Characteristics of the galanin-induced depolarization of mudpuppy parasympathetic postganglionic neurons

The depolarization of mudpuppy parasympathetic cardiac neurons, produced by pressure application of the neuropeptide galanin, has been characterized. The amplitude and duration of the depolarization were dependent on the duration of the galanin application. The amplitude of the depolarization increased with hyperpolarization and the reversal potential determined by extrapolation was approximately +10 mV. The amplitude and time course of the galanin-induced depolarization were not changed by substitution of either manganese or magnesium for extracellular calcium, but were decreased by exposure to 50-100 microM d-tubocurarine. It is proposed that the galanin-induced depolarization results from a receptor-activated, nonselective, cation channel; and further, that the receptor initiating depolarization differs from the galanin receptor mediating hyperpolarizing responses in these parasympathetic neurons.     

Afferent neurons of the hypoglossal nerve of the rat as demonstrated by horseradish peroxidase tracing

Summary Cell bodies of sensory neurons of the rat's hypoglossal nerve were demonstrated by the somatopetal horseradish peroxidase (HRP) transport technique. Labelled perikarya were found within the second and third cervical spinal ganglia and in the vagal sensory ganglia.After application of HRP to the cut peripheral trunk of the hypoglossal nerve about 200 labelled cell bodies were counted in each animal. The vast majority of the axons from cervical spinal ganglion cells reach the hypoglossal nerve via the descending ramus (N. descendens hypoglossi). However, there may exist an additional pathway, probably via the cervical sympathetic trunk.Application of HRP to the medial and lateral end branches led to a labelling of much fewer spinal ganglion cells while the number of labelled vagal sensory neurons remained unchanged. Thus, it is suggested that the majority of the cervical afferents of the hypoglossal nerve originates within the extrinsic tongue musculature and the geniohyoid muscle, whereas the vagal afferents may perhaps derive exclusively from the intrinsic muscles.Histograms of the mean diameters of labelled cell bodies show a predominance of very small perikarya. This contrasts with the diameter distribution of sensory perikarya labelled after HRP application to nerves supplying other skeletal muscles. It is therefore assumed that the afferent component of the hypoglossal nerve is composed mainly of small-calibre axons.Supported by the Hartmann Müller-Stiftung, ZürichPart of this work was presented at the 74. Versammlung der Anatomischen Gesellschaft in Regensburg, March 1979     

Parasympathetic postganglionic cells in the glossopharyngeal nerve trunk and their relationship to unmyelinated nerve fibers in the fungiform papillae of the frog

The glossopharyngeal nerve of the frog is made up of afferent nerve fibers and efferent, parasympathetic and sympathetic nerve fibers. The precise origin and course of the parasympathetic efferent nerve fibers in the fungiform papillae of the frog's tongue were investigated. We found the ganglionic cells in the lingual branch of the frog glossopharyngeal nerve. The surface of the ganglionic cell bodies was partly covered by synaptic endings that impinged upon it. Synaptic endings contained clear synaptic vesicles and large dense-cored vesicles. After cutting of the glossopharyngeal nerve proximal to the jugular ganglion, synaptic endings were found to show definite signs of degeneration. These findings led us to the conclusion that the ganglionic cells in the lingual branch of the glossopharyngeal nerve are the parasympathetic postganglionic cells. After cutting of the glossopharyngeal nerve distal to the jugular ganglion, some unmyelinated nerve fibers in the fungiform papillae and postganglionic cells in the lingual branch remained intact. These results strongly suggest that the origin of some of the unmyelinated nerve fibers is the parasympathetic postganglionic cell in the lingual branch.     

Evidence for parasympathetic vasodilator fibres in the rat masseter muscle

The present study was designed to examine (1) whether there are vasodilator fibres in the masseter muscle, and (2) if there are, to establish the neural pathways mediating these responses in urethane-anaesthetized rats. Electrical stimulation of the central cut end of the lingual nerve (LN) elicited intensity- and frequency-dependent increases of the blood flow in the masseter muscle (MBF) and lower lip (LBF). Increases in both the MBF and LBF evoked by the LN stimulation were reduced by hexamethonium in a dose-dependent manner (1–10 mg kg⁻¹). Pretreatment with phentolamine or propranolol at a dose of 100 μg kg⁻¹ had no effect on the increases in either MBF or LBF evoked by LN stimulation. Pretreatment with atropine (100 μg kg⁻¹) significantly reduced the MBF increase induced by LN stimulation, but not that in the LBF. The sectioning of the superior cervical sympathetic trunk did not affect the responses. MBF increases occurred with electrical stimulation of the trigeminal ganglion, and these increases were significantly reduced by the administration of hexamethonium and atropine. Lidocaine microinjection into the trigeminal spinal nucleus or salivatory nuclei caused a significant attenuation of the LN-induced MBF increases. When wheat germ agglutinin–horseradish peroxidase (WGA–HRP) was injected into the masseter muscle, labelled neurones were abundantly observed in the otic ganglion. The present study indicates that there are parasympathetic cholinergic and noncholinergic vasodilator fibres originating from cell bodies in the otic ganglion in the rat masseter muscle. The MBF increase evoked by activation of the parasympathetic fibres occurred via the trigeminal mediated reflex, suggesting that the novel parasympathetic vasodilator response may play an important role in the regulation of the haemodynamics of jaw muscles.     

Anatomical localization of afferent and postganglionic sympathetic neurons innervating the rat ovary

The fluorescent retrograde tracer, True blue, was applied directly to either the superior ovarian nerve (SON) or the ovarian plexus nerve (OPN) in the rat. Afferent perikarya were located in lower thoracic-upper lumbar dorsal root ganglia and projected to the ovary via both nerve routes. Postganglionic sympathetic efferent perikarya were located in both prevertebral and thoracolumbar paravertebral ganglia and also utilized both the SON and OPN to reach the ovary. The significance of the dual origin of postganglionic sympathetic neurons innervating the rat ovary is not known.     

Respiratory modulation of pre- and postganglionic lumbar vasomotor sympathetic neurons in the rat

The respiratory contribution to the activity of lumbar vasomotor pre- and postganglionic neurons was compared with previously reported respiratory patterns in the activity of neurons in the rostral ventrolateral medulla (RVLM-SE). Two patterns of respiratory modulation were observed characterized by (1) a depression of activity during inspiration and a postinspiratory peak (n = 19), and (2) a peak of activity during inspiration (n = 3). These patterns were similar to those previously reported in RVLM-SE neurons. The latency from the phrenic burst to the onset of respiratory modulation was consistent with the conduction time from the RVLM to the sympathetic chain. This suggests that respiratory modulation observed in lumbar sympathetic activity originates, in part, in RVLM-SE neurons.     

A subpopulation of preganglionic parasympathetic neurons in the rat contain adenosine deaminase

Immunohistochemical staining and retrograde fluorescent tracing techniques were used to demonstrate the presence of adenosine deaminase in preganglionic parasympathetic neurons. Both brainstem and sacral spinal cord parasympathetic nuclei were found to contain a subpopulation of neurons immunoreactive for adenosine deaminase. Immunostaining of preganglionic neurons in brainstem was restricted to a group of cells which were shown by retrograde tracing with Fast Blue to project exclusively to the sphenopalatine ganglion. This group was defined as the lacrimo-nasopalatine parasympathetic nucleus. Neurons in all other cranial preganglionic centers were devoid of adenosine deaminase immunoreactivity. In spinal cord adenosine deaminase-immunoreactive neurons were found in the intermediolateral gray matter in the region of the sacral parasympathetic nucleus. Injections of Fast Blue into the pelvic ganglion labeled large numbers of neurons in this nucleus, only some of which contained adenosine deaminase. The majority of neurons immunoreactive for adenosine deaminase were also shown to be immunoreactive for choline acetyltransferase in both brainstem and sacral parasympathetic nuclei. The present results show that a subclass of preganglionic parasympathetic neurons are among the few structures in the central nervous system that express what appear to be high levels of adenosine deaminase. This observation together with evidence suggesting that purines serve as neurotransmitters in some sacral parasympathetic neurons supports the notion that adenosine deaminase may constitute a marker for adenine nucleoside and/or nucleotide neurotransmission.     

细胞内记录大鼠离体颈上神经节后神经元膜电导的实验研究

应用细胞内生物电记录技术,观测大鼠离体颈上神经节后神经元在静息状态,快兴奋性突触后电位(f-EPSP)发生期间的膜电导以及膜时间常数和膜电容.静息状态下膜电导为(16.5±7.4)nS(n=45),快兴奋性突触后电位(f-EPSP)发生期间的膜电导为(27.2±5.6)nS(n=42),后者明显高于前者(P＜0.05);膜时间常数无明显变化;膜电容也有明显差异.快兴奋性突触后电位(f-EPSP)发生期间的膜电导的增大和翻转电位值16mV的结果提示交感神经节内快兴奋传递过程是几种阳离子通道(如Gk,Gna)同时开发的净效果.本实验为研究各种物理因素(电离辐射,电磁波,激光等)对交感神经节内快兴奋传递过程的影响提供基础理论依据.     

Synaptic potentials induced by postganglionic stimulations in cat bladder parasympathetic neurones

Intracellular recording techniques were used to examine and compare synaptic potentials evoked by stimulating pre- and postganglionic nerve trunks in cat bladder parasympathetic ganglia. In the 76 ganglion cells exammed, two types of responses were recorded on stimulating the postganglionic nerve: an antidromic action potential (type Post NS1;n=30) or a fast excitatory postsynaptic potential (f-EPSP; type PostNS2;n=46) which resulted in an orthodromic-like action potential. In some of the cells exhibiting a PostNS1 response (n=19), a fast depolarization was superimposed on the antidromic spike. This depolarization was due to the synaptic activation of nicotinic receptors. In many of the cells exhibiting either PostNS1 or PostNS2 responses, repetitive stimulation of the postganglionic nerve induced a slow hyperpolarization. Applying nicotinic (hexamethonium, methonium, 0.5–1 mM), muscarinic (atropine, 1 M), alpha-adrenergic (phentolamine, 1 M) and purinergic (caffeine, 0.5–1 mM) receptor antagonists completely inhibited the tetanus-induced slow hyperpolarization in some cells (n=5). In other cells (n=15), a slow hyperpolarization persisted in the presence of these antagonists. These results indicate that stimulation of the postganglionic nerve trunk of cat bladder parasympathetic ganglia can elicit not only an antidromic action potential, but also synaptic potentials which are mediated by the activation of cholinergic (nicotinic and muscarinic), noradrenergic and purinergic receptors, as well as a non-cholinergic, non-alpha-adrenergic and non-purinergic synaptic potential.     

The training-induced changes on automatism, conduction and myocardial refractoriness are not mediated by parasympathetic postganglionic neurons activity

The purpose of this study is to test the role that parasympathetic postganglionic neurons could play on the adaptive electrophysiological changes produced by physical training on intrinsic myocardial automatism, conduction and refractoriness. Trained rabbits were submitted to a physical training protocol on treadmill during 6 weeks. The electrophysiological study was performed in an isolated heart preparation. The investigated myocardial properties were: (a) sinus automatism, (b) atrioventricular and ventriculoatrial conduction, (c) atrial, conduction system and ventricular refractoriness. The parameters to study the refractoriness were obtained by means of extrastimulus test at four different pacing cycle lengths (10% shorter than spontaneous sinus cycle length, 250, 200 and 150 ms) and (d) mean dominant frequency (DF) of the induced ventricular fibrillation (VF), using a spectral method. The electrophysiological protocol was performed before and during continuous atropine administration (1 μM), in order to block cholinergic receptors. Cholinergic receptor blockade did not modify either the increase in sinus cycle length, atrioventricular conduction and refractoriness (left ventricular and atrioventricular conduction system functional refractory periods) or the decrease of DF of VF. These findings reveal that the myocardial electrophysiological modifications produced by physical training are not mediated by intrinsic cardiac parasympathetic activity.     

The inhibition of hypoglossal motoneurones by impulses in the glossopharyngeal nerve of the rat

Summary Stimulation of the glossopharyngeal nerve produced inhibitory post synaptic potentials in neurones of the hypoglossal nucleus of the rat. The corresponding pause in the amino acid induced firing of these cells was antagonized by electrophoretically administered strychnine but not by bicuculline. Strychnine and bicuculline antagonized the actions of glycine and GABA respectively on these cells. The findings suggest that the transmitter for this synaptic inhibition is a glycine-like amino acid.C. J. Martin Travelling Fellow.Wellcome Trust/Animal Health Trust Research Fellow.     

Glucose and leucine uptake in the hypoglossal nucleus after hypoglossal nerve transection with and without prevented regeneration in the Sprague-Dawley rat

We studied [14C]2-deoxyglucose and [14C]leucine uptake in the rat hypoglossal nucleus after hypoglossal nerve transection and when regeneration was prevented by placing a nylon ligature around the nerve proximal to the cut. Glucose and leucine uptake increased after nerve transection in both the animals with nerve transection alone and with the ligature. Both the glucose and leucine uptake increased more in animals with the ligature. The glucose and leucine uptakes returned to normal at 30 and 45 days, respectively, after transection alone and at 60 days in animals in whom regeneration was prevented with a ligature. This suggests that there is a more powerful stimulus to regeneration when regeneration is prevented but that some mechanism turns the process off after a fixed time.     

Fasting increases glucose and leucine uptake during regeneration of the hypoglossal nerve in the rat

Glucose uptake is increased during motoneuron regeneration. Since this glucose is probably used as an energy source for axonal regeneration we postulated that hypoglycemia might interfere with motoneuron regeneration. In order to partially test this hypothesis we attempted to induce moderate hypoglycemia by fasting rats for 3 days between the time of hypoglossal nerve transection and the time of [14C]2-deoxyglucose (2-DG) and [14C]leucine measurement. We transected one hypoglossal nerve, leaving the other intact, and measured the glucose uptake quantitatively or leucine uptake semiquantitatively in the hypoglossal nucleus. We found that both glucose and leucine uptake were increased in the hypoglossal nuclei during regeneration of the nerve in the fasted animals above that in the normally fed animals. This suggests that fasting creates a deficit of glucose and perhaps leucine which induces increased uptake.     

Axotomy induces intranuclear immunolocalization of neuron-specific enolase in facial and hypoglossal neurons of the rat

Summary Neuron-specific enolase as an enzyme of the glycolytic pathway is localized in the cytoplasm of nerve cells, but not in the cell nucleus. We have applied immunocytochemistry with 164 000 polyclonal anti-rat neuron-specific enolase to the brainstem of male and female adult Wistar rats following: (a) transection of the facial nerve with immediate microsurgical nerve suture (facial-facial anastomosis), (b) transection of the hypoglossal nerve with immediate suture (hypoglossal-hypoglossal anastomosis) and (c) transection of the facial and hypoglossal nerve with immediate suture of the proximal hypoglossal to the distal facial nerve stump (hypoglossal-facial anastomosis). Studying the intracellular immunolocalization of neuron-specific enolase in neurons of the facial and hypoglossal nucleus we detected that (1) in normal rats about 20% of all facial and hypoglossal neurons display not only cytoplasmic, but also intranuclear neuron-specific enolase-like immunoreactivity and (2) following any axotomy of the facial or hypoglossal peripheral nerve, the perikarya of all injured motoneurons react by an outstanding increase of neuron-specific enolase-like immunoreactivity in the karyoplasm. Similar findings were obtained in experiments on non-fixed cultured Neuro-2a cells that had been lesioned with hydrogen peroxide. Counting the absolute numbers of normal and reactive neurons at 1–365 days post axotomy revealed that the increase of neuron-specific enolase in neuronal cell nuclei is temporary and reversible. It is first detected at 2 days post axotomy, reaches its maximum at 10–18 days post axotomy and is no longer evident 56 days following surgery. These findings suggest that the intranuclear neuron-specific enolase-like immunoreactive material may serve a regulatory function on the genome.