Central distribution of afferent and efferent components of the pudendal nerve in cat

Central distribution of afferent and efferent components of the pudendal nerve was examined in the cat by the HRP method after applying HRP to the central cut end of the pudendal nerve. Retrogradely labeled neuronal cell bodies were located primarily in the feline homologue of the Onuf's X nucleus, constituting a slender longitudinal cell column in the ventral horn of the S1 and S2 cord segments. The Onuf's nucleus was present constantly from middle S1 to high S2 cord segments, and occasionally extended rostrally to high S1 or low L7, and caudally to middle S2, low S2, or high S3 cord segments. No sex differences were observed in the distribution pattern, number, and soma size of labeled neurons in the Onuf's nucleus. Transganglionically labeled dorsal root fibers were found to terminate ipsilaterally in the lamina I of the dorsal horn at levels of lower lumbar, sacral, and higher coccygeal cord segments and the gracile nucleus, and bilaterally with an ipsilateral predominance in the dorsal commissural gray and laminae III, IV, V, and VI of the dorsal horn at levels of lower lumbar, sacral, and higher coccygeal cord segments. Some labeled dorsal root fibers appeared to end ipsilaterally in the regions where the sacral parasympathetic preganglionic neurons have been shown to be located.     

Central distribution of primary afferent fibers in the Arnold's nerve (the auricular branch of the vagus nerve): A transganglionic HRP study in the cat

Central projections of the Arnold's nerve (the auricular branch of the vagus nerve; ABV) of the cat were examined by the transganglionic HRP method. After applying HRP to the central cut end of the ABV, HRP-labeled neuronal somata were seen in the superior ganglion of the vagus nerve. Main terminal labeling was seen ipsilaterally in the solitary nucleus, in the lateral portions of the ventral division of the principal sensory trigeminal nucleus, in the marginal regions of the interpolar subnucleus of the spinal trigeminal nucleus, in the marginal and magnocellular zones of the caudal subnucleus of the spinal trigeminal nucleus, in the ventrolateral portions of the cuneate nucleus, and in the dorsal horn of the C1–C3 cord segments. In the solitary nucleus, labeled terminals were seen in the interstitial, dorsal, dorsolateral and commissural subnuclei; some of these terminals may be connected monosynaptically with solitary nucleus neurons which send their axons to the somatomotor and/or visceromotor centers in the brainstem and spinal cord.     

Central distribution of efferent and afferent components of the pudendal nerve in macaque monkeys

Central distribution of efferent and afferent components of the pudendal nerve was studied by the horseradish peroxidase (HRP) method in 13 macaque monkeys, i.e., in nine Japanese monkeys (Macaca fuscata), two rhesus monkeys (Macaca mulatta), and two crab-eating monkeys (Macaca fascicularis). The enzyme was applied to the central cut end of the pudendal nerve; then the monkeys were allowed to survive for 36 to 72 hr. Retrogradely labeled neuronal cell bodies of pudendal motoneurons constituted a slender longitudinal cell column in the ventral horn. The cell column extended from high or middle S1 to high or middle S2 in eight monkeys, from middle or low L7 to high S2 in four monkeys, and from high L7 to middle S1 in a monkey. The cell column appeared to correspond to Onuf's X nucleus in man. No sex difference was recognized in the position of the cell column. The average number of HRP-labeled pudendal motoneurons was larger in male than in female adult Japanese monkeys, whereas no sex difference was found in the average soma diameter of the pudendal motoneurons. Transganglionically labeled axons entered into the spinal cord through the S1 and S2 dorsal roots in 12 monkeys and through the L7 and S1 dorsal roots in one monkey. Labeled axons were distributed ipsilaterally in laminae I-VI and X of the spinal cord at the same and adjacent levels of entry of HRP-labeled dorsal root fibers (from L7 to S3 in 12 monkeys and from L6 to S3 in one monkey).(ABSTRACT TRUNCATED AT 250 WORDS)     

Morphological and functional properties of trigeminal nucleus oralis neurons projecting to the trigeminal motor nucleus of the cat

Horseradish peroxidase (HRP) was injected into the somata located in the rostrodorsomedial part (Vo.r) of the trigeminal nucleus oralis; an axonal projection to the trigeminal motor nucleus (Vmo) was demonstrated in two Vo.r neurons. The two neurons differed in their morphological and functional properties. The first Vo.r neuron responded to stimulation of low-threshold mechanoreceptors and its stem axon gave off massive axon collaterals that issued terminal branches to the dorsolateral subdivision of Vmo, Vo.r, and the medial and lateral parts of the lower brainstem reticular formation. The second Vo.r neuron was activated by stimulation of the tooth pulp or lingual nerve at twice longer latency than that of the first neuron. This stem axon was divided into two main ascending and one descending branches, and one of the main ascending branches was further bifurcated into two branches. The main non-bifurcated ascending branch gave off 4 collaterals, two of which sent terminal branches into the dorsolateral subdivision of Vmo and others into the Vo.r and juxta-trigeminal regions. The somato-dendroarchitectonic differences were also described in the two Vo.r neurons stained.     

Central distribution and peripheral functional properties of afferent and efferent components of the superior laryngeal nerve: Morphological and electrophysiological studies in the rat

The central distribution of the afferent and efferent components of the superior laryngeal nerve (SLN), which in the rat is ramified into the three branches of the rostral branch (R.Br), middle branch (M.Br), and caudal branch (C.Br), was examined after application of horseradish peroxidase conjugated with wheat germ agglutinin (HRP-WGA) to the proximal cut end of each branch. In addition, the afferent and efferent neural activities of each branch were recorded to investigate the functional properties. The present study provided several new findings as to the distribution of each branch and the functional properties of the SLN. The following conclusions were drawn: 1) the R.Br, containing only afferent fibers projecting to the ipsilateral lateral region of the nucleus of the solitary tract (NST), extends between slightly below the obex and the region approximately 0.6 mm rostral from the obex, and it corresponds to the interstitial subnucleus of the NST; 2) the M.Br, innervating the cricothyroid muscle, contains only efferent fibers originating ipsilaterally from the motoneurons localized within the ambiguus nucleus (Amb) and in the area ventrolateral to the Amb; and 3) the C.Br, which innervates the inferior pharyngeal constrictor muscle, contains both efferent and afferent fibers. HRP-WGA-labeled cells are distributed within both the Amb and the dorsal motor nucleus of the vagus nerve, ipsilateral to the injection site. Afferent proprioceptive fibers project to the ipsilateral interstitial subnucleus of the NST. The present results provide evidence that each branch of the SLN has distinctive functional properties and contributes to the laryngeal functions. © 1996 Wiley-Liss, Inc.     

Retractor bulbi muscle responses to oculomotor nerve and nucleus stimulation in the cat

This study demonstratesthe presence of retractor bulbi motoneurons within the oculomotor nucleus which activate muscle units within all 4 slips of the cat retractor bulbi muscle. These muscle units are mechanically different and physiologically separate from retractor bulbi muscle units innervated by the abducens nerve. The retractor bulbi muscle, then, is innervated by two separate pools of motoneurons whose axons are carried in two different cranial nerves. These observations of mechanical properties of retractor bulbi muscle suggest that the oculomotor retractor bulbi motor units may be activated during patterned eye movements.     

The central distribution of the cervical vagus nerve and gastric afferent and efferent projections in the rat

The medullary distribution of afferent fibers and cells of origin of the cervical vagal trunk and of the vagal innervation of the stomach have been studied using the anterograde and retrograde transport of horseradish peroxidase (HRP). Injections of HRP were made into the cervical vagus nerve, the stomach wall, the proximal small intestine, or the peritoneal cavity. Two to four days following the injections, the rats were perfused and the medullae oblongatae and nodose ganglia were processed using the tetramethyl benzidine method. Cervical vagus nerve injections of HRP resulted in heavy anterograde labeling in the ipsilateral nucleus of the tractus solitarius (NTS) and the commissural nucleus. Lighter labeling was seen in these regions on the contralateral side, but did not extend as far rostrally in the NTS. Labeling was also seen in the area postrema. Retrogade labeling of somata was present in the ipsilateral side in the nodose ganglion, throughout the whole extent of the dorsal motor nucleus of the vagus, much of the nucleus ambiguus and in rostral levels of the cervical spinal cord. After stomach injections, labeling indicative of afferent fibers was observed bilaterally in the dorsomedial and medial portions of the NTS and in the commissural nucleus. Labeled efferent fibres arose from neurons in the dorsal motor nucleus of the vagus, nucleus ambiguus and the cervical spinal cord. Retrogradely labeled somata were found bilaterally, throughout the rostrocaudal length of the dorsal motor nucleus in all cases with stomach injections. In some, but not all cases, labeled somata were seen bilaterally in compact areas within the nucleus ambiguus, particularly rostrally. Control injections of HRP into the intestinal wall and peritoneal cavity indicated that the stomach was the primary source of afferent and efferent labeling in the medulla following subdiaphragmatic injections.     

Trigeminal mesencephalic neurons innervating functionally identified muscle spindles and involved in the monosynaptic stretch reflex of the lateral pterygoid muscle of the guinea pig

Location of the neurons in the trigeminal mesencephalic nucleus innervating stretch receptors of the lateral pterygoid muscle and the mode of their synaptic connection on the lateral pterygoid motoneurons of the guinea pig were studied physiologically as well as morphologically, in comparison with the trigeminal mesencephalic neurons innervating muscle spindles in the superficial masseter muscle, with the following results: stimulation of the caudal half of the trigeminal mesencephalic nucleus evoked monosynaptic excitatory postsynaptic potentials in the ipsilateral lateral pterygoid motoneurons. Stimulation of the lateral pterygoid nerve directly evoked spike potentials in the neurons located in the caudal half of the ipsilateral trigeminal mesencephalic nucleus, which responded with increased firing to stretch, and with silent period to twitch, of the ipsilateral lateral pterygoid muscle. Averaging of intracellular potentials of the lateral pterygoid motoneurons with extracellular spike potentials of these trigeminal mesencephalic neurons revealed excitatory postsynaptic potentials after a monosynaptic latency, but no inhibitory postsynaptic potentials. Injection of horseradish peroxidase into the lateral pterygoid muscle labeled 15-20 cells in the caudal half of the ipsilateral trigeminal mesencephalic nucleus, while 174-228 cells retrogradely labeled by horseradish peroxidase were found throughout the whole rostrocaudal extent of the ipsilateral trigeminal mesencephalic nucleus following injection of horseradish peroxidase into the masseter muscle. It was concluded that neurons in the caudal half of the trigeminal mesencephalic nucleus send their peripheral processes to stretch receptors, presumably muscle spindles, in the ipsilateral lateral pterygoid muscle and that their central processes have excitatory synapses on ipsilateral lateral pterygoid motoneurons, thus comprising the afferent limb of a monosynaptic stretch reflex arc of the lateral pterygoid muscle of the guinea pig.     

Ultrastructure of the dorsal motor nucleus of the vagus nerve in monkey with a comparison of synaptology in monkey and cat

Neurons of the dorsal motor nucleus of the vagus nerve were studied following injections of horseradish peroxidase into the vagus nerve in a monkey (Macaca fascicularis). In frozen sections, the dorsal motor nucleus appeared to be completely filled by labeled medium-sized (20-30 micron in long axis) neurons. Labeled dendrites from these neurons often extended outside the borders of the nucleus into the nucleus of the tractus solitarius. In 1 micron thick plastic sections and ultrathin sections of the dorsal motor nucleus, two distinct types of neurons were observed with the light and electron microscope. Medium-sized neurons with abundant cytoplasm and an oval nucleus were retrogradely labeled with HRP, while small (10-15 micron in long axis) neurons with a paucity of organelles and an invaginated nucleus remained unlabeled. Medium-sized neurons outnumbered the small neurons by approximately five to one. The synaptic organization of the dorsal motor nucleus in monkey was studied and compared with that in cat. The porportions of different types of axosomatic synapses were similar in both species. Terminals containing round vesicles and making symmetrical or asymmetrical contact with the postsynaptic structure were more common than synaptic terminals containing pleomorphic vesicles. In both species, there was a slightly greater synaptic density on the medium-sized neurons than on the small neurons. The synaptic density in the monkey dorsal nucleus was greatest on the smallest dendrites in the neuropil and least on the somata.     

Effect of electrical stimulation of the dorsal nucleus of the vagus nerve on gastric acid secretion in cats.

Electrical stimulation of 3 to 9 V, 100 impules/s 1-ms duration/impulse, applied to the right or left dorsal motor nucleus of the vagus nerve (DNV) produced a significant increase in volume, acidity, and gastric acid output in 14 cats under sodium pentobarbital anesthesia. The increase in acid output occurred during the first 15 min of stimulation or immediately after the stimulation and in some cats lasted for the next 30 min to more than 2 h. In no case did the stimulation within the DNV evoke a decrease in gastric acid secretion. Similar electrical stimulation in sites outside the DNV had no effect on gastric acid secretion. Motor effects such as opening of the mouth, movements of the tongue and whiskers, and salivation were observed to occur randomly during stimulation at sites both inside and outside the DNV zone and were not correlated with changes in gastric acid secretion. After recovery from the acute experiment, two cats were tested under chronic conditions. Electrical stimulation with low voltage applied to the previously effective electrode tips repeatedly produced an increase in the volume of secretion in one cat and an increase in both volume and acidity of secretion in the other cat. This study provided further evidence that the DNV is a secretomotor center.     

Differential distribution of cell bodies and central axons of mesencephalic trigeminal nucleus neurons supplying the jaw-closing muscles and periodontal tissue: A transganglionic tracer study in the cat

Distribution of cell bodies and central axons of mesencephalic trigeminal nucleus (MTN) neurons were examined in the cat by the method of transganglionic transport of horseradish peroxidase (HRP). Jaw-closing muscle afferent MTN neurons were distributed throughout the whole rostrocaudal extent of the MTN, and sent their axons ipsilaterally to the supratrigeminal and intertrigeminal regions, dorsolateral division of the motor trigeminal nucleus, lateral part of the medullary reticular formation, lamina VI of C1-C3 cord segments, and cerebellum. On the other hand, periodontal receptor afferent MTN neurons were located mainly in the caudal part of the MTN, and sent their axons ipsilaterally to the supratrigeminal region and cerebellum. The existence of multipolar MTN neurons with 1-9 smooth dendrites was also confirmed; most of them were jaw-closing muscle afferent neurons.     

Direct amygdaloid projections to the dorsal motor nucleus of the vagus nerve: a light and electron microscopic study in the rat

The projections from the central nucleus of the amygdala to the dorsal vagal complex were examined in the rat by means of anterograde and retrograde axonal transport of wheat germ agglutinin-horseradish peroxidase and anterograde degeneration. Light microscopic findings confirmed that the amygdala projects to the dorsal motor nucleus (DMV) and the nucleus of the solitary tract. Electron microscopic experiments demonstrated degenerating axosomatic and axodendritic terminals in the DMV following electrolytic lesions in the central nucleus of the amygdala.     

The distribution of glutamate, GABA and aspartate in the nucleus tractus solitarius of the cat

This report describes the distribution of glutamate, GABA and aspartate in the nucleus tractus solitarius (NTS), area postrema, dorsal vagal nucleus and hypoglossal nucleus. Glutamate levels were particularly high in the dorsal, medial and commissural nuclei of the NTS. Section of the IXth and Xth cranial nerves caused a bilateral decrease in glutamate (ipsilateral side = 48%; contralateral side = 36%) and ipsilateral decrease in GABA (27%) in the dorsal and medial NTS. The ipsilateral dorsal vagal nucleus showed a 48% decrease in glutamate and a 30% decrease in GABA after axotomy.     

The distribution of the cat''s carotid sinus nerve afferent and efferent cell bodies using the horseradish peroxidase technique

The location of both afferent and efferent carotid sinus nerve (CSN) cell bodies in the cat has been determined using the horseradish peroxidase (HRP) technique. Following a limited exposure of the central cut end of the CSN to HRP, labeled sensory ganglion cells were found in both the petrosal and superior ganglia of the IXth cranial nerve. An average of 387 in the former and 16 cells in the latter ganglion were labeled.

Retrogradely labeled neurons were found only within the ipsilateral medulla. These cells were both round and spindle shaped and had an average somal diameter of 19 μm. The number of these CSN efferent cell bodies ranged from 1 to a maximum of 20 in a given animal. They were found in both the nucleus parvocellularis and the retrofacial nucleus. In 8 cases axonal labeling was observed. Axons generally projected dorsomedially from the ventrolateral medulla.     

Primary afferent projections of the major splanchnic nerve to the spinal cord and gracile nucleus of the cat

Splanchnic afferent projections to the spinal cord and gracile nucleus were labeled following the application of HRP to the central cut end of the major splanchnic nerve. Labeled afferent fibers were detected in the ipsilateral dorsal column, in Lissauer's tract (LT), in laminae 1, 5, 7, and 10, and in the dorsal gray commissure at T1-T13 levels of the spinal cord. Afferent projections were not identified in laminae 2-4. Collaterals from LT projected ventrally along the lateral and medial margins of the dorsal horn (called lateral and medial pathways, respectively). Afferents in the lateral pathway formed small bundles, spaced rostrocaudally at intervals of 300-1,000 microns, which passed medially at the base of the dorsal horn into laminae 5, 7, and 10 and to the contralateral spinal cord. Some afferents in the lateral pathway projected to the intermediolateral nucleus where labeled sympathetic preganglionic neurons were located. Afferents in the medial pathway entered the lateral aspect of the dorsal column and projected as a group near the midline rostrally to the medulla. The dorsal column pathway terminated in the ventral gracile nucleus in four or five clusters, each occupying a region ranging in size from 0.01-0.1 mm3 and separated in the rostrocaudal axis by distances of 400-800 microns. These clusters were concentrated in the middle and caudal portions of the nucleus below the obex. A comparison of the present results with those from earlier experiments on the central projections of afferent fibers from the heart, kidney, and pelvic organs demonstrates a consistent pattern of visceral afferent termination in the thoracolumbar and sacral segments of the spinal cord. This is not unexpected, since visceral afferent pathways to different organs perform similar functions, such as the transmission of nociceptive information and the initiation of autonomic reflexes.     

Direct pathway from neurons in the ventrolateral medulla relaying cardiovascular afferent information to the supraoptic nucleus in the cat

In chloralose anesthetized cats experiments were done to electrophysiologically identify neurons in the ventrolateral medulla (VLM) which relay cardiovascular afferent information directly to the supraoptic nucleus (SON). Action potentials elicited antidromically by electrical stimulation of the SON were recorded from 69 histologically verified single units in the VLM. Single units responded with latencies corresponding to conduction velocities of 7.8 ± 0.6m/s. Of these units 26 were excited orthodromically by stimulation of the buffer nerves; 12 responded to stimulation of only the carotid sinus nerve, 7 responded to stimulation of only the aortic depressor nerve, and 7 responded to both buffer nerves. The axons of VLM units that responded to buffer nerves conducted at a significantly slower velocity than those of non-responsive units (5.7 ± 0.4and9.1 ± 0.8m/s, respectively). These data provide electrophysiological evidence of two different populations of VLM neurons which project directly to the SON, and suggest that the direct pathway from the VLM to the SON is involved in the release of vasopressin by SON neurons during activation of baroreceptor and chemoreceptor afferent fibers.     

Axonal transport of neurotrophins by visceral afferent and efferent neurons of the vagus nerve of the rat

The receptor-mediated axonal transport of [¹²⁵I]-labeled neurotrophins by afferent and efferent neurons of the vagus nerve was determined to predict the responsiveness of these neurons to neurotrophins in vivo. [¹²⁵I]-labeled neurotrophins were administered to the proximal stump of the transected cervical vagus nerve of adult rats. Vagal afferent neurons retrogradely transported [¹²⁵I]neurotrophin-3 (NT-3), [¹²⁵I]nerve growth factor (NGF), and [¹²⁵I]neurotrophin-4 (NT-4) to perikarya in the ipsilateral nodose ganglion, and transganglionically transported [¹²⁵I]NT-3, [¹²⁵I]NGF, and [¹²⁵I]NT-4 to the central terminal field, the nucleus tractus solitarius (NTS). Vagal afferent neurons showed minimal accumulation of [¹²⁵I]brain-derived neurotrophic factor (BDNF). In contrast, efferent (parasympathetic and motor) neurons located in the dorsal motor nucleus of the vagus and nucleus ambiguus retrogradely transported [¹²⁵I]BDNF, [¹²⁵I]NT-3, and [¹²⁵I]NT-4, but not [¹²⁵I]NGF. The receptor specificity of neurotrophin transport was examined by applying [¹²⁵I]-labeled neurotrophins with an excess of unlabeled neurotrophins. The retrograde transport of [¹²⁵I]NT-3 to the nodose ganglion was reduced by NT-3 and by NGF, and the transport of [¹²⁵I]NGF was reduced only by NGF, whereas the transport of [¹²⁵I]NT-4 was significantly reduced by each of the neurotrophins. The competition profiles for the transport of NT-3 and NGF are consistent with the presence of TrkA and TrkC and the absence of TrkB in the nodose ganglion, whereas the profile for NT-4 suggests a p75 receptor-mediated transport mechanism. The transport profiles of neurotrophins by efferent vagal neurons in the dorsal motor nucleus of the vagus and nucleus ambiguus are consistent with the presence of TrkB and TrkC, but not TrkA, in these nuclei. These observations describe the unique receptor-mediated axonal transport of neurotrophins in adult vagal afferent and efferent neurons and thus serve as a template to discern the role of specific neurotrophins in the functions of these visceral sensory and motor neurons in vivo. J. Comp. Neurol. 393:102–117, 1998. Published 1998 Wiley-Liss, Inc.

1 This article is a US government work and, as such, is in the public domain in the United States of America.