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PubMed1996

Sub-population of capsaicin sensitive primary afferent neurons in thoracic, lumbar and sacral dorsal root ganglion in young rats revealed by stimulated cobalt uptake.

The number of dorsal root ganglion (DRG) neurons, the relative number of capsaicin sensitive DRG cells and the diameter distribution of these neurons were investigated in the thoracic 11, lumbar 5 and sacral 1 DRG ganglia in young rats. The capsaicin sensitivity of DRG cells was shown by the stimulated cobalt uptake technique in in vitro conditions. Cobalt labelled and non-labelled neurons were counted using the dissector method. Our results show that the total number of DRG cells in the Th11, L5 and S1 segments (4200-6500 per ganglion) were not significantly different from each other and about 8% of these cells were capsaicin sensitive in the segments studied. These findings also show that the capsaicin sensitive DRG cells belong to the small diameter DRG cell population. Control experiments on neonatally capsaicin injected animals indicate that the capsaicin stimulated cobalt uptake provides selective and specific staining of capsaicin sensitive DRG neurons.

Animals↗
PubMed1999

Does electrical stimulation of deaf cochleae prevent spiral ganglion degeneration?

Thirty-six drug deafened guinea pigs were studied to determine how electrical stimulation of the cochlea affects spiral ganglion cell (SGC) survival. Animals were divided into two groups, extracochlear and intracochlear stimulation, and each group was further divided into four stimulus subgroups: no stimulation (implanted controls), the inferior colliculus electrically evoked potential (ICEEP) threshold-2 dB, ICEEP threshold+2 dB, and ICEEP threshold+6 dB. Stimuli consisted of 200 micros/phase charge balanced biphasic current pulses presented at 100 pulses per second using monopolar stimulation. Animals were stimulated 5 h/day, 5 days per week, for 8 weeks. The animals were then perfused and the cochleae serially sectioned at 4 microm saving every 8th section. We counted the number of intact SGCs, those containing a nucleus with chromatin, in each 20% segment of the cochlea and also measured SGC densities (number of neurons per mm2 of Rosenthal's canal). The number of surviving spiral ganglion neurons was not significantly different (P > 0.05) between the implanted and the unimplanted ears in any of the experimental groups. However, the spiral ganglion neuron densities were significantly elevated in the electrically stimulated ears (P < 0.001) but not in the implanted but not chronically stimulated ears (P > 0.05). We measured the volume of Rosenthal's canal in one subgroup (ICEEP threshold+2 dB) and found a decrease in this volume in the stimulated ear compared to the unstimulated ear (P < 0.01). These findings support the hypothesis that chronic monopolar electrical intracochlear or extracochlear stimulation is not a neurotrophic factor, increasing spiral ganglion neuron survival, but instead causes a narrowing of Rosenthal's canal that accounts for the increased spiral ganglion neuronal densities seen in the stimulated cochleae.

Animals↗
PubMed2001

Effects of testosterone on the electrical properties and nicotinic transmission of the major pelvic and coeliac ganglion neurones.

The effects of testosterone on the electrical properties and nicotinic activation of prevertebral ganglion neurones were investigated in vitro on the male rat major pelvic ganglion and rabbit coeliac ganglion. The electrical activity of the neurones was recorded using intracellular recording techniques. Nicotinic activation was triggered for neurones of the major pelvic ganglion by stimulating the hypogastric, pelvic and cavernous nerves and for coeliac neurones by stimulating the splanchnic nerves. Testosterone modified the resting membrane potential of neurones in the major pelvic ganglion by triggering a slow depolarization, and was without significant effect on the resting membrane potential of coeliac ganglion neurones. In neurones of the major pelvic and coeliac ganglia, testosterone had no significant effect on the firing pattern, on the characteristics of the action potential (firing threshold, duration, overshoot) and on the after-hyperpolarization (amplitude and duration). Testosterone affected, in opposite ways, the nicotinic activation of neurones of the two prevertebral ganglia. In the major pelvic ganglion, testosterone triggered an increase in the amplitude of excitatory postsynaptic potentials induced by stimulation of the hypogastric, pelvic and cavernous nerves with a single pulse, revealing a facilitation of nicotinic activation. On coeliac ganglion neurones, testosterone elicited a decrease in the amplitude of excitatory postsynaptic potentials induced by stimulation of the splanchnic nerves, indicating an inhibition of nicotinic activation. Our study shows that testosterone acts differently on neurones of prevertebral ganglia involved in the nervous control of different functions, its facilitatory action being exerted on neurones of the major pelvic ganglion which is particularly involved in the control of the urogenital tract. Our study reinforces the concept, derived from neuroanatomical and pharmacological studies, of the major pelvic ganglion as a major peripheral target for testosterone.

Animals↗
PubMed1975

Prolonged sympathetic activation and pulmonary surfactant: absence of effect in anesthetized cats.

Cats were anesthetized with either sodium pentobarbital or ketamine hydrochloride, paralyzed, and artifically ventilated. The stellate ganglion was electrically stimulated for one hour (10 V, frequency = 10 per sec, and 0.5 to 1.0 msec pulse duration), alternating periods of stimulation and rest of 20 sec each, while control animals were sham operated. After stimulation, static deflation pressure-volume relationships of the excised lungs were compared. Regardless of the anesthetic used, no change in static lung compliance was found between experimental and control groups, and one hour of stellate stimulation did not produce significant changes in lung volumes at maximum distending pressures, in lung weight/body weight ratios, or in minimum surface tension measurements of lung extracts. We concluded that prolonged intermittent stimulation of the stellate ganglion does not alter significantly the function of alveolar surfactant.

Anesthesia, General↗
PubMed1997

Psychophysical evidence for a selective loss of M ganglion cells in glaucoma.

We measured resolution acuity at 12 different retinal locations using sinusoidal gratings in a group of normals, ocular hypertensives and glaucoma patients. Resolution was measured using both stationary gratings, which selectively stimulate parvocellular ganglion cells (P cells), and gratings which phase reversed at 30 Hz, which selectively stimulate a higher proportion of magnocellular ganglion cells (M cells). With stationary gratings, peripheral resolution was found to be significantly reduced in glaucoma patients and, to a lesser extent, in ocular hypertensives. When the stimuli phase reversed at 30 Hz these differences between groups were larger. The ratio of resolution with and without phase reversal also showed a significant difference between the three groups. These results provide strong psychophysical evidence for a selective loss of M ganglion cell density over P ganglion cell density in glaucoma.

Aged↗
PubMed1998

Mechanism of neurogenic relaxation and modification of the response by enteric substances in isolated dog colon.

The mechanisms of neurogenic relaxation in the longitudinal muscle of the isolated canine colon and its modification by enteric substances were investigated. Relaxations induced by transmural electrical stimulation with electrical pulses, nicotine or K+ in the muscle strips contracted with bradykinin and treated with atropine were attenuated but not abolished by NG-nitro-L-arginine (L-NA), and the inhibition was reversed by L-arginine. Oxyhemoglobin and ouabain inhibited the response, whereas K+ channel inhibitors, such as glibenclamide, tetraethylammonium, apamin and charybdotoxin, were without effect. In L-NA-treated strips, stimulation-induced relaxations were reduced by ouabain but not by oxyhemoglobin. Among substances tested, only norepinephrine, ATP, vasoactive intestinal peptide (VIP) and galanin produced relaxations. However, alpha- and beta-adrenoceptor antagonists and aminophylline did not alter the response to nerve stimulation. In the strips made unresponsive to VIP and galanin, stimulation-induced relaxations were not influenced. Indomethacin, calcitonin gene-related peptide, cholecystokinin, peptide YY, substance P and serotonin did not modulate the neurogenic response. It is concluded that the relaxation associated with nerve stimulation is mediated by nitric oxide (NO) synthesized from L-arginine and also by substance(s) activating the electrogenic Na+ pump but not that opening K+ channels. Norepinephrine, ATP, VIP and galanin can be excluded as candidate inhibitory neurotransmitters, and the substances used so far are unlikely to modulate inhibitory nerve function.

Adenosine Triphosphate↗
PubMed2004

Chemical profile of vagal preganglionic motor cells innervating the airways in ferrets: the absence of noncholinergic neurons.

In ferrets, we investigated the presence of choline acetyltransferase (ChAT), vasoactive intestinal peptide (VIP), and markers for nitric oxide synthase (NOS) in preganglionic parasympathetic neurons innervating extrathoracic trachea and intrapulmonary airways. Cholera toxin beta-subunit, a retrograde axonal transganglionic tracer, was used to identify airway-related vagal preganglionic neurons. Double-labeling immunohistochemistry and confocal microscopy were employed to characterize the chemical nature of identified airway-related vagal preganglionic neurons at a single cell level. Physiological experiments were performed to determine whether activation of the VIP and ChAT coexpressing vagal preganglionic neurons plays a role in relaxation of precontracted airway smooth muscle tone after muscarinic receptor blockade. The results showed that 1) all identified vagal preganglionic neurons innervating extrathoracic and intrapulmonary airways are acetylcholine-producing cells, 2) cholinergic neurons innervating the airways coexpress ChAT and VIP but do not contain NOS, and 3) chemical stimulation of the rostral nucleus ambiguus had no significant effect on precontracted airway smooth muscle tone after muscarinic receptor blockade. These studies indicate that vagal preganglionic neurons are cholinergic in nature and coexpress VIP but do not contain NOS; their stimulation increases cholinergic outflow, without activation of inhibitory nonadrenergic, noncholinergic ganglionic neurons, stimulation of which induces airway smooth muscle relaxation. Furthermore, these studies do not support the possibility of direct inhibitory innervation of airway smooth muscle by vagal preganglionic fibers that contain VIP.

Animals↗
PubMed1982

Pharmacological characteristics of facilitation of hippocampal population spikes by cholinomimetics.

In rats under urethane anaesthesia, various cholinomimetics, acetylcholine-antagonists and other agents were released iontophoretically in the pyramidal layer of area CA1. Like acetylcholine, a variety of cholinomimetics readily enhanced population spikes evoked by fimbrial-commissural stimulation. Judging by the equipotent iontophoretic currents, the strongest muscarinic agonist was muscarine. Other potent agonists included carbachol, methacholine, propionylcholine, bethanechol and the much slower-acting arecoline, pilocarpine and oxotremorine. Choline was about 5 times weaker than acetylcholine. Though not as effective as acetylcholine, some nicotinic agonists also consistently enhanced population spikes, particularly dimethylphenylpiperazinium and acetylthiocholine. Other nicotinic agents, such as butyrylcholine, nicotine and tetramethylammonium were much less active. Both scopolamine and atropine, given systematically in high doses (10-80 mg/kg), strongly depressed or abolished the action of muscarinic agonists, but to a lesser and more variable extent the action of ACh. They did not antagonize dimethylphenylpiperazinium. When applied iontophoretically, alpha-bungarotoxin, tubocurarine or mecamylamine did not block the action of any of the cholinomimetics. Indeed, in higher doses they tended to promote population spikes (a comparable enhancement was also seen with larger iontophoretic doses of atropine or scopolamine). On the other hand, gallamine and dihydro-beta-erythroidine antagonized muscarine but not dimethylphenylpiperazinium; a less selective block of cholinomimetics was produced by suxamethonium. It was concluded that both muscarinic and nicotinic receptors (or receptors with mixed properties) appear to be involved in the facilitatory action of acetylcholine on population spikes evoked by fimbrial-commissural stimulation.

Acetylcholine↗
PubMed2004

Brain-derived neurotrophic factor signalling in adult pig retinal ganglion cell neurite regeneration in vitro.

Brain-derived neurotrophic factor (BDNF) has been implicated in stimulating retinal ganglion cell (RGC) survival and axonal regeneration in rodent animal models in vivo and in vitro, but very little data are available on neurotrophin effects in higher mammals. We hence analysed BDNF signalling in primary cultures of adult pig RGC. As detected by immunohistochemistry, HPLC analysis and RT-PCR, BDNF protein and mRNA were present within pig retina in vivo and in vitro, where it may be involved in baseline RGC neuritogenesis. Initial dose-response studies established optimal effects were induced by 20 ng/ml BDNF, leading to an approximately threefold increase in neurite length. We analysed the respective contributions of phosphatidyl inositol 3 kinase (PI3K) and mitogen activated protein kinase (MAPK) cascades to BDNF-induced neurite regeneration. Addition of either the PI3K inhibitor wortmannin or the MAPK inhibitor U0126 blocked 50-100% BDNF-induced neurite elongation; U0126 also significantly reduced neurite regeneration below untreated control levels. The trk receptor inhibitor K252a had no observable effect on neurite regeneration or morphology. These data hence demonstrate that BDNF is a potent stimulator of neurite growth in RGC prepared from an adult large mammal retina, and that at least two signalling pathways are causally involved. BDNF-based therapy may be of potential use in treating RGC degeneration in humans.

Animals↗
PubMed1999

Nitric oxide inhibits the positive chronotropic and inotropic responses to sympathetic nerve stimulation in the isolated guinea-pig atria.

This study was designed to determine whether nitric oxide (NO) modulates the positive chronotropic and inotropic (in paced atria) responses to cardiac sympathetic nerve stimulation (SNS) in the isolated guinea-pig double atrial/right stellate ganglion preparation. The ganglion was stimulated at 1, 2, 3 and 5 Hz at constant voltage and the changes in heart rate or force of contraction were measured. The selective neuronal NO synthase (nNOS) inhibitors TRIM (1-(2-trifluoromethylphenyl) imidazole; 100 microM) and 7-NiNa (Na+ salt of 7-nitroindazole; 100 microM) significantly enhanced the positive chronotropic and inotropic responses to SNS. Similar results for heart rate were seen with the non-isoform-selective NOS inhibitor N(omega)nitro-L-arginine (L-NA; 100 microM). All effects were reversed with L-arginine (1 mM). The NO donor sodium nitroprusside (SNP; 100 microM) increased baseline heart rate and force of contraction, and attenuated the positive chronotropic and inotropic responses to SNS. SNP also decreased the positive chronotropic response to bath-applied noradrenaline (NA; 1 microM). In contrast, 7-NiNa did not alter the increase in heart rate with bath-applied NA (0.1 or 1 microM). The guanylyl cyclase inhibitor ODQ (10 microM) enhanced (mimicking nNOS inhibition) and the cyclic GMP (guanosine 3':5'-cyclic monophosphate) analogue 8-Br-cGMP (8-bromoguanosine 3':5'-cyclic monophosphate; 1 mM) attenuated (mimicking exogenous NO) the positive inotropic response to SNS. Taken together, these results are consistent with endogenous NO, synthesized from nNOS, inhibiting the positive chronotropic and inotropic responses evoked by cardiac SNS via a cyclic GMP-dependent pathway.

Animals↗
PubMedDate not supplied

[Morphologic characteristics and responses of the neurons of the right parietal ganglion in Lymnaea stagnalis to stimulation of the sensory structures].

Intracellular recordings have been made of the responses of 22 neurons of the central part of the dorsal surface of the right parietal ganglion of the snail Lymnaea stagnalis to adequate stimulation of chemo-, photo- and mechanoreceptor cells of the mantle and head skin including tentacles and lips. It was shown that the main bulk of the neurons investigated has broad receptive fields in the body wall and mantle, being able to respond to all types of the applied stimuli. Alongside, single neurons were revealed which receive single-mode input, either a mechanosensory or chemosensory one. Morphological studies indicate that the neurons are unipolar and have usually one, sometimes several projections. They differ in the pattern of branching as well as in the projections to peripheral nerves. However, almost all of them have vast dendritic regions in the central nervous system including central sensory nucleus of the right parietal ganglion.

Animals↗
PubMed1982

Long-term synaptic potentiation in the superior cervical ganglion.

Brief tetanic stimulation of the preganglionic nerves to the superior cervical ganglion enhances the postganglionic response to single preganglionic stimuli for 1 to 3 hours. This long-term potentiation of transmission through the ganglion is apparently not attributable to a persistent muscarinic action of the preganglionic neurotransmitter, acetylcholine, since neither the magnitude nor the time course of the phenomenon is reduced by atropine. The decay of long-term potentiation can be described by a first-order kinetic process with a mean time constant of 80 minutes. We conclude that long-term potentiation, once considered a unique property of the hippocampus, is in fact a more general feature of synaptic function. This form of synaptic memory may significantly influence information processing and control in other regions of the nervous system, including autonomic ganglia.

Animals↗
PubMed1986

Percutaneous radio-frequency thermocoagulation with low temperature in the treatment of essential glossopharyngeal neuralgia.

Two cases of essential glossopharyngeal neuralgia treated successfully with percutaneous radio-frequency thermocoagulation are reported. In order to avoid cardiovascular complications due to interference with the vagus nerve, a modification of the technique previously used is proposed. The modification used in the cases presented here consists in the use of lower temperature during a shorter time with four progressive steps controlled with electrical stimulation. A small-surface active electrode, exact location in the petrous ganglion, permanent stimulation control, and a smaller thermal lesion are the cardinal features of the technique used in the cases reported.

Dermatologic Surgical Procedures↗
PubMed2002

Triggers of ventricular tachyarrhythmias and therapeutic effects of nicorandil in canine models of LQT2 and LQT3 syndromes.

OBJECTIVES: We sought to identify the triggers of ventricular tachyarrhythmia (VTA) in experimental models of long QT type 2 (LQT2) and long QT type 3 (LQT3) syndromes. BACKGROUND: Most adverse cardiac events occurring in the long QT type 1 syndrome are related to sympathetic nerve activity. In contrast, various factors may trigger VTA in patients with LQT2 and LQT3. METHODS: The mode of onset of VTA and therapeutic effects of the potassium-adenosine triphosphate channel opener nicorandil were compared in canine models of LQT2 and LQT3, using three induction protocols: 1) bradycardia produced by atrioventricular block (BRADY); 2) programmed ventricular stimulation; and 3) electrical stimulation of the left stellate ganglion (left stellate stimulation [LSS]). Transmural unipolar electrograms were recorded, and the activation-recovery interval (ARI) was measured. RESULTS: Ventricular tachyarrhythmias developed during BRADY in all six experiments in the LQT3 model, but in none of the six experiments in LQT2. Programmed ventricular stimulation induced VTA in two experiments of the LQT2 model, but in none of the LQT3 experiments. Stimulation of the left stellate ganglion induced VTA in three experiments in LQT2 and in two experiments in LQT3. Nicorandil caused greater shortening of ARI and greater attenuation of transmural ARI dispersion in the LQT2 model than in the LQT3 model. After treatment with nicorandil, a single VTA was induced in the LQT2 model by LSS, whereas in the LQT3 model, VTA remained inducible by BRADY in four experiments and LSS in one experiment. CONCLUSIONS: An abrupt increase in sympathetic activity appeared arrhythmogenic in both models. Nicorandil attenuated the heterogeneity of ventricular repolarization and suppressed the induction of VTA in the LQT2 model, but had a limited therapeutic effect in the LQT3 model.

Animals↗
PubMed1996

Monkey central retinal artery is innervated by nitroxidergic vasodilator nerves.

PURPOSE: To determine whether the monkey central retinal artery is innervated by vasodilator nerves and to analyze the mechanism underlying the neurogenic response. METHODS: Changes in isometric tension were recorded in helical strips of the arteries, which were stimulated by transmurally applied electrical pulses or nicotine. The presence of perivascular nerve fibers containing nitric oxide (NO) synthase immunoreactivity was determined histologically. RESULTS: Transmural electrical stimulation (5 Hz) and nicotine produced a relaxation of the arterial strips denuded of the endothelium, treated with prazosin, and contracted with prostaglandin F2 alpha. The response was not influenced by timolol, atropine, and indomethacin, but it was abolished by methylene blue and oxyhemoglobin. NG-nitro-L-arginine, a NO synthase inhibitor, abolished the neurogenic relaxation, and L-arginine restored the response. Antagonists of calcitonin gene-related peptide and vasoactive intestinal polypeptide in sufficient concentrations did not influence the response to nerve stimulation by nicotine. There were abundant nerve fibers and bundles containing NO synthase immunoreactivity in the adventitia. CONCLUSIONS: Monkey central retinal arteries are innervated by NO synthase-containing nerves that liberate NO possibly as a neurotransmitter on excitation to produce muscular relaxation.

Animals↗