H2S donors might be useful as bronchodilator agents for the treatment of lung diseases with persistent airflow limitation, such as asthma and chronic obstructive lung disease.

  15. Quantal potential fields around individual active zones of amphibian motor-nerve terminals.

    PubMed Central

    Bennett, M R; Farnell, L; Gibson, W G; Macleod, G T; Dickens, P

    2000-01-01

    The release of a quantum from a nerve terminal is accompanied by the flow of extracellular current, which creates a field around the site of transmitter action. We provide a solution for the extent of this field for the case of a quantum released from a site on an amphibian motor-nerve terminal branch onto the receptor patch of a muscle fiber and compare this with measurements of the field using three extracellular electrodes. Numerical solution of the equations for the quantal potential field in cylindrical coordinates show that the density of the field at the peak of the quantal current gives rise to a peak extracellular potential, which declines approximately as the inverse of the distance from the source at distances greater than about 4 microm from the source along the length of the fiber. The peak extracellular potential declines to 20% of its initial value in a distance of about 6 microm, both along the length of the fiber and in the circumferential direction around the fiber. Simultaneous recordings of quantal potential fields, made with three electrodes placed in a line at right angles to an FM1-43 visualized branch, gave determinations of the field strengths in accord with the numerical solutions. In addition, the three electrodes were placed so as to straddle the visualized release sites of a branch. The positions of these sites were correctly predicted on the basis of the theory and independently ascertained by FM1-43 staining of the sites. It is concluded that quantal potential fields at the neuromuscular junction that can be measured with available recording techniques are restricted to regions within about 10 microm of the release site. PMID:10692301

  16. Transgene expression and effective gene silencing in vagal afferent neurons in vivo using recombinant adeno-associated virus vectors

    PubMed Central

    Kollarik, M; Carr, M J; Ru, F; Ring, C J A; Hart, V J; Murdock, P; Myers, A C; Muroi, Y; Undem, B J

    2010-01-01

    Vagal afferent fibres innervating thoracic structures such as the respiratory tract and oesophagus are diverse, comprising several subtypes of functionally distinct C-fibres and A-fibres. Both morphological and functional studies of these nerve subtypes would be advanced by selective, effective and long-term transduction of vagal afferent neurons with viral vectors. Here we addressed the hypothesis that vagal sensory neurons can be transduced with adeno-associated virus (AAV) vectors in vivo, in a manner that would be useful for morphological assessment of nerve terminals, using enhanced green fluorescent protein (eGFP), as well as for the selective knock-down of specific genes of interest in a tissue-selective manner. We found that a direct microinjection of AAV vectors into the vagal nodose ganglia in vivo leads to selective, effective and long-lasting transduction of the vast majority of primary sensory vagal neurons without transduction of parasympathetic efferent neurons. The transduction of vagal neurons by pseudoserotype AAV2/8 vectors in vivo is sufficiently efficient such that it can be used to functionally silence TRPV1 gene expression using short hairpin RNA (shRNA). The eGFP encoded by AAV vectors is robustly transported to both the central and peripheral terminals of transduced vagal afferent neurons allowing for bright imaging of the nerve endings in living tissues and suitable for structure–function studies of vagal afferent nerve endings. Finally, the AAV2/8 vectors are efficiently taken up by the vagal nerve terminals in the visceral tissue and retrogradely transported to the cell body, allowing for tissue-specific transduction. PMID:20736420

  17. High-Bandwidth Atomic Force Microscopy Reveals A Mechanical spike Accompanying the Action Potential in mammalian Nerve Terminals

    NASA Astrophysics Data System (ADS)

    Salzberg, Brian M.

    2008-03-01

    Information transfer from neuron to neuron within nervous systems occurs when the action potential arrives at a nerve terminal and initiates the release of a chemical messenger (neurotransmitter). In the mammalian neurohypophysis (posterior pituitary), large and rapid changes in light scattering accompany secretion of transmitter-like neuropeptides. In the mouse, these intrinsic optical signals are intimately related to the arrival of the action potential (E-wave) and the release of arginine vasopressin and oxytocin (S-wave). We have used a high bandwidth (20 kHz) atomic force microscope (AFM) to demonstrate that these light scattering signals are associated with changes in nerve terminal volume, detected as nanometer-scale movements of a cantilever positioned on top of the neurohypophysis. The most rapid mechanical response, the ``spike'', has duration comparable to that of the action potential (˜2 ms) and probably reflects an increase in terminal volume due to H2O movement associated with Na^+-influx. Elementary calculations suggest that two H2O molecules accompanying each Na^+-ion could account for the ˜0.5-1.0 å increase in the diameter of each terminal during the action potential. Distinguishable from the mechanical ``spike'', a slower mechanical event, the ``dip'', represents a decrease in nerve terminal volume, depends upon Ca^2+-entry, as well as on intra-terminal Ca^2+-transients, and appears to monitor events associated with secretion. A simple hypothesis is that this ``dip'' reflects the extrusion of the dense core granule that comprises the secretory products. These dynamic high bandwidth AFM recordings are the first to monitor mechanical events in nervous systems and may provide novel insights into the mechanism(s) by which excitation is coupled to secretion at nerve terminals.

  18. Study on distribution of terminal branches of the facial nerve in mimetic muscles (orbicularis oculi muscle and orbicularis oris muscle).

    PubMed

    Mitsukawa, Nobuyuki; Moriyama, Hiroshi; Shiozawa, Kei; Satoh, Kaneshige

    2014-01-01

    There have been many anatomical reports to date regarding the course of the facial nerve to the mimetic muscles. However, reports are relatively scarce on the detailed distribution of the terminal branches of the facial nerve to the mimetic muscles. In this study, we performed detailed examination of the terminal facial nerve branches to the mimetic muscles, particularly the branches terminating in the orbicularis oculi muscle and orbicularis oris muscle. Examination was performed on 25 Japanese adult autopsy cases, involving 25 hemifaces. The mean age was 87.4 years (range, 60-102 years). There were 12 men and 13 women (12 left hemifaces and 13 right hemifaces). In each case, the facial nerve was exposed through a preauricular skin incision. The main trunk of the facial nerve was dissected from the stylomastoid foramen. A microscope was used to dissect the terminal branches to the periphery and observe them. The course and distribution were examined for all terminal branches of the facial nerve. However, focus was placed on the course and distribution of the zygomatic branch, buccal branch, and mandibular branch to the orbicularis oculi muscle and orbicularis oris muscle. The temporal branch was distributed to the orbicularis oculi muscle in all cases and the marginal mandibular branch was distributed to the orbicularis oris muscle in all cases. The zygomatic branch was distributed to the orbicularis oculi muscle in all cases, but it was also distributed to the orbicularis oris muscle in 10 of 25 cases. The buccal branch was not distributed to the orbicularis oris muscle in 3 of 25 cases, and it was distributed to the orbicularis oculi muscle in 8 cases. There was no significant difference in the variations. The orbicularis oculi muscle and orbicularis oris muscle perform particularly important movements among the facial mimetic muscles. According to textbooks, the temporal branch and zygomatic branch innervate the orbicularis oculi muscle, and the buccal branch

  19. Chylomicron components activate duodenal vagal afferents via a cholecystokinin A receptor-mediated pathway to inhibit gastric motor function in the rat.

    PubMed

    Glatzle, Jörg; Wang, Yuhua; Adelson, David W; Kalogeris, Theodore J; Zittel, Tilman T; Tso, Patrick; Wei, Jen-Yu; Raybould, Helen E

    2003-07-15

    Nutrients in the intestine initiate changes in secretory and motor function of the gastrointestinal (GI) tract. The nature of the 'sensors' in the intestinal wall is not well characterized. Intestinal lipid stimulates the release of cholecystokinin (CCK) from mucosal entero-endocrine cells, and it is proposed that CCK activates CCK A receptors on vagal afferent nerve terminals. There is evidence that chylomicron components are involved in this lipid transduction pathway. The aim of the present study was to determine (1) the pathway mediating reflex inhibition of gastric motility and (2) activation of duodenal vagal afferents in response to chylomicrons. Mesenteric lymph was obtained from awake rats fitted with lymph fistulas during intestinal perfusion of lipid (Intralipid, 170 micromol h(-1), chylous lymph) or a dextrose and/or electrolyte solution (control lymph). Inhibition of gastric motility was measured manometrically in urethane-anaesthetized recipient rats in response to intra-arterial injection of lymph close to the upper GI tract. Chylous lymph was significantly more potent than control lymph in inhibiting gastric motility. Functional vagal deafferentation by perineural capsaicin or CCK A receptor antagonist (devazepide, 1 mg kg(-1), i.v.) significantly reduced chylous lymph-induced inhibition of gastric motility. The discharge of duodenal vagal afferent fibres was recorded from the dorsal abdominal vagus nerve in an in vitro preparation of the duodenum. Duodenal vagal afferent nerve fibre discharge was significantly increased by close-arterial injection of CCK (1-100 pmol) in 43 of 83 units tested. The discharge of 88% of CCK-responsive fibres was increased by close-arterial injection of chylous lymph; devazepide (100 microg, i.a.) abolished the afferent response to chylous lymph in 83% of these units. These data suggest that in the intestinal mucosa, chylomicrons or their products release endogenous CCK which activates CCK A receptors on vagal afferent

  20. Some properties of the presynaptic nerve terminals in a mammalian sympathetic ganglion

    PubMed Central

    Dunant, Y.

    1972-01-01

    1. Superior cervical ganglia of adult rats were excised and maintained in vitro in stable conditions. Potentials were recorded with external electrodes. After transmission was blocked by mecamylamine, a small potential change was recorded from the rostral area of the ganglion in response to preganglionic stimulation. 2. This electrical response was identified as the presynaptic action potential recorded from the nerve terminals by a number of criteria based on histological and physiological considerations including the disappearance of the spike in a glucose free solution. As shown by Nicolescu, Dolivo, Rouiller & Foroglou-Kerameus (1966) on the same preparation this condition causes an irreversible and selective lesion of the presynaptic nerve endings. 3. A suitable concentration of mecamylamine permitted the presynaptic response and the excitatory post-synaptic potential (EPSP) to be recorded simultaneously. As the stimulus was increased, the EPSP increased linearly with the amplitude of the presynaptic response. 4. After replacement of potassium ions in the bathing solution by caesium and during the early phase of post-tetanic facilitation there was an increase in the presynaptic response accompanied by a disproportionate increase in the EPSP. 5. No changes in the presynaptic response were found in the presence of the following drugs, all of which depressed the EPSP: acetylcholine, hemicholinium, curare, further doses of ganglion-blocking agents, and high Mg2+ and low Ca2+ concentrations. 6. Ouabain (4·5 × 10-4 M) reversibly decreased the amplitude of the presynaptic response and increased the spontaneous release of transmitter. The EPSP was at first enhanced and then depressed. PMID:4335802

  1. Altered Active Zones, Vesicle Pools, Nerve Terminal Conductivity, and Morphology during Experimental MuSK Myasthenia Gravis

    PubMed Central

    Patel, Vishwendra; Oh, Anne; Voit, Antanina; Sultatos, Lester G.; Babu, Gopal J.; Wilson, Brenda A.; Ho, Mengfei; McArdle, Joseph J.

    2014-01-01

    Recent studies demonstrate reduced motor-nerve function during autoimmune muscle-specific tyrosine kinase (MuSK) myasthenia gravis (MG). To further understand the basis of motor-nerve dysfunction during MuSK-MG, we immunized female C57/B6 mice with purified rat MuSK ectodomain. Nerve-muscle preparations were dissected and neuromuscular junctions (NMJs) studied electrophysiologically, morphologically, and biochemically. While all mice produced antibodies to MuSK, only 40% developed respiratory muscle weakness. In vitro study of respiratory nerve-muscle preparations isolated from these affected mice revealed that 78% of NMJs produced endplate currents (EPCs) with significantly reduced quantal content, although potentiation and depression at 50 Hz remained qualitatively normal. EPC and mEPC amplitude variability indicated significantly reduced number of vesicle-release sites (active zones) and reduced probability of vesicle release. The readily releasable vesicle pool size and the frequency of large amplitude mEPCs also declined. The remaining NMJs had intermittent (4%) or complete (18%) failure of neurotransmitter release in response to 50 Hz nerve stimulation, presumably due to blocked action potential entry into the nerve terminal, which may arise from nerve terminal swelling and thinning. Since MuSK-MG-affected muscles do not express the AChR γ subunit, the observed prolongation of EPC decay time was not due to inactivity-induced expression of embryonic acetylcholine receptor, but rather to reduced catalytic activity of acetylcholinesterase. Muscle protein levels of MuSK did not change. These findings provide novel insight into the pathophysiology of autoimmune MuSK-MG. PMID:25438154

  2. Mechanistic relationship between the vagal afferent pathway, central nervous system and peripheral organs in appetite regulation.

    PubMed

    Ueno, Hiroaki; Nakazato, Masamitsu

    2016-11-01

    The hypothalamus is a center of food intake and energy metabolism regulation. Information signals from peripheral organs are mediated through the circulation or the vagal afferent pathway and input into the hypothalamus, where signals are integrated to determine various behaviors, such as eating. Numerous appetite-regulating peptides are expressed in the central nervous system and the peripheral organs, and interact in a complex manner. Of such peptides, gut peptides are known to bind to receptors at the vagal afferent pathway terminal that extend into the mucosal layer of the digestive tract, modulate the electrical activity of the vagus nerve, and subsequently send signals to the solitary nucleus and furthermore to the hypothalamus. All peripheral peptides other than ghrelin suppress appetite, and they synergistically suppress appetite through the vagus nerve. In contrast, the appetite-enhancing peptide, ghrelin, antagonizes the actions of appetite-suppressing peptides through the vagus nerve, and appetite-suppressing peptides have attenuated effects in obesity as a result of inflammation in the vagus nerve. With greater understanding of the mechanism for food intake and energy metabolism regulation, medications that apply the effects of appetite-regulating peptides or implantable devices that electrically stimulate the vagus nerve are being investigated as novel treatments for obesity in basic and clinical studies.

  3. Mitochondrial Calcium Uptake Modulates Synaptic Vesicle Endocytosis in Central Nerve Terminals.

    PubMed

    Marland, Jamie Roslin Keynes; Hasel, Philip; Bonnycastle, Katherine; Cousin, Michael Alan

    2016-01-29

    Presynaptic calcium influx triggers synaptic vesicle (SV) exocytosis and modulates subsequent SV endocytosis. A number of calcium clearance mechanisms are present in central nerve terminals that regulate intracellular free calcium levels both during and after stimulation. During action potential stimulation, mitochondria rapidly accumulate presynaptic calcium via the mitochondrial calcium uniporter (MCU). The role of mitochondrial calcium uptake in modulating SV recycling has been debated extensively, but a definitive conclusion has not been achieved. To directly address this question, we manipulated the expression of the MCU channel subunit in primary cultures of neurons expressing a genetically encoded reporter of SV turnover. Knockdown of MCU resulted in ablation of activity-dependent mitochondrial calcium uptake but had no effect on the rate or extent of SV exocytosis. In contrast, the rate of SV endocytosis was increased in the absence of mitochondrial calcium uptake and slowed when MCU was overexpressed. MCU knockdown did not perturb activity-dependent increases in presynaptic free calcium, suggesting that SV endocytosis may be controlled by calcium accumulation and efflux from mitochondria in their immediate vicinity.

  4. Micromolar-affinity benzodiazepine receptors regulate voltage-sensitive calcium channels in nerve terminal preparations.

    PubMed Central

    Taft, W C; DeLorenzo, R J

    1984-01-01

    Benzodiazepines in micromolar concentrations significantly inhibit depolarization-sensitive Ca2+ uptake in intact nerve-terminal preparations. Benzodiazepine inhibition of Ca2+ uptake is concentration dependent and stereospecific. Micromolar-affinity benzodiazepine receptors have been identified and characterized in brain membrane and shown to be distinct from nanomolar-affinity benzodiazepine receptors. Evidence is presented that micromolar, and not nanomolar, benzodiazepine binding sites mediate benzodiazepine inhibition of Ca2+ uptake. Irreversible binding to micromolar benzodiazepine binding sites also irreversibly blocked depolarization-dependent Ca2+ uptake in synaptosomes, indicating that these compounds may represent a useful marker for identifying the molecular components of Ca2+ channels in brain. Characterization of benzodiazepine inhibition of Ca2+ uptake demonstrates that these drugs function as Ca2+ channel antagonists, because benzodiazepines effectively blocked voltage-sensitive Ca2+ uptake inhibited by Mn2+, Co2+, verapamil, nitrendipine, and nimodipine. These results indicate that micromolar benzodiazepine binding sites regulate voltage-sensitive Ca2+ channels in brain membrane and suggest that some of the neuronal stabilizing effects of micromolar benzodiazepine receptors may be mediated by the regulation of Ca2+ conductance. PMID:6328498

  5. Micromolar-Affinity Benzodiazepine Receptors Regulate Voltage-Sensitive Calcium Channels in Nerve Terminal Preparations

    NASA Astrophysics Data System (ADS)

    Taft, William C.; Delorenzo, Robert J.

    1984-05-01

    Benzodiazepines in micromolar concentrations significantly inhibit depolarization-sensitive Ca2+ uptake in intact nerve-terminal preparations. Benzodiazepine inhibition of Ca2+ uptake is concentration dependent and stereospecific. Micromolar-affinity benzodiazepine receptors have been identified and characterized in brain membrane and shown to be distinct from nanomolar-affinity benzodiazepine receptors. Evidence is presented that micromolar, and not nanomolar, benzodiazepine binding sites mediate benzodiazepine inhibition of Ca2+ uptake. Irreversible binding to micromolar benzodiazepine binding sites also irreversibly blocked depolarization-dependent Ca2+ uptake in synaptosomes, indicating that these compounds may represent a useful marker for identifying the molecular components of Ca2+ channels in brain. Characterization of benzodiazepine inhibition of Ca2+ uptake demonstrates that these drugs function as Ca2+ channel antagonists, because benzodiazepines effectively blocked voltage-sensitive Ca2+ uptake inhibited by Mn2+, Co2+, verapamil, nitrendipine, and nimodipine. These results indicate that micromolar benzodiazepine binding sites regulate voltage-sensitive Ca2+ channels in brain membrane and suggest that some of the neuronal stabilizing effects of micromolar benzodiazepine receptors may be mediated by the regulation of Ca2+ conductance.

  6. Rescue of neuronal function by cross-regeneration of cutaneous afferents into muscle in cats.

    PubMed

    Nishimura, H; Johnson, R D; Munson, J B

    1993-07-01

    1. This study investigates the relation between the peripheral innervation of low-threshold cutaneous afferents and the postsynaptic potentials elicited by electrical stimulation of those afferents. 2. In cats deeply anesthetized with pentobarbital sodium, cord dorsum potentials (CDPs) and postsynaptic potentials (PSPs) in spinal motoneurons were elicited by stimulation of the caudal cutaneous sural nerve (CCS), the lateral cutaneous sural nerve (LCS), and the medial gastrocnemius (MG) muscle nerve. We tested 1) unoperated cats, and cats in which CCS has been 2) chronically axotomized and ligated, 3) cut and self-reunited, 4) cut and cross-united with LCS, or 5) cut and cross-united with the MG. Terminal experiments were performed 3-36 mo after initial surgery. 3. In cats in which the CCS had been self-reunited or cross-united distally with LCS, tactile stimulation of the hairy skin normally innervated by the distal nerve activated afferents in the CCS central to the coaptation, indicating that former CCS afferents had regenerated into native or foreign skin, respectively. 4. In cats in which the CCS had been cross-united distally with the MG, both stretch and contraction of the MG muscle activated the former CCS afferents. 5. In unoperated cats, CDPs elicited by stimulation of CCS and of LCS exhibited a low-threshold N1 wave and a higher-threshold N2 wave. These waves were greatly delayed and appeared to merge after chronic axotomy of CCS. Regeneration of CCS into itself, into LCS, or into MG restored the normal latencies and configurations of these potentials. 6. In unoperated cats, stimulation of CCS, of LCS, and of MG each produced PSPs of characteristic configurations in the various subpopulations of motoneurons of the triceps surae. CDPs and PSPs elicited by the CCS cross-regenerated into LCS or MG were typical of those generated by the normal CCS, i.e., there was no evidence of respecification of central synaptic connections to bring accord between center

  7. Platelets as potential peripheral markers to study functioning of the high-affinity sodium-dependent glutamate transporters in the nerve terminals of the brain

    NASA Astrophysics Data System (ADS)

    Borisova, T. A.; Kasatkina, L. A.

    Activity of the high-affinity sodium-dependent glutamate transporters in the brain nerve terminals is demonstrated to alter under artificial gravity conditions. A comparison analysis is made for L-[14C] glutamate transport in platelets and isolated nerve terminals. The kinetic characteristics of the transporters, [Na+]-dependence and influence of the transpoter inhibitor DL-threo-beta-benzyloxyaspartate on the L-[14C] glutamate uptake process are determined. It is shown that glutamate uptake process is very similar for platelets and nerve terminals. Thus it is reasonable to use platelets as a potential peripheral model for glutamate transport.

  8. Brain-derived neurotrophic factor inhibits calcium channel activation, exocytosis, and endocytosis at a central nerve terminal.

    PubMed

    Baydyuk, Maryna; Wu, Xin-Sheng; He, Liming; Wu, Ling-Gang

    2015-03-18

    Brain-derived neurotrophic factor (BDNF) is a neurotrophin that regulates synaptic function and plasticity and plays important roles in neuronal development, survival, and brain disorders. Despite such diverse and important roles, how BDNF, or more generally speaking, neurotrophins affect synapses, particularly nerve terminals, remains unclear. By measuring calcium currents and membrane capacitance during depolarization at a large mammalian central nerve terminal, the rat calyx of Held, we report for the first time that BDNF slows down calcium channel activation, including P/Q-type channels, and inhibits exocytosis induced by brief depolarization or single action potentials, inhibits slow and rapid endocytosis, and inhibits vesicle mobilization to the readily releasable pool. These presynaptic mechanisms may contribute to the important roles of BDNF in regulating synapses and neuronal circuits and suggest that regulation of presynaptic calcium channels, exocytosis, and endocytosis are potential mechanisms by which neurotrophins achieve diverse neuronal functions.

  9. Potassium channel blocking actions of beta-bungarotoxin and related toxins on mouse and frog motor nerve terminals.

    PubMed Central

    Rowan, E. G.; Harvey, A. L.

    1988-01-01

    1. beta-Bungarotoxin and other snake toxins with phospholipase activity augment acetylcholine release evoked from mouse motor nerve terminals before they produce blockade. This action of the toxins is independent of their phospholipase A2 activity, but the underlying mechanism for the facilitation of release is unclear. To determine whether the toxins affect ionic currents at motor nerve terminals, extracellular recordings were made from perineural sheaths of motor nerves innervating mouse triangularis sterni muscles. 2. Perineural waveforms had a characteristic shape, with two major negative deflections, the first being associated with nodal Na+ currents and the second with terminal K+ currents. Block of the K+ currents revealed a Ca2+-dependent component. 3. During the facilitatory phase of its action, beta-bungarotoxin (150 nM) reduced the second negative component of the perineural waveform by 30-50%. 4. The reduction could be a consequence of a decreased K+ ion contribution or of an increase in the current carried by Ca2+. As beta-bungarotoxin had similar effects in solutions which contained no added Ca2+, it is unlikely to be acting on the Ca2+ current. Also, it is unlikely to be blocking the Ca2+-activated K+ current, which is suppressed in zero Ca2+ conditions. 5. Other prejunctionally active snake toxins (taipoxin, notexin and crotoxin) had similar effects to those of beta-bungarotoxin, but a similar basic phospholipase of low toxicity from cobra venom had no effect. 6. Thus, beta-bungarotoxin and related toxins block a fraction of the K+ current in the motor nerve terminals of mouse preparations.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3263160

  10. Target-specific regulation of presynaptic release properties at auditory nerve terminals in the avian cochlear nucleus

    PubMed Central

    Ahn, J.

    2015-01-01

    Short-term synaptic plasticity (STP) acts as a time- and firing rate-dependent filter that mediates the transmission of information across synapses. In the auditory brain stem, the divergent pathways that encode acoustic timing and intensity information express differential STP. To investigate what factors determine the plasticity expressed at different terminals, we tested whether presynaptic release probability differed in the auditory nerve projections to the two divisions of the avian cochlear nucleus, nucleus angularis (NA) and nucleus magnocellularis (NM). Estimates of release probability were made with an open-channel blocker of N-methyl-d-aspartate (NMDA) receptors. Activity-dependent blockade of NMDA receptor-mediated excitatory postsynaptic currents (EPSCs) with application of 20 μM (+)-MK801 maleate was more rapid in NM than in NA, indicating that release probability was significantly higher at terminals in NM. Paired-pulse ratio (PPR) was tightly correlated with the blockade rate at terminals in NA, suggesting that PPR was a reasonable proxy for relative release probability at these synapses. To test whether release probability was similar across convergent inputs onto NA neurons, PPRs of different nerve inputs onto the same postsynaptic NA target neuron were measured. The PPRs, as well as the plasticity during short trains, were tightly correlated across multiple inputs, further suggesting that release probability is coordinated at auditory nerve terminals in a target-specific manner. This highly specific regulation of STP in the auditory brain stem provides evidence that the synaptic dynamics are tuned to differentially transmit the auditory information in nerve activity into parallel ascending pathways. PMID:26719087

  11. Uptake and metabolism of fructose by rat neocortical cells in vivo and by isolated nerve terminals in vitro

    PubMed Central

    Hassel, Bjørnar; Elsais, Ahmed; Frøland, Anne Sofie; Taubøll, Erik; Gjerstad, Leif; Quan, Yi; Dingledine, Ray; Rise, Frode

    2015-01-01

    Fructose reacts spontaneously with proteins in the brain to form advanced glycation end products (AGE) that may elicit neuroinflammation and cause brain pathology, including Alzheimer’s disease. We investigated whether fructose is eliminated by oxidative metabolism in neocortex. Injection of [14C]fructose or its AGE-prone metabolite [14C]glyceraldehyde into rat neocortex in vivo led to formation of 14C-labeled alanine, glutamate, aspartate, GABA, and glutamine. In isolated neocortical nerve terminals, [14C]fructose labeled glutamate, GABA, and aspartate, indicating uptake of fructose into nerve terminals and oxidative fructose metabolism in these structures. Hexokinase 1, which channels fructose into glycolysis, was highly expressed, and enzyme activity was similar with fructose or glucose as substrates, whereas the fructose-specific ketohexokinase was weakly expressed. The fructose transporter Glut5 was expressed at only ~4% of the level of neuronal glucose transporter Glut3, suggesting transport across plasma membranes of brain cells as the limiting factor in removal of extracellular fructose. Fructose may be formed from glucose through the polyol pathway. The genes encoding enzymes of this pathway, aldose reductase and sorbitol dehydrogenase, were expressed in rat neocortex. We conclude that fructose is transported into neocortical cells, including nerve terminals, and that it is metabolized and thereby detoxified primarily through hexokinase activity. PMID:25708447

  12. Comparison of Glutamate Turnover in Nerve Terminals and Brain Tissue During [1,6-(13)C2]Glucose Metabolism in Anesthetized Rats.

    PubMed

    Patel, Anant B; Lai, James C K; Chowdhury, Golam I M; Rothman, Douglas L; Behar, Kevin L

    2017-01-01

    The (13)C turnover of neurotransmitter amino acids (glutamate, GABA and aspartate) were determined from extracts of forebrain nerve terminals and brain homogenate, and fronto-parietal cortex from anesthetized rats undergoing timed infusions of [1,6-(13)C2]glucose or [2-(13)C]acetate. Nerve terminal (13)C fractional labeling of glutamate and aspartate was lower than those in whole cortical tissue at all times measured (up to 120 min), suggesting either the presence of a constant dilution flux from an unlabeled substrate or an unlabeled (effectively non-communicating on the measurement timescale) glutamate pool in the nerve terminals. Half times of (13)C labeling from [1,6-(13)C2]glucose, as estimated by least squares exponential fitting to the time course data, were longer for nerve terminals (GluC4, 21.8 min; GABAC2 21.0 min) compared to cortical tissue (GluC4, 12.4 min; GABAC2, 14.5 min), except for AspC3, which was similar (26.5 vs. 27.0 min). The slower turnover of glutamate in the nerve terminals (but not GABA) compared to the cortex may reflect selective effects of anesthesia on activity-dependent glucose use, which might be more pronounced in the terminals. The (13)C labeling ratio for glutamate-C4 from [2-(13)C]acetate over that of (13)C-glucose was twice as large in nerve terminals compared to cortex, suggesting that astroglial glutamine under the (13)C glucose infusion was the likely source of much of the nerve terminal dilution. The net replenishment of most of the nerve terminal amino acid pools occurs directly via trafficking of astroglial glutamine.

  13. A new technique for the direct demonstration of overlapping cutaneous innervation territories of peptidergic C-fibre afferents of rat hindlimb nerves.

    PubMed

    Dux, M; Jancsó, G

    1994-11-01

    A new technique based on the phenomenon of vascular labelling has been devised for the direct visualisation of overlapping innervation territories of cutaneous nerves. The saphenous, peroneal and sural nerves on one side in anaesthetised rats were exposed, cut centrally and successively stimulated antidromically to induce a neurogenic inflammatory response after an intravenous injection of either a 1% colloidal silver solution or a suspension of 3% Monastral Blue B. Light microscopic examination of transparent preparations of the dorsal hindpaw skin revealed labelled blood vessels of different colours which represented cutaneous territories served by different nerves. Blood vessels labelled with both substances were regarded as areas of overlapping innervation. Such areas were typically localised along the border of adjacent innervation territories. In addition, distinct areas exhibiting double-labelled blood vessels were regularly encountered in regions separate from this border zone. Areas of interest were drawn with the aid of a camera lucida and measured by means of a computerised system. The results indicate a significant, although topographically variable, degree of overlap of these cutaneous innervation areas. This new technique offers a possibility to explore the importance of normally existing overlap in the reinnervation of a denervated skin area by collateral nerve sprouting.

  14. The effect of 3,3-di-pyridyl-methyl-1-phenyl-2-indolinone on the nerve terminal currents of mouse skeletal muscles.

    PubMed

    Tsai, M C; Su, J L; Chen, M L; Fan, S Z; Cheng, C Y

    1992-09-01

    The effects of 3,3-dipyridyl-methyl-1-phenyl-2-indolinone (DPMPI), a new cognition enhancer, on perineural waveforms were assessed on triangularis sterni nerve-muscle preparations in the mouse. The perineural waveforms were recorded with extracellular electrodes placed in the perineural sheaths of motor nerves. At 64.5 microM, DPMPI decreased the fast potassium current of the nerve terminal. The sodium current, calcium currents and calcium-dependent potassium current of the nerve terminal were not affected. At a greater concentration (215 microM), DPMPI decreased all of the components of the waveforms associated with sodium, potassium and calcium currents. It is concluded that DPMPI affects potassium, as well as sodium currents in the nerve terminal. The effect may contribute to its pharmacological actions on synaptic transmission.

  15. Presynaptic Ca2+ influx and vesicle exocytosis at the mouse endbulb of Held: a comparison of two auditory nerve terminals

    PubMed Central

    Lin, Kun-Han; Oleskevich, Sharon; Taschenberger, Holger

    2011-01-01

    Abstract The functional properties of mammalian presynaptic nerve endings remain elusive since most terminals of the central nervous system are not accessible to direct electrophysiological recordings. In this study, direct recordings were performed for the first time at endbulb of Held terminals to characterize passive membrane properties, voltage-gated Ca2+ channels (VGCCs) and Ca2+-dependent exocytosis. Endbulb of Held terminals arise from endings of auditory nerve fibres contacting spherical bushy cells (SBCs) in the anterior ventral cochlear nucleus (AVCN). These terminals had a high mean input resistance (1.1 GΩ) and a small mean capacitance (4.3 pF). Presynaptic VGCCs were predominantly of the P/Q type (86%) and expressed at a high density with an estimated average number of 6400 channels per terminal. Presynaptic Ca2+ currents (ICa(V)) activated and deactivated rapidly. Simulations of action potential (AP)-driven gating of VGCCs suggests that endbulb APs trigger brief Ca2+ influx with a mean half-width of 240 μs and a peak amplitude of 0.45 nA which results from the opening of approximately 2600 channels. Unlike Ca2+ currents at the calyx of Held, ICa(V) of endbulb terminals showed no inactivation during trains of AP-like presynaptic depolarizations. Endbulb terminals are endowed with a large readily releasable vesicle pool (1064 vesicles) of which only a small fraction (<10%) is consumed during a single AP-like stimulus. Fast presynaptic APs together with rapidly gating VGCCs will generate brief intracellular Ca2+ transients that favour highly synchronous transmitter release. Collectively these characteristics ensure sustained and precise transmission of timing information from auditory stimuli at the endbulb→SBC synapse. PMID:21746778

  16. Distribution of muscarinic acetylcholine receptors and presynaptic nerve terminals in amphibian heart

    PubMed Central

    1980-01-01

    At many synapses, neurotransmitter receptor molecules in the postsynaptic membrane are selectively concentrated at a site directly opposite the presynaptic nerve terminal. In this paper, I examine acetylcholine (ACh) receptor distribution in cardiac muscle in relatin to the distribution of presynaptic axonal varicosities. The density of varicosities, stained with zinc iodide and osmium, ranges from 0.7/100 micrometer 2 in ventricle to 1.9/100 micrometer 2 in sinus venosus. It is estimated that < 3% of the muscle surface is apposed to presynaptic varicosities. ACh receptors, however, are randomly distributed on the muscle surface and not concentrated in patche. ACh receptor distribution was determined by iontophoretic application of ACh and mapping of ACh sensitivity and by [3H]QNB (quinuclidinyl benzilate) binding and autoradiography [3H]QNB binds with > 90% specificity to a single, saturable, high-affinity (Kd = 11.1 pM at 21 degrees C) class of binding sites. QNB binding sites are thought to correspond to ACh receptors, because muscarinic agonists compete for [3H]QNB binding and produce a hyperpolarization in the sinus venosus with the same order of potency. The concentrations of QNB binding sites in the sinus and atria are about twice those found in ventricle. The receptor density corresponds to the density of innervation measured by zinc iodide and osmium staining. Autoradiographic experiments show that [3H]QNB binding sites are distributed randomly over the entire surface of the muscle. This distribution of ACh receptors in cardiac muscle has important implications for the function of the cardiac neuroeffector junction. PMID:6968315

  17. Antidromic discharges of dorsal root afferents in the neonatal rat.

    PubMed

    Vinay, L; Brocard, F; Fellippa-Marques, S; Clarac, F

    1999-01-01

    Presynaptic inhibition of primary afferents can be evoked from at least three sources in the adult animal: 1) by stimulation of several supraspinal structures; 2) by spinal reflex action from sensory inputs; or 3) by the activity of spinal locomotor networks. The depolarisation in the intraspinal afferent terminals which is due, at least partly, to the activation of GABA(A) receptors may be large enough to reach firing threshold and evoke action potentials that are antidromically conducted into peripheral nerves. Little is known about the development of presynaptic inhibition and its supraspinal control during ontogeny. This article, reviewing recent experiments performed on the in vitro brainstem/spinal cord preparation of the neonatal rat, demonstrates that a similar organisation is present, to some extent, in the new-born rat. A spontaneous activity consisting of antidromic discharges can be recorded from lumbar dorsal roots. The discharges are generated by the underlying afferent terminal depolarizations reaching firing threshold. The number of antidromic action potentials increases significantly in saline solution with chloride concentration reduced to 50% of control. Bath application of the GABA(A) receptor antagonist, bicuculline (5-10 microM) blocks the antidromic discharges almost completely. Dorsal root discharges are therefore triggered by chloride-dependent GABA(A) receptor-mediated mechanisms; 1) activation of descending pathways by stimulation delivered to the ventral funiculus (VF) of the spinal cord at the C1 level; 2) activation of sensory inputs by stimulation of a neighbouring dorsal root; or 3) pharmacological activation of the central pattern generators for locomotion evokes antidromic discharges in dorsal roots. VF stimulation also inhibited the response to dorsal root stimulation. The time course of this inhibition overlapped with that of the dorsal root discharge suggesting that part of the inhibition of the monosynaptic reflex may be

  18. Imaging neuromuscular junctions by confocal fluorescence microscopy: individual endplates seen in whole muscles with vital intracellular staining of the nerve terminals

    PubMed Central

    MARQUES, M. J.; NETO, H. SANTO

    1998-01-01

    The mammalian neuromuscular junction has been extensively studied by different methods to understand better the biological aspects of its normal development, ageing and pathological conditions, such as disorders of neuromuscular transmission. In the present report, a new technique is described that combines confocal microscopy with the use of a vital nerve terminal dye (4-Di-2-ASP) and rhodamine-alpha-bungarotoxin to stain postsynaptic acetylcholine receptors in the same endplate. Nerve terminals in the sternomastoid muscles of living adult mice were stained with 4-Di-2-ASP, which labels intracellular compartments of the nerve terminal containing mitochondria. Slides of these muscles were viewed by confocal microscopy and images were stored on magnetic optical discs. This procedure was compatible with subsequent acetylcholine receptor staining with rhodamine-α-bungarotoxin and observation under the confocal microscope. Classical features of the adult neuromuscular junction were displayed, such as the branched-pattern distribution of the nerve terminals and receptors and their complete colocalisation. In addition, nerve fibres from intramuscular nerve branches with their neighbouring cells, nuclei and muscle fibre striations could also be visualised. We conclude that the present technique can complement existing methods of investigation of nerve terminal anatomy and pathology, particularly where preservation of 3-dimensional relationships is required and intracellular disturbances involving mitochondrial organisation, such as ageing or other degenerative disorders, may be present. PMID:9688508

  19. Terminal nerve-derived neuropeptide y modulates physiological responses in the olfactory epithelium of hungry axolotls (Ambystoma mexicanum).

    PubMed

    Mousley, Angela; Polese, Gianluca; Marks, Nikki J; Eisthen, Heather L

    2006-07-19

    The vertebrate brain actively regulates incoming sensory information, effectively filtering input and focusing attention toward environmental stimuli that are most relevant to the animal's behavioral context or physiological state. Such centrifugal modulation has been shown to play an important role in processing in the retina and cochlea, but has received relatively little attention in olfaction. The terminal nerve, a cranial nerve that extends underneath the lamina propria surrounding the olfactory epithelium, displays anatomical and neurochemical characteristics that suggest that it modulates activity in the olfactory epithelium. Using immunocytochemical techniques, we demonstrate that neuropeptide Y (NPY) is abundantly present in the terminal nerve in the axolotl (Ambystoma mexicanum), an aquatic salamander. Because NPY plays an important role in regulating appetite and hunger in many vertebrates, we investigated the possibility that NPY modulates activity in the olfactory epithelium in relation to the animal's hunger level. We therefore characterized the full-length NPY gene from axolotls to enable synthesis of authentic axolotl NPY for use in electrophysiological experiments. We find that axolotl NPY modulates olfactory epithelial responses evoked by l-glutamic acid, a food-related odorant, but only in hungry animals. Similarly, whole-cell patch-clamp recordings demonstrate that bath application of axolotl NPY enhances the magnitude of a tetrodotoxin-sensitive inward current, but only in hungry animals. These results suggest that expression or activity of NPY receptors in the olfactory epithelium may change with hunger level, and that terminal nerve-derived peptides modulate activity in the olfactory epithelium in response to an animal's changing behavioral and physiological circumstances.

  20. Optical Monitoring of Living Nerve Terminal Labeling in Hair Follicle Lanceolate Endings of the Ex Vivo Mouse Ear Skin

    PubMed Central

    Bewick, Guy S.; Banks, Robert W.

    2016-01-01

    A novel dissection and recording technique is described for optical monitoring staining and de-staining of lanceolate terminals surrounding hair follicles in the skin of the mouse pinna. The preparation is simple and relatively fast, reliably yielding extensive regions of multiple labeled units of living nerve terminals to study uptake and release of styryl pyridinium dyes extensively used in studies of vesicle recycling. Subdividing the preparations before labeling allows test vs. control comparisons in the same ear from a single individual. Helpful tips are given for improving the quality of the preparation, the labeling and the imaging parameters. This new system is suitable for assaying pharmacologically and mechanically-induced uptake and release of these vital dyes in lanceolate terminals in both wild-type and genetically modified animals. Examples of modulatory influences on labeling intensity are given. PMID:27077818

  1. Optical Monitoring of Living Nerve Terminal Labeling in Hair Follicle Lanceolate Endings of the Ex Vivo Mouse Ear Skin.

    PubMed

    Bewick, Guy S; Banks, Robert W

    2016-04-05

    A novel dissection and recording technique is described for optical monitoring staining and de-staining of lanceolate terminals surrounding hair follicles in the skin of the mouse pinna. The preparation is simple and relatively fast, reliably yielding extensive regions of multiple labeled units of living nerve terminals to study uptake and release of styryl pyridinium dyes extensively used in studies of vesicle recycling. Subdividing the preparations before labeling allows test vs. control comparisons in the same ear from a single individual. Helpful tips are given for improving the quality of the preparation, the labeling and the imaging parameters. This new system is suitable for assaying pharmacologically and mechanically-induced uptake and release of these vital dyes in lanceolate terminals in both wild-type and genetically modified animals. Examples of modulatory influences on labeling intensity are given.

  2. Effect of prolonged inactivity on skeletal motor nerve terminals during aestivation in the burrowing frog, Cyclorana alboguttata.

    PubMed

    Hudson, Nicholas J; Lavidis, Nickolas A; Choy, Peng T; Franklin, Craig E

    2005-04-01

    This study examined the effect of prolonged inactivity, associated with aestivation, on neuromuscular transmission in the green-striped burrowing frog, Cyclorana alboguttata. We compared the structure and function of the neuromuscular junctions on the iliofibularis muscle from active C. alboguttata and from C. alboguttata that had been aestivating for 6 months. Despite the prolonged period of immobility, there was no significant difference in the shape of the terminals (primary, secondary or tertiary branches) or the length of primary terminal branches between aestivators and non-aestivators. Furthermore, there was no significant difference in the membrane potentials of muscle fibres or in miniature end plate potential (EPP) frequency and amplitude. However, there was a significant decrease in evoked transmitter release characterised by a 56% decrease in mean EPP amplitude, and a 29% increase in the failure rate of nerve terminal action potentials to evoke transmitter release. The impact of this suite of neuromuscular characteristics on the locomotor performance of emergent frogs is discussed.

  3. On the calcium receptor that mediates depolarization-secretion coupling at cholinergic motor nerve terminals

    PubMed Central

    Silinsky, E.M.

    1981-01-01

    1 The behaviour of the divalent cations Ca and Sr as agonists for receptors that mediate the synchronous evoked secretion of acetylcholine (ACh) was studied in the hope of determining whether the relationship between Ca binding and ACh secretion is determined only by the law of mass action or by the mathematical framework of receptor theory. Experiments were designed to evaluate the assumption that maximum effect requires occupation of all receptors by testing for the presence of spare Ca receptors on presynaptic terminals. Frog cutaneous nerve-muscle preparations were employed in conjunction with conventional electrophysiological methods. 2 Curves of log [Ca] or log [Sr] against the mean number of ACh quanta released (m̄) were constructed to saturation. The log [Sr]-m̄ relationship was shifted to the right and had a smaller maximum than the log [Ca]-m̄ curve. This suggests that Ca has a higher efficacy than Sr and raises the possibility that spare binding sites are present for Ca. 3 As a qualitative test for spare Ca receptors, La3+ (≥0.5 μm) or 2-chloroadenosine (25 μm) was employed as an irreversible antagonist of the effects of extracellular Ca on evoked ACh release. Despite the irreversible blockade of a proportion of receptors, increases in the [Ca] overcame this antagonism and produced a parallel shift in the log [Ca]-m̄ relation to the right. This suggests an apparent receptor reserve for Ca. Antagonism of Sr-mediated ACh release by either La3+ or 2-chloroadenosine could not be overcome by increasing the [Sr]. 4 As a quantitative test for spare Ca binding sites, the equilibrium affinity constant for Sr(KSr) as a competitive inhibitor of Ca was determined and compared with values for KSr calculated by two other methods which invoke the spare receptor assumption. All three methods produced comparable results. (KSr = 0.24-0.27 mm-1). 5 The equilibrium affinity constant for Ca (KCa) was calculated by comparing reciprocal plots of the concentrations of

  4. Differences between nerve terminal impulses of polymodal nociceptors and cold sensory receptors of the guinea-pig cornea.

    PubMed

    Brock, J A; Pianova, S; Belmonte, C

    2001-06-01

    1. Extracellular recording techniques were used to study nerve terminal impulses (NTIs) recorded from single polymodal nociceptors and cold-sensitive receptors in guinea-pig cornea isolated in vitro. 2. The amplitude and time course of NTIs recorded from polymodal nociceptors was different from those of cold-sensitive receptors. 3. Bath application of tetrodotoxin (1 microM) changed the time course of spontaneous NTIs recorded from both polymodal and cold-sensitive receptors. 4. Bath application of lignocaine (lidocaine; 1-5 mM) abolished all electrical activity. 5. Local application of lignocaine (2.5 and 20 mM) through the recording electrode changed the time course of the NTIs recorded from polymodal nociceptors but not that of NTIs recorded from cold-sensitive nerve endings. 6. It is concluded that action potentials propagate actively in the sensory nerve endings of polymodal nociceptors. In contrast, cold-sensitive receptor nerve endings appear to be passively invaded from a point more proximal in the axon where the action potential can fail or be initiated.

  5. Regenerating sprouts of axotomized cat muscle afferents express characteristic firing patterns to mechanical stimulation.

    PubMed

    Johnson, R D; Munson, J B

    1991-12-01

    1. In cats, we studied the physiological properties of regenerating sprouts of muscle afferent fibers and compared them with sprouts from cutaneous afferent fibers. 2. Muscle nerves to the triceps surae and cutaneous sural nerves were axotomized in the popliteal fossa, and the proximal ends were inserted into nerve cuffs. Six days later, we recorded action potentials from single Groups I and II muscle and mostly Group II cutaneous afferents driven by mechanostimulation of the cuff. 3. Most muscle afferent sprouts (91%) had a regular slowly adapting discharge in response to sustained mechanical displacement of the cuff, particularly to sustained stretch stimuli, whereas most cutaneous afferents (92%) did not. Muscle afferents were more likely to have a spontaneous discharge and afterdischarge. 4. Group II muscle afferent sprouts had lower stretch thresholds and a higher incidence of spontaneous discharge compared with Group I fiber sprouts, whereas Group I fibers had a higher incidence of high-frequency afterdischarge to mechanical stimuli. 5. We conclude that, 6 days after axotomy, regenerating sprouts of muscle afferents, particularly Group II afferents, have become mechanosensitive in the absence of a receptor target and exhibit physiological properties similar to those found when innervating their native muscle but significantly different from sprouts of cutaneous afferents. Expression of these native muscle afferent firing patterns after the inappropriate reinnervation of hairy skin may be due to inherent properties of the muscle afferent fiber.

  6. Salvinorin A exerts opposite presynaptic controls on neurotransmitter exocytosis from mouse brain nerve terminals.

    PubMed

    Grilli, Massimo; Neri, Elisa; Zappettini, Stefania; Massa, Francesca; Bisio, Angela; Romussi, Giovanni; Marchi, Mario; Pittaluga, Anna

    2009-01-01

    We investigated the effects of salvinorin A on the basal and the 12 mM K(+)-evoked release of preloaded [(3)H]noradenaline ([(3)H]NA) and [(3)H]serotonin ([(3)H]5-HT) from mouse hippocampal nerve terminals (synaptosomes), as well as on the basal and 12mM K(+)-evoked release of preloaded [(3)H]dopamine ([(3)H]DA) from mouse striatal and prefrontal cortex (PFc) synaptosomes. Salvinorin A (0.1-1000 nM) failed to affect the basal release of amines, but inhibited the 12 mM K(+)-evoked, Ca(2+)-dependent, exocytotic-like release of [(3)H]5-HT and [(3)H]DA. At the same concentration, salvinorin A facilitated the 12 mM K(+)-evoked, Ca(2+)-dependent, exocytotic-like release of [(3)H]NA. These effects could not be observed in pertussis toxin (PTx) entrapped synaptosomes. The broad spectrum kappa-opioid receptor (KOR) antagonist norbinaltorphimine (norBNI, 1-100 nM) antagonized the inhibition of [(3)H]5-HT and [(3)H]DA exocytosis as well as the facilitation of [(3)H]NA overflow induced by 100 nM salvinorin A. The KOR agonist U69593 (1-100 nM) mimicked salvinorin A in inhibiting [(3)H]5-HT and of [(3)H]DA exocytosis, its effect being prevented by norBNI, but leaving unchanged the K(+)-evoked release of [(3)H]NA. The effects of Salvinorin A on neurotransmitter exocytosis were not prevented by the selective mu opioid (MOR) receptor antagonist CTAP (10-100 nM), whereas facilitation of [(3)H]NA exocytosis, but not inhibition of [(3)H]5-HT and [(3)H]DA K(+)-evoked release, was counteracted by the delta opioid receptor (DOR) antagonist naltrindole (1-100 nM). We conclude that salvinorin A presynaptically modulates central NA, 5-HT, and DA exocytosis evoked by a mild depolarizing stimulus by acting at presynaptic opioid receptors having different pharmacological profiles.

  7. 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

  8. Interaction of 125I-labeled botulinum neurotoxins with nerve terminals. I. Ultrastructural autoradiographic localization and quantitation of distinct membrane acceptors for types A and B on motor nerves

    PubMed Central

    1986-01-01

    The labeling patterns produced by radioiodinated botulinum neurotoxin (125I-BoNT) types A and B at the vertebrate neuromuscular junction were investigated using electron microscopic autoradiography. The data obtained allow the following conclusions to be made. 125I-BoNT type A, applied in vivo or in vitro to mouse diaphragm or frog cutaneous pectoris muscle, interacts saturably with the motor nerve terminal only; silver grains occur on the plasma membrane, within the synaptic bouton, and in the axoplasm of the nerve trunk, suggesting internalization and retrograde intra-axonal transport of toxin or fragments thereof. 125I-BoNT type B, applied in vitro to the murine neuromuscular junction, interacts likewise with the motor nerve terminal except that a lower proportion of internalized radioactivity is seen. This result is reconcilable with the similar, but not identical, pharmacological action of these toxin types. The saturability of labeling in each case suggested the involvement of acceptors; on preventing the internalization step with metabolic inhibitors, their precise location became apparent. They were found on all unmyelinated areas of the nerve terminal membrane, including the preterminal axon and the synaptic bouton. Although 125I-BoNT type A interacts specifically with developing terminals of newborn rats, the unmyelinated plasma membrane of the nerve trunk is not labeled, indicating that the acceptors are unique components restricted to the nerve terminal area. BoNT types A and B have distinct acceptors on the terminal membrane. Having optimized the conditions for saturation of these binding sites and calibrated the autoradiographic procedure, we found the densities of the acceptors for types A and B to be approximately 150 and 630/micron 2 of membrane, respectively. It is proposed that these membrane acceptors target BoNT to the nerve terminal and mediate its delivery to an intracellular site, thus contributing to the toxin's selective inhibitory action

  9. Calcium-activated potassium channels in isolated presynaptic nerve terminals from rat brain.

    PubMed Central

    Bartschat, D K; Blaustein, M P

    1985-01-01

    86Rb efflux was examined in isolated presynaptic nerve terminals (synaptosomes) from rat brain in a study designed to assess K permeability (PK) changes sensitive to alterations in internal Ca activity. Rb efflux from 86Rb-loaded synaptosomes into nominally Ca-free physiological saline (PSS) containing 5 mM-K was about 0.3-0.4%/s. Raising extracellular K concentration [( K]o), to depolarize the synaptosomes, stimulated the 86Rb efflux. Addition of Ca to the 5 mM-K PSS had no effect, but Ca did further stimulate 86Rb efflux into K-rich solutions. The effect of Ca was graded, with apparent half-maximal activation, KA approximately equal to 0.5 mM-Ca. These data fit the view that, during depolarization, Ca enters the terminals through voltage-regulated Ca channels, and that the rise in intracellular Ca concentration opens certain (Ca-activated) K channels. The Ca-dependent stimulation of 86Rb efflux was greatest during the initial seconds of incubation (component CT), and then declined to a much lower rate (component CS). Much of this change in rate could be attributed to inactivation of voltage-regulated Ca channels and reduced entry of Ca. The Ca-dependent increase in 86Rb efflux was completely inhibited by 100 microM-La. In the presence of Ca, but not in its absence, the Ca ionophore A23187 stimulated 86Rb efflux both in 5 and 100 mM-K PSS. The effect in 100 mM-K was quantitatively greater, perhaps because of the increased outward driving force on Rb in depolarized synaptosomes. When synaptosomes were suspended in media containing the voltage-sensitive fluorescent dye, DiS-C3-(5) (1,1'-dipentyl-2,2'-thiocarbocyanine), the addition of Ca+ A23187 decreased the fluorescence intensity (= synaptosome hyperpolarization) when the media contained 5 mM-K but not 100 mM-K. This implies that in the presence of Ca + A23187, PK was increased, and the membrane potential moved closer to the K equilibrium potential, EK. Quinine sulphate, a blocker of Ca-activated K channels

  10. Terminal Segment Surgical Anatomy of the Rat Facial Nerve: Implications for Facial Reanimation Study

    PubMed Central

    Henstrom, Doug; Hadlock, Tessa; Lindsay, Robin; Knox, Christopher J.; Malo, Juan; Vakharia, Kalpesh T.; Heaton, James T.

    2015-01-01

    Introduction Rodent whisking behavior is supported by the buccal and mandibular branches of the facial nerve, a description of how these branches converge and contribute to whisker movement is lacking. Methods Eight rats underwent isolated transection of either the buccal or mandibular branch and subsequent opposite branch transection. Whisking function was analyzed following both transections. Anatomical measurements, and video recording of stimulation to individual branches, were taken from both facial nerves in 10 rats. Results Normal to near-normal whisking was demonstrated after isolated branch transection. Following transection of both branches whisking was eliminated. The buccal and mandibular branches form a convergence just proximal to the whisker-pad, named the “distal pes.” Distal to this convergence, we identified consistent anatomy that demonstrated cross-innervation. Conclusion The overlap of efferent supply to the whisker pad must be considered when studying facial nerve regeneration in the rat facial nerve model. PMID:22499096

  11. Nicotinic modulation of glutamate receptor function at nerve terminal level: a fine-tuning of synaptic signals.

    PubMed

    Marchi, Mario; Grilli, Massimo; Pittaluga, Anna M

    2015-01-01

    This review focuses on a specific interaction occurring between the nicotinic cholinergic receptors (nAChRs) and the glutamatergic receptors (GluRs) at the nerve endings level. We have employed synaptosomes in superfusion and supplemented and integrated our findings with data obtained using techniques from molecular biology and immuno-cytochemistry, and the assessment of receptor trafficking. In particular, we characterize the following: (1) the direct and unequivocal localization of native α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and N-methyl-D-aspartate (NMDA) glutamatergic receptors on specific nerve terminals, (2) their pharmacological characterization and functional co-localization with nAChRs on the same nerve endings, and (3) the existence of synergistic or antagonistic interactions among them. Indeed, in the rat nucleus accumbens (NAc), the function of some AMPA and NMDA receptors present on the dopaminergic and glutamatergic nerve terminals can be regulated negatively or positively in response to a brief activation of nAChRs. This effect occurs rapidly and involves the trafficking of AMPA and NMDA receptors. The event takes place also at very low concentrations of nicotine and involves the activation of several nAChRs subtypes. This dynamic control by cholinergic nicotinic system of glutamatergic NMDA and AMPA receptors might therefore represent an important neuronal presynaptic adaptation associated with nicotine administration. The understanding of the role of these nicotine-induced functional changes might open new and interesting perspectives both in terms of explaining the mechanisms that underlie some of the effects of nicotine addiction and in the development of new drugs for smoking cessation.

  12. Molecular microdomains in a sensory terminal, the vestibular calyx ending.

    PubMed

    Lysakowski, Anna; Gaboyard-Niay, Sophie; Calin-Jageman, Irina; Chatlani, Shilpa; Price, Steven D; Eatock, Ruth Anne

    2011-07-06

    Many primary vestibular afferents form large cup-shaped postsynaptic terminals (calyces) that envelope the basolateral surfaces of type I hair cells. The calyceal terminals both respond to glutamate released from ribbon synapses in the type I cells and initiate spikes that propagate to the afferent's central terminals in the brainstem. The combination of synaptic and spike initiation functions in these unique sensory endings distinguishes them from the axonal nodes of central neurons and peripheral nerves, such as the sciatic nerve, which have provided most of our information about nodal specializations. We show that rat vestibular calyces express an unusual mix of voltage-gated Na and K channels and scaffolding, cell adhesion, and extracellular matrix proteins, which may hold the ion channels in place. Protein expression patterns form several microdomains within the calyx membrane: a synaptic domain facing the hair cell, the heminode abutting the first myelinated internode, and one or two intermediate domains. Differences in the expression and localization of proteins between afferent types and zones may contribute to known variations in afferent physiology.

  13. The active zone protein family ELKS supports Ca2+ influx at nerve terminals of inhibitory hippocampal neurons.

    PubMed

    Liu, Changliang; Bickford, Lydia S; Held, Richard G; Nyitrai, Hajnalka; Südhof, Thomas C; Kaeser, Pascal S

    2014-09-10

    In a presynaptic nerve terminal, synaptic vesicle exocytosis is restricted to specialized sites called active zones. At these sites, neurotransmitter release is determined by the number of releasable vesicles and their probability of release. Proteins at the active zone set these parameters by controlling the presynaptic Ca(2+) signal, and through docking and priming of synaptic vesicles. Vertebrate ELKS proteins are enriched at presynaptic active zones, but their functions are not well understood. ELKS proteins are produced by two genes in vertebrates, and each gene contributes ∼50% to total brain ELKS. We generated knock-out mice for ELKS1 and found that its constitutive removal causes lethality. To bypass lethality, and to circumvent redundancy between ELKS1 and ELKS2 in synaptic transmission, we used a conditional genetic approach to remove both genes in cultured hippocampal neurons after synapses are established. Simultaneous removal of ELKS1 and ELKS2 resulted in a 50% decrease of neurotransmitter release at inhibitory synapses, paralleled by a reduction in release probability. Removal of ELKS did not affect synapse numbers or their electron microscopic appearance. Using Ca(2+) imaging, we found that loss of ELKS caused a 30% reduction in single action potential-triggered Ca(2+) influx in inhibitory nerve terminals, consistent with the deficits in synaptic transmission and release probability. Unlike deletion of the active zone proteins RIM, RIM-BP, or bruchpilot, ELKS removal did not lead to a measurable reduction in presynaptic Ca(2+) channel levels. Our results reveal that ELKS is required for normal Ca(2+) influx at nerve terminals of inhibitory hippocampal neurons.

  14. Afferent innervation patterns of the saccule in pigeons

    NASA Technical Reports Server (NTRS)

    Zakir, M.; Huss, D.; Dickman, J. D.

    2003-01-01

    The innervation patterns of vestibular saccular afferents were quantitatively investigated in pigeons using biotinylated dextran amine as a neural tracer and three-dimensional computer reconstruction. Type I hair cells were found throughout a large portion of the macula, with the highest density observed in the striola. Type II hair cells were located throughout the macula, with the highest density in the extrastriola. Three classes of afferent innervation patterns were observed, including calyx, dimorph, and bouton units, with 137 afferents being anatomically reconstructed and used for quantitative comparisons. Calyx afferents were located primarily in the striola, innervated a number of type I hair cells, and had small innervation areas. Most calyx afferent terminal fields were oriented parallel to the anterior-posterior axis and the morphological polarization reversal line. Dimorph afferents were located throughout the macula, contained fewer type I hair cells in a calyceal terminal than calyx afferents and had medium sized innervation areas. Bouton afferents were restricted to the extrastriola, with multi-branching fibers and large innervation areas. Most of the dimorph and bouton afferents had innervation fields that were oriented dorso-ventrally but were parallel to the neighboring reversal line. The organizational morphology of the saccule was found to be distinctly different from that of the avian utricle or lagena otolith organs and appears to represent a receptor organ undergoing evolutionary adaptation toward sensing linear motion in terrestrial and aerial species.

  15. Electrophysiological identification of the functional presynaptic nerve terminals on an isolated single vasopressin neurone of the rat supraoptic nucleus.

    PubMed

    Ohbuchi, T; Yokoyama, T; Fujihara, H; Suzuki, H; Ueta, Y

    2010-05-01

    Release of arginine vasopressin (AVP) and oxytocin from magnocellular neurosecretory cells (MNCs) of the supraoptic nucleus (SON) is under the control of glutamate-dependent excitation and GABA-dependent inhibition. The possible role of the synaptic terminals attached to SON neurones has been investigated using whole-cell patch-clamp recording in in vitro rat brain slice preparations. Recent evidence has provided new insights into the repercussions of glial environment modifications on the physiology of MNCs at the synaptic level in the SON. In the present study, excitatory glutamatergic and inhibitory GABAergic synaptic inputs were recorded from an isolated single SON neurone cultured for 12 h, using the whole-cell patch clamp technique. Neurones expressed an AVP-enhanced green fluorescent protein (eGFP) fusion gene in MNCs. In addition, native synaptic terminals attached to a dissociated AVP-eGFP neurone were visualised with synaptic vesicle markers. These results suggest that the function of presynaptic nerve terminals may be evaluated directly in a single AVP-eGFP neurone. These preparations would be helpful in future studies aiming to electrophysiologically distinguish between the functions of synaptic terminals and glial modifications in the SON neurones.

  16. Comparative study of fluoxetine, sibutramine, sertraline and dexfenfluramine on the morphology of serotonergic nerve terminals using serotonin immunohistochemistry.

    PubMed

    Kalia, M; O'Callaghan, J P; Miller, D B; Kramer, M

    2000-03-06

    We compared the effects of treatment with high doses of fluoxetine, sibutramine, sertraline, and dexfenfluramine for 4 days on brain serotonergic nerve terminals in rats. Methylenedioxymethamphetamine (MDMA) and 5,7-dihydroxytryptamine (5,7-DHT) were used as positive controls because both compounds deplete brain serotonin. Food intake and body weight changes were also monitored and yoked, pair-fed animals were used to control for possible changes in morphology due to nutritional deficits. Fluoxetine, sibutramine, sertraline and dexfenfluramine all produced a significant reduction in body weight. Fluoxetine, sibutramine and sertraline treatment resulted in no depletion of brain serotonin but produced morphological abnormalities in the serotonergic immunoreactive nerve network. In contrast, dexfenfluramine and MDMA depleted brain serotonin and produced morphological changes in the serotonin nerve network. These results indicate that even though fluoxetine, sibutramine and sertraline do not deplete brain serotonin, they do produce morphological changes in several brain regions (as identified by serotonin immunohistochemistry). Dexfenfluramine and MDMA, on the other hand, markedly deplete brain serotonin and also produce morphological changes. Collectively, these results lend support to the concept that all compounds acting on brain serotonin systems, whether capable of producing serotonin depletion or not, could produce similar effects on the morphology of cerebral serotonin systems.

  17. 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.

  18. Primary afferent plasticity following deafferentation of the trigeminal brainstem nuclei in the adult rat.

    PubMed

    De Riu, Pier Luigi; Russo, Antonella; Pellitteri, Rosalia; Stanzani, Stefania; Tringali, Giovanni; Roccazzello, Anna Maria; De Riu, Giacomo; Marongiu, Patrizia; Mameli, Ombretta

    2008-09-01

    Alpha-tyrosinated tubulin is a cytoskeletal protein that is involved in axonal growth and is considered a marker of neuronal plasticity in adult mammals. In adult rats, unilateral ablation of the left facial sensorimotor cortical areas induces degeneration of corticotrigeminal projections and marked denervation of the contralateral sensory trigeminal nuclei. Western blotting and real-time-PCR of homogenates of the contralateral trigeminal ganglion (TG) revealed consistent overexpression of growth proteins 15 days after left decortication in comparison with the ipsilateral side. Immunohistochemical analyses indicated marked overexpression of alpha-tyrosinated tubulin in the cells of the ganglion on the right side. Cytoskeletal changes were primarily observed in the small ganglionic neurons. Application of HRP-CT, WGA-HRP, and HRP to infraorbital nerves on both sides 15 days after left decortication showed a significant degree of terminal sprouting and neosynaptogenesis from right primary afferents at the level of the right caudalis and interpolaris trigeminal subnuclei. These observations suggest that the adaptive response of TG neurons to central deafferentation, leading to overcrowding and rearrangement of the trigeminal primary afferent terminals on V spinal subnuclei neurons, could represent the anatomical basis for distortion of facial modalities, perceived as allodynia and hyperalgesia, despite nerve integrity.

  19. Stronger antinociceptive efficacy of opioids at the injured nerve trunk than at its peripheral terminals in neuropathic pain.

    PubMed

    Labuz, Dominika; Machelska, Halina

    2013-09-01

    Activation of opioid receptors on peripheral sensory neurons has the potential for safe pain control, as it lacks centrally mediated side effects. While this approach often only partially suppressed neuropathic pain in animal models, opioids were mostly applied to animal paws although neuropathy was induced at the nerve trunk. Here we aimed to identify the most relevant peripheral site of opioid action for efficient antinociception in neuropathy. On days 2 and 14 following a chronic constriction injury (CCI) of the sciatic nerve in mice, we evaluated dose and time relationships of the effects of μ-, δ-, and κ-opioid receptor agonists injected either at the CCI site or intraplantarly (i.pl.) into the lesioned nerve-innervated paw, on spontaneous paw lifting and heat and mechanical hypersensitivity (using Hargreaves and von Frey tests, respectively). We found that neither agonist diminished spontaneous paw lifting, despite the application site. Heat hypersensitivity was partially attenuated by i.pl. μ-receptor agonist only, while it was improved by all three agonists applied at the CCI site. Mechanical hypersensitivity was slightly diminished by all agonists administered i.pl., whereas it was completely blocked by all opioids injected at the CCI site. These antinociceptive effects were opioid receptor type-selective and site-specific. Thus, opioids might not be effective against spontaneous pain, but they improve heat and mechanical hypersensitivity in neuropathy. Importantly, efficient alleviation of hypersensitivity is governed by peripheral opioid receptors at the injured nerve trunk rather than at its peripheral terminals. Identifying the primary action site of analgesics is important for the development of adequate pain therapies.

  20. Interaction of /sup 125/I-labeled botulinum neurotoxins with nerve terminals. I. Ultrastructural autoradiographic localization and quantitation of distinct membrane acceptors for types A and B on motor nerves

    SciTech Connect

    Black, J.D.; Dolly, J.O.

    1986-01-01

    The labeling patterns produced by radioiodinated botulinum neurotoxin (/sup 125/I-BoNT) types A and B at the vertebrate neuromuscular junction were investigated using electron microscopic autoradiography. The data obtained allow the following conclusions to be made. (a) /sup 125/I-BoNT type A, applied in vivo or in vitro to mouse diaphragm or frog cutaneous pectoris muscle, interacts saturably with the motor nerve terminal only; silver grains occur on the plasma membrane, within the synaptic bouton, and in the axoplasm of the nerve trunk, suggesting internalization and retrograde intra-axonal transport of toxin or fragments thereof. (b) /sup 125/I-BoNT type B, applied in vitro to the murine neuromuscular junction, interacts likewise with the motor nerve terminal except that a lower proportion of internalized radioactivity is seen. This result is reconcilable with the similar, but not identical, pharmacological action of these toxin types. (c) The saturability of labeling in each case suggested the involvement of acceptors; on preventing the internalization step with metabolic inhibitors, their precise location became apparent. They were found on all unmyelinated areas of the nerve terminal membrane, including the preterminal axon and the synaptic bouton. (d) It is not proposed that these membrane acceptors target BoNT to the nerve terminal and mediate its delivery to an intracellular site, thus contributing to the toxin's selective inhibitory action on neurotransmitter release.

  1. Cortical Presynaptic Control of Dorsal Horn C–Afferents in the Rat

    PubMed Central

    Martínez-Lorenzana, Guadalupe; Condés-Lara, Miguel; Rojas-Piloni, Gerardo

    2013-01-01

    Lamina 5 sensorimotor cortex pyramidal neurons project to the spinal cord, participating in the modulation of several modalities of information transmission. A well-studied mechanism by which the corticospinal projection modulates sensory information is primary afferent depolarization, which has been characterized in fast muscular and cutaneous, but not in slow-conducting nociceptive skin afferents. Here we investigated whether the inhibition of nociceptive sensory information, produced by activation of the sensorimotor cortex, involves a direct presynaptic modulation of C primary afferents. In anaesthetized male Wistar rats, we analyzed the effects of sensorimotor cortex activation on post tetanic potentiation (PTP) and the paired pulse ratio (PPR) of dorsal horn field potentials evoked by C–fiber stimulation in the sural (SU) and sciatic (SC) nerves. We also explored the time course of the excitability changes in nociceptive afferents produced by cortical stimulation. We observed that the development of PTP was completely blocked when C-fiber tetanic stimulation was paired with cortex stimulation. In addition, sensorimotor cortex activation by topical administration of bicuculline (BIC) produced a reduction in the amplitude of C–fiber responses, as well as an increase in the PPR. Furthermore, increases in the intraspinal excitability of slow-conducting fiber terminals, produced by sensorimotor cortex stimulation, were indicative of primary afferent depolarization. Topical administration of BIC in the spinal cord blocked the inhibition of C–fiber neuronal responses produced by cortical stimulation. Dorsal horn neurons responding to sensorimotor cortex stimulation also exhibited a peripheral receptive field and responded to stimulation of fast cutaneous myelinated fibers. Our results suggest that corticospinal inhibition of nociceptive responses is due in part to a modulation of the excitability of primary C–fibers by means of GABAergic inhibitory

  2. Innocuous, Not Noxious, Input Activates PKCγ Interneurons of the Spinal Dorsal Horn via Myelinated Afferent Fibers

    PubMed Central

    Braz, Joao M.; Skinner, Kate; Llewellyn-Smith, Ida J.; Basbaum, Allan I.

    2008-01-01

    Protein kinase C γ (PKCγ), which is concentrated in interneurons of the inner part of lamina II of the dorsal horn, has been implicated in injury-induced allodynia, a condition wherein pain is produced by innocuous stimuli. Although it is generally assumed that these interneurons receive input from the nonpeptidergic, IB4-positive subset of nociceptors, the fact that PKCγ cells do not express Fos in response to noxious stimulation suggests otherwise. Here, we demonstrate that the terminal field of the nonpeptidergic population of nociceptors, in fact, lies dorsal to that of PKCγ interneurons. There was also no overlap between the PKCγ-expressing interneurons and the transganglionic tracer wheat germ agglutinin which, after sciatic nerve injection, labels all unmyelinated nociceptors. However, transganglionic transport of the β-subunit of cholera toxin, which marks the medium-diameter and large-diameter myelinated afferents that transmit non-noxious information, revealed extensive overlap with the layer of PKCγ interneurons. Furthermore, expression of a transneuronal tracer in myelinated afferents resulted in labeling of PKCγ interneurons. Light and electron microscopic double labeling further showed that the VGLUT1 subtype of vesicular glutamate transmitter, which is expressed in myelinated afferents, marks synapses that are presynaptic to the PKCγ interneurons. Finally, we demonstrate that a continuous non-noxious input, generated by walking on a rotarod, induces Fos in the PKCγ interneurons. These results establish that PKCγ interneurons are activated by myelinated afferents that respond to innocuous stimuli, which suggests that injury-induced mechanical allodynia is transmitted through a circuit that involves PKCγ interneurons and non-nociceptive, VGLUT1-expressing myelinated primary afferents. PMID:18685019

  3. Perineural capsaicin induces the uptake and transganglionic transport of choleratoxin B subunit by nociceptive C-fiber primary afferent neurons.

    PubMed

    Oszlács, O; Jancsó, G; Kis, G; Dux, M; Sántha, P

    2015-12-17

    The distribution of spinal primary afferent terminals labeled transganglionically with the choleratoxin B subunit (CTB) or its conjugates changes profoundly after perineural treatment with capsaicin. Injection of CTB conjugated with horseradish peroxidase (HRP) into an intact nerve labels somatotopically related areas in the ipsilateral dorsal horn with the exceptions of the marginal zone and the substantia gelatinosa, whereas injection of this tracer into a capsaicin-pretreated nerve also results in massive labeling of these most superficial layers of the dorsal horn. The present study was initiated to clarify the role of C-fiber primary afferent neurons in this phenomenon. In L5 dorsal root ganglia, analysis of the size frequency distribution of neurons labeled after injection of CTB-HRP into the ipsilateral sciatic nerve treated previously with capsaicin or resiniferatoxin revealed a significant increase in the proportion of small neurons. In the spinal dorsal horn, capsaicin or resiniferatoxin pretreatment resulted in intense CTB-HRP labeling of the marginal zone and the substantia gelatinosa. Electron microscopic histochemistry disclosed a dramatic, ∼10-fold increase in the proportion of CTB-HRP-labeled unmyelinated dorsal root axons following perineural capsaicin or resiniferatoxin. The present results indicate that CTB-HRP labeling of C-fiber dorsal root ganglion neurons and their central terminals after perineural treatment with vanilloid compounds may be explained by their phenotypic switch rather than a sprouting response of thick myelinated spinal afferents which, in an intact nerve, can be labeled selectively with CTB-HRP. The findings also suggest a role for GM1 ganglioside in the modulation of nociceptor function and pain.

  4. Correlation between afferent rearrangements and behavioral deficits after local excitotoxic insult in the mammalian vestibule: a rat model of vertigo symptoms

    PubMed Central

    Travo, Cécile; Saleur, Aurélie; Broussy, Audrey; Brugeaud, Aurore; Chabbert, Christian

    2016-01-01

    ABSTRACT Damage to inner ear afferent terminals is believed to result in many auditory and vestibular dysfunctions. The sequence of afferent injuries and repair, as well as their correlation with vertigo symptoms, remains poorly documented. In particular, information on the changes that take place at the primary vestibular endings during the first hours following a selective insult is lacking. In the present study, we combined histological analysis with behavioral assessments of vestibular function in a rat model of unilateral vestibular excitotoxic insult. Excitotoxicity resulted in an immediate but transient alteration of the balance function that was resolved within a week. Concomitantly, vestibular primary afferents underwent a sequence of structural changes followed by spontaneous repair. Within the first two hours after the insult, a first phase of pronounced vestibular dysfunction coincided with extensive swelling of afferent terminals. In the next 24 h, a second phase of significant but incomplete reduction of the vestibular dysfunction was accompanied by a resorption of swollen terminals and fiber retraction. Eventually, within 1 week, a third phase of complete balance restoration occurred. The slow and progressive withdrawal of the balance dysfunction correlated with full reconstitution of nerve terminals. Competitive re-innervation by afferent and efferent terminals that mimicked developmental synaptogenesis resulted in full re-afferentation of the sensory epithelia. By deciphering the sequence of structural alterations that occur in the vestibule during selective excitotoxic impairment, this study offers new understanding of how a vestibular insult develops in the vestibule and how it governs the heterogeneity of vertigo symptoms. PMID:27483344

  5. Functional selectivity and time-dependence of μ-opioid receptor desensitization at nerve terminals in the mouse ventral tegmental area

    PubMed Central

    Lowe, J D; Bailey, C P

    2015-01-01

    BACKGROUND AND PURPOSE The majority of studies examining desensitization of the μ-opioid receptor (MOR) have examined those located at cell bodies. However, MORs are extensively expressed at nerve terminals throughout the mammalian nervous system. This study is designed to investigate agonist-induced MOR desensitization at nerve terminals in the mouse ventral tegmental area (VTA). EXPERIMENTAL APPROACH MOR function was measured in mature mouse brain slices containing the VTA using whole-cell patch-clamp electrophysiology. Presynaptic MOR function was isolated from postsynaptic function and the functional selectivity, time-dependence and mechanisms of agonist-induced MOR desensitization were examined. KEY RESULTS MORs located at GABAergic nerve terminals in the VTA were completely resistant to rapid desensitization induced by the high-efficacy agonists DAMGO and Met-enkephalin. MORs located postsynaptically on GABAergic cell bodies readily underwent rapid desensitization in response to DAMGO. However, after prolonged (>7 h) treatment with Met-enkephalin, profound homologous MOR desensitization was observed. Morphine could induce rapid MOR desensitization at nerve terminals when PKC was activated. CONCLUSIONS AND IMPLICATIONS Agonist-induced MOR desensitization in GABAergic neurons in the VTA is compartment-selective as well as agonist-selective. When MORs are located at cell bodies, higher-efficacy agonists induce greater levels of rapid desensitization than lower-efficacy agonists. However, the converse is true at nerve terminals where agonists that induce MOR desensitization via PKC are capable of rapid agonist-induced desensitization while higher-efficacy agonists are not. MOR desensitization induced by higher-efficacy agonists at nerve terminals only takes place after prolonged receptor activation. LINKED ARTICLES This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http

  6. Probabilistic secretion of quanta at somatic motor-nerve terminals: the fusion-pore model, quantal detection and autoinhibition.

    PubMed

    Thomson, P C; Lavidis, N A; Robinson, J; Bennett, M R

    1995-08-29

    The probability of detecting first, second, and later quanta secreted at release sites of a motor-nerve terminal during the early release period following a nerve impulse has been addressed. The possibility that early quantal release autoinhibits later quantal release during this period has also been ascertained. In this investigation, a model for the secretion of a quantum at a release site is developed in which, following the influx and diffusion of calcium ions to a release site protein associated with synaptic vesicles, kappa steps of association of the ions with the protein then occur at rate alpha. The release site protein then undergoes a conformational change which may not go on to completion if calcium ions dissociate from the protein at rate gamma. If this process does reach completion then a fusion-pore between the vesicle and the presynaptic membrane is created; this happens at rate delta. Key assumptions of this fusion-pore model are that the quantal secretions from each site are independent of each other, and that there is a large number of vesicles, each with a small probability of secretion, so that the number of secretions is Poisson in nature. These assumptions allow analytical expressions to be obtained for predicting the times at which first, second and later quanta are secreted during the early release period following an impulse. To test the model, experiments were performed in which the times of first, second and later quantal releases were determined at discrete regions along the length of visualized motor-terminal branches in toad (Bufo marinus) muscles. Estimates of model rate constants and of kappa from the times for first quantal secretions failed to give satisfactory predictions of the observed times of later secretions. Therefore, either the model fails, or the procedure used for detecting later quantal events as a consequence of their being masked by earlier quantal events is inadequate. To solve this detection problem, a two

  7. Early Exposure to General Anesthesia Disrupts Spatial Organization of Presynaptic Vesicles in Nerve Terminals of the Developing Rat Subiculum.

    PubMed

    Lunardi, N; Oklopcic, A; Prillaman, M; Erisir, A; Jevtovic-Todorovic, V

    2015-10-01

    Exposure to general anesthesia (GA) during critical stages of brain development induces widespread neuronal apoptosis and causes long-lasting behavioral deficits in numerous animal species. Although several studies have focused on the morphological fate of neurons dying acutely by GA-induced developmental neuroapoptosis, the effects of an early exposure to GA on the surviving synapses remain unclear. The aim of this study is to study whether exposure to GA disrupts the fine regulation of the dynamic spatial organization and trafficking of synaptic vesicles in presynaptic terminals. We exposed postnatal day 7 (PND7) rat pups to a clinically relevant anesthetic combination of midazolam, nitrous oxide, and isoflurane and performed a detailed ultrastructural analysis of the synaptic vesicle architecture at presynaptic terminals in the subiculum of rats at PND 12. In addition to a significant decrease in the density of presynaptic vesicles, we observed a reduction of docked vesicles, as well as a reduction of vesicles located within 100 nm from the active zone, in animals 5 days after an initial exposure to GA. We also found that the synaptic vesicles of animals exposed to GA are located more distally with respect to the plasma membrane than those of sham control animals and that the distance between presynaptic vesicles is increased in GA-exposed animals compared to sham controls. We report that exposure of immature rats to GA during critical stages of brain development causes significant disruption of the strategic topography of presynaptic vesicles within the nerve terminals of the subiculum.

  8. Central projection of rat sciatic nerve fibres as revealed by Ricinus communis agglutinin and horseradish peroxidase tracers.

    PubMed

    Leong, S K; Tan, C K

    1987-10-01

    The central projection of afferent fibres in the rat sciatic nerve has been studied by means of the suicide transport of a lectin, Ricinus communis agglutinin 60 (RCA 60), and the transganglionic transport of horseradish peroxidase (HRP). The results obtained from these two methods are similar; however, the RCA method gave a more consistent and better localisation of the primary afferent terminals than the HRP method. The present study has shown that primary afferents from the sciatic nerve project predominantly to the ipsilateral gracile nucleus. In addition, they also project to several other brainstem nuclei; these include the contralateral nucleus gracilis, the ipsilateral main cuneate nucleus, the external cuneate nucleus and the presumptive nucleus z.

  9. A novel large-conductance Ca(2+)-activated potassium channel and current in nerve terminals of the rat neurohypophysis.

    PubMed Central

    Wang, G; Thorn, P; Lemos, J R

    1992-01-01

    1. Nerve terminals of the rat posterior pituitary were acutely dissociated and identified using a combination of morphological and immunohistochemical techniques. Terminal membrane currents were studied using the 'whole-cell' patch clamp technique and channels were studied using inside-out and outside-out patches. 2. In physiological solutions, but with 7 mM 4-aminopyridine (4-AP), depolarizing voltage clamp steps from different holding potentials (-90 or -50 mV) elicited a fast, inward current followed by a slow, sustained, outward current. This outward current did not appear to show any steady-state inactivation. 3. The threshold for activation of the outward current was -30 mV and the current-voltage relation was 'bell-shaped'. The amplitude increased with increasingly depolarized potential steps. The outward current reversal potential was measured using tail current analysis and was consistent with that of a potassium current. 4. The sustained potassium current was determined to be dependent on the concentration of intracellular calcium. Extracellular Cd2+ (80 microM), a calcium channel blocker, also reversibly abolished the outward current. 5. The current was delayed in onset and was sustained over the length of a 150 ms-duration depolarizing pulse. The outward current reached a peak plateau and then decayed slowly. The decay was fitted by a single exponential with a time constant of 9.0 +/- 2.2 s. The decay constants did not show a dependence on voltage but rather on intracellular Ca2+. The time course of recovery from this decay was complex with full recovery taking > 190 s. 6. 4-AP (7 mM), dendrotoxin (100 nM), apamin (40-80 nM), and charybdotoxin (10-100 nM) had no effect on the sustained outward current. In contrast Ba2+ (200 microM) and tetraethylammonium inhibited the current, the latter in a dose-dependent manner (apparent concentration giving 50% of maximal inhibition (IC50) = 0.51 mM). 7. The neurohypophysial terminal outward current recorded here

  10. The effect of calcium ions on the binomial statistic parameters that control acetylcholine release at preganglionic nerve terminals.

    PubMed Central

    Bennett, M R; Florin, T; Pettigrew, A G

    1976-01-01

    1. A study has been made of the effects of changing [Ca]O and [Mg]O on the binomial statistic parameters p and n that control the average quantal content (m) of the excitatory post-synaptic potential (e.p.s.p.) due to acetylcholine release at preganglionic nerve terminals. 2. When [Ca]O was increased in the range from 0-2 to 0-5 mM, p increased as the first power of [Ca]O whereas n increased as the 0-5 power of [Ca]O; when [Mg]O was increased in the range from 5 to 200 mM, p decreased as the first power of [Mg]O whereas n decreased as the 0-5 power of [Mg]O. 3. The increase in quantal release of a test impulse following a conditioning impulse was primarily due to an increase in n; the increase in quantal content of successive e.p.s.p.s in a short train was due to an increase in n and p, and the increase in n was quantitatively described in terms of the accumulation of a Ca-receptor complex in the nerve terminal. 4. The decrease in quantal content of successive e.p.s.p.s during long trains of impulses over several minutes was primarily due to a decrease in n. These results are discussed in terms of an hypothesis concerning the physical basis of n and p in the release process. PMID:181562

  11. Alpha-Synuclein Pathology in Sensory Nerve Terminals of the Upper Aerodigestive Tract of Parkinson’s Disease Patients

    PubMed Central

    Mu, Liancai; Chen, Jingming; Sobotka, Stanislaw; Nyirenda, Themba; Benson, Brian; Gupta, Fiona; Sanders, Ira; Adler, Charles H.; Caviness, John N.; Shill, Holly A.; Sabbagh, Marwan; Samanta, Johan E.; Sue, Lucia I.; Beach, Thomas G.

    2015-01-01

    Dysphagia is common in Parkinson’s disease (PD) and causes significant morbidity and mortality. PD dysphagia has usually been explained as dysfunction of central motor control, much like other motor symptoms that are characteristic of the disease. However, PD dysphagia does not correlate with severity of motor symptoms nor does it respond to motor therapies. It is known that PD patients have sensory deficits in the pharynx, and that impaired sensation may contribute to dysphagia. However, the underlying cause of the pharyngeal sensory deficits in PD is not known. We hypothesized that PD dysphagia with sensory deficits may be due to degeneration of the sensory nerve terminals in the upper aerodigestive tract (UAT). We have previously shown that Lewy-type synucleinopathy (LTS) is present in the main pharyngeal sensory nerves of PD patients, but not in controls. In this study, the sensory terminals in UAT mucosa were studied to discern the presence and distribution of LTS. Whole-mount specimens (tongue-pharynx-larynx-upper esophagus) were obtained from 10 deceased human subjects with clinically diagnosed and neuropathologically confirmed PD (five with dysphagia and five without) and four age-matched healthy controls. Samples were taken from six sites and immunostained for phosphorylated α-synuclein (PAS). The results showed the presence of PAS-immunoreactive (PAS-ir) axons in all the PD subjects and in none of the controls. Notably, PD patients with dysphagia had more PAS-ir axons in the regions that are critical for initiating the swallowing reflex. These findings suggest that Lewy pathology affects mucosal sensory axons in specific regions of the UAT and may be related to PD dysphagia. PMID:26041249

  12. Hypertonic enhancement of transmitter release from frog motor nerve terminals: Ca2+ independence and role of integrins

    NASA Technical Reports Server (NTRS)

    Kashani, A. H.; Chen, B. M.; Grinnell, A. D.

    2001-01-01

    Hyperosmotic solutions cause markedly enhanced spontaneous quantal release of neurotransmitter from many nerve terminals. The mechanism of this enhancement is unknown. We have investigated this phenomenon at the frog neuromuscular junction with the aim of determining the degree to which it resembles the modulation of release by stretch, which has been shown to be mediated by mechanical tension on integrins.The hypertonicity enhancement, like the stretch effect, does not require Ca2+ influx or release from internal stores, although internal release may contribute to the effect. The hypertonicity effect is sharply reduced (but not eliminated) by peptides containing the RGD sequence, which compete with native ligands for integrin bonds.There is co-variance in the magnitude of the stretch and osmotic effects; that is, individual terminals exhibiting a large stretch effect also show strong enhancement by hypertonicity, and vice versa. The stretch and osmotic enhancements also can partially occlude each other.There remain some clear-cut differences between osmotic and stretch forms of modulation: the larger range of enhancement by hypertonic solutions, the relative lack of effect of osmolarity on evoked release, and the reported higher temperature sensitivity of osmotic enhancement. Nevertheless, our data strongly implicate integrins in a significant fraction of the osmotic enhancement, possibly acting via the same mechanism as stretch modulation.

  13. Characteristics of rostral solitary tract nucleus neurons with identified afferent connections that project to the parabrachial nucleus in rats.

    PubMed

    Suwabe, Takeshi; Bradley, Robert M

    2009-07-01

    Afferent information derived from oral chemoreceptors is transmitted to second-order neurons in the rostral solitary tract nucleus (rNST) and then relayed to other CNS locations responsible for complex sensory and motor behaviors. Here we investigate the characteristics of rNST neurons sending information rostrally to the parabrachial nucleus (PBN). Afferent connections to these rNST-PBN projection neurons were identified by anterograde labeling of the chorda tympani (CT), glossopharyngeal (IX), and lingual (LV) nerves. We used voltage- and current-clamp recordings in brain slices to characterize the expression of both the transient A-type potassium current, IKA and the hyperpolarization-activated inward current, Ih, important determinants of neuronal repetitive discharge characteristics. The majority of rNST-PBN neurons express IKA, and these IKA-expressing neurons predominate in CT and IX terminal fields but were expressed in approximately half of the neurons in the LV field. rNST-PBN neurons expressing Ih were evenly distributed among CT, IX and LV terminal fields. However, expression patterns of IKA and Ih differed among CT, IX, and LV fields. IKA-expressing neurons frequently coexpress Ih in CT and IX terminal fields, whereas neurons in LV terminal field often express only Ih. After GABAA receptor block all rNST-PBN neurons responded to afferent stimulation with all-or-none excitatory synaptic responses. rNST-PBN neurons had either multipolar or elongate morphologies and were distributed throughout the rNST, but multipolar neurons were more often encountered in CT and IX terminal fields. No correlation was found between the biophysical and morphological characteristics of the rNST-PBN projection neurons in each terminal field.

  14. Fibroblast Growth Factor 22 Contributes to the Development of Retinal Nerve Terminals in the Dorsal Lateral Geniculate Nucleus

    PubMed Central

    Singh, Rishabh; Su, Jianmin; Brooks, Justin; Terauchi, Akiko; Umemori, Hisashi; Fox, Michael A.

    2012-01-01

    At least three forms of signaling between pre- and postsynaptic partners are necessary during synapse formation. First, “targeting” signals instruct presynaptic axons to recognize and adhere to the correct portion of a postsynaptic target cell. Second, trans-synaptic “organizing” signals induce differentiation in their synaptic partner so that each side of the synapse is specialized for synaptic transmission. Finally, in many regions of the nervous system an excess of synapses are initially formed, therefore “refinement” signals must either stabilize or destabilize the synapse to reinforce or eliminate connections, respectively. Because of both their importance in processing visual information and their accessibility, retinogeniculate synapses have served as a model for studying synaptic development. Molecular signals that drive retinogeniculate “targeting” and “refinement” have been identified, however, little is known about what “organizing” cues are necessary for the differentiation of retinal axons into presynaptic terminals. To identify such “organizing” cues, we used microarray analysis to assess whether any target-derived “synaptic organizers” were enriched in the mouse dorsal lateral geniculate nucleus (dLGN) during retinogeniculate synapse formation. One candidate “organizing” molecule enriched in perinatal dLGN was FGF22, a secreted cue that induces the formation of excitatory nerve terminals in muscle, hippocampus, and cerebellum. In FGF22 knockout mice, the development of retinal terminals in dLGN was impaired. Thus, FGF22 is an important “organizing” cue for the timely development of retinogeniculate synapses. PMID:22363257

  15. Molecular microdomains in a sensory terminal, the vestibular calyx ending

    PubMed Central

    Lysakowski, Anna; Gaboyard-Niay, Sophie; Calin-Jageman, Irina; Chatlani, Shilpa; Price, Steven D.; Eatock, Ruth Anne

    2011-01-01

    Many primary vestibular afferents form large cup-shaped postsynaptic terminals (calyces) that envelope the basolateral surfaces of type I hair cells. The calyceal terminals both respond to glutamate released from ribbon synapses in the type I cells and initiate spikes that propagate to the afferent’s central terminals in the brainstem. The combination of synaptic and spike initiation functions in these unique sensory endings distinguishes them from the axonal nodes of central neurons and peripheral nerves, such as the sciatic nerve, which have provided most of our information about nodal specializations. We show that rat vestibular calyces express an unusual mix of voltage-gated Na and K channels and scaffolding, cell adhesion, and extracellular matrix proteins, which may hold the ion channels in place. Protein expression patterns form several microdomains within the calyx membrane: a synaptic domain facing the hair cell, the heminode abutting the first myelinated internode, and one or two intermediate domains. Differences in the expression and localization of proteins between afferent types and zones may contribute to known variations in afferent physiology. PMID:21734302

  16. Afferent innervation of the utricular macula in pigeons

    NASA Technical Reports Server (NTRS)

    Si, Xiaohong; Zakir, Mridha Md; Dickman, J. David

    2003-01-01

    Biotinylated dextran amine (BDA) was used to retrogradely label afferents innervating the utricular macula in adult pigeons. The pigeon utriclar macula consists of a large rectangular-shaped neuroepithelium with a dorsally curved anterior edge and an extended medioposterior tail. The macula could be demarcated into several regions based on cytoarchitectural differences. The striola occupied 30% of the macula and contained a large density of type I hair cells with fewer type II hair cells. Medial and lateral extrastriola zones were located outside the striola and contained only type II hair cells. A six- to eight-cell-wide band of type II hair cells existed near the center of the striola. The reversal line marked by the morphological polarization of hair cells coursed throughout the epithelium, near the peripheral margin, and through the center of the type II band. Calyx afferents innervated type I hair cells with calyceal terminals that contained between 2 and 15 receptor cells. Calyx afferents were located only in the striola region, exclusive of the type II band, had small total fiber innervation areas and low innervation densities. Dimorph afferents innervated both type I and type II hair cells with calyceal and bouton terminals and were primarily located in the striola region. Dimorph afferents had smaller calyceal terminals with few type I hair cells, extended fiber branches with bouton terminals and larger innervation areas. Bouton afferents innervated only type II hair cells in the extrastriola and type II band regions. Bouton afferents innervating the type II band had smaller terminal fields with fewer bouton terminals and smaller innervation areas than fibers located in the extrastriolar zones. Bouton afferents had the most bouton terminals on the longest fibers, the largest innervation areas with the highest innervation densities of all afferents. Among all afferents, smaller terminal innervation fields were observed in the striola and large fields were

  17. Presynaptic selection of afferent inflow in the spinal cord.

    PubMed

    Rudomin, P

    1999-01-01

    The synaptic effectiveness of sensory fibers ending in the spinal cord of vertebrates can be centrally controlled by means of specific sets of GABAergic interneurons that make axo-axonic synapses with the terminal arborizations of the afferent fibers. In the steady state, the intracellular concentration of chloride ions in these terminals is higher than that predicted from a passive distribution, because of an active transport mechanism. Following the release of GABA by spinal interneurons and activation of GABA(A) receptors in the afferent terminals, there is an outwardly directed efflux of chloride ions that produces primary afferent depolarization (PAD) and reduces transmitter release (presynaptic inhibition). Studies made by intrafiber recording of PAD, or by measuring changes in the intraspinal threshold of single afferent terminals (which is reduced during PAD), have further indicated that muscle and cutaneous afferents have distinctive, but modifiable PAD patterns in response to segmental and descending stimuli. This has suggested that PAD and presynaptic inhibition in the various types of afferents is mediated by separate sets of last-order GABAergic interneurons. Direct activation, by means of intraspinal microstimulation, of single or small groups of last-order PAD-mediating interneurons shows that the monosynaptic PAD elicited in Ia and Ib afferents can remain confined to some sets of the intraspinal collaterals and not spread to nearby collaterals. The local character of PAD allows cutaneous and descending inputs to selectively inhibit the PAD of segmental and ascending intraspinal collaterals of individual muscle spindle afferents. It thus seems that the intraspinal branches of the sensory fibers are not hard wired routes that diverge excitation to spinal neurons, but are instead dynamic pathways that can be centrally controlled to address information to selected neuronal targets. This feature appears to play an important role in the selection of

  18. Single-channel properties of BK-type calcium-activated potassium channels at a cholinergic presynaptic nerve terminal

    PubMed Central

    Sun, Xiao-Ping; Schlichter, Lyanne C; Stanley, Elis F

    1999-01-01

    A high-conductance calcium-activated potassium channel (BK KCa) was characterized at a cholinergic presynaptic nerve terminal using the calyx synapse isolated from the chick ciliary ganglion.The channel had a conductance of 210 pS in a 150 mM:150 mM K+ gradient, was highly selective for K+ over Na+, and was sensitive to block by external charybdotoxin or tetraethylammonium (TEA) and by internal Ba2+. At +60 mV it was activated by cytoplasmic calcium [Ca2+]i with a Kd of ≈0.5 μM and a Hill coefficient of ≈2.0. At 10 μM [Ca2+]i the channel was 50 % activated (V½) at -8.0 mV with a voltage dependence (Boltzmann slope-factor) of 32.7 mV. The V½ values hyperpolarized with an increase in [Ca2+]i while the slope factors decreased. There were no overt differences in conductance or [Ca2+]i sensitivity between BK channels from the transmitter release face and the non-release face.Open and closed times were fitted by two and three exponentials, respectively. The slow time constants were strongly affected by both [Ca2+]i and membrane potential changes.In cell-attached patch recordings BK channel opening was enhanced by a prepulse permissive for calcium influx through the patch, suggesting that the channel can be activated by calcium ion influx through neighbouring calcium channels.The properties of the presynaptic BK channel are well suited for rapid activation during the presynaptic depolarization and Ca2+ influx that are associated with transmitter release. This channel may play an important role in terminating release by rapid repolarization of the action potential. PMID:10420003

  19. Munc18-1 redistributes in nerve terminals in an activity- and PKC-dependent manner

    PubMed Central

    Cijsouw, Tony; Weber, Jens P.; Broeke, Jurjen H.; Broek, Jantine A.C.; Schut, Desiree; Kroon, Tim; Saarloos, Ingrid

    2014-01-01

    Munc18-1 is a soluble protein essential for synaptic transmission. To investigate the dynamics of endogenous Munc18-1 in neurons, we created a mouse model expressing fluorescently tagged Munc18-1 from the endogenous munc18-1 locus. We show using fluorescence recovery after photobleaching in hippocampal neurons that the majority of Munc18-1 trafficked through axons and targeted to synapses via lateral diffusion together with syntaxin-1. Munc18-1 was strongly expressed at presynaptic terminals, with individual synapses showing a large variation in expression. Axon–synapse exchange rates of Munc18-1 were high: during stimulation, Munc18-1 rapidly dispersed from synapses and reclustered within minutes. Munc18-1 reclustering was independent of syntaxin-1, but required calcium influx and protein kinase C (PKC) activity. Importantly, a PKC-insensitive Munc18-1 mutant did not recluster. We show that synaptic Munc18-1 levels correlate with synaptic strength, and that synapses that recruit more Munc18-1 after stimulation have a larger releasable vesicle pool. Hence, PKC-dependent dynamic control of Munc18-1 levels enables individual synapses to tune their output during periods of activity. PMID:24590174

  20. Munc18-1 redistributes in nerve terminals in an activity- and PKC-dependent manner.

    PubMed

    Cijsouw, Tony; Weber, Jens P; Broeke, Jurjen H; Broek, Jantine A C; Schut, Desiree; Kroon, Tim; Saarloos, Ingrid; Verhage, Matthijs; Toonen, Ruud F

    2014-03-03

    Munc18-1 is a soluble protein essential for synaptic transmission. To investigate the dynamics of endogenous Munc18-1 in neurons, we created a mouse model expressing fluorescently tagged Munc18-1 from the endogenous munc18-1 locus. We show using fluorescence recovery after photobleaching in hippocampal neurons that the majority of Munc18-1 trafficked through axons and targeted to synapses via lateral diffusion together with syntaxin-1. Munc18-1 was strongly expressed at presynaptic terminals, with individual synapses showing a large variation in expression. Axon-synapse exchange rates of Munc18-1 were high: during stimulation, Munc18-1 rapidly dispersed from synapses and reclustered within minutes. Munc18-1 reclustering was independent of syntaxin-1, but required calcium influx and protein kinase C (PKC) activity. Importantly, a PKC-insensitive Munc18-1 mutant did not recluster. We show that synaptic Munc18-1 levels correlate with synaptic strength, and that synapses that recruit more Munc18-1 after stimulation have a larger releasable vesicle pool. Hence, PKC-dependent dynamic control of Munc18-1 levels enables individual synapses to tune their output during periods of activity.

  1. Static γ-motoneurones couple group Ia and II afferents of single muscle spindles in anaesthetised and decerebrate cats

    PubMed Central

    Gladden, M H; Matsuzaki, H

    2002-01-01

    Ideas about the functions of static γ-motoneurones are based on the responses of primary and secondary endings to electrical stimulation of single static γ-axons, usually at high frequencies. We compared these effects with the actions of spontaneously active γ-motoneurones. In anaesthetised cats, afferents and efferents were recorded in intramuscular nerve branches to single muscle spindles. The occurrence of γ-spikes, identified by a spike shape recognition system, was linked to video-taped contractions of type-identified intrafusal fibres in the dissected muscle spindles. When some static γ-motoneurones were active at low frequency (< 15 Hz) they coupled the firing of group Ia and II afferents. Activity of other static γ-motoneurones which tensed the intrafusal fibres appeared to enhance this effect. Under these conditions the secondary ending responded at shorter latency than the primary ending. In another series of experiments on decerebrate cats, responses of primary and secondary endings of single muscle spindles to activation of γ-motoneurones by natural stimuli were compared with their responses to electrical stimulation of single γ-axons supplying the same spindle. Electrical stimulation mimicked the natural actions of γ-motoneurones on either the primary or the secondary ending, but not on both together. However, γ-activity evoked by natural stimuli coupled the firing of afferents with the muscle at constant length, and also when it was stretched. Analysis showed that the timing and tightness of this coupling determined the degree of summation of excitatory postsynaptic potentials (EPSPs) evoked by each afferent in α-motoneurones and interneurones contacted by terminals of both endings, and thus the degree of facilitation of reflex actions of group II afferents. PMID:12181298

  2. α-Synuclein Mutation Inhibits Endocytosis at Mammalian Central Nerve Terminals

    PubMed Central

    Wu, Xin-Sheng; Sheng, Jiansong; Zhang, Zhen; Yue, Hai-Yuan; Sun, Lixin; Sgobio, Carmelo; Lin, Xian; Peng, Shiyong; Jin, Yinghui; Gan, Lin; Wu, Ling-Gang

    2016-01-01

    α-Synuclein (α-syn) missense and multiplication mutations have been suggested to cause neurodegenerative diseases, including Parkinson's disease (PD) and dementia with Lewy bodies. Before causing the progressive neuronal loss, α-syn mutations impair exocytosis, which may contribute to eventual neurodegeneration. To understand how α-syn mutations impair exocytosis, we developed a mouse model that selectively expressed PD-related human α-syn A53T (h-α-synA53T) mutation at the calyx of Held terminals, where release mechanisms can be dissected with a patch-clamping technique. With capacitance measurement of endocytosis, we reported that h-α-synA53T, either expressed transgenically or dialyzed in the short term in calyces, inhibited two of the most common forms of endocytosis, the slow and rapid vesicle endocytosis at mammalian central synapses. The expression of h-α-synA53T in calyces also inhibited vesicle replenishment to the readily releasable pool. These findings may help to understand how α-syn mutations impair neurotransmission before neurodegeneration. SIGNIFICANCE STATEMENT α-Synuclein (α-syn) missense or multiplication mutations may cause neurodegenerative diseases, such as Parkinson's disease and dementia with Lewy bodies. The initial impact of α-syn mutations before neuronal loss is impairment of exocytosis, which may contribute to eventual neurodegeneration. The mechanism underlying impairment of exocytosis is poorly understood. Here we report that an α-syn mutant, the human α-syn A53T, inhibited two of the most commonly observed forms of endocytosis, slow and rapid endocytosis, at a mammalian central synapse. We also found that α-syn A53T inhibited vesicle replenishment to the readily releasable pool. These results may contribute to accounting for the widely observed early synaptic impairment caused by α-syn mutations in the progression toward neurodegeneration. PMID:27098685

  3. Kinetic characterization of ecto-nucleoside triphosphate diphosphohydrolases in brain nerve terminals during rat postnatal development

    NASA Astrophysics Data System (ADS)

    Stanojević, I.; Drakulić, D.; Petrović, S.; Milošević, M.; Jovanović, N.; Horvat, A.

    2011-12-01

    A family of enzymes named ecto-nucleoside triphosphate diphosphohydrolase (NTPDases) catalyzes the termination of ATP and ADP actions. Three different NTPDases (NTPDase 1-3), differing in their preference for a substrate, have been localized in the brain of adult mammals. The goal of our study was to clarify ATP and ADP hydrolyzing activities and kinetic parameters of NTPDases in synaptic plasma membranes (SPM) isolated from 15-, 30-, 60- and 90-days-old female rat brains. ATP and ADP hydrolysis were maximal in the presence of Mg2+ and showed insensitivity to ion-transporting ATPase inhibitors. The pronounced increase in both, ATP and ADP hydrolysis, were found in the SPM isolated from rats in the first month of life, stayed at the same level in the second month, and then decreased in adulthood. Kinetic analysis are also developmental-dependent, and together with the rate of ATP:ADP hydrolysis, point that all three NTPDases are present in SPM isolated from different developmental stages, with different, developmental-dependent proportion of activities. The lowest velocity and the highest affinity were observed for ATP hydrolyses, while the highest velocity and lowest affinity were detected for ADP hydrolyses in SPM isolated from 15-day old rats. Since specific ATP and ADP hydrolysis were lowest in this stage, we concluded that velocity is crucial for ATPase-, while affinity is for ADPase-part of NTPDases. Increased NTPDases activities, changes in their hydrolysis velocity and substrates affinities during rat postnatal development indicate involvement of adenine nucleotides in processes implicated to neuronal maturation and augmented neuroprotection.

  4. The Structure of the Synaptic Vesicle-Plasma Membrane Interface Constrains SNARE Models of Rapid, Synchronous Exocytosis at Nerve Terminals

    PubMed Central

    Gundersen, Cameron B.

    2017-01-01

    Contemporary models of neurotransmitter release invoke direct or indirect interactions between the Ca2+ sensor, synaptotagmin and the incompletely zippered soluble, N-ethyl-maleimide-sensitive factor attachment protein receptor (SNARE) complex. However, recent electron microscopic (EM) investigations have raised pragmatic issues concerning the mechanism by which SNAREs trigger membrane fusion at nerve terminals. The first issue is related to the finding that the area of contact between a “fully primed” synaptic vesicle and the plasma membrane can exceed 600 nm2. Approximately four-thousands lipid molecules can inhabit this contact zone. Thus, renewed efforts will be needed to explain how the zippering of as few as two SNARE complexes mobilizes these lipids to achieve membrane fusion. The second issue emerges from the finding that “docking filaments” are sandwiched within the area of vesicle-plasma membrane contact. It is challenging to reconcile the location of these filaments with SNARE models of exocytosis. Instead, this commentary outlines how these data are more compatible with a model in which a cluster of synaptotagmins catalyzes exocytotic membrane fusion. PMID:28280457

  5. Visualization of the vesicular acetylcholine transporter in cholinergic nerve terminals and its targeting to a specific population of small synaptic vesicles.

    PubMed Central

    Weihe, E; Tao-Cheng, J H; Schäfer, M K; Erickson, J D; Eiden, L E

    1996-01-01

    Immunohistochemical visualization of the rat vesicular acetylcholine transporter (VAChT) in cholinergic neurons and nerve terminals has been compared to that for choline acetyltransferase (ChAT), heretofore the most specific marker for cholinergic neurons. VAChT-positive cell bodies were visualized in cerebral cortex, basal forebrain, medial habenula, striatum, brain stem, and spinal cord by using a polyclonal anti-VAChT antiserum. VAChT-immuno-reactive fibers and terminals were also visualized in these regions and in hippocampus, at neuromuscular junctions within skeletal muscle, and in sympathetic and parasympathetic autonomic ganglia and target tissues. Cholinergic nerve terminals contain more VAChT than ChAT immunoreactivity after routine fixation, consistent with a concentration of VAChT within terminal neuronal arborizations in which secretory vesicles are clustered. These include VAChT-positive terminals of the median eminence or the hypothalamus, not observed with ChAT antiserum after routine fixation. Subcellular localization of VAChT in specific organelles in neuronal cells was examined by immunoelectron microscopy in a rat neuronal cell line (PC 12-c4) expressing VAChT as well as the endocrine and neuronal forms of the vesicular monoamine transporters (VMAT1 and VMAT2). VAChT is targeted to small synaptic vesicles, while VMAT1 is found mainly but not exclusively on large dense-core vesicles. VMAT2 is found on large dense-core vesicles but not on the small synaptic vesicles that contain VAChT in PC12-c4 cells, despite the presence of VMAT2 immunoreactivity in central and peripheral nerve terminals known to contain monoamines in small synaptic vesicles. Thus, VAChT and VMAT2 may be specific markers for "cholinergic" and "adrenergic" small synaptic vesicles, with the latter not expressed in nonstimulated neuronally differentiated PC12-c4 cells. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 PMID:8622973

  6. Chicken (Gallus domesticus) inner ear afferents

    NASA Technical Reports Server (NTRS)

    Hara, H.; Chen, X.; Hartsfield, J. F.; Hara, J.; Martin, D.; Fermin, C. D.

    1998-01-01

    Neurons from the vestibular (VG) and the statoacoustic (SAG) ganglion of the chick (Gallus domesticus) were evaluated histologically and morphometrically. Embryos at stages 34 (E8 days), 39 (E13 days) and 44 (E18 days) were sacrificed and temporal bones microdissected. Specimens were embedded in JB-4 methacrylate plastic, and stained with a mixture of 0.2% toluidine blue (TB) and 0.1% basic Fuschin in 25% ethanol or with a mixture of 2% TB and 1% paraphenylenediamine (PDA) for axon and myelin measurement study. Images of the VIIIth nerve were produced by a V150 (R) color imaging system and the contour of 200-300 neuronal bodies (perikarya) was traced directly on a video screen with a mouse in real time. The cross-sectional area of VG perikarya was 67.29 micrometers2 at stage 34 (E8), 128.46 micrometers2 at stage 39 (E13) and 275.85 micrometers2 at stage 44 (E18). The cross-sectional area of SAG perikarya was 62.44 micrometers2 at stage 34 (E8), 102.05 micrometers2 at stage 39 (E13) and 165.02 micrometers2 at stage 44 (E18). A significant cross-sectional area increase of the VG perikarya between stage 39 (E13) and stage 44 (E18) was determined. We randomly measured the cross-sectional area of myelin and axoplasm of hatchling afferent nerves, and found a correspondence between axoplasmic and myelin cross-sectional area in the utricular, saccular and semicircular canal nerve branches of the nerve. The results suggest that the period between stage 34 (E8) and 39 (E13) is a critical period for afferent neuronal development. Physiological and behavioral vestibular properties of developing and maturing hatchlings may change accordingly. The results compliment previous work by other investigators and provide valuable anatomical measures useful to correlate physiological data obtained from stimulation of the whole nerve or its parts.

  7. Targeted delivery into motor nerve terminals of inhibitors for SNARE-cleaving proteases via liposomes coupled to an atoxic botulinum neurotoxin.

    PubMed

    Edupuganti, Om P; Ovsepian, Saak V; Wang, Jiafu; Zurawski, Tomas H; Schmidt, James J; Smith, Leonard; Lawrence, Gary W; Dolly, J Oliver

    2012-07-01

    A targeted drug carrier (TDC) is described for transferring functional proteins or peptides into motor nerve terminals, a pivotal locus for therapeutics to treat neuromuscular disorders. It exploits the pronounced selectivity of botulinum neurotoxin type B (BoNT/B) for interacting with acceptors on these cholinergic nerve endings and becoming internalized. The gene encoding an innocuous BoNT/B protease-inactive mutant (BoTIM) was fused to that for core streptavidin, expressed in Escherichia coli and the purified protein was conjugated to surface-biotinylated liposomes. Such decorated liposomes, loaded with fluorescein as traceable cargo, acquired pronounced specificity for motor nerve terminals in isolated mouse hemidiaphragms and facilitated the intraneuronal transfer of the fluor, as revealed by confocal microscopy. Delivery of the protease light chain of botulinum neurotoxin type A (BoNT/A) via this TDC accelerated the onset of neuromuscular paralysis, indicative of improved translocation of this enzyme into the presynaptic cytosol with subsequent proteolytic inactivation of synaptosomal-associated protein of molecular mass 25 kDa (SNAP-25), an exocytotic soluble N-ethyl-maleimide-sensitive factor attachment protein receptor (SNARE) essential for neurotransmitter release. BoTIM-coupled liposomes, loaded with peptide inhibitors of proteases, yielded considerable attenuation of the neuroparalytic effects of BoNT/A or BoNT/F as a result of their cytosolic transfer, the first in situ demonstration of the ability of designer antiproteases to suppress the symptoms of botulism ex vivo. Delivery of the BoNT/A inhibitor by liposomes targeted with the full-length BoTIM proved more effective than that mediated by its C-terminal neuroacceptor-binding domain. This demonstrated versatility of TDC for nonviral cargo transfer into cholinergic nerve endings has unveiled its potential for direct delivery of functional targets into motor nerve endings.

  8. Occlusion of carotid artery and hypergravity loading of animals caused similar effects on L-[14C]glutamate uptake in rat brain nerve terminals

    NASA Astrophysics Data System (ADS)

    Borisova, Tatiana; Sivko, Roman; Krisanova, Natalia

    Changes in sodium-dependent L-[14C]glutamate uptake in rat brain nerve terminals was com-paratively analysed after hypergravity loading of animals (centrifugation of rats in special con-tainers at 10 G for 1 hour) and unilateral occlusion of carotid artery (20 min). The initial velocity of L-[14C]glutamate uptake was decreased from 2.5 ± 0.2 nmol x min-1 x mg-1 of proteins to 2.05 ± 0.1 nmol x min-1 x mg-1 of proteins after hypergravity and after occlusion -up to 2.25 ± 0.1 nmol x min-1 x mg-1 of proteins. Recently, we have shown that a decrease in L-[14C]glutamate uptake was at least partially caused by the redaction in the membrane potential of nerve terminals and the proton gradient of synaptic vesicles. These parameters were analysed after unilateral occlusion of carotid artery, where one brain hemisphere was used as a control, whereas the second one as subjected to ischemic/hypoxic conditions. Similarly with hypergravity, we revealed a decrease in the membrane potential of nerve terminals by ˜ 10 % and a reduction of the proton gradient of synaptic vesicles by ˜ 5 % after occlusion of carotid artery. Thus, a decrease in the activity of glutamate transporters after hypergrav-ity and unilateral occlusion of carotid artery was at least partially caused by changes in the membrane potential of nerve terminals and the proton gradient of synaptic vesicles. This fact may be considered in support of the suggestion that ischemia/hypoxia was a main unspecific stressor, which caused the alterations in glutamatergic neurotransmission under conditions of hypergravity.

  9. Effects of potassium, veratridine, and scorpion venom on calcium accumulation and transmitter release by nerve terminals in vitro.

    PubMed Central

    Blaustein, M P

    1975-01-01

    1. 45-Ca uptake by pinched-off nerve terminals (synaptosomes) of rat brain incubated in standard physiological saline (including 132 mM-Na + 5mM-K + 1-2 mM-Ca) at 30 degrees C averages about 0-5 mumole Ca per g protein per minute. This may be equivalent to a Ca influx of about 0-03 p-mole/cm-2 sec. 2. The rate of 45-Ca uptake is increased when the concentration of K in the medium is increased above 15-20 mM, K replacing Na isosmotically. Maximum stimulation, a three- to six-fold increase in the rate of Ca uptake, occurs when [K]o is about 60 mM. The effect of increased [K]o is reversible. 3. The K-stimulated Ca uptake is associated primarily with the nerve terminal fraction of brain homogenates. The entering Ca is not accompanied by extracellular markers such as mannitol or inulin. Replacement of external chloride by methylsulphate or sulphate does not prevent the stimulation by K. 4. The effects of external K are quantitatively mimicked by Rb. Caesium also stimulates Ca uptake, but is only about one fifth as effective as K or Rb; Li is ineffective. 5. Two other depolarizing agents also stimulate Ca uptake by synaptosomes: veratridine (7-5 times 10- minus 6 to 7-5 times 10- minus 5 M) and scorpion (Leirus quinquestriatus) venom (6-7 times 10- minus 7 to 6-7 times 10- minus g/ml.). The stimulatory effects of veratridine and scorpion venom, but not of increased [K] are blocked by 2 times 10- minus 7 M tetrodotoxin. 6. Internal K also influences the rate of 45-Ca uptake by synaptosomes: lowering [K]i reduces the stimulatory effect of external K and veratridine. 7. Replacement of external Na by choline markedly inhibits the response to veratridine, but has a much smaller effect on the response to increased [K]o. 8. The Ca uptake mechanism has an apparent dissociation constant for Ca (KCa) of about 0-8 mM. Increasing [K]o increases the maximal rate of Ca uptake, but has no effect on KCa. The K-induced 45-Ca uptake is competitively inhibited by Mg-2+, Mn-2+ and La-3+. 9

  10. Cationic influences upon synaptic transmission at the hair cell-afferent fiber synapse of the frog

    NASA Technical Reports Server (NTRS)

    Cochran, S. L.

    1995-01-01

    The concentrations of inorganic cations (K+, Na+, and Ca2+) bathing the isolated frog labyrinth were varied in order to assess their role in influencing and mediating synaptic transmission at the hair cell-afferent fiber synapse. Experiments employed intracellular recordings of synaptic activity from VIIIth nerve afferents. Recordings were digitized continuously at 50 kHz, and excitatory postsynaptic potentials were detected and parameters quantified by computer algorithms. Particular attention was focused on cationic effects upon excitatory postsynaptic potential frequency of occurrence and excitatory postsynaptic potential amplitude, in order to discriminate between pre- and postsynaptic actions. Because the small size of afferents preclude long term stable recordings, alterations in cationic concentrations were applied transiently and their peak effects on synaptic activity were assessed. Increases in extracellular K+ concentration of a few millimolar produced a large increase in the frequency of occurrence of excitatory postsynaptic potentials with little change in amplitude, indicating that release of transmitter from the hair cell is tightly coupled to its membrane potential. Increasing extracellular Na+ concentration resulted in an increase in excitatory postsynaptic potential amplitude with no significant change in excitatory postsynaptic potential frequency of occurrence, suggesting that the transmitter-gated subsynaptic channel conducts Na+ ions. Decreases in extracellular Ca2+ concentration had little effect upon excitatory postsynaptic potential frequency, but increased excitatory postsynaptic potential frequency and amplitude. These findings suggest that at higher concentrations Ca2+ act presynaptically to prevent transmitter release and postsynaptically to prevent Na+ influx during the generation of the excitatory postsynaptic potential. The influences of these ions on synaptic activity at this synapse are remarkably similar to those reported at the

  11. Acetylcholine and ATP are coreleased from the electromotor nerve terminals of Narcine brasiliensis by an exocytotic mechanism.

    PubMed

    Unsworth, C D; Johnson, R G

    1990-01-01

    Although the exocytotic mechanism for quantal acetylcholine (ACh) release has been widely accepted for many years, it has repeatedly been challenged by reports that ACh released upon stimulation originates from the cytosol rather than synaptic vesicles. In this report, two independent experimental approaches were taken to establish the source of ACh released from the electromotor system of Narcine brasiliensis. Since ATP is colocalized with ACh in the cholinergic vesicle, the exocytotic theory predicts the corelease of these two components with a stoichiometry identical to that of the vesicle contents. The stimulated release of ATP from isolated synaptosomes could be accurately quantitated in the presence of the ATPase inhibitor adenosine 5'-[alpha, beta-methylene]triphosphate (500 microM), which prevented degradation of the released ATP. Various concentrations of elevated extracellular potassium (25-75 mM), veratridine (100 microM), and the calcium ionophore ionomycin (5 microM) all induced the corelease of ACh and ATP in a constant molar ratio of 5-6:1 (ACh/ATP), a stoichiometry consistent with that established for the vesicle content. In parallel to these stoichiometry studies, the compound 2-(4-phenylpiperidino)cyclohexanol (AH5183) was used to inhibit specifically the vesicular accumulation of newly synthesized (radiolabeled) ACh without affecting cytosolic levels of newly synthesized ACh in cholinergic nerve terminals. Treatment with AH5183 (10 microM) was shown to inhibit the release of newly synthesized ACh without markedly affecting total ACh release; thus, the entry of newly synthesized ACh into the synaptic vesicle is essential for its release. We conclude that ACh released upon stimulation originates exclusively from the vesicular pool and is coreleased stoichiometrically with other soluble vesicle contents.

  12. Pyridoxine inhibits depolarization-evoked glutamate release in nerve terminals from rat cerebral cortex: a possible neuroprotective mechanism?

    PubMed

    Yang, Tsung-Tair; Wang, Su-Jane

    2009-10-01

    Pyridoxine (vitamin B(6)) protects neurons against neurotoxicity. An excessive release of glutamate is widely considered to be one of the molecular mechanisms of neuronal damage in several neurological diseases. We investigated whether pyridoxine affected glutamate release in rat cerebral cortex nerve terminals (synaptosomes). Pyridoxine inhibited the release of glutamate that was evoked by exposing synaptosomes to the K(+) channel blocker 4-aminopyridine (4-AP), and this phenomenon was concentration-dependent. Inhibition of glutamate release by pyridoxine was prevented by the vesicular transporter inhibitor bafilomycin A1, or by chelating intraterminal Ca(2+), but was insensitive to DL-threo-beta-benzyl-oxyaspartate, a glutamate transporter inhibitor. Pyridoxine did not alter the resting synaptosomal membrane potential or 4-AP-mediated depolarization. Examination of the effect of pyridoxine on cytosolic [Ca(2+)] revealed that diminution of glutamate release could be attributed to a reduction in voltage-dependent Ca(2+) influx. Consistent with this, the pyridoxine-mediated inhibition of glutamate release was completely prevented by blocking the N- and P/Q-type Ca(2+) channels, but not by blocking intracellular Ca(2+) release or Na(+)/Ca(2+) exchange. Furthermore, the pyridoxine effect on 4-AP-evoked glutamate release was abolished by the protein kinase C (PKC) inhibitors bisindolylmaleimide I (GF109203X) or bisindolylmaleimide IX (Ro318220), and pyridoxine significantly decreased the 4-AP-induced phosphorylation of PKC, PKCalpha, and myristoylated alanine-rich C kinase substrate. Together, these results suggest that pyridoxine inhibits glutamate release from rat cortical synaptosomes, through the suppression of presynaptic voltage-dependent Ca(2+) entry and PKC activity.

  13. The importance of synapsin I and II for neurotransmitter levels and vesicular storage in cholinergic, glutamatergic and GABAergic nerve terminals.

    PubMed

    Bogen, Inger Lise; Haug, Kristin Huse; Roberg, Bjørg; Fonnum, Frode; Walaas, S Ivar

    2009-01-01

    The aim of this study was to examine the importance of the vesicle-associated synapsin I and II phosphoproteins for the accumulation of neurotransmitters in central cholinergic as compared to central glutamatergic and GABAergic nerve terminals. In brain homogenate samples from mice devoid of synapsin I and II, the levels of vesicular transporters for glutamate (VGLUT1-2) and GABA (VGAT) were decreased by 35-40% in striatum and cortex, while no change was apparent for the vesicular acetylcholine transporter (VAChT). The severe decrease in the levels of amino acid vesicular transporters caused only minor changes in the concentrations of the respective neurotransmitters in homogenates of the three selected brain areas from synapsin I- and II-deficient mice. However, when measured in a crude vesicular fraction, the concentrations of glutamate and GABA were decreased by 48-60% in synapsin-deficient mice, with a similar decrease in the levels of VGLUT1, VGLUT2 and VGAT. In comparison, the concentration of acetylcholine and the level of VAChT were not significantly different from wild-type in the vesicular fraction. No changes were seen in the activity of specific enzymes involved in the synthesis of acetylcholine, glutamate or GABA, however, immunoblotting indicated a decrease in the protein level of glutamic acid decarboxylase, isoform 65 (GAD(65)). In conclusion, the results indicate that neurotransmitter regulation in central cholinergic synapses may be less dependent on synapsin I and II compared to the marked alterations seen in the glutamatergic and GABAergic synapses.

  14. Mast cells drive mesenteric afferent signalling during acute intestinal ischaemia.

    PubMed

    Jiang, Wen; Kirkup, Anthony J; Grundy, David

    2011-08-01

    Acute intestinal ischaemia stimulates visceral afferent nerves but the mechanisms responsible for this excitation are not fully understood. Mast cells may participate in this process as they are known to signal to mesenteric afferents during intestinal anaphylaxis and contribute to early inflammation and neuronal damage in response to cerebral ischaemia. We therefore hypothesised that mast cells are early responders to acute intestinal ischaemia and their activation initiates rapid signalling to the CNS via the excitation of mesenteric afferents. Primary afferent firing was recorded from a mesenteric nerve bundle supplying a segment of jejunum in anaesthetized adult rats. Acute focal ischaemia was produced by clamping theme senteric vessels for 8 min, and reperfusion followed removal of the vessel clip. Two episodes of ischaemia–reperfusion (I–R) separated by a 30 min interval were performed. Drugs or their vehicles were administered 10 min before the 2nd I–R episode. Ischaemia caused a reproducible, intense and biphasic afferent firing that was temporally dissociated from the concomitantly triggered complex pattern of intestinal motor activity. The L-type calcium channel blocker, nifedipine, significantly attenuated this afferent firing by a mechanism independent of its action on intestinal tone. Ischaemia-induced afferent firing was also abrogated by the mast cell stabilizer, doxantrazole, and the H1 histamine receptor antagonist, pyrilamine. In contrast, the nicotinic receptor antagonist, hexamethonium, and the N-type calcium channel toxin, ω-conotoxin GVIA, each reduced the ischaemia-evoked motor inhibition but not the concurrent afferent discharge. Similarly, the cyclooxygenase inhibitor, naproxen, had no effect on the ischaemic afferent response but reduced the intestinal tone shortly from the onset of ischaemia to the early period of reperfusion. These data support a critical role for mast cell-derived histamine in the direct chemoexcitation of

  15. Cystitis increases colorectal afferent sensitivity in the mouse.

    PubMed

    Brumovsky, Pablo Rodolfo; Feng, Bin; Xu, Linjing; McCarthy, Carly Jane; Gebhart, G F

    2009-12-01

    Studies in humans and rodents suggest that colon inflammation promotes urinary bladder hypersensitivity and, conversely, that cystitis contributes to colon hypersensitivity, events referred to as cross-organ sensitization. To investigate a potential peripheral mechanism, we examined whether cystitis alters the sensitivity of pelvic nerve colorectal afferents. Male C57BL/6 mice were treated with cyclophosphamide (CYP) or saline, and the mechanosensitive properties of single afferent fibers innervating the colorectum were studied with an in vitro preparation. In addition, mechanosensitive receptive endings were exposed to an inflammatory soup (IS) to study sensitization. Urinary bladder mechanosensitive afferents were also tested. We found that baseline responses of stretch-sensitive colorectal afferents did not differ between treatment groups. Whereas IS excited a proportion of colorectal afferents CYP treatment did not alter the magnitude of this response. However, the number of stretch-sensitive fibers excited by IS was increased relative to saline-treated mice. Responses to IS were not altered by CYP treatment, but the proportion of IS-responsive fibers was increased relative to saline-treated mice. In bladder, IS application increased responses of muscular afferents to stretch, although no differences were detected between saline- and CYP-treated mice. In contrast, their chemosensitivity to IS was decreased in the CYP-treated group. Histological examination revealed no changes in colorectum and modest edema and infiltration in the urinary bladder of CYP-treated mice. In conclusion, CYP treatment increased mechanical sensitivity of colorectal muscular afferents and increased the proportion of chemosensitive colorectal afferents. These data support a peripheral contribution to cross-organ sensitization of pelvic organs.

  16. Kilohertz frequency nerve block enhances anti-inflammatory effects of vagus nerve stimulation

    PubMed Central

    Patel, Yogi A.; Saxena, Tarun; Bellamkonda, Ravi V.; Butera, Robert J.

    2017-01-01

    Efferent activation of the cervical vagus nerve (cVN) dampens systemic inflammatory processes, potentially modulating a wide-range of inflammatory pathological conditions. In contrast, afferent cVN activation amplifies systemic inflammatory processes, leading to activation of the hypothalamic-pituitary-adrenal (HPA) axis, the sympathetic nervous system through the greater splanchnic nerve (GSN), and elevation of pro-inflammatory cytokines. Ideally, to clinically implement anti-inflammatory therapy via cervical vagus nerve stimulation (cVNS) one should selectively activate the efferent pathway. Unfortunately, current implementations, in animal and clinical investigations, activate both afferent and efferent pathways. We paired cVNS with kilohertz electrical stimulation (KES) nerve block to preferentially activate efferent pathways while blocking afferent pathways. Selective efferent cVNS enhanced the anti-inflammatory effects of cVNS. Our results demonstrate that: (i) afferent, but not efferent, cVNS synchronously activates the GSN in a dose-dependent manner; (ii) efferent cVNS enabled by complete afferent KES nerve block enhances the anti-inflammatory benefits of cVNS; and (iii) incomplete afferent KES nerve block exacerbates systemic inflammation. Overall, these data demonstrate the utility of paired efferent cVNS and afferent KES nerve block for achieving selective efferent cVNS, specifically as it relates to neuromodulation of systemic inflammation. PMID:28054557

  17. Encoding of tangential torque in responses of tactile afferent fibres innervating the fingerpad of the monkey

    PubMed Central

    Birznieks, Ingvars; Wheat, Heather E; Redmond, Stephen J; Salo, Lauren M; Lovell, Nigel H; Goodwin, Antony W

    2010-01-01

    Torsional loads are ubiquitous during everyday dextrous manipulations. We examined how information about torque is provided to the sensorimotor control system by populations of tactile afferents. Torsional loads of different magnitudes were applied in clockwise and anticlockwise directions to a standard central site on the fingertip. Three different background levels of contact (grip) force were used. The median nerve was exposed in anaesthetized monkeys and single unit responses recorded from 66 slowly adapting type-I (SA-I) and 31 fast adapting type-I (FA-I) afferents innervating the distal segments of the fingertips. Most afferents were excited by torque but some were suppressed. Responses of the majority of both afferent types were scaled by torque magnitude applied in one or other direction, with the majority of FA-I afferent responses and about half of SA-I afferent responses scaled in both directions. Torque direction affected responses in both afferent types, but more so for the SA-I afferents. Latencies of the first spike in FA-I afferent responses depended on the parameters of the torque. We used a Parzen window classifier to assess the capacity of the SA-I and FA-I afferent populations to discriminate, concurrently and in real-time, the three stimulus parameters, namely background normal force, torque magnitude and direction. Despite the potentially confounding interactions between stimulus parameters, both the SA-I and the FA-I populations could extract torque magnitude accurately. The FA-I afferents signalled torque magnitude earlier than did the SA-I afferents, but torque direction was extracted more rapidly and more accurately by the SA-I afferent population. PMID:20142274

  18. 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

  19. Short-latency afferent inhibition in chronic spinal cord injury

    PubMed Central

    Bailey, Aaron Z.; Mi, Yiqun P.; Nelson, Aimee J.

    2015-01-01

    Background Short-latency afferent inhibition (SAI) results when somatosensory afferent input inhibits the corticospinal output from primary motor cortex (M1). The present study examined SAI in the flexor carpi radialis (FCR) muscle in individuals with spinal cord injury (SCI) and uninjured controls. Methods Short-latency afferent inhibition (SAI) was evoked by stimulating the median nerve at the elbow at intervals of 15, 20 and 25 ms in advance of a transcranial magnetic stimulation (TMS) pulse over M1. SAI was tested with the FCR at rest and also during ~20% of maximum voluntary contraction. Corticospinal output was assessed through measuring both motor thresholds and motor evoked potential (MEP) recruitment curves. The afferent volley was assessed via the N20–P25 amplitude of the somatosensory evoked potential (SEP) and the amplitude of sensory nerve action potentials (SNAP) recorded over the median nerve at the elbow. Results SAI is reduced in SCI in both the contracted and non-contracted FCR muscle. MEP recruitment curves and thresholds were decreased in SCI only in the active state and not the resting state. N20–P25 amplitude was similar between groups in both the resting and active states although SNAP was significantly reduced in SCI at rest. Conclusions We conclude that reduced SAI in SCI is likely attributed to neuroplasticity altering the intrinsic M1 circuitry mediating SAI and/or reduced afferent input traversing a direct thalamocortical route to M1. These data provide a new avenue of research aimed at identifying therapeutic approaches to alter SAI to improve upper limb function in individuals with SCI. PMID:28123808

  20. Complete mapping of glomeruli based on sensory nerve branching pattern in the primary olfactory center of the cockroach Periplaneta americana.

    PubMed

    Watanabe, Hidehiro; Nishino, Hiroshi; Nishikawa, Michiko; Mizunami, Makoto; Yokohari, Fumio

    2010-10-01

    Glomeruli are structural and functional units in the primary olfactory center in vertebrates and insects. In the cockroach Periplaneta americana, axons of different types of sensory neurons housed in sensilla on antennae form dorsal and ventral antennal nerves and then project to a number of glomeruli. In this study, we identified all antennal lobe (AL) glomeruli based on detailed innervation patterns of sensory tracts in addition to the shape, size, and locations in the cockroach. The number of glomeruli is approximately 205, and no sex-specific difference is observed. Anterograde dye injections into the antennal nerves revealed that axons supplying the AL are divided into 10 sensory tracts (T1-T10). Each of T1-T3 innervates small, oval glomeruli in the anteroventral region of the AL, with sensory afferents invading each glomerulus from multiple directions, whereas each of T4-T10 innervates large glomeruli with various shapes in the posterodorsal region, with a bundle of sensory afferents invading each glomerulus from one direction. The topographic branching patterns of all these tracts are conserved among individuals. Sensory afferents in a sub-tract of T10 had axon terminals in the dorsal margin of the AL and the protocerebrum, where they form numerous small glomerular structures. Sensory nerve branching pattern should reflect developmental processes to determine spatial arrangement of glomeruli, and thus the complete map of glomeruli based on sensory nerve branching pattern should provide a basis for studying the functional significance of spatial arrangement of glomeruli and its developmental basis.

  1. Interneurones in pathways from group II muscle afferents in sacral segments of the feline spinal cord.

    PubMed

    Jankowska, E; Riddell, J S

    1994-03-15

    1. Properties of dorsal horn interneurones that process information from group II muscle afferents in the sacral segments of the spinal cord have been investigated in the cat using both intracellular and extracellular recording. 2. The interneurones were excited by group II muscle afferents and cutaneous afferents but not by group I muscle afferents. They were most effectively excited by group II afferents of the posterior biceps, semitendinosus, triceps surae and quadriceps muscle nerves and by cutaneous afferents running in the cutaneous femoris, pudendal and sural nerves. The earliest synaptic actions were evoked monosynaptically and were very tightly locked to the stimuli. 3. EPSPs evoked monosynaptically by group II muscle afferents and cutaneous afferents of the most effective nerves were often cut short by disynaptic IPSPs. As a consequence of this negative feedback the EPSPs gave rise to single or double spike potentials and only a minority of interneurones responded with repetitive discharges. However, the neurones that did respond repetitively did so at a very high frequency of discharges (0.8-1.2 ms intervals between the first 2-3 spikes). 4. Sacral dorsal horn group II interneurones do not appear to act directly upon motoneurones because: (i) these interneurones are located outside the area within which last order interneurones have previously been found and (ii) the latencies of PSPs evoked in motoneurones by stimulation of the posterior biceps and semitendinosus, cutaneous femoris and pudendal nerves (i.e. the main nerves providing input to sacral interneurones) are compatible with a tri- but not with a disynaptic coupling. Spatial facilitation of EPSPs and IPSPs following synchronous stimulation of group II and cutaneous afferents of these nerves shows, however, that sacral interneurones may induce excitation or inhibition of motoneurones via other interneurones. 5. Comparison of the properties of group II interneurones in the sacral segments with

  2. Laryngeal reflex mechanism during deglutition--observation of subglottal pressure and afferent discharge.

    PubMed

    Shin, T; Maeyama, T; Morikawa, I; Umezaki, T

    1988-11-01

    In this investigation, particular attention was paid to elucidate the laryngeal reflex mechanism of protective closure and the sensory function of the larynx during deglutition. For this purpose, three different experimental procedures were adopted: (1) subglottal pressure of felines was measured during deglutition using a pressure transducer; (2) subglottal pressure of human beings was measured during deglutition using a pressure transducer; and (3) afferent discharges from superior and recurrent laryngeal nerves of felines were recorded. The following conclusions appear justified. (1) Feline and human subglottal pressure during deglutition showed the following pattern. The pressure rises with onset of deglutition, temporarily drops during laryngeal elevation, rises again during the downward movement of the larynx, and drops again at the end of the glutition. This pattern was not affected by the resection of the unilateral recurrent laryngeal nerve. (2) The superior laryngeal nerve is involved in the sensory function of the pharynx, larynx, and trachea. At least two types of afferent discharges from superficial and internal sensory nerves are suspected. Afferent discharges from the recurrent laryngeal nerves in the larynx and trachea are not as distinct as those of the superior laryngeal nerve, and this seems to correspond with various changes in the thorax. During deglutition, afferent discharges were recorded from superior to recurrent laryngeal nerves.

  3. Interactions between cutaneous and muscle afferent projections to cerebral cortex in man.

    PubMed

    Burke, D; Gandevia, S C; McKeon, B; Skuse, N F

    1982-04-01

    In order to demonstrate interactions between cutaneous and muscle afferent volleys in the ascending somatosensory pathways, different nerves of the lower limb were stimulated together in a conditioning-test paradigm, the changes in the earliest component of the cerebral potential evoked by the test stimulus being taken to indicate such an interaction. It was first confirmed that the cerebral potential evoked by stimulation of the posterior tibial nerve at the ankle is derived from muscle afferents in the mixed nerve and has shorter latencies than the cerebral potential evoked by purely cutaneous volleys in the sural nerve (see Burke et al. 1981). Complete suppression of the cerebral potential evoked by stimulation of muscle or cutaneous afferents was produced by conditioning volleys in a different nerve or in a different fascicle of the same nerve. The major factors determining the degree of suppression were found to be the relative sizes of the conditioning and test volleys and their timing, rather than whether the volleys were of cutaneous or muscular origin. It is concluded that the transmission of cutaneous or muscle afferent volleys to cortex can be profoundly altered in normal subjects by conditioning activity. The possibility that normal background afferent activity can similarly modify afferent transmission has implications for diagnostic studies, particularly when they are performed under non-standard conditions, such as in the operating theatre or intensive care unit. It is also concluded that, although a subject may perceive cutaneous paraesthesiae when the posterior tibial nerve is stimulated at the ankle, there may be no cutaneous component to the evoked cerebral potential.

  4. Activity-dependent formation and location of voltage-gated sodium channel clusters at a CNS nerve terminal during postnatal development.

    PubMed

    Xu, Jie; Berret, Emmanuelle; Kim, Jun Hee

    2017-02-01

    In auditory pathways, the precision of action potential (AP) propagation depends on axon myelination and high densities of voltage-gated Na (Nav) channels clustered at nodes of Ranvier. Changes in Nav channel expression at the heminode, the final node before the nerve terminal, can alter AP invasion into the presynaptic terminal. We studied the activity-dependent formation of Nav channel clusters before and after hearing onset at postnatal day 12 in the rat and mouse auditory brain stem. In rats, the Nav channel cluster at the heminode formed progressively during the second postnatal week, around hearing onset, whereas the Nav channel cluster at the nodes was present before hearing onset. Initiation of heminodal Nav channel clustering was correlated with the expression of scaffolding protein ankyrinG and paranodal protein Caspr. However, in whirler mice with congenital deafness, heminodal Nav channels did not form clusters and maintained broad expression, but Nav channel clustering was normal at the nodes. In addition, a clear difference in the distance from the heminodal Nav channel to the calyx across the mediolateral axis of the medial nucleus of the trapezoid body (MNTB) developed after hearing onset. In the medial MNTB, where neurons respond best to high-frequency sounds, the heminodal Nav channel cluster was located closer to the terminal than in the lateral MNTB, where neurons respond best to low-frequency sounds. Thus sound-mediated neuronal activities are potentially associated with the refinement of the heminode adjacent to the presynaptic terminal in the auditory brain stem.

  5. Evidence for the role of lipid rafts and sphingomyelin in Ca2+-gating of Transient Receptor Potential channels in trigeminal sensory neurons and peripheral nerve terminals.

    PubMed

    Sághy, Éva; Szőke, Éva; Payrits, Maja; Helyes, Zsuzsanna; Börzsei, Rita; Erostyák, János; Jánosi, Tibor Zoltán; Sétáló, György; Szolcsányi, János

    2015-10-01

    Transient Receptor Potential (TRP) cation channels, such as TRP Vanilloid 1 and TRP Ankyrin repeat domain 1 (TRPV1 and TRPA1) are nocisensors playing important role to signal pain. Two "melastatin" TRP receptors, like TRPM8 and TRPM3 are also expressed in a subgroup of primary sensory neurons. These channels serve as thermosensors with unique thermal sensitivity ranges and are activated also by several exogenous and endogenous chemical ligands inducing conformational changes from various allosteric ("multisteric") sites. We analysed the role of plasma membrane microdomains of lipid rafts on isolated trigeminal (TRG) neurons and TRPV1-expressing CHO cell line by measuring agonist-induced Ca2+ transients with ratiometric technique. Stimulation-evoked calcitonin gene related peptide (CGRP) release from sensory nerve endings of the isolated rat trachea by radioimmunoassay was also measured. Lipid rafts were disrupted by cleaving sphingomyelin (SM) with sphingomyelinase (SMase), cholesterol depletion with methyl β-cyclodextrin (MCD) and ganglioside breakdown with myriocin. It has been revealed that intracellular Ca2+ increase responses evoked by the TRPV1 agonist capsaicin, the TRPA1 agonsits allyl isothiocyanate (AITC) and formaldehyde as well as the TRPM8 activator icilin were inhibited after SMase, MCD and myriocin incubation but the response to the TRPM3 agonist pregnenolon sulphate was not altered. Extracellular SMase treatment did not influence the thapsigargin-evoked Ca2+-release from intracellular stores. Besides the cell bodies, SMase also inhibited capsaicin- or AITC-evoked CGRP release from peripheral sensory nerve terminals, this provides the first evidence for the importance of lipid raft integrity in TRPV1 and TRPA1 gating on capsaicin-sensitive nerve terminals. SM metabolites, ceramide and sphingosine, did not influence TRPA1 and TRPV1 activation on TRG neurons, TRPV1-expressing CHO cell line, and nerve terminals. We suggest, that the hydrophobic

  6. Partial compensation for N-type Ca(2+) channel loss by P/Q-type Ca(2+) channels underlines the differential release properties supported by these channels at cerebrocortical nerve terminals.

    PubMed

    Ladera, Carolina; Martín, Ricardo; Bartolomé-Martín, David; Torres, Magdalena; Sánchez-Prieto, José

    2009-03-01

    N-type and P/Q-type Ca(2+) channels support glutamate release at central synapses. To determine whether the glutamate release mediated by these channels exhibits distinct properties, we have isolated each release component in cerebrocortical nerve terminals from wild-type mice by specifically blocking N-type Ca(2+) channels with omega-conotoxin-GVIA and P/Q-type Ca(2+) channels with omega-agatoxin-IVA. In addition, we have determined the release properties at terminals from mice lacking the alpha(1B) subunit of N-type channels (Ca(v) 2.2) to test the possibility that P/Q-type channels can compensate for the loss of N-type Ca(2+) channels. We recently demonstrated that, while evoked glutamate release depends on P/Q- and N-type channels in wild-type nerve terminals, only P/Q-type channels participate in these knockout mice. Moreover, in nerve terminals expressing solely P/Q-type channels, metabotropic glutamate receptor 7 (mGluR7) fails to inhibit the evoked Ca(2+) influx and glutamate release. Here, we show that the failure of mGluR7 to modulate evoked glutamate release is not due to a lack of receptors, as nerve terminals from mice lacking N-type Ca(2+) channels express mGluR7. Indeed, we show that other receptor responses, such as the inhibition of forskolin-induced release, are preserved in these knockout mice. N-type channels are more loosely coupled to release than P/Q-type channels in nerve terminals from wild-type mice, as reflected by the tighter coupling of release in knockout nerve terminals. We conclude that the glutamate release supported by N- and P/Q-type channels exhibits distinct properties, and that P/Q-type channels cannot fully compensate for the loss of N-type channels.

  7. Organization of hindlimb muscle afferent projections to lumbosacral motoneurons in the chick embryo.

    PubMed

    Lee, M T; O'Donovan, M J

    1991-08-01

    We have examined the organization of muscle afferent projections to motoneurons in the lumbosacral spinal cord of chick embryos between stage 37, when muscle afferents first reach the motor nucleus, and stage 44, which is just before hatching. Connectivity between afferents and motoneurons was assessed by stimulating individual muscle nerves and recording the resulting motoneuron synaptic potentials intracellularly or electrotonically from other muscle nerves. Most of the recordings were made in the presence of DL-2-amino-5-phosphonovaleric acid (APV), picrotoxin, and strychnine to block long-latency excitatory and inhibitory pathways. Activation of muscle afferents evoked slow, positive potentials in muscle nerves but not in cutaneous nerves. These potentials were abolished in 0 mM Ca2+, 2mM Mn2+ solutions, indicating that they were generated by the action of chemical synapses. The muscle nerve recordings revealed a wide-spread pattern of excitatory connections between afferents and motoneurons innervating six different thigh muscles, which were not organized according to synergist-antagonist relationships. This pattern of connectivity was confirmed using intracellular recording from identified motoneurons, which allowed the latency of the responses to be determined. Short-latency potentials in motoneurons were produced by activation of homonymous afferents and the heteronymous afferents innervating the hip flexors sartorius and anterior iliotibialis. Stimulation of anterior iliotibialis afferents also resulted in some short-latency excitatory postsynaptic potentials (EPSPs) in motoneurons innervating the knee extensor femorotibialis, though other connections were of longer latency. Afferents from the adductor, a hip extensor, did not evoke short-latency EPSPs in any of these three types of motoneurons. Short-latency, but not long-latency EPSPs, persisted during repetitive stimulation at 5 Hz, suggesting that they were mediated monosynaptically. Long

  8. Stimulation Induced Changes in Frog Neuromuscular Junctions: A Quantitative Ultrastructural Comparison of Rapid-Frozen and Chemically Fixed Nerve Terminals

    DTIC Science & Technology

    1984-03-06

    mitochondria to sequester calcium has been well established ( Lehninger , 197O; Alnaes and Rahamimoff, 1975; Rahamimoff, 1976; Lehninger , Reynafarje...mitochondria swell as they sequester calcium (Greenawalt, Rossi and Lehninger , 1964; Peachy, 1964; Hackenbrock and Caplan, 1969) and mitochondria...Rossi and Lehninger , 1964; Peachy, 1964; Lehninger , Reynafarje, Vercesi and Tew, 1978). Mitochondrial swelling correlates with nerve stimulation in

  9. Afferent control of human stance and gait: evidence for blocking of group I afferents during gait.

    PubMed

    Dietz, V; Quintern, J; Berger, W

    1985-01-01

    The cerebral potentials (c.p.) evoked by electrical stimulation of the tibial nerve during stance and in the various phases of gait of normal subjects were compared with the c.p. and leg muscle e.m.g. responses evoked by perturbations of stance and gait. Over the whole step cycle of gait the c.p. evoked by an electrical stimulus were of smaller amplitude (3 microV and 9 microV, respectively) than that seen in the stance condition, and appeared with a longer latency (mean times to first positive peak: 63 and 43 ms, respectively). When the electrical stimulus was applied during stance after ischaemic blockade of group I afferents, the c.p. were similar to those evoked during gait. The c.p. evoked by perturbations were larger in amplitude than those produced by the electrical stimulus, but similar in latencies in both gait and stance (mean 26 microV and 40 microV; 65 ms and 42 ms, respectively) and configurations. The large gastrocnemius e.m.g. responses evoked by the stance and gait perturbations arose with a latency of 65 to 70 ms. Only in the stance condition was a smaller, shorter latency (40 ms) response seen. It is concluded that during gait the signals of group I afferents are blocked at both segmental and supraspinal levels which was tested by tibial nerve stimulation. It is suggested that the e.m.g. responses induced in the leg by gait perturbations are evoked by group II afferents and mediated via a spinal pathway. The c.p. evoked during gait most probably reflect the processing of this group II input by supraspinal motor centres for the coordination of widespread arm and trunk muscle activation, necessary to restablish body equilibrium.

  10. Effect of Microgravity on Afferent Innervation

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Presentations and publications are: (1) an audiovisual summary web presentation on results from SLM-MIR avian experiments. A color presentation summarizing results from the SLM-MIR and STS-29 avian experiments; (2) color threshold and ratio of S 100B MAP5, NF68/200, GABA and GAD; (3) chicken (Gallus domesticus) inner ear afferents; (4) microgravity in the STS-29 Space Shuttle Discovery affected the vestibular system of chick embryos; (5) expression of S 100B in sensory and secretory cells of the vertebrate inner ear; (6) otoconia biogenesis, phylogeny, composition and functional attributes;(7) the glycan keratin sulfate in inner ear crystals; (8) elliptical-P cells in the avian perilymphatic interface of the tegmentum vasculosum; and (9) LAMP2c and S100B upregulation in brain stem after VIIIth nerve deafferentation.

  11. Electrical interaction between antidromically stimulated frog motoneurones and dorsal root afferents: enhancement by gallamine and TEA

    PubMed Central

    Grinnell, Alan D.

    1970-01-01

    depolarization can increase transmitter release at terminals and increase coupling at electrical junctions. 7. Possible morphological correlates for the two electrical interactions are discussed. It is speculated that the motoneurone interaction arises at numerous areas of close apposition between dendrites in dendritic `thickets', and that the early VR-DRP is mediated by fewer, lower-resistance, electrical junctions between dendrites and afferent nerve terminals. PMID:5500776

  12. Neck muscle afferents influence oromotor and cardiorespiratory brainstem neural circuits.

    PubMed

    Edwards, I J; Lall, V K; Paton, J F; Yanagawa, Y; Szabo, G; Deuchars, S A; Deuchars, J

    2015-01-01

    Sensory information arising from the upper neck is important in the reflex control of posture and eye position. It has also been linked to the autonomic control of the cardiovascular and respiratory systems. Whiplash associated disorders (WAD) and cervical dystonia, which involve disturbance to the neck region, can often present with abnormalities to the oromotor, respiratory and cardiovascular systems. We investigated the potential neural pathways underlying such symptoms. Simulating neck afferent activity by electrical stimulation of the second cervical nerve in a working heart brainstem preparation (WHBP) altered the pattern of central respiratory drive and increased perfusion pressure. Tracing central targets of these sensory afferents revealed projections to the intermedius nucleus of the medulla (InM). These anterogradely labelled afferents co-localised with parvalbumin and vesicular glutamate transporter 1 indicating that they are proprioceptive. Anterograde tracing from the InM identified projections to brain regions involved in respiratory, cardiovascular, postural and oro-facial behaviours--the neighbouring hypoglossal nucleus, facial and motor trigeminal nuclei, parabrachial nuclei, rostral and caudal ventrolateral medulla and nucleus ambiguus. In brain slices, electrical stimulation of afferent fibre tracts lateral to the cuneate nucleus monosynaptically excited InM neurones. Direct stimulation of the InM in the WHBP mimicked the response of second cervical nerve stimulation. These results provide evidence of pathways linking upper cervical sensory afferents with CNS areas involved in autonomic and oromotor control, via the InM. Disruption of these neuronal pathways could, therefore, explain the dysphagic and cardiorespiratory abnormalities which may accompany cervical dystonia and WAD.

  13. Early postnatal development of GABAergic presynaptic inhibition of Ia proprioceptive afferent connections in mouse spinal cord.

    PubMed

    Sonner, Patrick M; Ladle, David R

    2013-04-01

    Sensory feedback is critical for normal locomotion and adaptation to external perturbations during movement. Feedback provided by group Ia afferents influences motor output both directly through monosynaptic connections and indirectly through spinal interneuronal circuits. For example, the circuit responsible for reciprocal inhibition, which acts to prevent co-contraction of antagonist flexor and extensor muscles, is driven by Ia afferent feedback. Additionally, circuits mediating presynaptic inhibition can limit Ia afferent synaptic transmission onto central neuronal targets in a task-specific manner. These circuits can also be activated by stimulation of proprioceptive afferents. Rodent locomotion rapidly matures during postnatal development; therefore, we assayed the functional status of reciprocal and presynaptic inhibitory circuits of mice at birth and compared responses with observations made after 1 wk of postnatal development. Using extracellular physiological techniques from isolated and hemisected spinal cord preparations, we demonstrate that Ia afferent-evoked reciprocal inhibition is as effective at blocking antagonist motor neuron activation at birth as at 1 wk postnatally. In contrast, at birth conditioning stimulation of muscle nerve afferents failed to evoke presynaptic inhibition sufficient to block functional transmission at synapses between Ia afferents and motor neurons, even though dorsal root potentials could be evoked by stimulating the neighboring dorsal root. Presynaptic inhibition at this synapse was readily observed, however, at the end of the first postnatal week. These results indicate Ia afferent feedback from the periphery to central spinal circuits is only weakly gated at birth, which may provide enhanced sensitivity to peripheral feedback during early postnatal experiences.

  14. Morphologically mixed chemical-electrical synapses formed by primary afferents in rodent vestibular nuclei as revealed by immunofluorescence detection of connexin36 and vesicular glutamate transporter-1

    PubMed Central

    Nagy, James I.; Bautista, Wendy; Blakley, Brian; Rash, John E.

    2013-01-01

    Axon terminals forming mixed chemical/electrical synapses in the lateral vestibular nucleus of rat were described over forty years ago. Because gap junctions formed by connexins are the morphological correlate of electrical synapses, and with demonstrations of widespread expression of the gap junction protein connexin36 (Cx36) in neurons, we investigated the distribution and cellular localization of electrical synapses in the adult and developing rodent vestibular nuclear complex, using immunofluorescence detection of Cx36 as a marker for these synapses. In addition, we examined Cx36 localization in relation to that of the nerve terminal marker vesicular glutamate transporter-1 (vglut-1). An abundance of immunolabelling for Cx36 in the form of Cx36-puncta was found in each of the four major vestibular nuclei of adult rat and mouse. Immunolabelling was associated with somata and initial dendrites of medium and large neurons, and was absent in vestibular nuclei of Cx36 knockout mice. Cx36-puncta were seen either dispersed or aggregated into clusters on the surface of neurons, and were never found to occur intracellularly. Nearly all Cx36-puncta were localized to large nerve terminals immunolabelled for vglut-1. These terminals and their associated Cx36-puncta were substantially depleted after labyrinthectomy. Developmentally, labelling for Cx36 was already present in the vestibular nuclei at postnatal day 5, where it was only partially co-localized with vglut-1, and did not become fully associated with vglut-1-positive terminals until postnatal day 20 to 25. The results show that vglut-1-positive primary afferent nerve terminals form mixed synapses throughout the vestibular nuclear complex, that the gap junction component of these synapses contain Cx36, that multiple Cx36-containing gap junctions are associated with individual vglut-1 terminals and that the development of these mixed synapses is protracted over several postnatal weeks. PMID:23912039

  15. Morphologically mixed chemical-electrical synapses formed by primary afferents in rodent vestibular nuclei as revealed by immunofluorescence detection of connexin36 and vesicular glutamate transporter-1.

    PubMed

    Nagy, J I; Bautista, W; Blakley, B; Rash, J E

    2013-11-12

    Axon terminals forming mixed chemical/electrical synapses in the lateral vestibular nucleus of rat were described over 40 years ago. Because gap junctions formed by connexins are the morphological correlate of electrical synapses, and with demonstrations of widespread expression of the gap junction protein connexin36 (Cx36) in neurons, we investigated the distribution and cellular localization of electrical synapses in the adult and developing rodent vestibular nuclear complex, using immunofluorescence detection of Cx36 as a marker for these synapses. In addition, we examined Cx36 localization in relation to that of the nerve terminal marker vesicular glutamate transporter-1 (vglut-1). An abundance of immunolabeling for Cx36 in the form of Cx36-puncta was found in each of the four major vestibular nuclei of adult rat and mouse. Immunolabeling was associated with somata and initial dendrites of medium and large neurons, and was absent in vestibular nuclei of Cx36 knockout mice. Cx36-puncta were seen either dispersed or aggregated into clusters on the surface of neurons, and were never found to occur intracellularly. Nearly all Cx36-puncta were localized to large nerve terminals immunolabeled for vglut-1. These terminals and their associated Cx36-puncta were substantially depleted after labyrinthectomy. Developmentally, labeling for Cx36 was already present in the vestibular nuclei at postnatal day 5, where it was only partially co-localized with vglut-1, and did not become fully associated with vglut-1-positive terminals until postnatal day 20-25. The results show that vglut-1-positive primary afferent nerve terminals form mixed synapses throughout the vestibular nuclear complex, that the gap junction component of these synapses contains Cx36, that multiple Cx36-containing gap junctions are associated with individual vglut-1 terminals and that the development of these mixed synapses is protracted over several postnatal weeks.

  16. Afferent fibers involved in the bradykinin-induced cardiovascular reflexes from the ovary in rats.

    PubMed

    Uchida, Sae; Kagitani, Fusako; Hotta, Harumi

    2015-12-01

    Bleeding or rupture of the ovary often accompanies ovarian cysts and causes severe pain and autonomic responses such as hypotension. It would be expected that ovarian afferents contribute to cardiovascular responses induced by ovarian failure. The present study examined cardiovascular responses to noxious chemical stimulation of the ovary by bradykinin, an algesic substance released by tissue damage, and explored the role of ovarian afferents in the ovarian-cardiovascular responses in anesthetized rats. Non-pregnant adult rats were anesthetized with pentobarbital and artificially ventilated. The carotid artery was cannulated to monitor blood pressure and heart rate. Noxious chemical stimulation was achieved by applying a small piece of cotton soaked with bradykinin to the surface of the ovary for 30s. Application of bradykinin (10(-4) M) to the ovary decreased heart rate and blood pressure. These cardiovascular responses were not significantly influenced by severance of the vagal nerves or the superior ovarian nerve, but were abolished by severance of the ovarian nerve plexus (ONP). Application of bradykinin (10(-4) M) to the ovary evoked afferent activity of the ONP both in vivo and in vitro preparations. These results indicate that the decreases in heart rate and blood pressure following chemical noxious stimulation of the ovary with bradykinin are reflex responses, whose afferent nerve pathway is mainly through afferent fibers in the ONP.

  17. Callosal projections in rat somatosensory cortex are altered by early removal of afferent input.

    PubMed Central

    Koralek, K A; Killackey, H P

    1990-01-01

    During the first postnatal week, the distribution of callosal projection neurons in the rat somatosensory cortex changes from a uniform to a discontinuous pattern. To determine if this change is influenced by afferent inputs to the somatosensory cortex, the effect of both early unilateral infraorbital nerve section and unilateral removal of the dorsal thalamus on the distribution of callosal projections in rat somatosensory cortex was examined. One month after either of the above manipulations at birth, the tangential distribution of callosal projections in the somatosensory cortex was examined using the combined retrograde and anterograde transport of horseradish peroxidase. Both manipulations alter the distribution of callosal projection neurons and terminations in the somatosensory cortex. After infraorbital nerve section, the distribution of callosal projections is altered in the contralateral primary somatosensory cortex. The abnormalities observed are consistent with the altered distribution of thalamocortical projections. In addition, consistent abnormalities were observed in the pattern of callosal projections of the second somatosensory area of both hemispheres. Most notably, they are absent in a portion of the region that contains the representation of the mystacial vibrissae and sinus hairs in this area. Thalamic ablation resulted in highly aberrant patterns of callosal projections in the somatosensory cortex on the operated side, where abnormal bands and clusters of callosal projections were observed in apparently random locations. These results are interpreted as evidence that both peripheral and central inputs influence the maturational changes in the distribution of callosal projection neurons. Images PMID:2304906

  18. Determinants of Spatial and Temporal Coding by Semicircular Canal Afferents

    PubMed Central

    Highstein, Stephen M.; Rabbitt, Richard D.; Holstein, Gay R.; Boyle, Richard D.

    2010-01-01

    The vestibular semicircular canals are internal sensors that signal the magnitude, direction, and temporal properties of angular head motion. Fluid mechanics within the 3-canal labyrinth code the direction of movement and integrate angular acceleration stimuli over time. Directional coding is accomplished by decomposition of complex angular accelerations into 3 biomechanical components—one component exciting each of the 3 ampullary organs and associated afferent nerve bundles separately. For low-frequency angular motion stimuli, fluid displacement within each canal is proportional to angular acceleration. At higher frequencies, above the lower corner frequency, real-time integration is accomplished by viscous forces arising from the movement of fluid within the slender lumen of each canal. This results in angular velocity sensitive fluid displacements. Reflecting this, a subset of afferent fibers indeed report angular acceleration to the brain for low frequencies of head movement and report angular velocity for higher frequencies. However, a substantial number of afferent fibers also report angular acceleration, or a signal between acceleration and velocity, even at frequencies where the endolymph displacement is known to follow angular head velocity. These non-velocity-sensitive afferent signals cannot be attributed to canal biomechanics alone. The responses of non-velocity-sensitive cells include a mathematical differentiation (first-order or fractional) imparted by hair-cell and/or afferent complexes. This mathematical differentiation from velocity to acceleration cannot be attributed to hair cell ionic currents, but occurs as a result of the dynamics of synaptic transmission between hair cells and their primary afferent fibers. The evidence for this conclusion is reviewed below. PMID:15845995

  19. Monosynaptic convergence of chorda tympani and glossopharyngeal afferents onto ascending relay neurons in the nucleus of the solitary tract: A high-resolution confocal and correlative electron microscopy approach

    PubMed Central

    Corson, James A.; Erisir, Alev

    2014-01-01

    While physiological studies suggested convergence of chorda tympani and glossopharyngeal afferent axons onto single neurons of the rostral nucleus of the solitary tract (rNTS), anatomical evidence has been elusive. The current study uses high-magnification confocal microscopy to identify putative synaptic contacts from afferent fibers of the two nerves onto individual projection neurons. Imaged tissue is re-visualized with electron microscopy, confirming that overlapping fluorescent signals in confocal z-stacks accurately identify appositions between labeled terminal and dendrite pairs. Monte Carlo modeling reveals that the probability of overlapping fluorophores is stochastically unrelated to the density of afferent label suggesting that convergent innervation in the rNTS is selective rather than opportunistic. Putative synaptic contacts from each nerve are often compartmentalized onto dendrite segments of convergently innervated neurons. These results have important implications for orosensory processing in the rNTS, and the techniques presented here have applications in investigations of neural microcircuitry with an emphasis on innervation patterning. PMID:23640852

  20. 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

  1. Mechanisms underlying presynaptic Ca2+ transient and vesicular glutamate release at a CNS nerve terminal during in vitro ischaemia

    PubMed Central

    Lee, Seul Yi; Kim, Jun Hee

    2015-01-01

    Key points Here we demonstrate presynaptic responses and mechanisms of increased vesicular glutamate release during in vitro ischaemia in the calyx of Held terminal, an experimentally accessible presynaptic terminal in the CNS. The ischaemia-induced increase in presynaptic Ca2+ was mediated by both Ca2+ influx and Ca2+-induced Ca2+ release from intracellular stores. The reverse operation of the plasma membrane Na+/Ca2+ exchanger (NCX) plays a key role in Ca2+ influx for triggering Ca2+ release from intracellular stores at presynaptic terminals during in vitro ischaemia. Ca2+ uptake via NCX underlies the ischaemia-induced Ca2+ rise and the consequent increase in vesicular glutamate release from presynaptic terminals in the early phase of brain ischaemia. Abstract An early consequence of brain ischaemia is an increase in vesicular glutamate release from presynaptic terminals. However, the mechanisms of this increased glutamate release are not fully understood. Here we studied presynaptic responses and mechanisms of increased glutamate release during in vitro ischaemia, using pre- and postsynaptic whole-cell recordings and presynaptic Ca2+ imaging at the calyx of Held synapse in rat brainstem slices. Consistent with results from other brain regions, in vitro ischaemia significantly increased the frequency of spontaneous excitatory postsynaptic currents (sEPSCs) without affecting their amplitude, suggesting that ischaemia enhances vesicular glutamate release from presynaptic terminals. We found that ischaemia-induced vesicular glutamate release was dependent on a rise in basal Ca2+ at presynaptic terminals, which resulted from extracellular Ca2+ influx and Ca2+ release from intracellular stores. During early ischaemia, increased Ca2+ influx into presynaptic terminals was due to reverse operation of the plasma membrane Na+/Ca2+ exchanger (NCX) rather than presynaptic depolarization or voltage-activated Ca2+ currents. KB-R7943, an inhibitor of NCX, prevented the

  2. Segmental and supraspinal control of synaptic effectiveness of functionally identified muscle afferents in the cat.

    PubMed

    Enríquez, M; Jiménez, I; Rudomin, P

    1996-01-01

    The present investigation documents the patterns of primary afferent depolarization (PAD) of single, functionally identified muscle afferents from the medial gastrocnemius nerve in the intact, anesthetized cat. Classification of the impaled muscle afferents as from muscle spindles or from tendon organs was made according to several criteria, which comprised measurement of conduction velocity and electrical threshold of the peripheral axons, and the maximal frequency followed by the afferent fibers during vibration, as well as the changes in discharge frequency during longitudinal stretch, the projection of the afferent fiber to the motor pool, and, in unparalyzed preparations, the changes in afferent activity during a muscle twitch. In confirmation of a previous study, we found that most muscle spindle afferents (46.1-66.6%, depending on the combination of criteria utilized for receptor classification) had a type A PAD pattern. That is, they were depolarized by stimulation of group I fibers of the posterior biceps and semitendinosus (PBSt) nerve, but not by stimulation of cutaneous nerves (sural and superficial peroneus) or the bulbar reticular formation (RF), which in many cases inhibited the PBSt-induced PAD. In addition, we found a significant fraction of muscle spindle primaries that were depolarized by stimulation of group I PBSt fibers and also by stimulation of the bulbar RF. Stimulation of cutaneous nerves produced PAD in 9.1-31.2% of these fibers (type B PAD pattern) and no PAD in 8.2-15.4% (type C PAD pattern). In contrast to muscle spindle afferents, only the 7.7-15.4% of fibers from tendon organs had a type A PAD pattern, 23-46.1% had a type B and 50-61.5% a type C PAD pattern. These observations suggest that the neuronal circuitry involved in the control of the synaptic effectiveness of muscle spindles and tendon organs is subjected to excitatory as well as to inhibitory influences from cutaneous and reticulospinal fibers. As shown in the accompanying

  3. Intraspinal nerve terminals immunoreactive for tyrosine hydroxylase, serotonin and substance P in guinea-pigs with acute experimental allergic encephalomyelitis.

    PubMed

    Vyas, D; Bieger, D; White, S R

    1988-07-01

    Spinal cord axons and terminals stained for tyrosine hydroxylase-, serotonin- and substance P-like immunoreactivity were examined in guinea-pigs in the paraplegic phase of acute experimental allergic encephalomyelitis, an animal disease model for multiple sclerosis. Fibers positive for monoamine and substance P-like staining that terminated in the lumbar ventral horn appeared to be markedly damaged during the disease. However, no changes were detected in those substance P-containing fibers that terminated in the dorsal horn. It was concluded that small diameter, thinly myelinated or unmyelinated axons that course for long distances in the spinal cord, and, therefore, have a high probability for encountering inflammatory foci, are particularly vulnerable to damage during experimental allergic encephalomyelitis. Damage to these monoaminergic and peptidergic fibers may contribute to the neurological deficits that are associated with this autoimmune nervous system disease.

  4. H-REFLEX UP-CONDITIONING ENCOURAGES RECOVERY OF EMG ACTIVITY AND H-REFLEXES AFTER SCIATIC NERVE TRANSECTION AND REPAIR IN RATS

    PubMed Central

    Chen, Yi; Wang, Yu; Chen, Lu; Sun, Chenyuo; English, Arthur W.; Wolpaw, Jonathan R.; Chen, Xiang Yang

    2010-01-01

    Operant conditioning of the spinal stretch reflex or its electrical analog, the H-reflex, produces spinal cord plasticity and can thereby affect motoneuron responses to primary afferent input. To explore whether this conditioning can affect the functional outcome after peripheral nerve injury, we assessed the effect of up-conditioning soleus (SOL) H-reflex on SOL and tibialis anterior (TA) function after sciatic nerve transection and repair. Sprague-Dawley rats were implanted with EMG electrodes in SOL and TA and stimulating cuffs on the posterior tibial nerve. After control data collection, the sciatic nerve was transected and repaired and the rat was exposed for 120 days to continued control data collection (TC rats) or SOL H-reflex up-conditioning (TU rats). At the end of data collection, motoneurons that had reinnervated SOL and TA were labeled retrogradely. Putative primary afferent terminals (i.e., terminals containing vesicular glutamate transporter-1 (VGLUT1)) on SOL motoneurons were studied immunohistochemically. SOL (and probably TA) background EMG activity recovered faster in TU rats than in TC rats, and the final recovered SOL H-reflex was significantly larger in TU than in TC rats. TU and TC rats had significantly fewer labeled motoneurons and higher proportions of double-labeled motoneurons than untransected rats. VGLUT1 terminals were significantly more numerous on SOL motoneurons of TU than TC rats. Combined with the larger H-reflexes in TU rats, this anatomical finding supports the hypothesis that SOL H-reflex up-conditioning strengthened primary afferent reinnervation of SOL motoneurons. These results suggest that H-reflex up-conditioning may improve functional recovery after nerve injury and repair. PMID:21123559

  5. H-reflex up-conditioning encourages recovery of EMG activity and H-reflexes after sciatic nerve transection and repair in rats.

    PubMed

    Chen, Yi; Wang, Yu; Chen, Lu; Sun, Chenyou; English, Arthur W; Wolpaw, Jonathan R; Chen, Xiang Yang

    2010-12-01

    Operant conditioning of the spinal stretch reflex or its electrical analog, the H-reflex, produces spinal cord plasticity and can thereby affect motoneuron responses to primary afferent input. To explore whether this conditioning can affect the functional outcome after peripheral nerve injury, we assessed the effect of up-conditioning soleus (SOL) H-reflex on SOL and tibialis anterior (TA) function after sciatic nerve transection and repair. Sprague Dawley rats were implanted with EMG electrodes in SOL and TA and stimulating cuffs on the posterior tibial nerve. After control data collection, the sciatic nerve was transected and repaired and the rat was exposed for 120 d to continued control data collection (TC rats) or SOL H-reflex up-conditioning (TU rats). At the end of data collection, motoneurons that had reinnervated SOL and TA were labeled retrogradely. Putative primary afferent terminals [i.e., terminals containing vesicular glutamate transporter-1 (VGLUT1)] on SOL motoneurons were studied immunohistochemically. SOL (and probably TA) background EMG activity recovered faster in TU rats than in TC rats, and the final recovered SOL H-reflex was significantly larger in TU than in TC rats. TU and TC rats had significantly fewer labeled motoneurons and higher proportions of double-labeled motoneurons than untransected rats. VGLUT1 terminals were significantly more numerous on SOL motoneurons of TU than TC rats. Combined with the larger H-reflexes in TU rats, this anatomical finding supports the hypothesis that SOL H-reflex up-conditioning strengthened primary afferent reinnervation of SOL motoneurons. These results suggest that H-reflex up-conditioning may improve functional recovery after nerve injury and repair.

  6. Synaptic ultrastructure changes in trigeminocervical complex posttrigeminal nerve injury.

    PubMed

    Park, John; Trinh, Van Nancy; Sears-Kraxberger, Ilse; Li, Kang-Wu; Steward, Oswald; Luo, Z David

    2016-02-01

    Trigeminal nerves collecting sensory information from the orofacial area synapse on second-order neurons in the dorsal horn of subnucleus caudalis and cervical C1/C2 spinal cord (Vc/C2, or trigeminocervical complex), which is critical for sensory information processing. Injury to the trigeminal nerves may cause maladaptive changes in synaptic connectivity that plays an important role in chronic pain development. Here we examined whether injury to the infraorbital nerve, a branch of the trigeminal nerves, led to synaptic ultrastructural changes when the injured animals have developed neuropathic pain states. Transmission electron microscopy was used to examine synaptic profiles in Vc/C2 at 3 weeks postinjury, corresponding to the time of peak behavioral hypersensitivity following chronic constriction injury to the infraorbital nerve (CCI-ION). Using established criteria, synaptic profiles were classified as associated with excitatory (R-), inhibitory (F-), and primary afferent (C-) terminals. Each type was counted within the superficial dorsal horn of the Vc/C2 and the means from each rat were compared between sham and injured animals; synaptic contact length was also measured. The overall analysis indicates that rats with orofacial pain states had increased numbers and decreased mean synaptic length of R-profiles within the Vc/C2 superficial dorsal horn (lamina I) 3 weeks post-CCI-ION. Increases in the number of excitatory synapses in the superficial dorsal horn of Vc/C2 could lead to enhanced activation of nociceptive pathways, contributing to the development of orofacial pain states.

  7. Differences in the osmotic fragility of recycling and reserve synaptic vesicles from the cholinergic electromotor nerve terminals of Torpedo and their possible significance for vesicle recycling.

    PubMed

    Giompres, P E; Whittaker, V P

    1984-03-14

    In this study we demonstrate differences in the osmotic fragility of two metabolically and physically heterogeneous synaptic vesicle populations from stimulated electromotor nerve terminals. When synaptic vesicles isolated on sucrose density gradients are submitted to solutions of decreasing osmolarity 50% of VP2-type vesicles lysed at (mean + S.E. (number of experiments] 332 +/- 14 (4) mosM and 50% of VP1-type vesicles lysed at 573 +/- 8 (3) mosM. These results indicate that recycling vesicles are more resistant to hypo-osmotic lysis and they are consistent with our earlier conclusion that changes in water content on recycling are secondary to changes in the content of the osmotically active small-molecular-mass constituents acetylcholine and ATP.

  8. Endogenous Interleukin-1β in Neuropathic Rats Enhances Glutamate Release from the Primary Afferents in the Spinal Dorsal Horn through Coupling with Presynaptic N-Methyl-d-aspartic Acid Receptors*♦

    PubMed Central

    Yan, Xisheng; Weng, Han-Rong

    2013-01-01

    Excessive activation of glutamate receptors and overproduction of proinflammatory cytokines, including interleukin-1β (IL-1β) in the spinal dorsal horn, are key mechanisms underlying the development and maintenance of neuropathic pain. In this study, we investigated the mechanisms by which endogenous IL-1β alters glutamatergic synaptic transmission in the spinal dorsal horn in rats with neuropathic pain induced by ligation of the L5 spinal nerve. We demonstrated that endogenous IL-1β in neuropathic rats enhances glutamate release from the primary afferent terminals and non-NMDA glutamate receptor activities in postsynaptic neurons in the spinal dorsal horn. Myeloid differentiation primary response protein 88 (MyD88) is a mediator used by IL-1β to enhance non-NMDA glutamate receptor activities in postsynaptic neurons in the spinal dorsal horn. Presynaptic NMDA receptors are effector receptors used by the endogenous IL-1β to enhance glutamate release from the primary afferents in neuropathic rats. This is further supported by the fact that NMDA currents recorded from small neurons in the dorsal root ganglion of normal rats are potentiated by exogenous IL-1β. Furthermore, we provided evidence that functional coupling between IL-1β receptors and presynaptic NMDA receptors at the primary afferent terminals is mediated by the neutral sphingomyelinase/ceramide signaling pathway. Hence, functional coupling between IL-1β receptors and presynaptic NMDA receptors at the primary afferent terminals is a crucial mechanism leading to enhanced glutamate release and activation of non-NMDA receptors in the spinal dorsal horn neurons in neuropathic pain conditions. Interruption of such functional coupling could be an effective approach for the treatment of neuropathic pain. PMID:24003233

  9. Effect of differential nerve block on inhibition of the monosynaptic reflex by vibration in man

    PubMed Central

    Moddel, G.; Best, B.; Ashby, P.

    1977-01-01

    The differential nerve block produced by ischaemia has been used in an attempt to identify the afferent nerve fibres responsible for vibratory inhibition of the monosynaptic reflex in man. It is concluded that the inhibition arises mainly from receptors in the lower leg and is carried by myelinated afferent fibres larger than A-delta. PMID:599354

  10. Age-Related Changes in Vagal Afferents Innervating the Gastrointestinal Tract

    PubMed Central

    Phillips, Robert J.; Walter, Gary C.; Powley, Terry L.

    2009-01-01

    Recent progress in understanding visceral afferents, some of it reviewed in the present issue, serves to underscore how little is known about the aging of the visceral afferents in the gastrointestinal (GI) tract. In spite of the clinical importance of the issue--with age, GI function often becomes severely compromised--only a few initial observations on age-related structural changes of visceral afferents are available. Primary afferent cell bodies in both the nodose ganglia and dorsal root ganglia lose Nissl material and accumulate lipofucsin, inclusions, aggregates, and tangles. Additionally, in changes that we focus on in the present review, vagal visceral afferent terminals in both the muscle wall and the mucosa of the GI tract exhibit age-related structural changes. In aged animals, both of the vagal terminal types examined, namely intraganglionic laminar endings and villus afferents, exhibit dystrophic or regressive morphological changes. These neuropathies are associated with age-related changes in the structural integrity of the target organs of the affected afferents, suggesting that local changes in trophic environment may give rise to the aging of GI innervation. Given the clinical relevance of GI tract aging, a more complete understanding both of how aging alters the innervation of the gut and of how such changes might be mitigated should be made research priorities. PMID:19665435

  11. Glutamatergic modulation of synaptic-like vesicle recycling in mechanosensory lanceolate nerve terminals of mammalian hair follicles.

    PubMed

    Banks, Robert W; Cahusac, Peter M B; Graca, Anna; Kain, Nakul; Shenton, Fiona; Singh, Paramjeet; Njå, Arild; Simon, Anna; Watson, Sonia; Slater, Clarke R; Bewick, Guy S

    2013-05-15

    Our aim in the present study was to determine whether a glutamatergic modulatory system involving synaptic-like vesicles (SLVs) is present in the lanceolate ending of the mouse and rat hair follicle and, if so, to assess its similarity to that of the rat muscle spindle annulospiral ending we have described previously. Both types of endings are formed by the peripheral sensory terminals of primary mechanosensory dorsal root ganglion cells, so the presence of such a system in the lanceolate ending would provide support for our hypothesis that it is a general property of fundamental importance to the regulation of the responsiveness of the broad class of primary mechanosensory endings. We show not only that an SLV-based system is present in lanceolate endings, but also that there are clear parallels between its operation in the two types of mechanosensory endings. In particular, we demonstrate that, as in the muscle spindle: (i) FM1-43 labels the sensory terminals of the lanceolate ending, rather than the closely associated accessory (glial) cells; (ii) the dye enters and leaves the terminals primarily by SLV recycling; (iii) the dye does not block the electrical response to mechanical stimulation, in contrast to its effect on the hair cell and dorsal root ganglion cells in culture; (iv) SLV recycling is Ca(2+) sensitive; and (v) the sensory terminals are enriched in glutamate. Thus, in the lanceolate sensory ending SLV recycling is itself regulated, at least in part, by glutamate acting through a phospholipase D-coupled metabotropic glutamate receptor.

  12. Primary afferent depolarization of muscle afferents elicited by stimulation of joint afferents in cats with intact neuraxis and during reversible spinalization.

    PubMed

    Quevedo, J; Eguibar, J R; Jiménez, I; Schmidt, R F; Rudomin, P

    1993-11-01

    1. In the anesthetized and artificially ventilated cat, stimulation of the posterior articular nerve (PAN) with low strengths (1.2-1.4 x T) produced a small negative response (N1) in the cord dorsum of the lumbosacral spinal cord with a mean onset latency of 5.2 ms. Stronger stimuli (> 1.4 x T) produced two additional components (N2 and N3) with longer latencies (mean latencies 7.5 and 15.7 ms, respectively), usually followed by a slow positivity lasting 100-150 ms. With stimulus strengths above 10 x T there was in some experiments a delayed response (N4; mean latency 32 ms). 2. Activation of posterior knee joint nerve with single pulses and intensities producing N1 responses only, usually produced no dorsal root potentials (DRPs), or these were rather small. Stimulation with strengths producing N2 and N3 responses produced distinct DRPs. Trains of pulses were clearly more effective than single pulses in producing DRPs, even in the low-intensity range. 3. Cooling the thoracic spinal cord to block impulse conduction, increased the DRPs and the N3 responses produced by PAN stimulation without significantly affecting the N2 responses. Reversible spinalization also increased the DRPs produced by stimulation of cutaneous nerves. In contrast, the DRPs produced by stimulation of group I afferents from flexors were reduced. 4. Conditioning electrical stimulation of intermediate and high-threshold myelinated fibers in the PAN depressed the DRPs produced by stimulation of group I muscle and of cutaneous nerves. 5. Analysis of the intraspinal threshold changes of single Ia and Ib fibers has provided evidence that stimulation of intermediate and high threshold myelinated fibers in the posterior knee joint nerve inhibits the primary afferent depolarization (PAD) of Ia fibers, and may either produce PAD or inhibit the PAD in Ib fibers, in the same manner as stimulation of cutaneous nerves. In 7/16 group I fibers the inhibition of the PAD was increased during reversible

  13. The effects of antidromic discharges on orthodromic firing of primary afferents in the cat.

    PubMed

    Gossard, J P; Bouyer, L; Rossignol, S

    1999-04-17

    This study investigated the effects of antidromically conducted nerve impulses on the transmission of orthodromic volleys in primary afferents of the hindlimb in decerebrated paralyzed cats. Two protocols were used: (A) Single skin and muscle afferents (N=20) isolated from the distal part of cut dorsal rootlets (L7-S1) were recorded while stimulation was applied more caudally. The results showed that during the trains of three to 20 stimuli, the orthodromic firing frequency decreased or ceased, depending on the frequency of stimulation. Remarkably, subsequent to these trains, the occurrence of orthodromic spikes could be delayed for hundreds of ms (15/20 afferents) and sometimes stopped for several seconds (10/20 afferents). Longer stimulation trains, simulating antidromic bursts reported during locomotion, caused a progressive decrease, and a slow recovery of, orthodromic firing frequency (7/20 afferents), indicating a cumulative long-lasting depressing effect from successive bursts. (B) Identified stretch-sensitive muscle afferents were recorded intra-axonally and antidromic spikes were evoked by the injection of square pulses of current through the micropipette. In this case, one to three antidromic spikes were sufficient to delay the occurrence of the next orthodromic spike by more than one control inter-spike interval. If the control inter-spike interval was decreased by stretching the muscle, the delay evoked by antidromic spikes decreased proportionally. Overall, these findings suggest that antidromic activity could alter the mechanisms underlying spike generation in peripheral sensory receptors and modify the orthodromic discharges of afferents during locomotion.

  14. Fifth lumbar spinal nerve injury causes neurochemical changes in corresponding as well as adjacent spinal segments: a possible mechanism underlying neuropathic pain.

    PubMed

    Shehab, Safa Al-Deen Saudi

    2014-01-01

    Previous investigations of the anatomical basis of the neuropathic-like manifestations in the spinal nerve ligation animal model have shown that the central terminations of the unmyelinated primary afferents of L5 spinal nerve are not restricted to the corresponding L5 spinal segment, and rather extend to two spinal segments rostrally and one segment caudally where they intermingle with primary afferents of the adjacent L4 spinal nerve. The aim of the present study was to investigate the neurochemical changes in the dorsal horn of the spinal cord and DRGs after L5 nerve injury in rats. In the first experiment, the right L5 nerve was ligated and sectioned for 14 days, and isolectin B4 (IB4, a tracer for unmyelinated primary afferents) was injected into the left L5 nerve. The results showed that the vasoactive intestinal peptide (VIP) was up-regulated in laminae I-II of L3-L6 spinal segments on the right side in exactly the same areas where IB4 labelled terminals were revealed on the left side. In the second experiment, L5 was ligated and sectioned and the spinal cord and DRGs were stained immunocytochemically with antibodies raised against various peptides known to be involved in pain transmission and hyperalgesia. The results showed that L5 nerve lesion caused down-regulation of substance P, calcitonin-gene related peptide and IB4 binding and up-regulation of neuropeptide Y and neurokinin-1 receptor in the dorsal horn of L4 and L5 spinal segments. Similar neurochemical changes were observed only in the corresponding L5 DRG with minimal effects observed in L3, L4 and L6 DRGs. Although, L5 nerve injury caused an up-regulation in NPY, no change in SP and CGRP immunoreactivity was observed in ipsilateral garcile nucleus. These neuroplastic changes in the dorsal horn of the spinal cord, in the adjacent uninjured territories of the central terminations of the adjacent uninjured nerves, might explain the mechanism of hyperalgesia after peripheral nerve injury.

  15. Ziram, a pesticide associated with increased risk for Parkinson’s disease, differentially affects the presynaptic function of aminergic and glutamatergic nerve terminals at the Drosophila neuromuscular junction

    PubMed Central

    Martin, Ciara A.; Myers, Katherine M.; Chen, Audrey; Martin, Nathan T.; Barajas, Angel; Schweizer, Felix E.; Krantz, David E.

    2015-01-01

    Multiple populations of aminergic neurons are affected in Parkinson’s disease (PD), with serotonergic and noradrenergic loci responsible for some non-motor symptoms. Environmental toxins, such as the dithiocarbamate fungicide ziram, significantly increase the risk of developing PD and the attendant spectrum of both motor and non-motor symptoms. The mechanisms by which ziram and other environmental toxins increase the risk of PD, and the potential effects of these toxins on aminergic neurons, remain unclear. To determine the relative effects of ziram on the synaptic function of aminergic versus non-aminergic neurons, we used live-imaging at the Drosophila melanogaster larval neuromuscular junction (NMJ). In contrast to nearly all other studies of this model synapse, we imaged presynaptic function at both glutamatergic Type Ib and aminergic Type II boutons, the latter responsible for storage and release of octopamine, the invertebrate equivalent of noradrenalin. To quantify the kinetics of exo- and endo- cytosis, we employed an acid-sensitive form of GFP fused to the Drosophila vesicular monoamine transporter (DVMAT-pHluorin). Additional genetic probes were used to visualize intracellular calcium flux (GCaMP) and voltage changes (ArcLight). We find that at glutamatergic Type Ib terminals, exposure to ziram increases exocytosis and inhibits endocytosis. By contrast, at octopaminergic Type II terminals, ziram has no detectable effect on exocytosis and dramatically inhibits endocytosis. In contrast to other reports on the neuronal effects of ziram, these effects do not appear to result from perturbation of the UPS or calcium homeostasis. Unexpectedly, ziram also caused spontaneous and synchronized bursts of calcium influx (measured by GCaMP) and electrical activity (measured by ArcLight) at aminergic Type II, but not glutamatergic Type Ib, nerve terminals. These events are sensitive to both tetrodotoxin and cadmium chloride, and thus appear to represent spontaneous

  16. Presynaptic depolarization of unmyelinated primary afferent fibers in the spinal cord of the cat.

    PubMed

    Calvillo, O; Madrid, J; Rudomín, P

    1982-06-01

    Low intensity (1-20 micro A) intraspinal stimulation produces in the sural nerve of the anesthetized cat short latency responses (3-4 ms) due to antidromic activation of fibers conducting in the A range (43-65 m/s). With higher stimulus intensities (up to 400 micro A) late responses (120-250 ms latency) may also be recorded. Simultaneous recording from two sites in the sural nerve shows that the peripheral processes of the fibers generating the late responses have a conduction velocity between 0.8-1.3 m/s. Collision between antidromic and orthodromic responses further indicates that these fibers have a peripheral threshold 20-25 times that of the A fibers. The late responses were largest when the intraspinal stimulating electrode was located in the dorsal horn, in the region corresponding to Laminae II and III of Rexed. The above observations suggest that the late responses are due to population responses of C fibers which are antidromically activated in the dorsal horn. The excitability of the C fiber terminals is increased by conditioning stimuli applied to other cutaneous afferents with a time course resembling that of the excitability increase of the A fibers on the same nerve. It is suggested that the effectiveness of synaptic transmission from C fibers to second order cells may be modulated presynaptically. In the decerebrate cat the antidromic responses of C fibers are reduced, but not abolished, by reversible spinalization produced by cooling or by sectioning the thoracic spinal cord. This suggests in addition that in the decerebrate preparation the presynaptic effectiveness of the C fiber (presumably nociceptive) input may be tonically decreased by supraspinal influences.

  17. Vagus Nerve Stimulation.

    PubMed

    Howland, Robert H

    2014-06-01

    The vagus nerve is a major component of the autonomic nervous system, has an important role in the regulation of metabolic homeostasis, and plays a key role in the neuroendocrine-immune axis to maintain homeostasis through its afferent and efferent pathways. Vagus nerve stimulation (VNS) refers to any technique that stimulates the vagus nerve, including manual or electrical stimulation. Left cervical VNS is an approved therapy for refractory epilepsy and for treatment resistant depression. Right cervical VNS is effective for treating heart failure in preclinical studies and a phase II clinical trial. The effectiveness of various forms of non-invasive transcutaneous VNS for epilepsy, depression, primary headaches, and other conditions has not been investigated beyond small pilot studies. The relationship between depression, inflammation, metabolic syndrome, and heart disease might be mediated by the vagus nerve. VNS deserves further study for its potentially favorable effects on cardiovascular, cerebrovascular, metabolic, and other physiological biomarkers associated with depression morbidity and mortality.

  18. Vagus Nerve Stimulation

    PubMed Central

    Howland, Robert H.

    2014-01-01

    The vagus nerve is a major component of the autonomic nervous system, has an important role in the regulation of metabolic homeostasis, and plays a key role in the neuroendocrine-immune axis to maintain homeostasis through its afferent and efferent pathways. Vagus nerve stimulation (VNS) refers to any technique that stimulates the vagus nerve, including manual or electrical stimulation. Left cervical VNS is an approved therapy for refractory epilepsy and for treatment resistant depression. Right cervical VNS is effective for treating heart failure in preclinical studies and a phase II clinical trial. The effectiveness of various forms of non-invasive transcutaneous VNS for epilepsy, depression, primary headaches, and other conditions has not been investigated beyond small pilot studies. The relationship between depression, inflammation, metabolic syndrome, and heart disease might be mediated by the vagus nerve. VNS deserves further study for its potentially favorable effects on cardiovascular, cerebrovascular, metabolic, and other physiological biomarkers associated with depression morbidity and mortality. PMID:24834378

  19. Fusimotor reflexes in relaxed forearm muscles produced by cutaneous afferents from the human hand.

    PubMed Central

    Gandevia, S C; Wilson, L; Cordo, P J; Burke, D

    1994-01-01

    1. This study was designed to determine whether cutaneous receptors in the hand exert reflex effects on fusimotor neurones innervating relaxed muscles. Recordings were made from fifty-four muscle spindle afferents in the radial nerve while the arm was held relaxed in a supporting frame. Cutaneous afferents were activated by trains of stimuli at non-noxious levels to the superficial radial nerve or to the palmar surface of the fingers. 2. For the population of muscle spindle afferents, the mean discharge rate was 7.1 +/- 6.4 Hz (range 0-24 Hz). Thirty-three per cent had no background discharge, and this occurred significantly more often in finger extensors than wrist extensors. 3. Trains of cutaneous stimuli produced no change in the discharge rates of the majority of spindle endings irrespective of whether the spindle afferent had a background discharge or was given one by muscle stretch. However, with two of forty afferents, the stimuli produced an increase in discharge at latencies of 135 and 155 ms. 4. With a further fourteen muscle spindle endings, the dynamic responses to stretch were measured 100-400 ms after the trains of cutaneous stimuli. For four spindle afferents there was a statistically significant change in the dynamic response to stretch occurring at conditioned-stretch intervals of 100-200 ms. For two afferents the dynamic response decreased by 17 and 26% and for two others it increased by about 24 and 37%. 5. While these results support the view that the level of background fusimotor drive is low in the relaxed state, they suggest that there is some dynamic fusimotor drive to completely relaxed muscles operating on the human hand, and that this drive can be altered reflexly by cutaneous afferent inputs from the hand. Images Figure 4 PMID:7837105

  20. Effects of antidromic discharges in crayfish primary afferents.

    PubMed

    Cattaert, Daniel; Bévengut, Michelle

    2002-10-01

    Contrary to orthodromic spikes that are generated in sensory organs and conveyed to CNS, antidromic spikes are generated in the axon terminals of the sensory neurons within the CNS and are conveyed to the peripheral sensory organ. Antidromic discharges are observed in primary afferent neurons of both vertebrates and invertebrates and seem to be related to the rhythmic activity of central neural networks. In this study, we analyzed the effect of antidromic discharges on the sensory activity of a leg proprioceptor in in vitro preparations of the crayfish CNS. Intracellular microelectrodes were used both to record the orthodromic spikes and to elicit antidromic spikes by injecting squares pulses of depolarizing current at various frequencies. Experiments were performed on the three types of identified sensory afferents (tonic, phasotonic, and phasic). The main results showed a reduction of the firing frequency of the orthodromic activity in 82% of the tested afferents. In tonic afferents, during their occurrences and according to their frequency, antidromic spikes or bursts reduced or suppressed the orthodromic activity. Following their terminations, they also induced a silent period and a gradual recovery of the orthodromic activity, both of which increased as the duration and the frequency of the antidromic bursts increased. In phasotonic and phasic afferents, antidromic bursts reduced or suppressed the phasic responses as their frequency and durations increased. In phasotonic afferents, if elicited prior to the movements, long-duration bursts with increasing frequency reduced more rapidly the tonic background activity than the phasic one whereas short-duration bursts at high frequency produced strong decreases of both. The effect of antidromic bursts accumulated when they are repetitively elicited. Antidromic bursts induced a much larger decrease of the sensory activity than adaptation alone. The occurrences of antidromic spikes or bursts may have a functional role

  1. Mechanisms of pruritogen-induced activation of itch nerves in isolated mouse skin.

    PubMed

    Ru, F; Sun, H; Jurcakova, D; Herbstsomer, R A; Meixong, J; Dong, X; Undem, B J

    2017-02-19

    Chloroquine (CQ) and histamine are pruritogens commonly used to study itch in the mouse. A novel skin-nerve preparation was used to evaluate chloroquine (CQ)- and histamine- induced activation of afferent nerves in the dorsal thoracic skin of the mouse. All CQ sensitive nerves were C-fibres, and were also sensitive to histamine. The response to CQ, but not histamine, was largely absent in mrgpr cluster Δ -/- mice supporting the hypothesis that CQ evokes itch largely via stimulation of MrgprA3 receptors. The CQ-induced action potential discharge was largely absent in phospholipase Cβ3 knockout animals. The CQ and histamine responses were not influenced by removal of TRPA1, TRPV1, TRPC3 or TRPC6, nor by the TRP channel blocker Ruthenium Red. The bouts of scratching in response to CQ was not different between wild type and TRPA1 deficient mice. A selective inhibitor of TMEM16A, N-((4-methoxy)-2-naphthyl)-5-nitroanthranilic acid (MONNA) inhibited CQ-induced action potential discharge at itch nerve terminals and bouts of scratching by about 50%. Although TRPA1 and TRPV1 channels may be involved in the scratching responses to intradermal pruitogens, this is unlikely due to an effect at the nerve terminals, where chloride channels may play a more important role. This article is protected by copyright. All rights reserved.

  2. Differential modulation of primary afferent depolarization of segmental and ascending intraspinal collaterals of single muscle afferents in the cat spinal cord.

    PubMed

    Rudomin, P; Lomelí, J; Quevedo, J

    2004-06-01

    We examined primary afferent depolarization (PAD) in the anesthetized cat elicited in 109 pairs of intraspinal collaterals of single group I afferents from the gastrocnemius nerve, one of the pair ending in the L3 segment, around the Clarke's column nuclei, and the other in the L6 segment within the intermediate zone. Tests for refractoriness were made to assess whether the responses produced by intraspinal stimulation in the L3 and L6 segments were due to activation of collaterals of the same afferent fiber. PAD in each collateral was estimated by independent computer-controlled measurement of the intraspinal current required to maintain a constant probability of antidromic firing. In most fibers, stimulation of the ipsilateral posterior biceps and semitendinosus (PBSt) nerve with trains of pulses maximal for group I afferents had a qualitatively similar effect but produced a larger PAD in the L6 than in the L3 collaterals. Stimulation of cutaneous nerves (sural and superficial peroneus) with single pulses and of the posterior articular nerve, the ipsilateral reticular formation, nucleus raphe magnus and contralateral motor cortex with trains of pulses often had qualitatively different effects. They could produce PAD and/or facilitate the PBSt-induced PAD in one collateral, and produce PAH and/or inhibit the PAD in the other collateral. These patterns could be changed in a differential manner by sensory or supraspinal conditioning stimulation. In summary, the present investigation suggests that the segmental and ascending collaterals of individual afferents are not fixed routes for information transmission, but parts of dynamic systems in which information transmitted to segmental reflex pathways and to Clarke's column neurons by common sources can be decoupled by sensory and descending inputs and funneled to specific targets according to the motor tasks to be performed.

  3. Role of peptidergic nerve terminals in the skin: reversal of thermal sensation by calcitonin gene-related peptide in TRPV1-depleted neuropathy.

    PubMed

    Hsieh, Yu-Lin; Lin, Chih-Lung; Chiang, Hao; Fu, Yaw-Syan; Lue, June-Horng; Hsieh, Sung-Tsang

    2012-01-01

    To investigate the contribution of peptidergic intraepidermal nerve fibers (IENFs) to nociceptive responses after depletion of the thermal-sensitive receptor, transient receptor potential vanilloid subtype 1 (TRPV1), we took advantage of a resiniferatoxin (RTX)-induced neuropathy which specifically affected small-diameter dorsal root ganglion (DRG) neurons and their corresponding nerve terminals in the skin. Thermal hypoalgesia (p<0.001) developed from RTX-treatment day 7 (RTXd7) and became normalized from RTXd56 to RTXd84. Substance P (SP)(+) and TRPV1(+) neurons were completely depleted (p = 0.0001 and p<0.0001, respectively), but RTX had a relatively minor effect on calcitonin gene-related peptide (CGRP)(+) neurons (p = 0.029). Accordingly, SP(+) (p<0.0001) and TRPV1(+) (p = 0.0008) IENFs were permanently depleted, but CGRP(+) IENFs (p = 0.012) were only transiently reduced and had recovered by RTXd84 (p = 0.83). The different effects of RTX on peptidergic neurons were attributed to the higher co-localization ratio of TRPV1/SP than of TRPV1/CGRP (p = 0.029). Thermal hypoalgesia (p = 0.0018) reappeared with an intraplantar injection of botulinum toxin type A (botox), and the temporal course of withdrawal latencies in the hot-plate test paralleled the innervation of CGRP(+) IENFs (p = 0.0003) and CGRP contents in skin (p = 0.01). In summary, this study demonstrated the preferential effects of RTX on depletion of SP(+) IENFs which caused thermal hypoalgesia. In contrast, the skin was reinnervated by CGRP(+) IENFs, which resulted in a normalization of nociceptive functions.

  4. Estradiol alters the chemosensitive cardiac afferent reflex in female rats by augmenting sympathoinhibition and attenuating sympathoexcitation.

    PubMed

    Pinkham, Maximilian I; Barrett, Carolyn J

    2015-06-01

    The chemosensitive cardiac vagal and sympathetic afferent reflexes are implicated in driving pathophysiological changes in sympathetic nerve activity (SNA) in cardiovascular disease states. This study investigated the impact of sex and ovarian hormones on the chemosensitive cardiac afferent reflex. Experiments were performed in anaesthetized, sinoaortic baroreceptor denervated male, female and ovariectomized female (OVX) Wistar rats with either intact cardiac innervation or bilateral vagotomy. To investigate the chemosensitive cardiac afferent reflexes renal SNA, heart rate (HR) and arterial pressure (AP) were recorded before and following application of capsaicin onto the epicardial surface of the left ventricle. Compared to males, ovary-intact females displayed similar cardiac afferent reflex mediated changes in renal SNA albeit with a reduced maximum sympathetic reflex driven increase in renal SNA. In females, ovariectomy significantly attenuated the cardiac vagal afferent reflex mediated inhibition of renal SNA (renal SNA decreased 2 ± 17% in OVX versus -50 ± 4% in ovary-intact females, P < 0.05) and augmented cardiac sympathetic afferent reflex mediated sympathoexcitation (renal SNA increased 91 ± 11% in OVX vs 62 ± 9% in ovary-intact females, P < 0.05) so that overall increases in reflex driven sympathoexcitation were significantly enhanced. Chronic estradiol replacement, but not progesterone replacement, begun at time of ovariectomy restored cardiac afferent reflex responses to be similar as ovary-intact females. Vagal denervation eliminated all group differences. The current findings show ovariectomy in female rats, mimicking menopause in women, results in greater chemosensitive cardiac afferent reflex driven sympathoexcitation and does so, at least partly, via the loss of estradiols actions on the cardiac vagal afferent reflex pathway.

  5. beta-NAD is a novel nucleotide released on stimulation of nerve terminals in human urinary bladder detrusor muscle.

    PubMed

    Breen, Leanne T; Smyth, Lisa M; Yamboliev, Ilia A; Mutafova-Yambolieva, Violeta N

    2006-02-01

    Endogenous nucleotides with extracellular functions may be involved in the complex neural control of human urinary bladder (HUB). Using HPLC techniques with fluorescence detection, we observed that in addition to ATP and its metabolites ADP, AMP and adenosine, electrical field stimulation (EFS; 4-16 Hz, 0.1 ms, 15 V, 60 s) of HUB detrusor smooth muscle coreleases novel nucleotide factors, which produce etheno-1N(6)-ADP-ribose (eADPR) on etheno-derivatization at high temperature. A detailed HPLC fraction analysis determined that nicotinamide adenine dinucleotide (beta-NAD+; 7.0 +/- 0.7 fmol/mg tissue) is the primary nucleotide that contributes to the formation of eADPR. The tissue superfusates collected during EFS also contained the beta-NAD+ metabolite ADPR (0.35 +/- 0.2 fmol/mg tissue) but not cyclic ADPR (cADPR). HUB failed to degrade nicotinamide guanine dinucleotide (NGD+), a specific substrate of ADP ribosyl cyclase, suggesting that the activity of this enzyme in the HUB is negligible. The EFS-evoked release of beta-NAD+ was frequency dependent and is reduced in the presence of tetrodotoxin (TTX; 0.3 micromol/l), omega-conotoxin GVIA (50 nmol/l), and botulinum neurotoxin A (BoNT/A; 100 nmol/l), but remained unchanged in the presence of guanethidine (3 micromol/l), omega-agatoxin IVA (50 nmol/l), or charbachol (1 micromol/l). Capsaicin (10 micromol/l) increased both the resting and EFS-evoked overflow of beta-NAD+. Exogenous beta-NAD+ (1 micromol/l) reduced both the frequency and amplitude of spontaneous contractions. In conclusion, we detected nerve-evoked overflow of beta-NAD+ and ADPR in HUB. The beta-NAD(+)/ADPR system may constitute a novel inhibitory extracellular nucleotide mechanism of neural control of the human bladder.

  6. Central terminal sensitization of TRPV1 by descending serotonergic facilitation modulates chronic pain

    PubMed Central

    Han, Liang; Li, Man; Li, Zhe; LaVinka, Pamela Colleen; Sun, Shuohao; Tang, Zongxiang; Park, Kyoungsook; Caterina, Michael J.; Ren, Ke; Dubner, Ronald; Wei, Feng; Dong, Xinzhong

    2014-01-01

    SUMMARY The peripheral terminals of primary nociceptive neurons play an essential role in pain detection mediated by membrane receptors like TRPV1, a molecular sensor of heat and capsaicin. However, the contribution of central terminal TRPV1 in the dorsal horn to chronic pain has not been investigated directly. Combining primary sensory neuron-specific GCaMP3 imaging with a trigeminal neuropathic pain model, we detected robust neuronal hyperactivity in injured and uninjured nerves in the skin, soma in trigeminal ganglion, and central terminals in the spinal trigeminal nucleus. Extensive TRPV1 hyperactivity was observed in central terminals innervating all dorsal horn laminae. The central terminal TRPV1 sensitization was maintained by descending serotonergic (5-HT) input from the brainstem. Central blockade of TRPV1 or 5-HT/5-HT3A receptors attenuated central terminal sensitization, excitatory primary afferent inputs, and mechanical hyperalgesia in the territories of injured and uninjured nerves. Our results reveal new central mechanisms facilitating central terminal sensitization underlying chronic pain. PMID:24462040

  7. Central terminal sensitization of TRPV1 by descending serotonergic facilitation modulates chronic pain.

    PubMed

    Kim, Yu Shin; Chu, Yuxia; Han, Liang; Li, Man; Li, Zhe; Lavinka, Pamela Colleen; Sun, Shuohao; Tang, Zongxiang; Park, Kyoungsook; Caterina, Michael J; Ren, Ke; Dubner, Ronald; Wei, Feng; Dong, Xinzhong

    2014-02-19

    The peripheral terminals of primary nociceptive neurons play an essential role in pain detection mediated by membrane receptors like TRPV1, a molecular sensor of heat and capsaicin. However, the contribution of central terminal TRPV1 in the dorsal horn to chronic pain has not been investigated directly. Combining primary sensory neuron-specific GCaMP3 imaging with a trigeminal neuropathic pain model, we detected robust neuronal hyperactivity in injured and uninjured nerves in the skin, soma in trigeminal ganglion, and central terminals in the spinal trigeminal nucleus. Extensive TRPV1 hyperactivity was observed in central terminals innervating all dorsal horn laminae. The central terminal TRPV1 sensitization was maintained by descending serotonergic (5-HT) input from the brainstem. Central blockade of TRPV1 or 5-HT/5-HT3A receptors attenuated central terminal sensitization, excitatory primary afferent inputs, and mechanical hyperalgesia in the territories of injured and uninjured nerves. Our results reveal central mechanisms facilitating central terminal sensitization underlying chronic pain.

  8. Release of beta-nicotinamide adenine dinucleotide upon stimulation of postganglionic nerve terminals in blood vessels and urinary bladder.

    PubMed

    Smyth, Lisa M; Bobalova, Janette; Mendoza, Michael G; Lew, Christy; Mutafova-Yambolieva, Violeta N

    2004-11-19

    Chemical signaling in autonomic neuromuscular transmission involves agents that function as neurotransmitters and/or neuromodulators. Using high performance liquid chromatography techniques with fluorescence and electrochemical detection we observed that, in addition to ATP and norepinephrine (NE), electrical field stimulation (EFS, 4-16 Hz, 0.1-0.3 ms, 15 V, 60-120 s) of isolated vascular and non-vascular preparations co-releases a previously unidentified compound with apparent nucleotide or nucleoside structure. Extensive screening of more than 25 nucleotides and nucleosides followed by detailed peak identification revealed that beta-nicotinamide adenine dinucleotide (beta-NAD) is released in tissue superfusates upon EFS of canine mesenteric artery (CMA), canine urinary bladder, and murine urinary bladder in the amounts of 7.1 +/- 0.7, 26.5 +/- 4.5, and 15.1 +/- 3.2 fmol/mg of tissue, respectively. Smaller amounts of the beta-NAD metabolites cyclic adenosine 5'-diphosphoribose (cADPR) and ADPR were also present in the superfusates collected during EFS of CMA (2.5 +/- 0.9 and 5.8 +/- 0.8 fmol/mg of tissue, respectively), canine urinary bladder (1.8 +/- 0.5 and 9.0 +/- 6.0 fmol/mg of tissue, respectively), and murine urinary bladder (1.4 +/- 0.1 and 6.2 +/- 2.4 fmol/mg of tissue, respectively). The three nucleotides were also detected in the samples collected before EFS (0.2-1.6 fmol/mg of tissue). Exogenous beta-NAD, cADPR, and ADPR (all 100 nm) reduced the release of NE in CMA at 16 Hz from 27.8 +/- 6.0 fmol/mg of tissue to 15.5 +/- 5.0, 12 +/- 3.0, and 10.0 +/- 4.0 fmol/mg of tissue, respectively. In conclusion, we detected constitutive and nerve-evoked overflow of beta-NAD, cADPR, and ADPR in vascular and non-vascular smooth muscles, beta-NAD being the prevailing compound. These substances modulate the release of NE, implicating novel nucleotide mechanisms of autonomic nervous system control of smooth muscle.

  9. Local control of information flow in segmental and ascending collaterals of single afferents.

    PubMed

    Lomelí, J; Quevedo, J; Linares, P; Rudomin, P

    1998-10-08

    In the vertebrate spinal cord, the activation of GABA(gamma-amino-butyric acid)-releasing interneurons that synapse with intraspinal terminals of sensory fibres leading into the central nervous system (afferent fibres) produces primary afferent depolarization and presynaptic inhibition. It is not known to what extent these presynaptic mechanisms allow a selective control of information transmitted through specific sets of intraspinal branches of individual afferents. Here we study the local nature of the presynaptic control by measuring primary afferent depolarization simultaneously in two intraspinal collaterals of the same muscle spindle afferent. One of these collaterals ends at the L6-L7 segmental level in the intermediate nucleus, and the other ascends to segment L3 within Clarke's column, the site of origin of spinocerebellar neurons. Our results indicate that there are central mechanisms that are able to affect independently the synaptic effectiveness of segmental and ascending collaterals of individual muscle spindle afferents. Focal control of presynaptic inhibition thus allows the intraspinal branches of afferent fibres to function as a dynamic assembly that can be fractionated to convey information to selected neuronal targets. This may be a mechanism by which different spinal postsynaptic targets that are coupled by sensory input from a common source could be uncoupled.

  10. The dual phosphatase activity of Synaptojanin1 is required for both efficient synaptic vesicle internalization and re-availability at nerve terminals

    PubMed Central

    Mani, Meera; Lee, Sang Yoon; Lucast, Louise; Cremona, Ottavio; Di Paolo, Gilbert; De Camilli, Pietro; Ryan, Timothy A.

    2013-01-01

    Summary Phosphoinositides have been implicated in synaptic vesicle recycling largely based on studies of enzymes that regulate phosphoinositide synthesis and hydrolysis. One such enzyme is Synaptojanin1, a multifunctional protein conserved from yeast to humans, which contains two phospho-inositol phosphatase domains and a proline-rich domain. Genetic ablation of Synaptojanin1 leads to pleiotropic defects in presynaptic function, including accumulation of free clathrin-coated vesicles and delayed vesicle re-availability, implicating this enzyme in post-endocytic uncoating of vesicles. To further elucidate the role of Synaptojanin1 at nerve terminals, we performed quantitative synaptic vesicle recycling assays in synj1−/− neurons. Our studies show that Synaptojanin1 is also required for normal vesicle endocytosis. Defects in both endocytosis and post-endocytic vesicle re-availability can be fully restored upon reintroduction of Synaptojanin1. However, expression of Synaptojanin1 with mutations abolishing catalytic activity of each phosphatase domain reveals that the dual action of both domains is required for normal synaptic vesicle internalization and re-availability. PMID:18093523

  11. The Metabotropic Glutamate Receptor mGlu7 Activates Phospholipase C, Translocates Munc-13-1 Protein, and Potentiates Glutamate Release at Cerebrocortical Nerve Terminals*

    PubMed Central

    Martín, Ricardo; Durroux, Thierry; Ciruela, Francisco; Torres, Magdalena; Pin, Jean-Philippe; Sánchez-Prieto, José

    2010-01-01

    At synaptic boutons, metabotropic glutamate receptor 7 (mGlu7 receptor) serves as an autoreceptor, inhibiting glutamate release. In this response, mGlu7 receptor triggers pertussis toxin-sensitive G protein activation, reducing presynaptic Ca2+ influx and the subsequent depolarization evoked release. Here we report that receptor coupling to signaling pathways that potentiate release can be seen following prolonged exposure of nerve terminals to the agonist l-(+)-phosphonobutyrate, l-AP4. This novel mGlu7 receptor response involves an increase in the release induced by the Ca2+ ionophore ionomycin, suggesting a mechanism that is independent of Ca2+ channel activity, but dependent on the downstream exocytotic release machinery. The mGlu7 receptor-mediated potentiation resists exposure to pertussis toxin, but is dependent on phospholipase C, and increased phosphatidylinositol (4,5)-bisphosphate hydrolysis. Furthermore, the potentiation of release does not depend on protein kinase C, although it is blocked by the diacylglycerol-binding site antagonist calphostin C. We also found that activation of mGlu7 receptors translocate the active zone protein essential for synaptic vesicle priming, munc13-1, from soluble to particulate fractions. We propose that the mGlu7 receptor can facilitate or inhibit glutamate release through multiple pathways, thereby exerting homeostatic control of presynaptic function. PMID:20375012

  12. 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

  13. Prostaglandin H synthase-catalyzed bioactivation of amphetamines to free radical intermediates that cause CNS regional DNA oxidation and nerve terminal degeneration.

    PubMed

    Jeng, Winnie; Ramkissoon, Annmarie; Parman, Toufan; Wells, Peter G

    2006-04-01

    Reactive oxygen species (ROS) are implicated in amphetamine-initiated neurodegeneration, but the mechanism is unclear. Here, we show that amphetamines are bioactivated by CNS prostaglandin H synthase (PHS) to free radical intermediates that cause ROS formation and neurodegenerative oxidative DNA damage. In vitro incubations of purified PHS-1 with 3,4-methylenedioxyamphetamine (MDA) and methamphetamine (METH) demonstrated PHS-catalyzed time- and concentration-dependent formation of an amphetamine carbon- and/or nitrogen-centered free radical intermediate, and stereoselective oxidative DNA damage, evidenced by 8-oxo-2'-deoxyguanosine (8-oxo-dG) formation. Similarly in vivo, MDA and METH caused dose- and time-dependent DNA oxidation in multiple brain regions, remarkably dependent on the regional PHS levels, including the striatum and substantia nigra, wherein neurodegeneration of dopaminergic nerve terminals was evidenced by decreased immunohistochemical staining of tyrosine hydroxylase. Motor impairment using the rotarod test was evident within 3 wk after the last drug dose, and persisted for at least 6 months. Pretreatment with the PHS inhibitor acetylsalicylic acid blocked MDA-initiated DNA oxidation and protected against functional motor impairment for at least 1.5 months after drug treatment. This is the first direct evidence for PHS-catalyzed bioactivation of amphetamines causing temporal and regional differences in CNS oxidative DNA damage directly related to structural and functional neurodegenerative consequences.

  14. Combined Changes in Chloride Regulation and Neuronal Excitability Enable Primary Afferent Depolarization to Elicit Spiking without Compromising its Inhibitory Effects

    PubMed Central

    2016-01-01

    The central terminals of primary afferent fibers experience depolarization upon activation of GABAA receptors (GABAAR) because their intracellular chloride concentration is maintained above electrochemical equilibrium. Primary afferent depolarization (PAD) normally mediates inhibition via sodium channel inactivation and shunting but can evoke spikes under certain conditions. Antidromic (centrifugal) conduction of these spikes may contribute to neurogenic inflammation while orthodromic (centripetal) conduction could contribute to pain in the case of nociceptive fibers. PAD-induced spiking is assumed to override presynaptic inhibition. Using computer simulations and dynamic clamp experiments, we sought to identify which biophysical changes are required to enable PAD-induced spiking and whether those changes necessarily compromise PAD-mediated inhibition. According to computational modeling, a depolarizing shift in GABA reversal potential (EGABA) and increased intrinsic excitability (manifest as altered spike initiation properties) were necessary for PAD-induced spiking, whereas increased GABAAR conductance density (ḡGABA) had mixed effects. We tested our predictions experimentally by using dynamic clamp to insert virtual GABAAR conductances with different EGABA and kinetics into acutely dissociated dorsal root ganglion (DRG) neuron somata. Comparable experiments in central axon terminals are prohibitively difficult but the biophysical requirements for PAD-induced spiking are arguably similar in soma and axon. Neurons from naïve (i.e. uninjured) rats were compared before and after pharmacological manipulation of intrinsic excitability, and against neurons from nerve-injured rats. Experimental data confirmed that, in most neurons, both predicted changes were necessary to yield PAD-induced spiking. Importantly, such changes did not prevent PAD from inhibiting other spiking or from blocking spike propagation. In fact, since the high value of ḡGABA required for PAD

  15. Comparison of baroreceptive to other afferent synaptic transmission to the medial solitary tract nucleus.

    PubMed

    Andresen, Michael C; Peters, James H

    2008-11-01

    Cranial nerve visceral afferents enter the brain stem to synapse on neurons within the solitary tract nucleus (NTS). The broad heterogeneity of both visceral afferents and NTS neurons makes understanding afferent synaptic transmission particularly challenging. To study a specific subgroup of second-order neurons in medial NTS, we anterogradely labeled arterial baroreceptor afferents of the aortic depressor nerve (ADN) with lipophilic fluorescent tracer (i.e., ADN+) and measured synaptic responses to solitary tract (ST) activation recorded from dye-identified neurons in medial NTS in horizontal brain stem slices. Every ADN+ NTS neuron received constant-latency ST-evoked excitatory postsynaptic currents (EPSCs) (jitter < 192 micros, SD of latency). Stimulus-recruitment profiles showed single thresholds and no suprathreshold recruitment, findings consistent with EPSCs arising from a single, branched afferent axon. Frequency-dependent depression of ADN+ EPSCs averaged approximately 70% for five shocks at 50 Hz, but single-shock failure rates did not exceed 4%. Whether adjacent ADN- or those from unlabeled animals, other second-order NTS neurons (jitters < 200 micros) had ST transmission properties indistinguishable from ADN+. Capsaicin (CAP; 100 nM) blocked ST transmission in some neurons. CAP-sensitive ST-EPSCs were smaller and failed over five times more frequently than CAP-resistant responses, whether ADN+ or from unlabeled animals. Variance-mean analysis of ST-EPSCs suggested uniformly high probabilities for quantal glutamate release across second-order neurons. While amplitude differences may reflect different numbers of contacts, higher frequency-dependent failure rates in CAP-sensitive ST-EPSCs may arise from subtype-specific differences in afferent axon properties. Thus afferent transmission within medial NTS differed by axon class (e.g., CAP sensitive) but was indistinguishable by source of axon (e.g., baroreceptor vs. nonbaroreceptor).

  16. Role of TRPV1 in high-threshold rat colonic splanchnic afferents is revealed by inflammation.

    PubMed

    Phillis, Benjamin D; Martin, Chris M; Kang, Daiwu; Larsson, Håkan; Lindström, Erik A; Martinez, Vicente; Blackshaw, L Ashley

    2009-08-07

    The vanilloid-1 receptor TRPV1 is known to play a role in extrinsic gastrointestinal afferent function. We investigated the role of TRPV1 in mechanosensitivity in afferents from normal and inflamed tissue. Colonic mechanosensitivity was determined in an in vitro rat colon preparation by recording from attached splanchnic nerves. Recordings were made from serosal/mesenteric afferents responding only at high thresholds to graded mechanical stimulation with von Frey probes. Colonic inflammation was induced by adding 5% dextran sulphate sodium (DSS) to the drinking water for 5 days, and was confirmed by histopathology. The selective TRPV1 antagonist, SB-750364 (10(-8) to 10(-6)M), was tested on mechanosensory stimulus response functions of afferents from normal and inflamed preparations (N=7 each). Mechanosensory responses had thresholds of 1-2g, and maximal responses were observed at 12 g. The stimulus response function was not affected by DSS-induced colitis. SB-750364 had no effect on stimulus response functions in normal preparations, but reduced (up to 60%) in a concentration-dependent manner those in inflammation (2-way ANOVA, p<0.05). Moreover, in inflamed tissue, spontaneous afferent activity showed a dose-dependent trend toward reduction with SB-750364. We conclude that mechanosensitivity of high-threshold serosal colonic splanchnic afferents to graded stimuli is unaffected during DSS colitis. However, there is a positive influence of TRPV1 in mechanosensitivity in inflammation, suggesting up-regulation of excitatory TRPV1-mediated mechanisms.

  17. Primary afferent neurons express functional delta opioid receptors in inflamed skin.

    PubMed

    Brederson, Jill-Desiree; Honda, Christopher N

    2015-07-21

    Peripherally-restricted opiate compounds attenuate hyperalgesia in experimental models of inflammatory pain, but have little discernable effect on nociceptive behavior in normal animals. This suggests that activation of opioid receptors on peripheral sensory axons contributes to decreased afferent activity after injury. Previously, we reported that direct application of morphine to cutaneous receptive fields decreased mechanical and heat-evoked responses in a population of C-fiber nociceptors in inflamed skin. Consistent with reported behavioral studies, direct application of morphine had no effect on fiber activity in control skin. The aim of the present study was to determine whether mechanical responsiveness of nociceptors innervating inflamed skin was attenuated by direct activation of delta opioid receptors (DORs) on peripheral terminals. An ex vivo preparation of rat plantar skin and tibial nerve was used to examine effects of a selective DOR agonist, deltorphin II, on responsiveness of single fibers innervating inflamed skin. Electrical recordings were made eighteen hours after injection of complete Freund's adjuvant into the hindpaw. Deltorphin II produced an inhibition of the mechanical responsiveness of single fibers innervating inflamed skin; an effect blocked by the DOR-selective antagonist, naltrindole. The population of units responsive to deltorphin II was identified as consisting of C fiber mechanical nociceptors.

  18. Primary Afferent Neurons Express Functional Delta Opioid Receptors in Inflamed Skin

    PubMed Central

    Brederson, Jill-Desiree; Honda, Christopher N.

    2015-01-01

    Peripherally-restricted opiate compounds attenuate hyperalgesia in experimental models of inflammatory pain, but have little discernable effect on nociceptive behavior in normal animals. This suggests that activation of opioid receptors on peripheral sensory axons contributes to decreased afferent activity after injury. Previously, we reported that direct application of morphine to cutaneous receptive fields decreased mechanical and heat-evoked responses in a population of C-fiber nociceptors in inflamed skin. Consistent with reported behavioral studies, direct application of morphine had no effect on fiber activity in control skin. The aim of the present study was to determine whether mechanical responsiveness of nociceptors innervating inflamed skin was attenuated by direct activation of delta opioid receptors (DOR) on peripheral terminals. An ex vivo preparation of rat plantar skin and tibial nerve was used to examine effects of a selective DOR agonist, deltorphin II, on responsiveness of single fibers innervating inflamed skin. Electrical recordings were made eighteen hours after injection of complete Freund’s adjuvant into the hindpaw. Deltorphin II produced an inhibition of the mechanical responsiveness of single fibers innervating inflamed skin; an effect blocked by the DOR-selective antagonist, naltrindole. The population of units responsive to deltorphin II was identified as consisting of C fiber mechanical nociceptors. PMID:25911583

  19. The influence of sensory afferent input on local motor cortical excitatory circuitry in humans.

    PubMed

    Cash, Robin F H; Isayama, Reina; Gunraj, Carolyn A; Ni, Zhen; Chen, Robert

    2015-04-01

    In human, sensorimotor integration can be investigated by combining sensory input and transcranial magnetic stimulation (TMS). Short latency afferent inhibition (SAI) refers to motor cortical inhibition 20-25 ms after median nerve stimulation. We investigated the interaction between SAI and short-interval intracortical facilitation (SICF), an excitatory motor cortical circuit. Seven experiments were performed. Contrary to expectations, SICF was facilitated in the presence of SAI (SICF(SAI)). This effect is specific to SICF since there was no effect at SICF trough 1 when SICF was absent. Furthermore, the facilitatory SICF(SAI) interaction increased with stronger SICF or SAI. SAI and SICF correlated between individuals, and this relationship was maintained when SICF was delivered in the presence of SAI, suggesting an intrinsic relationship between SAI and SICF in sensorimotor integration. The interaction was present at rest and during muscle contraction, had a broad degree of somatotopic influence and was present in different interneuronal SICF circuits induced by posterior-anterior and anterior-posterior current directions. Our results are compatible with the finding that projections from sensory to motor cortex terminate in both superficial layers where late indirect (I-) waves are thought to originate, as well as deeper layers with more direct effect on pyramidal output. This interaction is likely to be relevant to sensorimotor integration and motor control.

  20. Afferent projections to the deep mesencephalic nucleus in the rat

    SciTech Connect

    Veazey, R.B.; Severin, C.M.

    1982-01-10

    Afferent projections to the deep mesencephalic nucleus (DMN) of the rat were demonstrated with axonal transport techniques. Potential sources for projections to the DMN were first identified by injecting the nucleus with HRP and examining the cervical spinal cord, brain stem, and cortex for retrogradely labeled neurons. Areas consistently labeled were then injected with a tritiated radioisotope, the tissue processed for autoradiography, and the DMN examined for anterograde labeling. Afferent projections to the medial and/or lateral parts of the DMN were found to originate from a number of spinal, bulbar, and cortical centers. Rostral brain centers projecting to both medial and lateral parts of the DMN include the ipsilateral motor and somatosensory cortex, the entopeduncular nucleus, and zona incerta. at the level of the midbrain, the ipsilateral substantia nigra and contralateral DMN likewise project to the DMN. Furthermore, the ipsilateral superior colliculus projects to the DMN, involving mainly the lateral part of the nucleus. Afferents from caudal centers include bilateral projections from the sensory nucleus of the trigeminal complex and the nucleus medulla oblongata centralis, as well as from the contralateral dentate nucleus. The projections from the trigeminal complex and nucleus medullae oblongatae centralis terminate in the intermediate and medial parts of the DMN, whereas projections from the contralateral dentate nucleus terminate mainly in its lateral part. In general, the afferent connections of the DMN arise from diverse areas of the brain. Although most of these projections distribute throughout the entire extent of the DMN, some of them project mainly to either medial or lateral parts of the nucleus, thus suggesting that the organization of the DMN is comparable, at least in part, to that of the reticular formation of the pons and medulla, a region in which hodological differences between medial and lateral subdivisions are known to exist.

  1. Tonic and phasic differential GABAergic inhibition of synaptic actions of joint afferents in the cat.

    PubMed

    Rudomin, P; Hernández, E; Lomelí, J

    2007-01-01

    The aim of this study was to examine the functional organization of the spinal neuronal networks activated by myelinated afferent fibers in the posterior articular nerve (PAN) of the anesthetized cat. Particular attention was given to the tonic and phasic GABAa inhibitory modulation of these networks. Changes in the synaptic effectiveness of the joint afferents were inferred from changes in the intraspinal focal potentials produced by electrical stimulation of the PAN. We found that conditioning stimulation of cutaneous nerves (sural, superficial peroneus and saphenous) and of the nucleus raphe magnus often inhibited, in a differential manner, the early and late components of the intraspinal focal potentials produced by stimulation of low and high threshold myelinated PAN afferents, respectively. The degree of the inhibition depended on the strength of both the conditioning and test stimuli and on the segmental level of recording. Conditioning stimulation of group I muscle afferents was less effective, but marked depression of the early and late focal potentials was produced by stimuli exceeding 5 xT. The i.v. injection of 1-2.5 mg/kg of picrotoxin, a GABAa blocker, had relatively minor effects on the early components of the PAN focal potentials, but was able to induce a significant increase of the late components. It also reduced the inhibitory effects of cutaneous and joint nerve conditioning on PAN focal responses. Conditioning autogenetic stimulation with high-frequency trains depressed the PAN focal potentials. The late components of the PAN responses remained depressed several minutes after discontinuing the conditioning train, even after picrotoxin administration. The present observations indicate that the neuronal networks activated by the low threshold PAN afferents show a relatively small post-activation depression and appear to be subjected to a minor tonic inhibitory GABAa control. In contrast, the pathways activated by stimulation of high threshold

  2. The influence of sensory afferent input on local motor cortical excitatory circuitry in humans

    PubMed Central

    Cash, Robin F H; Isayama, Reina; Gunraj, Carolyn A; Ni, Zhen; Chen, Robert

    2015-01-01

    Key points In the human, sensorimotor integration can be investigated using combined sensory and transcranial magnetic stimulation (TMS). Short latency afferent inhibition (SAI) refers to motor cortical inhibition 20–25ms after median nerve stimulation. We investigated the influence of SAI on a local excitatory interneuronal motor cortical circuit known as short-interval intracortical facilitation (SICF) and found that, contrary to expectations, SICF was facilitated in the presence of SAI (SICFSAI); this effect is specific to SICF since there was no effect in control conditions in which SICF was not elicited, and the facilitatory SICFSAI interaction increased with increasing strength of SICF or SAI. The influence of sensory input on excitatory motor cortical circuitry was similar across different bodily regions, different circuits within motor cortex and across functional states, suggesting that this interaction may have general applicability in sensorimotor integration and motor control. SAI and SICF were found to correlate between individuals in that those with high SAI were found to have high SICF, and this relationship was maintained when SICF was delivered in the presence of SAI, suggesting an intrinsic relationship between SAI and SICF; these findings are compatible with brain-slice studies of sensorimotor circuitry and add to our understanding of sensorimotor integration. Abstract In human, sensorimotor integration can be investigated by combining sensory input and transcranial magnetic stimulation (TMS). Short latency afferent inhibition (SAI) refers to motor cortical inhibition 20–25 ms after median nerve stimulation. We investigated the interaction between SAI and short-interval intracortical facilitation (SICF), an excitatory motor cortical circuit. Seven experiments were performed. Contrary to expectations, SICF was facilitated in the presence of SAI (SICFSAI). This effect is specific to SICF since there was no effect at SICF trough 1 when SICF was

  3. The action of knee joint afferents and the concomitant influence of cutaneous (sural) afferents on the discharge of triceps surae gamma-motoneurones in the cat.

    PubMed

    Ellaway, P H; Davey, N J; Ferrell, W R; Baxendale, R H

    1996-01-01

    Electrical stimulation of group II joint afferents of the posterior articular nerve (PAN) to the knee evoked short-latency facilitation and/or inhibition of the background discharge of gastrocnemius-soleus (GS) gamma-motoneurones in decerebrated spinal cats. The latencies of these responses were consistent with mediation via segmental oligosynaptic spinal pathways. In addition, a longer-latency facilitation was frequently observed. Mechanical non-noxious stimulation of the skin within the field of innervation of the sural nerve, on the lateral aspect of the heel, suppressed the short-latency facilitation, but not the inhibition or long-latency facilitation. Brief mechanical indentation of the posterior aspect of the knee joint capsule could elicit facilitation or inhibition of gamma-motoneurones. Facilitation, but not inhibition, was blocked by anaesthesia or section of the PAN. Both actions could be suppressed by mechanical stimulation of the heel. We conclude that GS gamma-motoneurones receive both facilitatory and inhibitory segmental inputs from group II articular afferents arising in the knee joint. Cutaneous afferents from the sural field exert a selective inhibitory influence over the facilitation of fusimotor discharge by articular afferents.

  4. Afferent connections of the cerebellum in various types of reptiles.

    PubMed

    Bangma, G C; ten Donkelaar, H

    1982-05-20

    The origin of cerebellar afferents was studied in various types of reptiles, viz., the turtles Pseudemys scripta elegans and Testudo hermanni, the lizard Varanus exanthematicus, and the snake Python regius, with retrograde tracers (the enzyme horseradish peroxidase and the fluorescent tracer "Fast Blue"). Projections to the cerebellum were demonstrated from the nucleus of the basal optic root, the interstitial nucleus of the fasciculus longitudinalis medialis, the vestibular ganglion, and the vestibular nuclear complex, two somatosensory nuclei, viz., the descending nucleus of the trigeminal nerve and the nucleus of the dorsal funiculus, the nucleus of the solitary tract, the reticular formation, and throughout the spinal cord. A distinct bilateral projection to the cerebellum was found to arise in a nucleus previously called nucleus parvocellularis medialis (Ebbesson, '67). In the present study this cell mass is termed the perihypoglossal nuclear complex, considering its comparable position and fiber connections to the perihypoglossal nuclei in mammals. In all reptilian species studied a contralateral cerebellar projection of a cell mass located in the caudal brainstem adjacent to the nucleus raphes inferior was observed. It seems likely that this cell mass represents the reptilian homologue of the mammalian inferior olive. Most of the spinocerebellar fibers appeared to arise in neurons located in area VII-VIII of the gray matter. In this respect the origin of the spinocerebellar projection in reptiles resembles the origin of the rostral and ventral spinocerebellar tracts in mammals. No indications for the existence of a column of Clarke or a central cervical nucleus in the reptilian spinal cord were obtained. On comparison of the cerebellum afferents in reptiles with the known connections of the cerebellum in amphibians, birds, and mammals, a basic pattern of cerebellar afferent projections appears to exist in these vertebrate classes, including retinal

  5. Tonic Investigation Concept of Cervico-vestibular Muscle Afferents

    PubMed Central

    Dorn, Linda Josephine; Lappat, Annabelle; Neuhuber, Winfried; Scherer, Hans; Olze, Heidi; Hölzl, Matthias

    2016-01-01

    Introduction Interdisciplinary research has contributed greatly to an improved understanding of the vestibular system. To date, however, very little research has focused on the vestibular system's somatosensory afferents. To ensure the diagnostic quality of vestibular somatosensory afferent data, especially the extra cranial afferents, stimulation of the vestibular balance system has to be precluded. Objective Sophisticated movements require intra- and extra cranial vestibular receptors. The study's objective is to evaluate an investigation concept for cervico-vestibular afferents with respect to clinical feasibility. Methods A dedicated chair was constructed, permitting three-dimensional trunk excursions, during which the volunteer's head remains fixed. Whether or not a cervicotonic provocation nystagmus (c-PN) can be induced with static trunk excursion is to be evaluated and if this can be influenced by cervical monophasic transcutaneous electrical nerve stimulation (c-TENS) with a randomized test group. 3D-video-oculography (VOG) was used to record any change in cervico-ocular examination parameters. The occurring nystagmuses were evaluated visually due to the small caliber of nystagmus amplitudes in healthy volunteers. Results The results demonstrate: no influence of placebo-controlled c-TENS on the spontaneous nystagmus; a significant increase of the vertical nystagmus on the 3D-trunk-excursion chair in static trunk flexion with cervical provocation in all young healthy volunteers (n = 49); and a significant difference between vertical and horizontal nystagmuses during static trunk excursion after placebo-controlled c-TENS, except for the horizontal nystagmus during trunk torsion. Conclusion We hope this cervicotonic investigation concept on the 3D trunk-excursion chair will contribute to new diagnostic and therapeutic perspectives on cervical pathologies in vestibular head-to-trunk alignment. PMID:28050208

  6. Anatomy and physiology of the afferent visual system.

    PubMed

    Prasad, Sashank; Galetta, Steven L

    2011-01-01

    The efficient organization of the human afferent visual system meets enormous computational challenges. Once visual information is received by the eye, the signal is relayed by the retina, optic nerve, chiasm, tracts, lateral geniculate nucleus, and optic radiations to the striate cortex and extrastriate association cortices for final visual processing. At each stage, the functional organization of these circuits is derived from their anatomical and structural relationships. In the retina, photoreceptors convert photons of light to an electrochemical signal that is relayed to retinal ganglion cells. Ganglion cell axons course through the optic nerve, and their partial decussation in the chiasm brings together corresponding inputs from each eye. Some inputs follow pathways to mediate pupil light reflexes and circadian rhythms. However, the majority of inputs arrive at the lateral geniculate nucleus, which relays visual information via second-order neurons that course through the optic radiations to arrive in striate cortex. Feedback mechanisms from higher cortical areas shape the neuronal responses in early visual areas, supporting coherent visual perception. Detailed knowledge of the anatomy of the afferent visual system, in combination with skilled examination, allows precise localization of neuropathological processes and guides effective diagnosis and management of neuro-ophthalmic disorders.

  7. Tetanic depression is overcome by tonic adenosine A2A receptor facilitation of L-type Ca2+ influx into rat motor nerve terminals

    PubMed Central

    Oliveira, Laura; Timóteo, M Alexandrina; Correia-de-Sá, Paulo

    2004-01-01

    Motor nerve terminals possess multiple voltage-sensitive calcium channels operating acetylcholine (ACh) release. In this study, we investigated whether facilitation of neuromuscular transmission by adenosine generated during neuronal firing was operated by Ca2+ influx via ‘prevalent’ P-type or via the recruitment of ‘silent’ L-type channels. The release of [3H]ACh from rat phrenic nerve endings decreased upon increasing the stimulation frequency of the trains (750 pulses) from 5 Hz (83 ± 4 × 103 disintegrations per minute per gram (d.p.m. g−1); n = 11) to 50 Hz (30 ± 3 × 103 d.p.m. g−1; n = 5). The P-type Ca2+ channel blocker, ω-agatoxin IVA (100 nm) reduced (by 40 ± 10%; n = 6) the release of [3H]ACh evoked by 50-Hz trains, while nifedipine (1 μm, an L-type blocker) was inactive. Tetanic depression was overcome (88 ± 6 × 103 d.p.m. g−1; n = 12) by stimulating the phrenic nerve with 50-Hz bursts (five bursts of 150 pulses, 20 s interburst interval). In these conditions, ω-agatoxin IVA (100 nm) failed to affect transmitter release, but nifedipine (1 μm) decreased [3H]ACh release by 21 ± 7% (n = 4). Inactivation of endogenous adenosine with adenosine deaminase (ADA, 0.5 U ml−1) reduced (by 54 ± 8%, n = 5) the release of [3H]ACh evoked with 50-Hz bursts. This effect was opposite to the excitatory actions of adenosine (0.5 mm), S-(p-nitrobenzyl)-6-thioinosine (5 μm, an adenosine uptake blocker) and CGS 21680C (3 nm, a selective A2A receptor agonist); as the A1 receptor agonist R-N6-phenylisopropyl adenosine (R-PIA, 300 nm) failed to affect the release of [3H]ACh, the results indicate that adenosine generated during 50-Hz bursts exerts an A2A-receptor-mediated tonus. The effects of ADA (0.5 U ml−1) and CGS 21680C (3 nm) were prevented by nifedipine (1 μm). Blocking tonic A2A receptor activation, with ADA (0.5 U ml−1) or 3,7-dimethyl-1-propargyl xanthine (10 μm, an A2A antagonist), recovered ω-agatoxin IVA (100 nm) inhibition and

  8. TRPA1 mediates amplified sympathetic responsiveness to activation of metabolically sensitive muscle afferents in rats with femoral artery occlusion.

    PubMed

    Xing, Jihong; Lu, Jian; Li, Jianhua

    2015-01-01

    Autonomic responses to activation of mechanically and metabolically sensitive muscle afferent nerves during static contraction are augmented in rats with femoral artery occlusion. Moreover, metabolically sensitive transient receptor potential cation channel subfamily A, member 1 (TRPA1) has been reported to contribute to sympathetic nerve activity (SNA) and arterial blood pressure (BP) responses evoked by static muscle contraction. Thus, in the present study, we examined the mechanisms by which afferent nerves' TRPA1 plays a role in regulating amplified sympathetic responsiveness due to a restriction of blood flow directed to the hindlimb muscles. Our data show that 24-72 h of femoral artery occlusion (1) upregulates the protein levels of TRPA1 in dorsal root ganglion (DRG) tissues; (2) selectively increases expression of TRPA1 in DRG neurons supplying metabolically sensitive afferent nerves of C-fiber (group IV); and (3) enhances renal SNA and BP responses to AITC (a TRPA1 agonist) injected into the hindlimb muscles. In addition, our data demonstrate that blocking TRPA1 attenuates SNA and BP responses during muscle contraction to a greater degree in ligated rats than those responses in control rats. In contrast, blocking TRPA1 fails to attenuate SNA and BP responses during passive tendon stretch in both groups. Overall, results of this study indicate that alternations in muscle afferent nerves' TRPA1 likely contribute to enhanced sympathetically mediated autonomic responses via the metabolic component of the muscle reflex under circumstances of chronic muscle ischemia.

  9. TRPA1 mediates amplified sympathetic responsiveness to activation of metabolically sensitive muscle afferents in rats with femoral artery occlusion

    PubMed Central

    Xing, Jihong; Lu, Jian; Li, Jianhua

    2015-01-01

    Autonomic responses to activation of mechanically and metabolically sensitive muscle afferent nerves during static contraction are augmented in rats with femoral artery occlusion. Moreover, metabolically sensitive transient receptor potential cation channel subfamily A, member 1 (TRPA1) has been reported to contribute to sympathetic nerve activity (SNA) and arterial blood pressure (BP) responses evoked by static muscle contraction. Thus, in the present study, we examined the mechanisms by which afferent nerves' TRPA1 plays a role in regulating amplified sympathetic responsiveness due to a restriction of blood flow directed to the hindlimb muscles. Our data show that 24–72 h of femoral artery occlusion (1) upregulates the protein levels of TRPA1 in dorsal root ganglion (DRG) tissues; (2) selectively increases expression of TRPA1 in DRG neurons supplying metabolically sensitive afferent nerves of C-fiber (group IV); and (3) enhances renal SNA and BP responses to AITC (a TRPA1 agonist) injected into the hindlimb muscles. In addition, our data demonstrate that blocking TRPA1 attenuates SNA and BP responses during muscle contraction to a greater degree in ligated rats than those responses in control rats. In contrast, blocking TRPA1 fails to attenuate SNA and BP responses during passive tendon stretch in both groups. Overall, results of this study indicate that alternations in muscle afferent nerves' TRPA1 likely contribute to enhanced sympathetically mediated autonomic responses via the metabolic component of the muscle reflex under circumstances of chronic muscle ischemia. PMID:26441669

  10. Kinetics, Ca2+ dependence, and biophysical properties of integrin-mediated mechanical modulation of transmitter release from frog motor nerve terminals

    NASA Technical Reports Server (NTRS)

    Chen, B. M.; Grinnell, A. D.

    1997-01-01

    Neurotransmitter release from frog motor nerve terminals is strongly modulated by change in muscle length. Over the physiological range, there is an approximately 10% increase in spontaneous and evoked release per 1% muscle stretch. Because many muscle fibers do not receive suprathreshold synaptic inputs at rest length, this stretch-induced enhancement of release constitutes a strong peripheral amplifier of the spinal stretch reflex. The stretch modulation of release is inhibited by peptides that block integrin binding of natural ligands. The modulation varies linearly with length, with a delay of no more than approximately 1-2 msec and is maintained constant at the new length. Moreover, the stretch modulation persists in a zero Ca2+ Ringer and, hence, is not dependent on Ca2+ influx through stretch activated channels. Eliminating transmembrane Ca2+ gradients and buffering intraterminal Ca2+ to approximately normal resting levels does not eliminate the modulation, suggesting that it is not the result of release of Ca2+ from internal stores. Finally, changes in temperature have no detectable effect on the kinetics of stretch-induced changes in endplate potential (EPP) amplitude or miniature EPP (mEPP) frequency. We conclude, therefore, that stretch does not act via second messenger pathways or a chemical modification of molecules involved in the release pathway. Instead, there is direct mechanical modulation of release. We postulate that tension on integrins in the presynaptic membrane is transduced mechanically into changes in the position or conformation of one or more molecules involved in neurotransmitter release, altering sensitivity to Ca2+ or the equilibrium for a critical reaction leading to vesicle fusion.

  11. Excessive activation of ionotropic glutamate receptors induces apoptotic hair-cell death independent of afferent and efferent innervation

    PubMed Central

    Sheets, Lavinia

    2017-01-01

    Accumulation of excess glutamate plays a central role in eliciting the pathological events that follow intensely loud noise exposures and ischemia-reperfusion injury. Glutamate excitotoxicity has been characterized in cochlear nerve terminals, but much less is known about whether excess glutamate signaling also contributes to pathological changes in sensory hair cells. I therefore examined whether glutamate excitotoxicity damages hair cells in zebrafish larvae exposed to drugs that mimic excitotoxic trauma. Exposure to ionotropic glutamate receptor (iGluR) agonists, kainic acid (KA) or N-methyl-D-aspartate (NMDA), contributed to significant, progressive hair cell loss in zebrafish lateral-line organs. To examine whether hair-cell loss was a secondary effect of excitotoxic damage to innervating neurons, I exposed neurog1a morphants—fish whose hair-cell organs are devoid of afferent and efferent innervation—to KA or NMDA. Significant, dose-dependent hair-cell loss occurred in neurog1a morphants exposed to either agonist, and the loss was comparable to wild-type siblings. A survey of iGluR gene expression revealed AMPA-, Kainate-, and NMDA-type subunits are expressed in zebrafish hair cells. Finally, hair cells exposed to KA or NMDA appear to undergo apoptotic cell death. Cumulatively, these data reveal that excess glutamate signaling through iGluRs induces hair-cell death independent of damage to postsynaptic terminals. PMID:28112265

  12. Postsynaptic effects of long-range afferents in distant segments caudal to their entry point in rat spinal cord under the influence of picrotoxin or strychnine.

    PubMed

    Wall, P D; Bennett, D L

    1994-12-01

    1. Previous work has shown that substantial numbers of arriving myelinated afferent nerve fibers travel for many segments caudal to their entry point and terminate in the gray matter of distant segments. This fact is surprising because no monosynaptic post-synaptic responses attributable to these long-range afferents are observable in the distant segments. Evidence has been produced to explain this paradox by showing that impulse transmission is normally blocked in these long-range afferents by the tonic operation of a primary afferent depolarization (PAD) mechanism. Impulse transmission is restored if the PAD mechanism is disabled with gamma-aminobutyric acid antagonists. In this paper we examine the postsynaptic consequence of restoring conduction in the long-range afferents with picrotoxin. Because picrotoxin blocks PAD and increases the excitability of cells, we here contrast its action with that of the glycine antagonist strychnine, which increases the excitability of dorsal horn cells but does not affect PAD. 2. The preparation used throughout these experiments was decerebrate and spinal at T11. On one side dorsal roots T12, T13, and L1 were intact but all more caudal roots on that side were cut. Recordings of single units were made in the L6 segment with a rigid search pattern. The innervated area of skin on the flank was repeatedly stimulated with pressure in a repeated pattern. In the control state, few cells were detected responding in the L6 segment, which was five to seven segments caudal to the intact dorsal roots. After picrotoxin, the number of cells with excitatory receptive fields rose by a factor of 8, whereas there was no change in the number of inhibited cells. By contrast, after strychnine there was no change in the number of excited cells but the number of inhibited cells rose by a factor of 10. Details of the size of receptive fields, adequate stimuli, and location of the responding cells are provided. 3. To determine the number of synapses

  13. Merkel cells transduce and encode tactile stimuli to drive Aβ-afferent impulses.

    PubMed

    Ikeda, Ryo; Cha, Myeounghoon; Ling, Jennifer; Jia, Zhanfeng; Coyle, Dennis; Gu, Jianguo G

    2014-04-24

    Sensory systems for detecting tactile stimuli have evolved from touch-sensing nerves in invertebrates to complicated tactile end organs in mammals. Merkel discs are tactile end organs consisting of Merkel cells and Aβ-afferent nerve endings and are localized in fingertips, whisker hair follicles, and other touch-sensitive spots. Merkel discs transduce touch into slowly adapting impulses to enable tactile discrimination, but their transduction and encoding mechanisms remain unknown. Using rat whisker hair follicles, we show that Merkel cells rather than Aβ-afferent nerve endings are primary sites of tactile transduction and identify the Piezo2 ion channel as the Merkel cell mechanical transducer. Piezo2 transduces tactile stimuli into Ca(2+)-action potentials in Merkel cells, which drive Aβ-afferent nerve endings to fire slowly adapting impulses. We further demonstrate that Piezo2 and Ca(2+)-action potentials in Merkel cells are required for behavioral tactile responses. Our findings provide insights into how tactile end-organs function and have clinical implications for tactile dysfunctions.

  14. Reflex control of locomotion as revealed by stimulation of cutaneous afferents in spontaneously walking premammillary cats.

    PubMed

    Duysens, J

    1977-07-01

    1. Stimulation of different hindlimb nerves in spontaneously walking premammillary cats was used in order to examine the effects of sensory input on the rhythmic motor output. 2. Stimulation of the tibial or sural nerve at low intensities caused the burst of activity in the triceps surae or semimembranosus to be prolonged if stimuli were given during the extension phase. When applied during the flexion phase, the same stimuli shortened the burst of activity in the pretibial flexors and induced an early onset of the extensor activity, except if stimuli were given at the very beginning of the flexion phase, when flexor burst prolongations or rebounds were observed instead. 3. These effects were related to activation of large cutaneous afferents in these nerves since the results could be duplicated by low-intensity stimulation of the tibial nerve at the ankle or by direct stimulation of the pad. 4. In contrast, activation of smaller afferents by high-intensity stimulation resulted prolongations of the flexor burst and/or shortenings of the extensor burst for stimuli applied before or during these bursts, respectively. 5. It was concluded that the large and small cutaneous afferents make, respectively, inhibitory and excitatory connections with the central structure involved in the generation of flexion during walking.

  15. Skeletal muscle afferent regulation of bioassayable growth hormone in the rat pituitary

    NASA Technical Reports Server (NTRS)

    Gosselink, K. L.; Grindeland, R. E.; Roy, R. R.; Zhong, H.; Bigbee, A. J.; Grossman, E. J.; Edgerton, V. R.

    1998-01-01

    There are forms of growth hormone (GH) in the plasma and pituitary of the rat and in the plasma of humans that are undetected by presently available immunoassays (iGH) but can be measured by bioassay (bGH). Although the regulation of iGH release is well documented, the mechanism(s) of bGH release is unclear. On the basis of changes in bGH and iGH secretion in rats that had been exposed to microgravity conditions, we hypothesized that neural afferents play a role in regulating the release of these hormones. To examine whether bGH secretion can be modulated by afferent input from skeletal muscle, the proximal or distal ends of severed hindlimb fast muscle nerves were stimulated ( approximately 2 times threshold) in anesthetized rats. Plasma bGH increased approximately 250%, and pituitary bGH decreased approximately 60% after proximal nerve trunk stimulation. The bGH response was independent of muscle mass or whether the muscles were flexors or extensors. Distal nerve stimulation had little or no effect on plasma or pituitary bGH. Plasma iGH concentrations were unchanged after proximal nerve stimulation. Although there may be multiple regulatory mechanisms of bGH, the present results demonstrate that the activation of low-threshold afferents from fast skeletal muscles can play a regulatory role in the release of bGH, but not iGH, from the pituitary in anesthetized rats.

  16. Selective cortical and segmental control of primary afferent depolarization of single muscle afferents in the cat spinal cord.

    PubMed

    Eguibar, J R; Quevedo, J; Rudomin, P

    1997-03-01

    This study was primarily aimed at investigating the selectivity of the cortico-spinal actions exerted on the pathways mediating primary afferent depolarization (PAD) of muscle spindle and tendon organ afferents ending within the intermediate nucleus at the L6-L7 segmental level. To this end we analyzed, in the anesthetized cat, the effects produced by electrical stimulation of sensory nerves and of the cerebral cortex on (a) the intraspinal threshold of pairs of single group I afferent fibers belonging to the same or to different hindlimb muscles and (b) the intraspinal threshold of two collaterals of the same muscle afferent fiber. Afferent fibers were classified in three categories, according to the effects produced by stimulation of segmental nerves and of the cerebral cortex. Twenty-five of 40 fibers (62.5%) were depolarized by stimulation of group I posterior biceps and semitendinosus (PBSt) or tibialis (Tib) fibers, but not by stimulation of the cerebral cortex or of cutaneous and joint nerves, which instead inhibited the PBSt- or Tib-induced PAD (type A PAD pattern, usually seen in Ia fibers). The remaining 15 fibers (37.5%) were all depolarized by stimulation of the PBSt or Tib nerves and the cerebral cortex. Stimulation of cutaneous and joint nerves produced PAD in 10 of those 15 fibers (type B PAD pattern) and inhibited the PBSt- or Tib-induced PAD in the 5 remaining fibers (type C PAD pattern). Fibers with a type B or C PAD pattern are likely to be Ib. Not all sites in the cerebral cortex inhibited with the same effectiveness the segmentally induced PAD of group I fibers with a type A PAD pattern. With the weakest stimulation of the cortical surface, the most effective sites that inhibited the PAD of individual fibers were surrounded by less effective sites, scattered all along the motor cortex (area 4gamma and 6) and sensory cortex (areas 3, 2 and 1), far beyond the area of projection of group I fibers from the hindlimb. With higher strengths of

  17. Isolation of TRPV1 independent mechanisms of spontaneous and asynchronous glutamate release at primary afferent to NTS synapses.

    PubMed

    Fenwick, Axel J; Wu, Shaw-Wen; Peters, James H

    2014-01-01

    Cranial visceral afferents contained within the solitary tract (ST) contact second-order neurons in the nucleus of the solitary tract (NTS) and release the excitatory amino acid glutamate via three distinct exocytosis pathways; synchronous, asynchronous, and spontaneous release. The presence of TRPV1 in the central terminals of a majority of ST afferents conveys activity-dependent asynchronous glutamate release and provides a temperature sensitive calcium conductance which largely determines the rate of spontaneous vesicle fusion. TRPV1 is present in unmyelinated C-fiber afferents and these facilitated forms of glutamate release may underlie the relative strength of C-fibers in activating autonomic reflex pathways. However, pharmacological blockade of TRPV1 signaling eliminates only ~50% of the asynchronous profile and attenuates the temperature sensitivity of spontaneous release indicating additional thermosensitive calcium influx pathways may exist which mediate these forms of vesicle release. In the present study we isolate the contribution of TRPV1 independent forms of glutamate release at ST-NTS synapses. We found ST afferent innervation at NTS neurons and synchronous vesicle release from TRPV1 KO mice was not different to control animals; however, only half of TRPV1 KO ST afferents completely lacked asynchronous glutamate release. Further, temperature driven spontaneous rates of vesicle release were not different from 33 to 37°C between control and TRPV1 KO afferents. These findings suggest additional temperature dependent mechanisms controlling asynchronous and thermosensitive spontaneous release at physiological temperatures, possibly mediated by additional thermosensitive TRP channels in primary afferent terminals.

  18. An Analysis of Hamster Afferent Taste Nerve Response Functions

    PubMed Central

    Frank, Marion

    1973-01-01

    Sensitivities to moderately intense stimuli representing four taste qualities to man were determined for 79 hamster chorda tympani fibers. Some fibers were very sensitive to sucrose, sodium chloride, or hydrochloric acid, but none were very sensitive to quinine. These sensitivities were not randomly distributed among fibers: the sucrose sensitivity was separated from and negatively correlated with the other sensitivities which were associated and positively correlated with each other. Moreover, there were a limited number of sensitivity patterns: (a) fibers responding best to sucrose responded second-best to salt, less to acid, not to quinine; (b) fibers responding best to salt either responded second-best to sucrose and not to acid or quinine; or second-best to acid, less to quinine, and not to sucrose; and (c) fibers responding best to acid responded second-best to salt, more to quinine, and less to sucrose than other fibers. Therefore, if four stimuli of different taste qualities are ordered from acceptable to unacceptable, neural response functions of most hamster chorda tympani taste fibers peak at one point. Sensitivities to nine other moderately intense stimuli which vary in quality to man were also determined for 46–49 of the fibers. Sensitivities to sweet stimuli were always associated with each other and separated from sensitivities to nonsweet stimuli. Sensitivities to nonsweet stimuli were all associated with each other; however, the strongest correlations were between sensitivities to stimuli of like quality, e.g., the three acids or the two sodium salts. PMID:4705639

  19. Single low-threshold afferents innervating the skin of the human foot modulate ongoing muscle activity in the upper limbs.

    PubMed

    Bent, Leah R; Lowrey, Catherine R

    2013-03-01

    We have shown for the first time that single cutaneous afferents in the foot dorsum have significant reflex coupling to motoneurons supplying muscles in the upper limb, particularly posterior deltoid and triceps brachii. These observations strengthen what we know from whole nerve stimulation, that skin on the foot and ankle can contribute to the modulation of interlimb muscles in distant innervation territories. The current work provides evidence of the mechanism behind the reflex, where one single skin afferent can evoke a reflex response, rather than a population. Nineteen of forty-one (46%) single cutaneous afferents isolated in the dorsum or plantar surface of the foot elicited a significant modulation of muscle activity in the upper limb. Identification of single afferents in this reflex indicates the strength of the connection and, ultimately, the importance of foot skin in interlimb coordination. The median response magnitude was 2.29% of background EMG, and the size of the evoked response did not significantly differ among the four mechanoreceptor classes (P > 0.1). Interestingly, although the distribution of afferents types did not differ across the foot dorsum, there was a significantly greater coupling response from receptors located on the medial aspect of the foot dorsum (P < 0.01). Furthermore, the most consistent coupling with upper limb muscles was demonstrated by type I afferents (fast and slowly adapting). This work contributes to the current literature on receptor specificity, supporting the view that individual classes of cutaneous afferents may subserve specific roles in kinesthesia, reflexes, and tactile perception.

  20. Cerebral, subcortical, and cerebellar activation evoked by selective stimulation of muscle and cutaneous afferents: an fMRI study.

    PubMed

    Wardman, Daniel L; Gandevia, Simon C; Colebatch, James G

    2014-01-01

    Abstract We compared the brain areas that showed significant flow changes induced by selective stimulation of muscle and cutaneous afferents using fMRI BOLD imaging. Afferents arising from the right hand were studied in eight volunteers with electrical stimulation of the digital nerve of the index finger and over the motor point of the FDI muscle. Both methods evoked areas of significant activation cortically, subcortically, and in the cerebellum. Selective muscle afferent stimulation caused significant activation in motor-related areas. It also caused significantly greater activation within the contralateral precentral gyrus, insula, and within the ipsilateral cerebellum as well as greater areas of reduced blood flow when compared to the cutaneous stimuli. We demonstrated separate precentral and postcentral foci of excitation with muscle afferent stimulation. We conclude, contrary to the findings with evoked potentials, that muscle afferents evoke more widespread cortical, subcortical, and cerebellar activation than do cutaneous afferents. This emphasizes the importance, for studies of movement, of matching the kinematic aspects in order to avoid the results being confounded by alterations in muscle afferent activation. The findings are consistent with clinical observations of the movement consequences of sensory loss and may also be the basis for the contribution of disturbed sensorimotor processing to disorders of movement.

  1. Cerebral, subcortical, and cerebellar activation evoked by selective stimulation of muscle and cutaneous afferents: an fMRI study

    PubMed Central

    Wardman, Daniel L.; Gandevia, Simon C.; Colebatch, James G.

    2014-01-01

    Abstract We compared the brain areas that showed significant flow changes induced by selective stimulation of muscle and cutaneous afferents using fMRI BOLD imaging. Afferents arising from the right hand were studied in eight volunteers with electrical stimulation of the digital nerve of the index finger and over the motor point of the FDI muscle. Both methods evoked areas of significant activation cortically, subcortically, and in the cerebellum. Selective muscle afferent stimulation caused significant activation in motor‐related areas. It also caused significantly greater activation within the contralateral precentral gyrus, insula, and within the ipsilateral cerebellum as well as greater areas of reduced blood flow when compared to the cutaneous stimuli. We demonstrated separate precentral and postcentral foci of excitation with muscle afferent stimulation. We conclude, contrary to the findings with evoked potentials, that muscle afferents evoke more widespread cortical, subcortical, and cerebellar activation than do cutaneous afferents. This emphasizes the importance, for studies of movement, of matching the kinematic aspects in order to avoid the results being confounded by alterations in muscle afferent activation. The findings are consistent with clinical observations of the movement consequences of sensory loss and may also be the basis for the contribution of disturbed sensorimotor processing to disorders of movement. PMID:24771687

  2. Innervation of enteric mast cells by primary spinal afferents in guinea pig and human small intestine.

    PubMed

    Wang, Guo-Du; Wang, Xi-Yu; Liu, Sumei; Qu, Meihua; Xia, Yun; Needleman, Bradley J; Mikami, Dean J; Wood, Jackie D

    2014-10-01

    Mast cells express the substance P (SP) neurokinin 1 receptor and the calcitonin gene-related peptide (CGRP) receptor in guinea pig and human small intestine. Enzyme-linked immunoassay showed that activation of intramural afferents by antidromic electrical stimulation or by capsaicin released SP and CGRP from human and guinea pig intestinal segments. Electrical stimulation of the afferents evoked slow excitatory postsynaptic potentials (EPSPs) in the enteric nervous system. The slow EPSPs were mediated by tachykinin neurokinin 1 and CGRP receptors. Capsaicin evoked slow EPSP-like responses that were suppressed by antagonists for protease-activated receptor 2. Afferent stimulation evoked slow EPSP-like excitation that was suppressed by mast cell-stabilizing drugs. Histamine and mast cell protease II were released by 1) exposure to SP or CGRP, 2) capsaicin, 3) compound 48/80, 4) elevation of mast cell Ca²⁺ by ionophore A23187, and 5) antidromic electrical stimulation of afferents. The mast cell stabilizers cromolyn and doxantrazole suppressed release of protease II and histamine when evoked by SP, CGRP, capsaicin, A23187, electrical stimulation of afferents, or compound 48/80. Neural blockade by tetrodotoxin prevented mast cell protease II release in response to antidromic electrical stimulation of mesenteric afferents. The results support a hypothesis that afferent innervation of enteric mast cells releases histamine and mast cell protease II, both of which are known to act in a diffuse paracrine manner to influence the behavior of enteric nervous system neurons and to elevate the sensitivity of spinal afferent terminals.

  3. Innervation of enteric mast cells by primary spinal afferents in guinea pig and human small intestine

    PubMed Central

    Wang, Guo-Du; Wang, Xi-Yu; Liu, Sumei; Qu, Meihua; Xia, Yun; Needleman, Bradley J.; Mikami, Dean J.

    2014-01-01

    Mast cells express the substance P (SP) neurokinin 1 receptor and the calcitonin gene-related peptide (CGRP) receptor in guinea pig and human small intestine. Enzyme-linked immunoassay showed that activation of intramural afferents by antidromic electrical stimulation or by capsaicin released SP and CGRP from human and guinea pig intestinal segments. Electrical stimulation of the afferents evoked slow excitatory postsynaptic potentials (EPSPs) in the enteric nervous system. The slow EPSPs were mediated by tachykinin neurokinin 1 and CGRP receptors. Capsaicin evoked slow EPSP-like responses that were suppressed by antagonists for protease-activated receptor 2. Afferent stimulation evoked slow EPSP-like excitation that was suppressed by mast cell-stabilizing drugs. Histamine and mast cell protease II were released by 1) exposure to SP or CGRP, 2) capsaicin, 3) compound 48/80, 4) elevation of mast cell Ca2+ by ionophore A23187, and 5) antidromic electrical stimulation of afferents. The mast cell stabilizers cromolyn and doxantrazole suppressed release of protease II and histamine when evoked by SP, CGRP, capsaicin, A23187, electrical stimulation of afferents, or compound 48/80. Neural blockade by tetrodotoxin prevented mast cell protease II release in response to antidromic electrical stimulation of mesenteric afferents. The results support a hypothesis that afferent innervation of enteric mast cells releases histamine and mast cell protease II, both of which are known to act in a diffuse paracrine manner to influence the behavior of enteric nervous system neurons and to elevate the sensitivity of spinal afferent terminals. PMID:25147231

  4. Group I extensor afferents evoke disynaptic EPSPs in cat hindlimb extensor motorneurones during fictive locomotion.

    PubMed Central

    Angel, M J; Guertin, P; Jiménez, T; McCrea, D A

    1996-01-01

    1. Intracellular recording from extensor motoneurones in paralysed decerebrate cats was used to examine the distribution of short-latency non-monosynaptic excitation by group I afferents during fictive locomotion produced by stimulation of the mesencephalic locomotor region (MLR). 2. During the extension but not the flexion phase of fictive locomotion, stimulation of ankle extensor nerves at 1.2-2.0 times threshold evoked excitatory postsynaptic potentials (EPSPs) in motoneurones innervating hip, knee and ankle extensors. Disynaptic EPSPs were also evoked by selective activation of group Ia muscle spindle afferents by muscle stretch. 3. The central latencies of these group I-evoked EPSPs (mean, 1.55 ms) suggest their mediation by a disynaptic pathway with a single interneurone interposed between extensor group I afferents and extensor motoneurones. Disynaptic EPSPs were also evoked during periods of spontaneous locomotion following the cessation of MLR stimulation. 4. Hip extensor motoneurones received disynaptic EPSPs during extension following stimulation of both homonymous and ankle extensor nerves. Stimulation of hip extensor nerves did not evoke disynaptic EPSPs in ankle extensor motoneurones. 5. The appearance of disynaptic EPSPs during extension appears to result from cyclic disinhibition of an unidentified population of excitatory spinal interneurones and not postsynaptic voltage-dependent conductances in motoneurones or phasic presynaptic inhibition of group I afferents during flexion. 6. The reorganization of group I reflexes during fictive locomotion includes the appearance of disynaptic excitation of hip, knee and ankle extensor motoneurones. This excitatory reflex is one of the mechanisms by which group I afferents can enhance extensor activity and increase force production during stance. PMID:8865080

  5. Afferent discharges from coronary arterial and ventricular receptors in anaesthetized dogs.

    PubMed Central

    Drinkhill, M J; Moore, J; Hainsworth, R

    1993-01-01

    1. Previous work has shown that increases in aortic root pressure result in reflex vasodilation, and that this response is likely to result mainly from stimulation of receptors in the coronary arteries, although contribution from left ventricular receptors was not excluded. This investigation was undertaken to resolve this question and to determine the afferent nerve fibres likely to be involved in this reflex. 2. In chloralose-anaesthetized dogs a perfusion circuit was used which allowed us to change the pressures in: (a) the aortic root, coronary arteries and the left ventricle; (b) aortic root and coronary arteries at constant ventricular pressure; and (c) the left ventricle with mean (although not pulse) aortic pressure constant. Electrophysiological recordings were made from slips dissected from the vagus nerve which responded with an increase in discharge to either combined increases in the pressures, or to aortic root injections of veratridine. 3. Recordings were made from twenty-one vagal afferents. On the basis of their conduction velocities, eleven were classified as non-myelinated and ten as myelinated. 4. Three non-myelinated afferents responded to veratridine injections only, three to both veratridine and combined aortic root and ventricular pressure changes, and five to pressure changes only. Responses to pressure occurred only when ventricular systolic pressure exceeded 30 kPa. 5. None of the myelinated afferents responded to veratridine. All showed increases in discharge to combined increases in mean aortic root, coronary arterial and left ventricular systolic pressures, which would be graded over a range similar to that which caused reflex changes. All were more sensitive to changes in mean coronary pressure than to changes in ventricular systolic pressure. 6. We conclude that myelinated vagal afferent nerve fibres, which respond predominantly to changes in mean coronary arterial pressure, are likely to be responsible for the vasodilation to the

  6. Modelling spinal circuitry involved in locomotor pattern generation: insights from the effects of afferent stimulation

    PubMed Central

    Rybak, Ilya A; Stecina, Katinka; Shevtsova, Natalia A; McCrea, David A

    2006-01-01

    A computational model of the mammalian spinal cord circuitry incorporating a two-level central pattern generator (CPG) with separate half-centre rhythm generator (RG) and pattern formation (PF) networks has been developed from observations obtained during fictive locomotion in decerebrate cats. Sensory afferents have been incorporated in the model to study the effects of afferent stimulation on locomotor phase switching and step cycle period and on the firing patterns of flexor and extensor motoneurones. Here we show that this CPG structure can be integrated with reflex circuits to reproduce the reorganization of group I reflex pathways occurring during locomotion. During the extensor phase of fictive locomotion, activation of extensor muscle group I afferents increases extensor motoneurone activity and prolongs the extensor phase. This extensor phase prolongation may occur with or without a resetting of the locomotor cycle, which (according to the model) depends on the degree to which sensory input affects the RG and PF circuits, respectively. The same stimulation delivered during flexion produces a temporary resetting to extension without changing the timing of following locomotor cycles. The model reproduces this behaviour by suggesting that this sensory input influences the PF network without affecting the RG. The model also suggests that the different effects of flexor muscle nerve afferent stimulation observed experimentally (phase prolongation versus resetting) result from opposing influences of flexor group I and II afferents on the PF and RG circuits controlling the activity of flexor and extensor motoneurones. The results of modelling provide insights into proprioceptive control of locomotion. PMID:17008375

  7. Pharmacologically Distinct Nicotinic Acetylcholine Receptors Drive Efferent-Mediated Excitation in Calyx-Bearing Vestibular Afferents

    PubMed Central

    Kewin, Kevin; Jordan, Paivi M.; Cameron, Peter; Klapczynski, Marcin; McIntosh, J. Michael; Crooks, Peter A.; Dwoskin, Linda P.; Lysakowski, Anna

    2015-01-01

    Electrical stimulation of vestibular efferent neurons rapidly excites the resting discharge of calyx/dimorphic (CD) afferents. In turtle, this excitation arises when acetylcholine (ACh), released from efferent terminals, directly depolarizes calyceal endings by activating nicotinic ACh receptors (nAChRs). Although molecular biological data from the peripheral vestibular system implicate most of the known nAChR subunits, specific information about those contributing to efferent-mediated excitation of CD afferents is lacking. We sought to identify the nAChR subunits that underlie the rapid excitation of CD afferents and whether they differ from α9α10 nAChRs on type II hair cells that drive efferent-mediated inhibition in adjacent bouton afferents. We recorded from CD and bouton afferents innervating the turtle posterior crista during electrical stimulation of vestibular efferents while applying several subtype-selective nAChR agonists and antagonists. The α9α10 nAChR antagonists, α-bungarotoxin and α-conotoxin RgIA, blocked efferent-mediated inhibition in bouton afferents while leaving efferent-mediated excitation in CD units largely intact. Conversely, 5-iodo-A-85380, sazetidine-A, varenicline, α-conotoxin MII, and bPiDDB (N,N-dodecane-1,12-diyl-bis-3-picolinium dibromide) blocked efferent-mediated excitation in CD afferents without affecting efferent-mediated inhibition in bouton afferents. This pharmacological profile suggested that calyceal nAChRs contain α6 and β2, but not α9, nAChR subunits. Selective blockade of efferent-mediated excitation in CD afferents distinguished dimorphic from calyx afferents by revealing type II hair cell input. Dimorphic afferents differed in having higher mean discharge rates and a mean efferent-mediated excitation that was smaller in amplitude yet longer in duration. Molecular biological data demonstrated the expression of α9 in turtle hair cells and α4 and β2 in associated vestibular ganglia. PMID:25716861

  8. Synaptic ultrastructure changes in trigeminocervical complex post trigeminal nerve injury

    PubMed Central

    Park, John; Trinh, Van Nancy; Sears-Kraxberger, Ilse; Li, Kang-Wu; Steward, Oswald; Luo, Z. David

    2015-01-01

    Trigeminal nerves collecting sensory information from the orofacial area synapse on second order neurons in the dorsal horn of subnucleus caudalis and cervical C1/C2 spinal cord (Vc/C2, or trigeminocervical complex), which is critical for sensory information processing. Injury to the trigeminal nerves may cause maladaptive changes in synaptic connectivity that plays an important role in chronic pain development. Here, we examined whether injury to the infraorbital nerve, a branch of the trigeminal nerves, led to synaptic ultrastructural changes when the injured animals have developed neuropathic pain states. Transmission electron microscopy was used to examine synaptic profiles in Vc/C2 at three-weeks post-injury, corresponding to the time of peak behavioral hypersensitivity following chronic constriction injury to the infraorbital nerve (CCI-ION). Using established criteria, synaptic profiles were classified as associated with excitatory (R-), inhibitory (F-), and primary afferent (C-) terminals. Each type was counted within the superficial dorsal horn of the Vc/C2 and the means from each rat were compared between sham and injured animals; synaptic contact length was also measured. The overall analysis indicates that rats with orofacial pain states had increased numbers and decreased mean synaptic length of R-profiles within the Vc/C2 superficial dorsal horn (lamina I) three-weeks post CCI-ION. Increases in the number of excitatory synapses in the superficial dorsal horn of Vc/C2 could lead to enhanced activation of nociceptive pathways, contributing to the development of orofacial pain states. PMID:26132987

  9. Involvement of capsaicin-sensitive afferents and the Transient Receptor Potential Vanilloid 1 Receptor in xylene-induced nocifensive behaviour and inflammation in the mouse.

    PubMed

    Sándor, Katalin; Helyes, Zsuzsanna; Elekes, Krisztián; Szolcsányi, János

    2009-02-27

    The inflammatory actions of xylene, an aromatic irritant and sensitizing agent, were described to be predominantly neurogenic in the rat, but the mechanism and the role of the Transient Receptor Potential Vanilloid 1 (TRPV1) capsaicin receptor localized on a subpopulation of sensory nerves has not been elucidated. This paper characterizes the involvement of capsaicin-sensitive afferents and the TRPV1 receptor in nociceptive and acute inflammatory effects of xylene in the mouse. Topical application of xylene on the paw induced a short, intensive nocifensive behaviour characterized by paw liftings and shakings, which was more intensive in Balb/c than in C57Bl/6 mice. Genetic deletion of the TRPV1 receptor as well as destroying capsaicin-sensitive nerve terminals with resiniferatoxin (RTX) pretreatment markedly reduced, but did not abolish nocifensive behaviours. In respect to the xylene-induced plasma protein extravasation detected by Evans blue leakage, significant difference was neither observed between the Balb/c and C57Bl/6 strains, nor the ear and the dorsal paw skin. These inflammatory responses were diminished in the RTX pretreated group, but not in the TRPV1 gene-deleted one. Injection of the antioxidant N-acetylcysteine 15min prior to xylene smearing significantly reduced plasma protein extravasation at both sites. These results demonstrate that xylene-induced acute nocifensive behaviour is mediated by capsaicin-sensitive afferents via TRPV1 receptor activation in mice. Neurogenic inflammatory components play an important role in xylene-induced plasma protein extravasation, but independently of the TRPV1 ion channel. Reactive oxygen or carbonyl species participate in this process presumably via stimulation of the TRPA1 channel.

  10. The auriculo-vagal afferent pathway and its role in seizure suppression in rats

    PubMed Central

    2013-01-01

    Background The afferent projections from the auricular branch of the vagus nerve (ABVN) to the nucleus tractus solitaries (NTS) have been proposed as the anatomical basis for the increased parasympathetic tone seen in auriculo-vagal reflexes. As the afferent center of the vagus nerve, the NTS has been considered to play roles in the anticonvulsant effect of cervical vagus nerve stimulation (VNS). Here we proposed an “auriculo-vagal afferent pathway” (AVAP), by which transcutaneous auricular vagus nerve stimulation (ta-VNS) suppresses pentylenetetrazol (PTZ)-induced epileptic seizures by activating the NTS neurons in rats. Results The afferent projections from the ABVN to the NTS were firstly observed in rats. ta-VNS increased the first grand mal latency of the epileptic seizure and decreased the seizure scores in awake rats. Furthermore, when the firing rates of the NTS neurons decreased, epileptiform activity manifested as electroencephalogram (EEG) synchronization increased with 0.37±0.12 s delay in anaesthetized rats. The change of instantaneous frequency, mean frequency of the NTS neurons was negative correlated with the amplitude of the epileptic activity in EEG traces. ta-VNS significantly suppressed epileptiform activity in EEG traces via increasing the firing rates of the neurons of the NTS. In comparison with tan-VNS, the anticonvulsant durations of VNS and ta-VNS were significantly longer (P<0.01). There was no significant difference between the anticonvulsant durations of VNS and ta-VNS (P>0.05). The anticonvulsant effect of ta-VNS was weakened by reversible cold block of the NTS. Conclusions There existed an anatomical relationship between the ABVN and the NTS, which strongly supports the concept that ta-VNS has the potential for suppressing epileptiform activity via the AVAP in rats. ta-VNS will provide alternative treatments for neurological disorders, which can avoid the disadvantage of VNS. PMID:23927528

  11. [Effects of pulpal inflammation on the activities of periodontal mechanoreceptive afferent fibers].

    PubMed

    Matsumoto, Hiroyuki

    2010-06-01

    Response properties of periodontal single afferents were investigated in cats with inflammatory irritant-induced pulpitis. A deep dentin cavity was prepared on the right mandibular canine in order to apply an inflammatory agent and small fiber excitant, allyl-isothiocyanate (mustard oil: MO), and single afferents innervating the canine periodontal mechanoreceptor were dissected from the mandibular nerve bundle by examining impulse responses while applying mechanical stimuli to the tip of the crown. Evoked impulses by mechanical stimuli were increased in number for 15 minutes with MO application to the pulp when compared with those with mineral oil. The mechanoreceptive thresholds of single nerve fibers were decreased after the MO application to the pulp when compared with those with mineral oil. These results suggest that the alteration of responses in the periodontal afferent fiber, or the peripheral sensitization, can be produced by MO-induced pulpal inflammation probably due to the axon reflex mechanism in the furcating branches of nerve fibers innervating both the tooth pulp and periodontal ligament.

  12. Manipulation of isolated brain nerve terminals by an external magnetic field using D-mannose-coated γ-Fe2O3 nano-sized particles and assessment of their effects on glutamate transport

    PubMed Central

    Krisanova, Natalia; Borуsov, Arsenii; Sivko, Roman; Ostapchenko, Ludmila; Babic, Michal; Horak, Daniel

    2014-01-01

    Summary The manipulation of brain nerve terminals by an external magnetic field promises breakthroughs in nano-neurotechnology. D-Mannose-coated superparamagnetic nanoparticles were synthesized by coprecipitation of Fe(II) and Fe(III) salts followed by oxidation with sodium hypochlorite and addition of D-mannose. Effects of D-mannose-coated superparamagnetic maghemite (γ-Fe2O3) nanoparticles on key characteristics of the glutamatergic neurotransmission were analysed. Using radiolabeled L-[14C]glutamate, it was shown that D-mannose-coated γ-Fe2O3 nanoparticles did not affect high-affinity Na+-dependent uptake, tonic release and the extracellular level of L-[14C]glutamate in isolated rat brain nerve terminals (synaptosomes). Also, the membrane potential of synaptosomes and acidification of synaptic vesicles was not changed as a result of the application of D-mannose-coated γ-Fe2O3 nanoparticles. This was demonstrated with the potential-sensitive fluorescent dye rhodamine 6G and the pH-sensitive dye acridine orange. The study also focused on the analysis of the potential use of these nanoparticles for manipulation of nerve terminals by an external magnetic field. It was shown that more than 84.3 ± 5.0% of L-[14C]glutamate-loaded synaptosomes (1 mg of protein/mL) incubated for 5 min with D-mannose-coated γ-Fe2O3 nanoparticles (250 µg/mL) moved to an area, in which the magnet (250 mT, gradient 5.5 Т/m) was applied compared to 33.5 ± 3.0% of the control and 48.6 ± 3.0% of samples that were treated with uncoated nanoparticles. Therefore, isolated brain nerve terminals can be easily manipulated by an external magnetic field using D-mannose-coated γ-Fe2O3 nanoparticles, while the key characteristics of glutamatergic neurotransmission are not affected. In other words, functionally active synaptosomes labeled with D-mannose-coated γ-Fe2O3 nanoparticles were obtained. PMID:24991515

  13. Manipulation of isolated brain nerve terminals by an external magnetic field using D-mannose-coated γ-Fe2O3 nano-sized particles and assessment of their effects on glutamate transport.

    PubMed

    Borisova, Tatiana; Krisanova, Natalia; Borуsov, Arsenii; Sivko, Roman; Ostapchenko, Ludmila; Babic, Michal; Horak, Daniel

    2014-01-01

    The manipulation of brain nerve terminals by an external magnetic field promises breakthroughs in nano-neurotechnology. D-Mannose-coated superparamagnetic nanoparticles were synthesized by coprecipitation of Fe(II) and Fe(III) salts followed by oxidation with sodium hypochlorite and addition of D-mannose. Effects of D-mannose-coated superparamagnetic maghemite (γ-Fe2O3) nanoparticles on key characteristics of the glutamatergic neurotransmission were analysed. Using radiolabeled L-[(14)C]glutamate, it was shown that D-mannose-coated γ-Fe2O3 nanoparticles did not affect high-affinity Na(+)-dependent uptake, tonic release and the extracellular level of L-[(14)C]glutamate in isolated rat brain nerve terminals (synaptosomes). Also, the membrane potential of synaptosomes and acidification of synaptic vesicles was not changed as a result of the application of D-mannose-coated γ-Fe2O3 nanoparticles. This was demonstrated with the potential-sensitive fluorescent dye rhodamine 6G and the pH-sensitive dye acridine orange. The study also focused on the analysis of the potential use of these nanoparticles for manipulation of nerve terminals by an external magnetic field. It was shown that more than 84.3 ± 5.0% of L-[(14)C]glutamate-loaded synaptosomes (1 mg of protein/mL) incubated for 5 min with D-mannose-coated γ-Fe2O3 nanoparticles (250 µg/mL) moved to an area, in which the magnet (250 mT, gradient 5.5 Т/m) was applied compared to 33.5 ± 3.0% of the control and 48.6 ± 3.0% of samples that were treated with uncoated nanoparticles. Therefore, isolated brain nerve terminals can be easily manipulated by an external magnetic field using D-mannose-coated γ-Fe2O3 nanoparticles, while the key characteristics of glutamatergic neurotransmission are not affected. In other words, functionally active synaptosomes labeled with D-mannose-coated γ-Fe2O3 nanoparticles were obtained.

  14. Peripheral Afferent Mechanisms Underlying Acupuncture Inhibition of Cocaine Behavioral Effects in Rats

    PubMed Central

    Lee, Bong Hyo; Bae, Jong Han; Kim, Kwang Joong; Steffensen, Scott C.; Leem, Joong Woo; Yang, Chae Ha; Kim, Hee Young

    2013-01-01

    Administration of cocaine increases locomotor activity by enhancing dopamine transmission. To explore the peripheral mechanisms underlying acupuncture treatment for drug addiction, we developed a novel mechanical acupuncture instrument (MAI) for objective mechanical stimulation. The aim of this study was to evaluate whether acupuncture inhibition of cocaine-induced locomotor activity is mediated through specific peripheral nerves, the afferents from superficial or deep tissues, or specific groups of nerve fibers. Mechanical stimulation of acupuncture point HT7 with MAI suppressed cocaine-induced locomotor activity in a stimulus time-dependent manner, which was blocked by severing the ulnar nerve or by local anesthesia. Suppression of cocaine-induced locomotor activity was elicited after HT7 stimulation at frequencies of either 50 (for Meissner corpuscles) or 200 (for Pacinian corpuscles) Hz and was not affected by block of C/Aδ-fibers in the ulnar nerve with resiniferatoxin, nor generated by direct stimulation of C/Aδ-fiber afferents with capsaicin. These findings suggest that HT7 inhibition of cocaine-induced locomotor activity is mediated by A-fiber activation of ulnar nerve that originates in superficial and deep tissue. PMID:24260531

  15. Diverse mechanisms for assembly of branchiomeric nerves.

    PubMed

    Cox, Jane A; Lamora, Angela; Johnson, Stephen L; Voigt, Mark M

    2011-09-15

    The formation of branchiomeric nerves (cranial nerves V, VII, IX and X) from their sensory, motor and glial components is poorly understood. The current model for cranial nerve formation is based on the Vth nerve, in which sensory afferents are formed first and must enter the hindbrain in order for the motor efferents to exit. Using transgenic zebrafish lines to discriminate between motor neurons, sensory neurons and peripheral glia, we show that this model does not apply to the remaining three branchiomeric nerves. For these nerves, the motor efferents form prior to the sensory afferents, and their pathfinding show no dependence on sensory axons, as ablation of cranial sensory neurons by ngn1 knockdown had no effect. In contrast, the sensory limbs of the IXth and Xth nerves (but not the Vth or VIIth) were misrouted in gli1 mutants, which lack hindbrain bmn, suggesting that the motor efferents are crucial for appropriate sensory axon projection in some branchiomeric nerves. For all four nerves, peripheral glia were the intermediate component added and had a critical role in nerve integrity but not in axon guidance, as foxd3 null mutants lacking peripheral glia exhibited defasciculation of gVII, gIX, and gX axons. The bmn efferents were unaffected in these mutants. These data demonstrate that multiple mechanisms underlie formation of the four branchiomeric nerves. For the Vth, sensory axons initiate nerve formation, for the VIIth the sensory and motor limbs are independent, and for the IXth/Xth the motor axons initiate formation. In all cases the glia are patterned by the initiating set of axons and are needed to maintain axon fasciculation. These results reveal that coordinated interactions between the three neural cell types in branchiomeric nerves differ according to their axial position.

  16. Hydrogen sulfide determines HNO-induced stimulation of trigeminal afferents.

    PubMed

    Wild, Vanessa; Messlinger, Karl; Fischer, Michael J M

    2015-08-18

    Endogenous NO and hydrogen sulfide form HNO, which causes CGRP release via TRPA1 channel activation in sensory nerves. In the present study, stimulation of intact trigeminal afferent neuron preparations with NO donors, Na2S or both was analyzed by measuring CGRP release as an index of mass activation. Combined stimulation was able to activate all parts of the trigeminal system and acted synergistic compared to stimulation with both substances alone. To investigate the contribution of both substances, we varied their ratio and tracked intracellular calcium in isolated neurons. Our results demonstrate that hydrogen sulfide is the rate-limiting factor for HNO formation. CGRP has a key role in migraine pathophysiology and HNO formation at all sites of the trigeminal system should be considered for this novel means of activation.

  17. Melittin selectively activates capsaicin-sensitive primary afferent fibers.

    PubMed

    Shin, Hong Kee; Kim, Jin Hyuk

    2004-08-06

    Whole bee venom (WBV)-induced pain model has been reported to be very useful for the study of pain. However, the major constituent responsible for the production of pain by WBV is not apparent. Intraplantar injection of WBV and melittin dramatically reduced mechanical threshold, and increased flinchings and paw thickness. In behavioral experiments, capsaicin pretreatment almost completely prevented WBV- and melittin-induced reduction of mechanical threshold and flinchings. Intraplantar injection of melittin increased discharge rate of dorsal horn neurons only with C fiber input from peripheral receptive field, which was completely blocked by topical application of capsaicin to sciatic nerve. These results suggest that both melittin and WBV induce nociceptive responses by selective activation of capsaicin-sensitive afferent fibers.

  18. Distribution of voltage-gated potassium (Kv) and hyperpolarization-activated (HCN) channels in sensory afferent fibers in the rat carotid body

    PubMed Central

    Buniel, Maria; Glazebrook, Patricia A.; Ramirez-Navarro, Angelina; Kunze, Diana L.

    2008-01-01

    The chemosensory glomus cells of the carotid body (CB) detect changes in O2-tension. Carotid sinus nerve fibers, which originate from peripheral sensory neurons located within the petrosal ganglion, innervate the CB. Release of transmitter from glomus cells activates the sensory afferent fibers to transmit information to the nucleus of the solitary tract in the brainstem. The ion channels expressed within the sensory nerve terminals play an essential role in the ability of the terminal to initiate action potentials in response to transmitter-evoked depolarization. However, with a few exceptions, the identity of ion channels expressed in these peripheral nerve fibers is unknown. This study addresses the expression of voltage-gated channels in the sensory fibers with a focus on channels that set the resting membrane potential and regulate discharge patterns. Using immunohistochemistry and fluorescence confocal microscopy, potassium channel subunits and HCN (hyperpolarization-activated) family members were localized both in petrosal neurons that expressed tyrosine hydroxylase, and the CSN axons within the carotid body. Channels contributing to resting membrane potential including HCN2, responsible in part for Ih current, and the KCNQ2 and KCNQ5 subunits thought to underlie the neuronal “M current” were identified in the sensory neurons and their axons innervating the carotid body. In addition, the results presented here demonstrate expression of several potassium channels that shape the action potential and the frequency of discharge including Kv1.4, Kv1.5, Kv4.3, KCa (BK). The role of these channels should be considered in interpretation of the fiber discharge in response to perturbation of the carotid body environment. PMID:18668683

  19. Retinal Afferent Ingrowth to Neocortical Transplants in the Adult Rat Superior Colliculus is due to the Regeneration of Damaged Axons

    PubMed Central

    Ross, D. T.; Das, G. D.

    1994-01-01

    Retinal afferent ingrowth to embryonic neural transplants in the adult rat superior colliculus may represent either sprouting of intact axons or the regeneration of transected axons. If ingrowth represents regeneration of damaged retinofugai axons, then lesions that axotomize more retinofugal axons at the transplantation site should induce greater retinal afferent ingrowth. Alternately, if ingrowth represents terminal or collateral sprouting of intact retinofugal axons at or near the transplant/host optic layer interface, then the magnitude of retinal afferent ingrowth should be directly related to the total area of this interface. To test between these two hypotheses surgical knife wounds were made either parallel (in the sagittal plane) or perpendicular (in the transverse plane) to the course of axons in the stratum opticum, embryonic neocortical tissue was transplanted at the coordinates of these tectal slits, and retinal afferent ingrowth visualized 1-90 days after surgery using anterogradely transported HRP. A zone of traumatic reaction (ztr) in the optic layers was seen in every case, characterized by hypertrophied axons and swollen terminal clubs at 1 day. Between 30 and 90 days the damaged retinofugal axons in the zone formed dense fascicles and neuroma-like tangles. Retinal afferent ingrowth occurred only across transplant interface regions with the ztr. The magnitude of ingrowth was directly related to the area of the ztr interface and not the total optic layer interface area. Retinal afferent ingrowth appears to reflect the intrinsic regenerative capacity of adult mammalian retinal ganglion cells and not sprouting of undamaged axons. PMID:7703292

  20. TRPA1-expressing primary afferents synapse with a morphologically identified subclass of substantia gelatinosa neurons in the adult rat spinal cord.

    PubMed

    Uta, Daisuke; Furue, Hidemasa; Pickering, Anthony E; Rashid, Md Harunor; Mizuguchi-Takase, Hiroko; Katafuchi, Toshihiko; Imoto, Keiji; Yoshimura, Megumu

    2010-06-01

    The TRPA1 channel has been proposed to be a molecular transducer of cold and inflammatory nociceptive signals. It is expressed on a subset of small primary afferent neurons both in the peripheral terminals, where it serves as a sensor, and on the central nerve endings in the dorsal horn. The substantia gelatinosa (SG) of the spinal cord is a key site for integration of noxious inputs. The SG neurons are morphologically and functionally heterogeneous and the precise synaptic circuits of the SG are poorly understood. We examined how activation of TRPA1 channels affects synaptic transmission onto SG neurons using whole-cell patch-clamp recordings and morphological analyses in adult rat spinal cord slices. Cinnamaldehyde (TRPA1 agonist) elicited a barrage of excitatory postsynaptic currents (EPSCs) in a subset of the SG neurons that responded to allyl isothiocyanate (less specific TRPA1 agonist) and capsaicin (TRPV1 agonist). Cinnamaldehyde evoked EPSCs in vertical and radial but not islet or central SG cells. Notably, cinnamaldehyde produced no change in inhibitory postsynaptic currents and nor did it produce direct postsynaptic effects. In the presence of tetrodotoxin, cinnamaldehyde increased the frequency but not amplitude of miniature EPSCs. Intriguingly, cinnamaldehyde had a selective inhibitory action on monosynaptic C- (but not Adelta-) fiber-evoked EPSCs. These results indicate that activation of spinal TRPA1 presynaptically facilitates miniature excitatory synaptic transmission from primary afferents onto vertical and radial cells to initiate action potentials. The presence of TRPA1 channels on the central terminals raises the possibility of bidirectional modulatory action in morphologically identified subclasses of SG neurons.

  1. Neural Blockade Anaesthesia of the Mandibular Nerve and Its Terminal Branches: Rationale for Different Anaesthetic Techniques Including Their Advantages and Disadvantages

    PubMed Central

    Khoury, Jason; Townsend, Grant

    2011-01-01

    Anaesthesia of structures innervated by the mandibular nerve is necessary to provide adequate pain control when performing dental and localised surgical procedures. To date, numerous techniques have been described and, although many of these methods are not used routinely, there are some situations where their application may be indicated. Patient factors as well as anatomical variability of the mandibular nerve and associated structures dictate that no one technique can be universally applied with a 100% success rate. This fact has led to a proliferation of alternative techniques that have appeared in the literature. This selective review of the literature provides a brief description of the different techniques available to the clinician as well as the underlying anatomy which is fundamental to successfully anaesthetising the mandibular nerve. PMID:21716730

  2. Botulinum toxin in Migraine: Role of transport in trigemino-somatic and trigemino-vascular afferents

    PubMed Central

    Roshni, Ramachandran; Carmen, Lam; Yaksh Tony, L

    2015-01-01

    Migraine secondary to meningeal input is referred to extracranial regions innervated by somatic afferents that project to homologous regions in the trigeminal nucleus caudalis (TNC). Reported efficacy of extracranial botulinum toxin (BoNT) in treating migraine is surprising since a local extracranial effect of BoNT cannot account for its effect upon meningeal input. We hypothesize that intradermal BoNT acts through central transport in somatic afferents. Anesthetized C57Bl/6 mice (male) received unilateral supraorbital (SO) injections of BoNT-B (1.5 U/40 μl) or saline. 3 days later, mice received ipsilateral (ipsi) -SO capsaicin (2.5 μg/30 μl) or meningeal capsaicin (4 μl of 1mg/ml). Pre-treatment with ipsi-SO BONT-B i) decreased nocicsponsive ipsilateral wiping behavior following ipsi-SO capsaicin; ii) produced cleavage of VAMP in the V1 region of ipsi-TG and in TG neurons showing WGA after SO injection; iii) reduced expression of c-fos in ipsi-TNC following ipsi-SO capsaicin; iv) reduced c-fos activation and NK-1 internalization in ipsi-TNC secondary to ipsi-meningeal capsaicin; vi) SO WGA did not label dural afferents. We conclude that BoNT-B is taken up by peripheral afferents and transported to central terminals where it inhibits transmitter release resulting in decreased activation of second order neurons. Further, this study supports the hypothesis that SO BoNT exerts a trans-synaptic action on either the second order neuron (which receives convergent input from the meningeal afferent) or the terminal/TG of the converging meningeal afferent. PMID:25958249

  3. Botulinum toxin in migraine: Role of transport in trigemino-somatic and trigemino-vascular afferents.

    PubMed

    Ramachandran, Roshni; Lam, Carmen; Yaksh, Tony L

    2015-07-01

    Migraine secondary to meningeal input is referred to extracranial regions innervated by somatic afferents that project to homologous regions in the trigeminal nucleus caudalis (TNC). Reported efficacy of extracranial botulinum toxin (BoNT) in treating migraine is surprising since a local extracranial effect of BoNT cannot account for its effect upon meningeal input. We hypothesize that intradermal BoNT acts through central transport in somatic afferents. Anesthetized C57Bl/6 mice (male) received unilateral supraorbital (SO) injections of BoNT-B (1.5 U/40 μl) or saline. 3 days later, mice received ipsilateral (ipsi)-SO capsaicin (20 μl of 0.5mM solution) or meningeal capsaicin (4 μl of 0.35 μM). Pre-treatment with ipsi-SO BoNT-B i) decreased nocicsponsive ipsilateral wiping behavior following ipsi-SO capsaicin; ii) produced cleavage of VAMP in the V1 region of ipsi-TG and in TG neurons showing WGA after SO injection; iii) reduced expression of c-fos in ipsi-TNC following ipsi-SO capsaicin; iv) reduced c-fos activation and NK-1 internalization in ipsi-TNC secondary to ipsi-meningeal capsaicin; and vi) SO WGA did not label dural afferents. We conclude that BoNT-B is taken up by peripheral afferents and transported to central terminals where it inhibits transmitter release resulting in decreased activation of second order neurons. Further, this study supports the hypothesis that SO BoNT exerts a trans-synaptic action on either the second order neuron (which receives convergent input from the meningeal afferent) or the terminal/TG of the converging meningeal afferent.

  4. [Anatomical variants of the medial calcaneal nerve and the Baxter nerve in the tarsal tunnel].

    PubMed

    Martín-Oliva, X; Elgueta-Grillo, J; Veliz-Ayta, P; Orosco-Villaseñor, S; Elgueta-Grillo, M; Viladot-Perice, R

    2013-01-01

    The tarsal tunnel is composed of the posterior border of the medial malleoulus, the posterior aspect of the talus and the medial aspect of the calcaneus. The medial calcaneal nerve emerges from the posterior aspect of the posterior tibial nerve in 75% of cases and from the lateral plantar nerve in the remaining 25%. Finally, the medial calcaneal nerve ends as a single terminal branch in 79% of cases and in numerous terminal branches in the remaining 21%. To describe the anatomical variants of the posterior tibial nerve and its terminal branches. To describe the steps for tarsal tunnel release. To describe Baxter nerve release. The anatomical variants of the posterior tibial nerve and its terminal branches within the tarsal tunnel were studied. Then the Lam technique was performed; it consists of: 1) opening of the laciniate ligament, 2) opening of the fascia over the abductor hallucis muscle, 3) exoneurolysis of the posterior tibial nerve and its terminal branches, identifying the emergence and pathway of the medial calcaneal branch, the lateral plantar nerve and its Baxter nerve branch and the medial plantar nerve. Baxter nerve was found in 100% of cases. In 100% of cases in our series the nerve going to the abductor digiti minimi muscle of the foot was found; 87.5% of cases had two terminal branches. The dissections proved that a crucial step was the release of the distal tarsal tunnel.

  5. [Innervation of the anterior byssus retractor muscle (ABRM) in Mytilus edulis L. III. Histochemical localisation of the terminal nerves through 5-hydroxytryptamine (author's transl)].

    PubMed

    Gilloteaux, J

    1977-04-04

    Detection of nerve structures containing 5-HT were described in the anterior byssus retractor muscle (ABRM) in Mytilus edulis L. after using the fluorescence microscope technique of Flack. We are able to confirm our previous results and assumptions given by histology and electron microscope studies: the neuromuscular "en passage" junctions, largely distributed within the ABRM, contain 5-HT.

  6. Effects of electrical and natural stimulation of skin afferents on the gamma-spindle system of the triceps surae muscle.

    PubMed

    Johansson, H; Sjölander, P; Sojka, P; Wadell, I

    1989-08-01

    The aim of the present study was to investigate the extent to which skin receptors might influence the responses of primary muscle spindle afferents via reflex actions on the fusimotor system. The experiments were performed on 43 cats anaesthetized with alpha-chloralose. The alterations in fusimotor activity were assessed from changes in the responses of the muscle spindle afferents to sinusoidal stretching of their parent muscles (triceps surae and plantaris). The mean rate of firing and the modulation of the afferent response were determined. Control measurements were made in absence of any cutaneous stimulation. Tests were made (a) during physiological stimulation of skin afferents of the ipsilateral pad or of the contralateral hindlimb, or (b) during repetitive electrical stimulation of the sural nerve in the ipsilateral hindlimb, or of sural or superficial peroneal nerve in the contralateral hindlimb. Of the total number of 113 units tested with repetitive electrical stimulation of the ipsilateral sural nerve (at 20 Hz), 24.8% exhibited predominantly dynamic fusimotor reflexes, 5.3% mixed or predominantly static fusimotor reflexes. One unit studied in a preparation with intact spinal cord exhibited static reflexes at low stimulation intensities and dynamic ones at higher stimulation strengths. The remaining units (69%) were uninfluenced. When the receptor-bearing muscle was held at constant length and a train of stimuli (at 20 Hz) was applied to the ipsilateral sural nerve, the action potentials in the primary muscle spindle afferent could be stimulus-locked to the 3rd or 4th pulse in the train (and to the pulses following thereafter), with a latency of about 24 ms from the effective pulse. This 1:1 pattern of driving seemed to be mediated via static and/or dynamic fusimotor neurons. Natural stimulation influenced comparatively few units (3 of 65 units tested from the ipsilateral pad and 10 of 98 tested from the contralateral hindlimb), but when the effects

  7. AB320. SPR-47 Monitoring nerve activity during bladder filling in a rat model

    PubMed Central

    Tiwari, Ekta; Lemay, Michel A.; Braverman, Alan S.; Obeid, Iyad; Barbe, Mary F.; Ruggieri, Michael R.

    2016-01-01

    Objective Surgical rerouting of neuronal pathways may allow functional reinnervation of the bladder. We aim to develop techniques to monitor afferent (sensory) nerve activity during bladder filling in normal intact bladders for eventual application to monitoring sensory reinnervation of the bladder following nerve transfer. Methods Electroneurogram recordings were performed in anesthetized rats under isoflurane (1–2% induction dose, inhalation) of: (I) sciatic nerves during stimulation of the hindpaw with Semmes-Weinstein monofilaments of varying forces (10–300 g); and (II) bladder nerves during bladder filling with infusion rate of 0.5 mL/min, in acute experiments. Bipolar cuff electrodes were wrapped around the sciatic nerve (n=7) and ureter (and associated bladder nerves) proximal to the bladder wall (n=7), to record sciatic and bladder nerve discharges, respectively. The sciatic nerve was transected between the spinal cord and the electrode, to eliminate efferent nerve signals and record afferent fibers discharge only with hindpaw stimulation. Whereas, recordings were made of the discharges of both afferent and efferent fibers from bladder nerves during bladder filling. All recordings were performed using a low noise amplifier (SR560, filtered 300 Hz–10 kHz, gain ×10k), sampled at 20 kHz using PowerLab software (AD Instruments) and displayed using LabChart software. Bladder pressure was also recorded during filling. Results Sciatic nerve recordings consistently showed increased afferent fibers discharge with increased size of monofilament used to stimulate the hindpaw, with the highest discharge observed with the 300 g monofilament and lowest with 10 g. In contrast, recording from bladder nerves showed that combined afferent and efferent discharges increased substantially in response to bladder filling in 2 of 7 rats, and increased moderately in 2 other rats. However, there was no response in the remaining rats, perhaps due to nerve damage during cuff

  8. Afferent Connectivity of the Zebrafish Habenulae

    PubMed Central

    Turner, Katherine J.; Hawkins, Thomas A.; Yáñez, Julián; Anadón, Ramón; Wilson, Stephen W.; Folgueira, Mónica

    2016-01-01

    The habenulae are bilateral nuclei located in the dorsal diencephalon that are conserved across vertebrates. Here we describe the main afferents to the habenulae in larval and adult zebrafish. We observe afferents from the subpallium, nucleus rostrolateralis, posterior tuberculum, posterior hypothalamic lobe, median raphe; we also see asymmetric afferents from olfactory bulb to the right habenula, and from the parapineal to the left habenula. In addition, we find afferents from a ventrolateral telencephalic nucleus that neurochemical and hodological data identify as the ventral entopeduncular nucleus (vENT), confirming and extending observations of Amo et al. (2014). Fate map and marker studies suggest that vENT originates from the diencephalic prethalamic eminence and extends into the lateral telencephalon from 48 to 120 hour post-fertilization (hpf). No afferents to the habenula were observed from the dorsal entopeduncular nucleus (dENT). Consequently, we confirm that the vENT (and not the dENT) should be considered as the entopeduncular nucleus “proper” in zebrafish. Furthermore, comparison with data in other vertebrates suggests that the vENT is a conserved basal ganglia nucleus, being homologous to the entopeduncular nucleus of mammals (internal segment of the globus pallidus of primates) by both embryonic origin and projections, as previously suggested by Amo et al. (2014). PMID:27199671

  9. N-acetylcysteine alters apoptotic gene expression in axotomised primary sensory afferent subpopulations.

    PubMed

    Reid, Adam J; Shawcross, Susan G; Hamilton, Alex E; Wiberg, Mikael; Terenghi, Giorgio

    2009-10-01

    Novel approaches are required in peripheral nerve injury management because current surgical techniques, which do not address axotomy-induced neuronal death, lead to deficient sensory recovery. Sensory neuronal death has functional preference with cutaneous neurons dying in great numbers whilst muscle afferents survive axotomy. This offers the potential of comparing similar cell types that suffer distinct fates upon nerve injury. Here, a novel approach, combining in vivo rat nerve injury model with laser microdissection and quantitative real-time polymerase chain reaction, identifies crucial disparities in apoptotic gene expression attributable to subpopulations of differing sensory modalities and examines the response to N-acetylcysteine (NAC) therapy. We show that axotomised muscle afferent neurons survive injury due to a neuroprotective response which markedly downregulates Bax and caspase-3 mRNA. In contrast, axotomised cutaneous sensory neurons significantly upregulate caspase-3 and alter both Bcl-2 and Bax expression such that pro-apoptotic Bax predominates. N-Acetylcysteine (NAC) intervention promotes neuroprotection of cutaneous sensory neurons through considerable upregulation of Bcl-2 and downregulation of both Bax and caspase-3 mRNA. The data presented identifies differential activation of apoptotic genes in axotomised neuronal subpopulations. Furthermore, NAC therapy instigates apoptotic gene expression changes in axotomised neurons, thereby offering pharmacotherapeutic potential in the clinical treatment of nerve injury.

  10. Is the vagus nerve stimulation a way to decrease body weight in humans?

    PubMed

    Bugajski, Andrzej; Gil, Krzysztof

    2012-01-01

    Obesity and its complications constitute an important health problem in growing number of people. Behavioral and pharmacological treatment is not much effective and surgical treatment carries too many threats. Promising method to be used is pharmacological or electric manipulation of vagus nerves. Regulation of food intake and energy utilization is a complex process regulated by centers in hypothalamus and brainstem which are receiving information from the peripheral via afferent neural pathways and sending peripherally adequate instructions by efferent neural pathways. In these signals conduction an important role plays vagus nerve. Additionally central nervous system stays under influence of endocrine, paracrine and neuroendocrine signals taking part in these regulations, functioning directly onto the centre or on the afferent neural endings. 80-90% fibers of vagus nerve are afferent fibers, so their action is mainly afferent, but possible contribution of the efferent fibers cannot be excluded. Efferent stimulation induces motility and secretion in the intestinal tract. Afferent unmyelinated C-type fibres of the vagus nerve are more sensitive and easily electrically stimulated. Information from vagus nerve is transmitted to nucleus tractus solitarius, which has projections to nucleus arcuate of the medio-basal hypothalamus, involved in the control of feeding behavior. It is suggested, that interaction onto the vagus nerve (stimulation or blocking) can be an alternative for other ways of obesity treatment. Through the manipulation of the vagus nerve activity the goal is achieved by influence on central nervous system regulating the energy homeostasis.

  11. Allodynia mediated by C-tactile afferents in human hairy skin

    PubMed Central

    Nagi, Saad S; Rubin, Troy K; Chelvanayagam, David K; Macefield, Vaughan G; Mahns, David A

    2011-01-01

    Abstract We recently showed a contribution of low-threshold cutaneous mechanoreceptors to vibration-evoked changes in the perception of muscle pain. Neutral-touch stimulation (vibration) of the hairy skin during underlying muscle pain evoked an overall increase in pain intensity, i.e. allodynia. This effect appeared to be dependent upon cutaneous afferents, as allodynia was abolished by intradermal anaesthesia. However, it remains unclear whether allodynia results from activation of a single class of cutaneous afferents or the convergence of inputs from multiple classes. Intriguingly, no existing human study has examined the contribution of C-tactile (CT) afferents to allodynia. Detailed psychophysical observations were made in 29 healthy subjects (18 males and 11 females). Sustained muscle pain was induced by infusing hypertonic saline (HS: 5%) into tibialis anterior muscle (TA). Sinusoidal vibration (200 Hz–200 μm) was applied to the hairy skin overlying TA. Pain ratings were recorded using a visual analogue scale (VAS). In order to evaluate the role of myelinated and unmyelinated cutaneous afferents in the expression of vibration-evoked allodynia, compression block of the sciatic nerve, and low-dose intradermal anaesthesia (Xylocaine 0.25%) were used, respectively. In addition, the modulation of muscle pain by gentle brushing (1.0 and 3.0 cm s−1) – known to excite CT fibres – was examined. Brushing stimuli were applied to the hairy skin with all fibres intact and following the blockade of myelinated afferents. During tonic muscle pain (VAS 4–6), vibration evoked a significant and reproducible increase in muscle pain (allodynia) that persisted following compression of myelinated afferents. During compression block, the sense of vibration was abolished, but the vibration-evoked allodynia persisted. In contrast, selective anaesthesia of unmyelinated cutaneous afferents abolished the allodynia, whereas the percept of vibration remained unaffected

  12. Comparison of the inhibitory response to tendon and cutaneous afferent stimulation in the human lower limb.

    PubMed

    Rogasch, Nigel C; Burne, John A; Türker, Kemal S

    2012-01-01

    A powerful early inhibition is seen in triceps surae after transcutaneous electrical stimulation of the Achilles tendon [tendon electrical stimulation (TES)]. The aim of the present study was to confirm results from surface electromyogram (SEMG) recordings that the inhibition is not wholly or partly due to stimulation of cutaneous afferents that may lie within range of the tendon electrodes. Because of methodological limitations, SEMG does not reliably identify the time course of inhibitory and excitatory reflex components. This issue was revisited here with an analysis of changes in single motor unit (SMU) firing rate [peristimulus frequencygram (PSF)] and probability [peristimulus time histogram (PSTH)] to reexamine the time course of inhibitory SMU events that follow purely cutaneous (superficial sural) nerve stimulation. Results were then compared with similar data from TES. When compared with the reflex response to TES, sural nerve stimulation resulted in a longer onset latency of the primary inhibition and a weaker effect on SMU firing probability and rate. PSF also revealed that decreased SMU firing rates persisted during the excitation phase in SEMG, suggesting that the initial inhibition was more prolonged than previously reported. In a further study, the transcutaneous SEMG Achilles tendon response was compared with that from direct intratendon stimulation with insulated needle electrodes. This method should attenuate the SEMG response if it is wholly or partly dependent on cutaneous afferents. However, subcutaneous stimulation of the tendon produced similar components in the SEMG, confirming that cutaneous afferents made little or no contribution to the initial inhibition following TES.

  13. Neuronal pathways from foot pad afferents to hindlimb motoneurons in the low spinalized cats.

    PubMed

    Wada, N; Kanda, Y; Takayama, R

    1998-07-01

    Experiments were performed on 16 adult spinalized (L2) cats. Postsynaptic potentials (PSPs) produced by electrical stimulation of afferent nerves innervating foot pads were recorded from hindlimb motoneurons innervating the following hindlimb muscles: the posterior biceps and semitendinosus (PBSt), anterior biceps and semimembranosus (ABSm), lateral gastrocnemius and soleus (LGS), medial gastrocnemius (MG), plantaris (P1), tibialis anterior (TA), popliteus (Pop), flexor digitorum longus and flexor hallucis longus (FDHL) and peroneus longus (Per.l). The rate of occurrence of different types of PSPs (EPSPs, IPSPs and mixed PSPs), the size of the PSPs and their central latencies were analyzed for each group of motoneurons to identify the neural pathways from the afferents innervating foot pads to hindlimb motoneurons. The rates of occurrence of different types of PSPs did not depend on the foot pad stimulated in PBSt, ABSm and LGS motoneurons, but for other groups of motoneurons their rates of occurrence depended on the foot pad stimulated. It was often noted that the size of PSPs in the same motoneurons differed according to the foot pad stimulated. Measurements of the central latencies of the PSPs indicated that the shortest neural pathways for EPSPs and IPSPs were disynaptic (central latencies < 1.8 ms). The functional role of neuronal pathways from afferent nerves innervating foot pads to hindlimb motoneurons could be to maintain stability of the foot during different postural and motor activities.

  14. Short-latency tachycardia evoked by stimulation of muscle and cutaneous afferents.

    PubMed

    Gelsema, A J; Bouman, L N; Karemaker, J M

    1985-04-01

    The short-latency effect on heart rate of peripheral nerve stimulation was studied in decerebrate cats. Selective activation (17-40 microA, 100 Hz, 1 s long) of low-threshold fibers in the nerves to the triceps surae muscle yielded isometric contractions of maximal force that were accompanied by a cardiac cycle length shortening within 0.4 s from the start of stimulation. This effect was abolished by pharmacologically induced neuromuscular blockade. The cardiac cycle length shortening during paralysis reappeared after a 6- to 10-fold increase of the stimulation strength. Cutaneous (sural) nerve stimulation (15-25 microA, 100 Hz, 1 s long) elicited reflex contractions in the stimulated limb, which were also accompanied by a cardiac acceleration with similar latency. Paralysis prevented the reflex contractions and reduced the cardiac response in some cats and abolished it in others. The response reappeared in either case after a 5- to 10-fold increase of the stimulus strength. It is concluded that muscle nerve and cutaneous nerve activity both cause a similar cardiac acceleration with a latency of less than 0.4 s. The response to muscle nerve stimulation is elicited by activity in group III afferents. It is excluded that the cardiac response to nerve stimulation is secondary to a change in the respiratory pattern.

  15. Deep-tissue confocal imaging of the central projections of ovipositor sensory afferents in the Egyptian cotton leafworm, Spodoptera littoralis.

    PubMed

    Seada, Mervat A; Ghaninia, Majid

    2016-03-01

    The pre-ovipositon behavior of moths is largely dependent upon the cues that a gravid female perceives while assessing potential oviposition sites. Assessment of such sites is accomplished, at least in part, by mechanosensory and gustatory sensilla located on the ovipositor whose sensory neurons project into the terminal abdominal ganglion (TAG). Using anterograde backfill staining, confocal laser scanning microscopy, and three dimensional reconstruction, we traced and analyzed the central projections of the sensory neurons housed in the sensilla located on the ovipositor papillae and explored the neuropilar composition of the TAG in the Egyptian cotton leafworm, Spodoptera littoralis. The TAG consists of three fused neuromeres (6-8th Ner) associated with the 6-8th abdominal segments. Within the TAG, and specifically in the 8th neuromere, four unstructured neuropilar compartments are present; the dorso-ipsilateral motor neuropil (MN), the medio-ipsilateral mechanosensory neuropil (MchN), the medio-ipsilateral small gustatory neuropil (GN), and the medio-contralateral posterior ovipositor glomerulus (Og). The Og appears quite compact, with a hollow core free of terminal arborizations. The MchN is further subdivided into 4 unstructured glomeruli in the 8th neuromere, whose afferents are subsequently extended into 3 glomeruli in the 7th and 6th neuromeres. Few neurites of the Og are populated with large dense varicosities reminiscent of neurosecretory vesicles. Given that all ovipositor nerves converge into a common ganglionic center, the TAG, we assume that this ganglion may be a center for coordination of oviposition behaviors, including movements of the ovipositor during assessment of oviposition substrates and egg laying in S. littoralis.

  16. Terminal arbor degeneration (TAD): a novel lesion produced by the antineoplastic agent, paclitaxel

    PubMed Central

    Bennett, Gary J.; Liu, Guo Kai; Xiao, Wen Hua; Jin, Hai Wei; Siau, Chiang

    2011-01-01

    The anti-neoplastic agent, paclitaxel, causes a dose-limiting distal, symmetrical, sensory peripheral neuropathy that is often accompanied by a neuropathic pain syndrome. In a low-dose model of paclitaxel-evoked painful peripheral neuropathy in the rat, we have shown that the drug causes degeneration of intraepidermal nerve fibers (IENFs), i.e., the fibers which give rise to the sensory afferent’s terminal receptor arbour. However, we did not find any evidence for axonal degeneration in samples taken at the mid-nerve level. Here we aimed to determine whether the absence of degenerating peripheral nerve axons was due to sampling a level that was too proximal. We used electron microscopy to study the distal-most branches of the nerves innervating the hind paw glabrous skin of normal and paclitaxel-treated rats. We confirmed that we sampled at a time when IENF degeneration was prominent. Because degeneration might be easier to detect with higher paclitaxel doses, we examined a four-fold cumulative dose range (8–32 mg/kg). We found no evidence of degeneration in the superficial subepidermal axon bundles (sSAB) that are located just a few microns below the epidermal basal lamina. Specifically, for all three dose groups there was no change in the number of sSAB per mm of epidermal border, no change in the number of axons per sSAB, and no change in the diameter of sSAB axons. We conclude that paclitaxel produces a novel type of lesion that is restricted to the afferent axon’s terminal arbor; we name this lesion “terminal arbor degeneration (TAD)”. PMID:21395870

  17. Modulation of synaptic transmission from segmental afferents by spontaneous activity of dorsal horn spinal neurones in the cat.

    PubMed

    Manjarrez, E; Rojas-Piloni, J G; Jimenez, I; Rudomin, P

    2000-12-01

    We examined, in the anaesthetised cat, the influence of the neuronal ensembles producing spontaneous negative cord dorsum potentials (nCDPs) on segmental pathways mediating primary afferent depolarisation (PAD) of cutaneous and group I muscle afferents and on Ia monosynaptic activation of spinal motoneurones. The intraspinal distribution of the field potentials associated with the spontaneous nCDPs indicated that the neuronal ensembles involved in the generation of these potentials were located in the dorsal horn of lumbar segments, in the same region of termination of low-threshold cutaneous afferents. During the occurrence of spontaneous nCDPs, transmission from low-threshold cutaneous afferents to second order neurones in laminae III-VI, as well as transmission along pathways mediating PAD of cutaneous and Ib afferents, was facilitated. PAD of Ia afferents was instead inhibited. Monosynaptic reflexes of flexors and extensors were facilitated during the spontaneous nCDPs. The magnitude of the facilitation was proportional to the amplitude of the 'conditioning' spontaneous nCDPs. This led to a high positive correlation between amplitude fluctuations of spontaneous nCDPs and fluctuations of monosynaptic reflexes. Stimulation of low-threshold cutaneous afferents transiently reduced the probability of occurrence of spontaneous nCDPs as well as the fluctuations of monosynaptic reflexes. It is concluded that the spontaneous nCDPs were produced by the activation of a population of dorsal horn neurones that shared the same functional pathways and involved the same set of neurones as those responding monosynaptically to stimulation of large cutaneous afferents. The spontaneous activity of these neurones was probably the main cause of the fluctuations of the monosynaptic reflexes observed under anaesthesia and could provide a dynamic linkage between segmental sensory and motor pathways.

  18. Modulation of synaptic transmission from segmental afferents by spontaneous activity of dorsal horn spinal neurones in the cat

    PubMed Central

    Manjarrez, E; Rojas-Piloni, J G; Jiménez, I; Rudomin, P

    2000-01-01

    We examined, in the anaesthetised cat, the influence of the neuronal ensembles producing spontaneous negative cord dorsum potentials (nCDPs) on segmental pathways mediating primary afferent depolarisation (PAD) of cutaneous and group I muscle afferents and on Ia monosynaptic activation of spinal motoneurones. The intraspinal distribution of the field potentials associated with the spontaneous nCDPs indicated that the neuronal ensembles involved in the generation of these potentials were located in the dorsal horn of lumbar segments, in the same region of termination of low-threshold cutaneous afferents. During the occurrence of spontaneous nCDPs, transmission from low-threshold cutaneous afferents to second order neurones in laminae III-VI, as well as transmission along pathways mediating PAD of cutaneous and Ib afferents, was facilitated. PAD of Ia afferents was instead inhibited. Monosynaptic reflexes of flexors and extensors were facilitated during the spontaneous nCDPs. The magnitude of the facilitation was proportional to the amplitude of the ‘conditioning’ spontaneous nCDPs. This led to a high positive correlation between amplitude fluctuations of spontaneous nCDPs and fluctuations of monosynaptic reflexes. Stimulation of low-threshold cutaneous afferents transiently reduced the probability of occurrence of spontaneous nCDPs as well as the fluctuations of monosynaptic reflexes. It is concluded that the spontaneous nCDPs were produced by the activation of a population of dorsal horn neurones that shared the same functional pathways and involved the same set of neurones as those responding monosynaptically to stimulation of large cutaneous afferents. The spontaneous activity of these neurones was probably the main cause of the fluctuations of the monosynaptic reflexes observed under anaesthesia and could provide a dynamic linkage between segmental sensory and motor pathways. PMID:11101653

  19. PAD patterns of physiologically identified afferent fibres from the medial gastrocnemius muscle.

    PubMed

    Jiménez, I; Rudomin, P; Solodkin, M

    1988-01-01

    Intracellular recordings were made in the barbiturate-anesthetized cat from single afferent fibres left in continuity with the medial gastrocnemius muscle to document the transmembrane potential changes produced in functionally identified fibres by stimulation of sensory nerves and of the contralateral red nucleus (RN). Fifty five fibres from muscle spindles had conduction velocities above 70 m/s and were considered as from group Ia. Stimulation of group I afferent fibres of the posterior biceps and semitendinosus nerve (PBSt) produced primary afferent depolarization (PAD) in 30 (54%) Ia fibres. Stimulation of the sural (SU) nerve produced no transmembrane potential changes in 39 (71%) group Ia fibres and dorsal root reflex-like activity (DRRs) in 16 (29%) fibres. In 17 out of 28 group Ia fibres (60.7%) SU conditioning inhibited the PAD generated by stimulation of the PBSt nerve. Facilitation of the PBSt-induced PAD by SU conditioning was not seen. Repetitive stimulation of the RN had mixed effects: it produced PAD in 1 out of 8 fibres and inhibited the PAD induced by PBSt stimulation in 2 other fibres. Nine fibres connected to muscle spindles had conduction velocities below 70 m/s and were considered to be group II afferents. No PAD was produced in these fibres by SU stimulation but DRRs were generated in 5 of them. In 23 out of 31 fibres identified as from tendon organs group I PBSt volleys produced PAD. However, stimulation of the SU nerve produced PAD only in 3 out of 34 fibres, no transmembrane potential changes in 30 fibres and DRRs in 1 fibre. The effects of SU conditioning on the PAD produced by PBSt stimulation were tested in 19 Ib fibres and were inhibitory in 12 of them. In 9 of these fibres SU alone produced no transmembrane potential changes. Repetitive stimulation of the RN produced PAD in 3 out of 9 Ib fibres. SU conditioning inhibited the RN-induced PAD. The present findings support the existence of an alternative inhibitory pathway from cutaneous

  20. Immunolocalization of the Ca2+-Activated K+ Channel Slo1 in Axons and Nerve Terminals of Mammalian Brain and Cultured Neurons

    PubMed Central

    Misonou, Hiroaki; Menegola, Milena; Buchwalder, Lynn; Park, Eunice W.; Meredith, Andrea; Rhodes, Kenneth J.; Aldrich, Richard W.; Trimmer, James S.

    2008-01-01

    Ca2+-activated voltage-dependent K+ channels (Slo1, KCa1.1, Maxi-K, or BK channel) play a crucial role in controlling neuronal signaling by coupling channel activity to both membrane depolarization and intracellular Ca2+ signaling. In mammalian brain, immunolabeling experiments have shown staining for Slo1 channels predominantly localized to axons and presynaptic terminals of neurons. We have developed anti-Slo1 mouse monoclonal antibodies that have been extensively characterized for specificity of staining against recombinant Slo1 in heterologous cells, and native Slo1 in mammalian brain, and definitively by the lack of detectable immunoreactivity against brain samples from Slo1 knockout mice. Here we provide precise immunolocalization of Slo1 in rat brain with one of these monoclonal antibodies and show that Slo1 is accumulated in axons and synaptic terminal zones associated with glutamatergic synapses in hippocampus and GABAergic synapses in cerebellum. By using cultured hippocampal pyramidal neurons as a model system, we show that heterologously expressed Slo1 is initially targeted to the axonal surface membrane, and with further development in culture, become localized in presynaptic terminals. These studies provide new insights into the polarized localization of Slo1 channels in mammalian central neurons and provide further evidence for a key role in regulating neurotransmitter release in glutamatergic and GABAergic terminals. PMID:16566008

  1. Transmitter release modulation by intracellular Ca2+ buffers in facilitating and depressing nerve terminals of pyramidal cells in layer 2/3 of the rat neocortex indicates a target cell-specific difference in presynaptic calcium dynamics

    PubMed Central

    Rozov, A; Burnashev, N; Sakmann, B; Neher, E

    2001-01-01

    In connections formed by nerve terminals of layer 2/3 pyramidal cells onto bitufted interneurones in young (postnatal day (P)14–15) rat somatosensory cortex, the efficacy and reliability of synaptic transmission were low. At these connections release was facilitated by paired-pulse stimulation (at 10 Hz). In connections formed by terminals of layer 2/3 pyramids with multipolar interneurones efficacy and reliability were high and release was depressed by paired-pulse stimulation. In both types of terminal, however, the voltage-dependent Ca2+ channels that controlled transmitter release were predominantly of the P/Q- and N-subtypes. The relationship between unitary EPSP amplitude and extracellular calcium concentration ([Ca2+]o) was steeper for facilitating than for depressing terminals. Fits to a Hill equation with nH= 4 indicated that the apparent KD of the Ca2+ sensor for vesicle release was two- to threefold lower in depressing terminals than in facilitating ones. Intracellular loading of pyramidal neurones with the fast and slowly acting Ca2+ buffers BAPTA and EGTA differentially reduced transmitter release in these two types of terminal. Unitary EPSPs evoked by pyramidal cell stimulation in bitufted cells were reduced by presynaptic BAPTA and EGTA with half-effective concentrations of ∼0.1 and ∼1 mm, respectively. Unitary EPSPs evoked in multipolar cells were reduced to one-half of control at higher concentrations of presynaptic BAPTA and EGTA (∼0.5 and ∼7 mm, respectively). Frequency-dependent facilitation of EPSPs in bitufted cells was abolished by EGTA at concentrations of > 0.2 mm, suggesting that accumulation of free Ca2+ is essential for facilitation in the terminals contacting bitufted cells. In contrast, facilitation was unaffected or even slightly increased in the terminals loaded with BAPTA in the concentration range 0.02–0.5 mm. This is attributed to partial saturation of exogenously added BAPTA. However, BAPTA at concentrations > 1 mm

  2. Phase-dependent reversal of the crossed conditioning effect on the soleus Hoffmann reflex from cutaneous afferents during walking in humans.

    PubMed

    Suzuki, Shinya; Nakajima, Tsuyoshi; Futatsubashi, Genki; Mezzarane, Rinaldo A; Ohtsuka, Hiroyuki; Ohki, Yukari; Komiyama, Tomoyoshi

    2016-02-01

    We previously demonstrated that non-noxious electrical stimulation of the cutaneous nerve innervating the contralateral foot modified the excitability of the Hoffmann (H-) reflex in the soleus muscle (SOL) in a task-dependent manner during standing and walking in humans. To date, however, it remains unclear how the crossed conditioning effect on the SOL H-reflex from the contralateral foot is modified during the various phases of walking. We sought to answer this question in the present study. The SOL H-reflex was evoked in healthy volunteers by an electrical test stimulation (TS) of the right (ipsilateral) posterior tibial nerve at five different phases during treadmill walking (4 km/h). A non-noxious electrical stimulation was delivered to the superficial peroneal nerve of the left (contralateral) ankle ~100 ms before the TS as a conditioning stimulation (CS). This CS significantly suppressed the H-reflex amplitude during the early stance phase, whereas the same CS significantly facilitated the H-reflex amplitude during the late stance phase. The CS alone did not produce detectable changes in the full-wave rectified electromyogram of the SOL. This result indicates that presynaptic mechanisms driven by the activation of low-threshold cutaneous afferents in the contralateral foot play a role in regulating the transmission between the Ia terminal and motoneurons in a phase-dependent manner. The modulation pattern of the crossed conditioning effect on the SOL H-reflex may be functionally relevant for the left-right coordination of leg movements during bipedal walking.

  3. β-Adrenergic Receptors Activate Exchange Protein Directly Activated by cAMP (Epac), Translocate Munc13-1, and Enhance the Rab3A-RIM1α Interaction to Potentiate Glutamate Release at Cerebrocortical Nerve Terminals*

    PubMed Central

    Ferrero, Jose J.; Alvarez, Ana M.; Ramírez-Franco, Jorge; Godino, María C.; Bartolomé-Martín, David; Aguado, Carolina; Torres, Magdalena; Luján, Rafael; Ciruela, Francisco; Sánchez-Prieto, José

    2013-01-01

    The adenylyl cyclase activator forskolin facilitates synaptic transmission presynaptically via cAMP-dependent protein kinase (PKA). In addition, cAMP also increases glutamate release via PKA-independent mechanisms, although the downstream presynaptic targets remain largely unknown. Here, we describe the isolation of a PKA-independent component of glutamate release in cerebrocortical nerve terminals after blocking Na+ channels with tetrodotoxin. We found that 8-pCPT-2′-O-Me-cAMP, a specific activator of the exchange protein directly activated by cAMP (Epac), mimicked and occluded forskolin-induced potentiation of glutamate release. This Epac-mediated increase in glutamate release was dependent on phospholipase C, and it increased the hydrolysis of phosphatidylinositol 4,5-bisphosphate. Moreover, the potentiation of glutamate release by Epac was independent of protein kinase C, although it was attenuated by the diacylglycerol-binding site antagonist calphostin C. Epac activation translocated the active zone protein Munc13-1 from soluble to particulate fractions; it increased the association between Rab3A and RIM1α and redistributed synaptic vesicles closer to the presynaptic membrane. Furthermore, these responses were mimicked by the β-adrenergic receptor (βAR) agonist isoproterenol, consistent with the immunoelectron microscopy and immunocytochemical data demonstrating presynaptic expression of βARs in a subset of glutamatergic synapses in the cerebral cortex. Based on these findings, we conclude that βARs couple to a cAMP/Epac/PLC/Munc13/Rab3/RIM-dependent pathway to enhance glutamate release at cerebrocortical nerve terminals. PMID:24036110

  4. Presynaptic modulation of Ia afferents in young and old adults when performing force and position control.

    PubMed

    Baudry, Stéphane; Maerz, Adam H; Enoka, Roger M

    2010-02-01

    The present work investigated presynaptic modulation of Ia afferents in the extensor carpi radialis (ECR) when young and old adults exerted a wrist extension force either to support an inertial load (position control) or to achieve an equivalent constant torque against a rigid restraint (force control) at 5, 10, and 15% of the maximal force. H reflexes were evoked in the ECR by stimulating the radial nerve above the elbow. A conditioning stimulus was applied to the median nerve above the elbow to assess presynaptic inhibition of homonymous Ia afferents (D1 inhibition) or at the wrist (palmar branch) to assess the ongoing presynaptic inhibition of heteronymous Ia afferents that converge onto the ECR motor neuron pool (heteronymous Ia facilitation). The young adults had less D1 inhibition and greater heteronymous Ia facilitation during the position task (79 and 132.1%, respectively) compared with the force task (69.1 and 115.1%, respectively, P < 0.05). In contrast, the old adults exhibited no difference between the two tasks for either D1 inhibition ( approximately 72%) or heteronymous Ia facilitation ( approximately 114%). Contraction intensity did not influence the amount of D1 inhibition or heteronymous Ia facilitation for either group of subjects. The amount of antagonist coactivation was similar between tasks for young adults, whereas it was greater in the position task for old adults (P = 0.02). These data indicate that in contrast to young adults, old adults did not modulate presynaptic inhibition of Ia afferents when controlling the position of a compliant load but rather increased coactivation of the antagonist muscle.

  5. The ultrastructure of the sensory nerve endings in the articular capsule of the knee joint of the domestic cat (Ruffini corpuscles and Pacinian corpuscles).

    PubMed Central

    Halata, Z

    1977-01-01

    Two types of mechanoreceptor have been found in the articular capsule of the knee joint of the domestic cat--Ruffini corpuscles and Pacinian corpuscles. Ruffini corpuscles are situated in the stratum fibrosum and consist of 2 to 6 cylinders. Each cylinder is made up of an afferent axon (diameter 3-4 micrometer), its swellings and terminal processes, Schwann cells enveloping the nerve swellings and terminal processes, endoneural connective tissue and a perineural capsule. The perineural capsule is incomplete in Ruffini corpuscles. The Pacinian corpuscles are 20 to 40 micrometer wide and 150-250 micrometer long. They are situated in groups of up to five at the boundary between the stratum synoviale and the stratum fibrosum. The afferent axon is myelinated (diameter 3-5 micrometer). Its terminal portion is inside the inner bulb which is formed of modified Schwann cells. Each corpuscle is enveloped by a perineural capsule (4-8 layers). The ultrastructure of the Pacinian corpuscles is compared with the ultrastructure of the skin receptors in the cat. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 PMID:604339

  6. Functional capacities of tactile afferent fibres in neonatal kittens

    PubMed Central

    Ferrington, D. G.; Rowe, Mark J.

    1980-01-01

    1. Responses were recorded from individual tactile afferent fibres isolated by microdissection from the median nerve of pentobarbitone-anaesthetized neonatal kittens (1-5 days post-natal age). Experiments were also conducted on adult cats to permit precise comparisons between neonatal and adult fibres. 2. Neonatal fibres with receptive fields on the glabrous skin of the foot pads were classified into two broad groups, a slowly adapting class (40%) which responded throughout a 1 sec period of steady indentation and a rapidly adapting or dynamically sensitive class comprising 60% of units. Fibres in these two groups had overlapping conduction velocities in the range 4·3 to 7·5 m/sec and were believed to be the developing Group II afferents of the adult. 3. Neonatal slowly adapting fibres qualitatively resembled their adult counter-parts. They displayed graded stimulus-response relations which, over the steepest segment of the curves, had mean slopes of 15·7 impulses/100 μm of indentation. Plateau levels of response were often reached at amplitudes of skin indentation of < 0·5-0·7 mm. 4. Dynamically sensitive fibres with receptive fields on the glabrous skin were studied using sinusoidal cutaneous vibration which in the adult enables them to be divided into two distinct classes. However, in the neonate, they formed a continuum whether criteria of sensitivity or responsiveness were used. 5. In response to vibration neonatal fibres differed from adult ones according to the following quantitative indices: (i) sensitivity as measured by both absolute thresholds and thresholds for a 1: 1 pattern of response, both of which were higher in the neonate than in the adult at all frequencies > 50 Hz and differed by an order of magnitude at frequencies ≥ 200 Hz; (ii) responsiveness based on the mean impulse rate evoked at a fixed amplitude of cutaneous vibration; (iii) band width of vibratory sensitivity which in the neonate was confined to approximately 5-300 Hz whereas

  7. Identification of multisegmental nociceptive afferents that modulate locomotor circuits in the neonatal mouse spinal cord.

    PubMed

    Mandadi, Sravan; Hong, Peter; Tran, Michelle A; Bráz, Joao M; Colarusso, Pina; Basbaum, Allan I; Whelan, Patrick J

    2013-08-15

    Compared to proprioceptive afferent collateral projections, less is known about the anatomical, neurochemical, and functional basis of nociceptive collateral projections modulating lumbar central pattern generators (CPG). Quick response times are critical to ensure rapid escape from aversive stimuli. Furthermore, sensitization of nociceptive afferent pathways can contribute to a pathological activation of motor circuits. We investigated the extent and role of collaterals of capsaicin-sensitive nociceptive sacrocaudal afferent (nSCA) nerves that directly ascend several spinal segments in Lissauer's tract and the dorsal column and regulate motor activity. Anterograde tracing demonstrated direct multisegmental projections of the sacral dorsal root 4 (S4) afferent collaterals in Lissauer's tract and in the dorsal column. Subsets of the traced S4 afferent collaterals expressed transient receptor potential vanilloid 1 (TRPV1), which transduces a nociceptive response to capsaicin. Electrophysiological data revealed that S4 dorsal root stimulation could evoke regular rhythmic bursting activity, and our data suggested that capsaicin-sensitive collaterals contribute to CPG activation across multiple segments. Capsaicin's effect on S4-evoked locomotor activity was potent until the lumbar 5 (L5) segments, and diminished in rostral segments. Using calcium imaging we found elevated calcium transients within Lissauer's tract and dorsal column at L5 segments when compared to the calcium transients only within the dorsal column at the lumbar 2 (L2) segments, which were desensitized by capsaicin. We conclude that lumbar locomotor networks in the neonatal mouse spinal cord are targets for modulation by direct multisegmental nSCA, subsets of which express TRPV1 in Lissauer's tract and the dorsal column. J. Comp. Neurol. 521:2870-2887, 2013. © 2013 Wiley Periodicals, Inc.

  8. Excitatory actions of mushroom poison (acromelic acid) on unmyelinated muscular afferents in the rat.

    PubMed

    Taguchi, Toru; Tomotoshi, Kimihiko; Mizumura, Kazue

    2009-06-05

    Ingestion of a poisonous mushroom, Clitocybe acromelalga, results in strong and long-lasting allodynia, burning pain, redness and swelling in the periphery of the body. Acromelic acid (ACRO), a kainate analogue isolated from the mushroom, is assumed to be involved in the poisoning. ACRO has two isomers, ACRO-A and ACRO-B. The potency of ACRO-A is a million times higher than that of ACRO-B for induction of allodynia when intrathecally administered in mice. The effect of ACRO on the primary afferents of somatic tissues remains largely unknown. The aim of the present study was to examine the effect of ACRO-A on the response behavior of unmyelinated afferents in the skeletal muscle. For this purpose single fiber recordings of C-afferents were made from rat extensor digitorum longus (EDL) muscle-common peroneal nerve preparations in vitro. Intramuscular injections of ACRO-A at three different concentrations (10(-12), 10(-10) and 10(-8)M, 5 microl over 5s) near the receptive field in the EDL muscle elicited excitation of C-afferents (12%, 50% and 44%, respectively). ACRO-A at the concentration of 10(-10)M induced the strongest excitation. The incidence of ACRO-A responsive fibers at the concentration of 10(-10) and 10(-8)M was significantly higher than that at 10(-12)M. The responses to mechanical and heat stimulations did not differ between ACRO-A sensitive and insensitive fibers. These results clearly demonstrated the powerful excitatory action of ACRO-A on mechanosensitive unmyelinated afferents in the rat skeletal muscle.

  9. Botulinum toxin B in the sensory afferent: transmitter release, spinal activation, and pain behavior.

    PubMed

    Marino, Marc J; Terashima, Tetsuji; Steinauer, Joanne J; Eddinger, Kelly A; Yaksh, Tony L; Xu, Qinghao

    2014-04-01

    We addressed the hypothesis that intraplantar botulinum toxin B (rimabotulinumtoxin B: BoNT-B) has an early local effect upon peripheral afferent terminal releasing function and, over time, will be transported to the central terminals of the primary afferent. Once in the terminals it will cleave synaptic protein, block spinal afferent transmitter release, and thereby prevent spinal nociceptive excitation and behavior. In mice, C57Bl/6 males, intraplantar BoNT-B (1 U) given unilaterally into the hind paw had no effect upon survival or motor function, but ipsilaterally decreased: (1) intraplantar formalin-evoked flinching; (2) intraplantar capsaicin-evoked plasma extravasation in the hind paw measured by Evans blue in the paw; (3) intraplantar formalin-evoked dorsal horn substance P (SP) release (neurokinin 1 [NK1] receptor internalization); (4) intraplantar formalin-evoked dorsal horn neuronal activation (c-fos); (5) ipsilateral dorsal root ganglion (DRG) vesicle-associated membrane protein (VAMP); (6) ipsilateral SP release otherwise evoked bilaterally by intrathecal capsaicin; (7) ipsilateral activation of c-fos otherwise evoked bilaterally by intrathecal SP. These results indicate that BoNT-B, after unilateral intraplantar delivery, is taken up by the peripheral terminal, is locally active (blocking plasma extravasation), is transported to the ipsilateral DRG to cleave VAMP, and is acting presynaptically to block release from the spinal peptidergic terminal. The observations following intrathecal SP offer evidence for a possible transsynaptic effect of intraplantar BoNT. These results provide robust evidence that peripheral BoNT-B can alter peripheral and central terminal release from a nociceptor and attenuate downstream nociceptive processing via a presynaptic effect, with further evidence suggesting a possible postsynaptic effect.

  10. Chronic exposure to low dose bacterial lipopolysaccharide inhibits leptin signaling in vagal afferent neurons.

    PubMed

    de La Serre, Claire B; de Lartigue, Guillaume; Raybould, Helen E

    2015-02-01

    Bacterially derived factors are implicated in the causation and persistence of obesity. Ingestion of a high fat diet in rodents and obesity in human subjects is associated with chronic elevation of low plasma levels of lipopolysaccharide (LPS), a breakdown product of Gram-negative bacteria. The terminals of vagal afferent neurons are positioned within the gut mucosa to convey information from the gut to the brain to regulate food intake and are responsive to LPS. We hypothesized that chronic elevation of LPS could alter vagal afferent signaling. We surgically implanted osmotic mini-pumps that delivered a constant, low-dose of LPS into the intraperitoneal cavity of rats (12.5 μg/kg/hr for 6 weeks). LPS-treated rats developed hyperphagia and showed marked changes in vagal afferent neuron function. Chronic LPS treatment reduced vagal afferent leptin signaling, characterized by a decrease in leptin-induced STAT3 phosphorylation. In addition, LPS treatment decreased cholecystokinin-induced satiety. There was no alteration in leptin signaling in the hypothalamus. These findings offer a mechanism by which a change in gut microflora can promote hyperphagia, possibly leading to obesity.

  11. Evidence of neuroanatomical connection between the superior cervical ganglion and hypoglossal nerve in the hamster as revealed by tract-tracing and degeneration methods

    PubMed Central

    TSENG, CHI-YU; LUE, JUNE-HORNG; LEE, SHIH-HSIUNG; WEN, CHEN-YUAN; SHIEH, JENG-YUNG

    2001-01-01

    Previous studies have shown the existence of a sympathetic component in some cranial nerves including the hypoglossal nerve. In this study, the horseradish peroxidase (HRP) tract-tracing retrograde technique and experimental degeneration method were used to elucidate the possible neuroanatomical relationship between the superior cervical ganglion (SCG) and the hypoglossal nerve of hamsters. About 10% of the SCG principal neurons were HRP positive following the tracer application to the trunk of hypoglossal nerve. Most of the HRP-labelled neurons were multipolar and were randomly distributed in the ganglion. When HRP was injected into the medial branch of the hypoglossal nerve, some of the SCG neurons were labelled, but they were not detected when HRP was injected into the lateral branch. The present findings suggest that postganglionic sympathetic fibres from the SCG may travel along the hypoglossal nerve trunk via its medial branch to terminate in visceral targets such as the intralingual glands. By electron microscopy, the HRP reaction product was localised in the neuronal somata and numerous unmyelinated fibres in the SCG. In addition, HRP-labelled axon profiles considered to be the collateral branches of the principal neurons contained numerous clear round and a few dense core vesicles. Besides the above, some HRP-labelled small myelinated fibres, considered to be visceral afferents, were also present. Results of experimental degeneration following the severance of the hypoglossal nerve showed the presence of degenerating neuronal elements both in the hypoglossal nucleus and the SCG. This confirms that the hypoglossal nerve contains sympathetic component from the SCG which may be involved in regulation of the autonomic function of the tongue. PMID:11327203

  12. Electrophysiological characterization of vagal afferents relevant to mucosal nociception in the rat upper oesophagus

    PubMed Central

    Lennerz, J K M; Dentsch, C; Bernardini, N; Hummel, T; Neuhuber, W L; Reeh, P W

    2007-01-01

    Emerging evidence indicates a nociceptive role of vagal afferents. A distinct oesophageal innervation in the rat, with muscular and mucosal afferents travelling predominantly in the recurrent (RLN) and superior laryngeal nerve (SLN), respectively, enabled characterization of mucosal afferents with nociceptive properties, using novel isolated oesophagus–nerve preparations. SLN and RLN single-fibre recordings identified 55 and 14 units, respectively, with none conducting faster than 8.7 m s−1. Mucosal response characteristics in the SLN distinguished mechanosensors (n= 13), mechanosensors with heat sensitivity (18) from those with cold sensitivity (19) and a mechanoinsensitive group (5). The mechanosensitive fibres, all slowly adapting, showed a unimodal distribution of mechanical thresholds (1.4–128 mN, peak ∼5.7 mN). No difference in response characteristics of C and Aδ fibres was encountered. Mucosal proton stimulation (pH 5.4 for 3 min), mimicking gastro-oesophageal reflux disease (GORD), revealed in 31% of units a desensitizing response that peaked around 20 s and faded within 60 s. Cold stimulation (15°C) was proportionally encoded but the response showed slow adaptation. In contrast, the noxious heat (48°C) response showed no obvious adaptation with discharge rates reflecting the temperature's time course. Polymodal (69%) mucosal units, > 30% proton sensitive, were found in each fibre category and were considered nociceptors; they are tentatively attributed to vagal nerve endings type I, IV and V, previously morphologically described. All receptive fields were mapped and the distribution indicates that the posterior upper oesophagus may serve as a ‘cutbank’, detecting noxious matters, ingested or regurgitated, and triggering nocifensive reflexes such as bronchoconstriction in GORD. PMID:17478536

  13. Evaluation of dermal myelinated nerve fibers in diabetes mellitus.

    PubMed

    Peltier, Amanda C; Myers, M Iliza; Artibee, Kay J; Hamilton, Audra D; Yan, Qing; Guo, Jiasong; Shi, Yaping; Wang, Lily; Li, Jun

    2013-06-01

    Skin biopsies have primarily been used to study the non-myelinated nerve fibers of the epidermis in a variety of neuropathies. In this study, we have expanded the skin biopsy technique to glabrous, non-hairy skin to evaluate myelinated nerve fibers in the most highly prevalent peripheral nerve disease, diabetic polyneuropathy (DPN). Twenty patients with DPN (Type I, n = 9; Type II, n = 11) and 16 age-matched healthy controls (age 29-73) underwent skin biopsy of the index finger, nerve conduction studies (NCS), and composite neuropathy scoring. In patients with DPN, we found a statistically significant reduction of both mechanoreceptive Meissner corpuscles (MCs) and their afferent myelinated nerve fibers (p = 0.01). This myelinated nerve fiber loss was correlated with the decreased amplitudes of sensory/motor responses in NCS. This study supports the utilization of skin biopsy to quantitatively evaluate axonal loss of myelinated nerve fibers in patients with DPN.

  14. Nerve biopsy

    MedlinePlus

    ... Loss of axon tissue Metabolic neuropathies Necrotizing vasculitis Sarcoidosis Risks Allergic reaction to the local anesthetic Discomfort ... Neurosarcoidosis Peripheral neuropathy Primary amyloidosis Radial nerve dysfunction Sarcoidosis Tibial nerve dysfunction Review Date 6/1/2015 ...

  15. Improved bladder emptying in urinary retention by electrical stimulation of pudendal afferents

    NASA Astrophysics Data System (ADS)

    Peng, Chih-Wei; Chen, Jia-Jin Jason; Cheng, Chen-Li; Grill, Warren M.

    2008-06-01

    Urinary retention is the inability to empty the bladder completely, and may result from bladder hypocontractility, increases in outlet resistance or both. Chronic urinary retention can lead to several urological complications and is often refractory to pharmacologic, behavioral and surgical treatments. We sought to determine whether electrical stimulation of sensory fibers in the pudendal nerve could engage an augmenting reflex and thereby improve bladder emptying in an animal model of urinary retention. We measured the efficiency of bladder emptying with and without concomitant electrical stimulation of pudendal nerve afferents in urethane-anesthetized rats. Voiding efficiency (VE = voided volume/initial volume) was reduced from 72 ± 7% to 29 ± 7% following unilateral transection of the sensory branch of the pudendal nerve (UST) and from 70 ± 5% to 18 ± 4% following bilateral transection (BST). Unilateral electrical stimulation of the proximal transected sensory pudendal nerve during distention-evoked voiding contractions significantly improved VE. Low-intensity stimulation at frequencies of 1-50 Hz increased VE to 40-51% following UST and to 39-49% following BST, while high-intensity stimulation was ineffective at increasing VE. The increase in VE was mediated by increases in the duration of distention-evoked voiding bladder contractions, rather than increases in contraction amplitude. These results are consistent with an essential role for pudendal sensory feedback in efficient bladder emptying, and raise the possibility that electrical activation of pudendal nerve afferents may provide a new approach to restore efficient bladder emptying in persons with urinary retention.

  16. IMPROVED BLADDER EMPTYING IN URINARY RETENTION BY ELECTRICAL STIMULATION OF PUDENDAL AFFERENTS

    PubMed Central

    Peng, Chih-Wei; Chen, Jia-Jin Jason; Cheng, Chen-Li; Grill, Warren M.

    2013-01-01

    Urinary retention is the inability to empty the bladder completely, and may result from bladder hypocontractility, increases in outlet resistance, or both. Chronic urinary retention can lead to several urological complications and is often refractory to pharmacologic, behavioral, and surgical treatments. We sought to determine whether electrical stimulation of sensory fibers in the pudendal nerve could engage an augmenting reflex and thereby improve bladder emptying in an animal model of urinary retention. We measured the efficiency of bladder emptying with and without concomitant electrical stimulation of pudendal nerve afferents in urethane anesthetized rats. Voiding efficiency (VE=voided volume/initial volume) was reduced from 72±7% to 29±7% following unilateral transection of the sensory branch of the pudendal nerve (UST) and from 70±5% to 18±4% following bilateral transection (BST). Unilateral electrical stimulation of the proximal transected sensory pudendal nerve during distention-evoked voiding contractions significantly improved VE. Low intensity stimulation at frequencies of 1–50 Hz increased VE to 40–51% following UST and to 39–49% following BST, while high intensity stimulation was ineffective at increasing VE. The increase in VE was mediated by increases in the duration of distention-evoked voiding bladder contractions, rather than increases in contraction amplitude. These results are consistent with an essential role for pudendal sensory feedback in efficient bladder emptying, and raise the possibility that electrical activation of pudendal nerve afferents may provide a new approach to restore efficient bladder emptying in persons with urinary retention. PMID:18430976

  17. HuD-mediated distinct BDNF regulatory pathways promote regeneration after nerve injury.

    PubMed

    Sanna, Maria Domenica; Ghelardini, Carla; Galeotti, Nicoletta

    2017-03-15

    Up-regulation of brain-derived neurotrophic factor (BDNF) synthesis is an important mechanism of peripheral nerve regeneration after injury. However, the cellular and molecular mechanisms underlying this process are not fully understood. This study examines the role of BDNF in the spared nerve injury (SNI) mice model. Protein expression and cellular localization were investigated in the dorsal root ganglia (DRG) and spinal cord by western blotting and immunofluorescence experiments respectively. BDNF protein was markedly increased 3 and 7days post-injury in the spinal cord and DRG. Following nerve injury sensory neurons produce molecules to promote regeneration, such as growth-associated protein 43 (GAP-43) and cytoskeletal proteins. Our results show that the expression of GAP-43 was increased in the DRG and spinal cord while, an increased of p-NFH content was detected in the spinal cord, with no modification in the DRG. Both events were counteracted by the administration of an anti-BDNF antibody. In DRG of SNI mice we also detected an increase of HuD expression, a RNA-binding protein known to stabilize BDNF and GAP-43 mRNA. Silencing of HuD prevented the nerve injury-induced BDNF and GAP-43 enhanced expression in the DRG. HuD-mediated BDNF synthesis in the primary sensory neurons, is followed by an anterograde transport of the neurotrophin to the central terminals of the primary afferents in the spinal dorsal horn, to modulate GAP-43 and NFH activation. Our data suggest that BDNF, GAP-43 and p-NFH proteins increase are linked events required for the enhanced regeneration after nerve injury.

  18. Development, plasticity and modulation of visceral afferents

    PubMed Central

    Christianson, Julie A.; Bielefeldt, Klaus; Altier, Christophe; Cenac, Nicolas; Davis, Brian M.; Gebhart, Gerald F.; High, Karin W.; Kollarik, Marian; Randich, Alan; Undem, Brad; Vergnolle, Nathalie

    2010-01-01

    Visceral pain is the most common reason for doctor visits in the US. Like somatic pain, virtually all visceral pain sensations begin with the activation of primary sensory neurons innervating the viscera and/or the blood vessels associated with these structures. Visceral afferents also play a central role in tissue homeostasis. Recent studies show that in addition to monitoring the state of the viscera, they perform efferent functions through the release of small molecules (e.g. peptides like CGRP) that can drive inflammation, thereby contributing to the development of visceral pathologies (e.g. diabetes Razavi, R., Chan, Y., Afifiyan, F.N., Liu, X.J., Wan, X., Yantha, J., Tsui, H., Tang, L., Tsai, S., Santamaria, P., Driver, J.P., Serreze, D., Salter, M.W., Dosch, H.M., 2006. TRPV1+ sensory neurons control beta cell stress and islet inflammation in autoimmune diabetes, Cell 127 1123–1135). Visceral afferents are heterogeneous with respect to their anatomy, neurochemistry and function. They are also highly plastic in that their cellular environment continuously influences their response properties. This plasticity makes them susceptible to long-term changes that may contribute significantly to the development of persistent pain states such as those associated with irritable bowel syndrome, pancreatitis, and visceral cancers. This review examines recent insights into visceral afferent anatomy and neurochemistry and how neonatal insults can affect the function of these neurons in the adult. New approaches to the treatment of visceral pain, which focus on primary afferents, will also be discussed. PMID:19150371

  19. Cadaveric nerve allotransplantation in the treatment of persistent thoracic neuralgia.

    PubMed

    Barbour, John R; Yee, Andrew; Moore, Amy M; Trulock, Elbert P; Buchowski, Jacob M; Mackinnon, Susan E

    2015-04-01

    When relief from neuralgia cannot be achieved with traditional methods, neurectomy may be considered to abate the stimulus, and primary opposition of the terminal nerve ending is recommended to prevent neuroma. Nerve repair with autograft is limited by autologous nerves available for large nerve defects. Cadaveric allografts provide an unlimited graft source without donor-site morbidities, but are rapidly rejected unless appropriate immunosuppression is achieved. An optimal treatment method for nerve allograft transplantation would minimize rejection while simultaneously permitting nerve regeneration. This report details a novel experience of nerve allograft transplantation using cadaveric nerve grafts to desensitize persistent postoperative thoracic neuralgia.

  20. Loss of neurotrophin-3 from smooth muscle disrupts vagal gastrointestinal afferent signaling and satiation.

    PubMed

    Fox, Edward A; Biddinger, Jessica E; Baquet, Zachary C; Jones, Kevin R; McAdams, Jennifer

    2013-12-01

    A large proportion of vagal afferents are dependent on neurotrophin-3 (NT-3) for survival. NT-3 is expressed in developing gastrointestinal (GI) smooth muscle, a tissue densely innervated by vagal mechanoreceptors, and thus could regulate their survival. We genetically ablated NT-3 from developing GI smooth muscle and examined the pattern of loss of NT-3 expression in the GI tract and whether this loss altered vagal afferent signaling or feeding behavior. Meal-induced c-Fos activation was reduced in the solitary tract nucleus and area postrema in mice with a smooth muscle-specific NT-3 knockout (SM-NT-3(KO)) compared with controls, suggesting a decrease in vagal afferent signaling. Daily food intake and body weight of SM-NT-3(KO) mice and controls were similar. Meal pattern analysis revealed that mutants, however, had increases in average and total daily meal duration compared with controls. Mutants maintained normal meal size by decreasing eating rate compared with controls. Although microstructural analysis did not reveal a decrease in the rate of decay of eating in SM-NT-3(KO) mice, they ate continuously during the 30-min meal, whereas controls terminated feeding after 22 min. This led to a 74% increase in first daily meal size of SM-NT-3(KO) mice compared with controls. The increases in meal duration and first meal size of SM-NT-3(KO) mice are consistent with reduced satiation signaling by vagal afferents. This is the first demonstration of a role for GI NT-3 in short-term controls of feeding, most likely involving effects on development of vagal GI afferents that regulate satiation.

  1. Hemispheric asymmetry and somatotopy of afferent inhibition in healthy humans.

    PubMed

    Helmich, R C G; Bäumer, T; Siebner, H R; Bloem, B R; Münchau, A

    2005-11-01

    A conditioning electrical stimulus to a digital nerve can inhibit the motor-evoked potentials (MEPs) in adjacent hand muscles elicited by transcranial magnetic stimulation (TMS) to the contralateral primary motor cortex (M1) when given 25-50 ms before the TMS pulse. This is referred to as short-latency afferent inhibition (SAI). We studied inter-hemispheric differences (Experiment 1) and within-limb somatotopy (Experiment 2) of SAI in healthy right-handers. In Experiment 1, conditioning electrical