Neurons of origin of the internal ramus of the rabbit accessory nerve: localization in the dorsal nucleus of the vagus nerve and the nucleus retroambigualis

The neurons of origin of the internal ramus of the rabbit accessory nerve were identified in the dorsal nucleus of the vagus nerve, using bilateral injections of horseradish peroxidase into the inferior vagal ganglion, soft palate, and pharynx, which were preceded by different combinations of the unilateral intracranial severings of the rootlets of the vagus and glossopharyngeal nerves, those of the cranial root of the accessory nerve, and the trunk of its spinal root. The neurons of origin occupied the caudal four-fifths of the dorsal vagal nucleus extending from about 1.0 mm rostral to the obex as far caudally as the second cervical spinal segment, with their number being about half the total number of neurons of the nucleus. Although considerably fewer, they were also located in the nucleus retroambigualis of the caudal half of the first cervical spinal segment and the second segment. Axons of most internal ramus neurons traversed the rootlets of the cranial accessory root. Axons of the few neurons located more caudally than about 1.0 mm caudal to the obex emerged from the upper cervical spinal cord to run along the trunk of the spinal accessory root before finally joining the internal ramus; caudal to the midlevel of the first cervical segment, the dorsal vagal nucleus and the nucleus retroambigualis contained neurons whose axons followed only that course.     

The relationship of the medullary catecholamine containing neurones to the vagal motor nuclei

We have re-examined in the rat the nuclear localization of the medullary catecholamine-containing cell groups (A1 and A2) and their relation to the vagal motor nuclei using a double labeling method. The vagal nuclei were defined by the retrograde transport of horseradish peroxidase applied to the cervical vagus, and noradrenergic and adrenergic neurons were stained with the peroxidase-antiperoxidase immunocytochemical method using an antibody to dopamine beta-hydrolase. The method allows visualization of both labels within single neurons. The neurons of the A2 group are primarily distributed in both the nucleus of the solitary tract and the dorsal motor nucleus of the vagus in a complex interrelationship that depends on the rostrocaudal level. Caudal to the obex, cells of the dorsal motor nucleus of the vagus are scattered among cells immunoreactive for dopamine beta-hydroxylase in the area considered to be the commissural subnucleus of the nucleus of the solitary tract. At levels near and slightly rostral to the obex, the dopamine beta-hydroxylase-positive cells are largely confined to nucleus of the solitary tract. However, the rostral third of the A2 group lies predominantly within dorsal motor nucleus, as defined by horseradish peroxidase labeled cells, with only a few cells in the nucleus of the solitary tract. A subset of the dopamine beta-hydroxylase positive cells within the rostral dorsal motor nucleus of the vagus are also vagal efferents. Our results suggest that a second population of dopamine beta-hydroxylase positive vagal efferents may exist ventrolaterally where neurons of the AI cell group intermingle with those of nucleus ambiguus.     

Autoradiographic localization of 3H-digoxin binding by neural cells in the medulla

The purpose of this investigation was to localize binding sites for the cardiac glycoside digoxin in the medulla of the rat in vivo. Adult male Sprague-Dawley rats were injected (IV) with 3H-digoxin and killed 30 minutes later. Autoradiographs of medullas showed evidence of 3H-digoxin binding to small- and medium-sized neural cells in the regions of the nucleus solitarius, dorsal motor nucleus of the vagus, area postrema, and in the zone between the area postrema and the underlying neuropil. However, the parasympathetic preganglionic neurons of the dorsal motor nucleus were not labeled. The 3H-digoxin-labeled cells in the medulla were located mainly in the commissural and medial portions of nucleus solitarius at the level of the area postrema. Animals injected with unlabeled digoxin followed by 3H-digoxin showed reduced binding of radioactivity. The small- and medium-sized neurons of the caudal portions of the nucleus solitarius are internuncial in position with respect to cardiovascular afferents of the glossopharyngeal and vagus nerves and sympathetic and parasympathetic cardiovascular efferent neurons of the medulla. The results of this study suggest that these 3H-digoxin-labeled cells, presumably neurons of nucleus solitarius, may possess high affinity binding sites for digoxin. Further, the area postrema, which lacks a blood-brain barrier, may provide a portal of entry for 3H-digoxin into regions of the medulla known to contain neurons that play a role in the regulation of cardiac rhythm.     

Persistence of fluoro-gold following degeneration of labeled motoneurons is due to phagocytosis by microglia and macrophages.

When the neural tracer Fluoro-Gold is used to retrogradely label a population of axotomized neurons, cellular labeling can persist in the axotomized nucleus even when Nissl staining indicates that the injured neurons have degenerated. In order to determine the identity of the labeled cells that remain, this study combines retrograde transport of Fluoro-Gold with immunocytochemical methods for identification of specific non-neuronal cell types following peripheral axotomy and Fluoro-Gold labeling of motoneurons in the dorsal motor nucleus of the vagus in neonatal and adult rats. Fourteen days following cervical vagotomy in neonatal rats, Nissl staining revealed a virtually complete loss of vagal motoneurons. Fourteen days after cervical vagotomy in adult rats, vagal motoneuronal loss was not yet extensive but chromatolysis had clearly begun. Injection of Fluoro-Gold into the vagus nerve just prior to the vagotomy led to Fluoro-Gold labeling of remaining vagal motoneurons. In addition, many other small, brightly labeled cells were present in the lesioned vagal nuclei of all rats. Immunofluorescent identification of astrocytes with anti-glial fibrillary acidic protein and microglia and macrophages with OX42 (anti-C3bi complement receptor) and ED1 (anti-monocyte/macrophage cytoplasmic antigen) demonstrated that the small, bright Fluoro-Gold-labeled cells were non-neuronal, non-astrocytic phagocytes, including microglia. These results indicate that phagocytic microglia and other macrophages sequester Fluoro-Gold in the axotomized dorsal motor nucleus of the vagus of neonatal and adult rats, leading to persistence of fluorescent cellular labeling following the loss of retrogradely labeled axotomized neurons.     

Nodose ganglionectomy selectively reduces muscarinic cholinergic and delta opioid binding sites in the dorsal vagal complex of the cat

The dorsal vagal complex of the medulla oblongata, comprising the nucleus tractus solitarii, the area postrema and the dorsal motor nucleus of the vagus nerve, is an important brainstem regulatory center for the autonomic nervous system. The major afferent input from abdominal and thoracic viscera to this region is via vagal sensory neurons which have their cell bodies in the nodose ganglion. Autoradiography has been used to study the effects of unilateral nodose ganglionectomy on receptor binding sites in this region of the brain for the neurotransmitters acetylcholine, norepinephrine, and opioids. Nodose ganglionectomy had no discernible effect on alpha 2 noradrenergic ([3H]p-aminoclonidine) or mu opioid [( 3H]Tyr-D-Ala-Gly-(NMePhe)-Gly-ol) binding sites. However, ganglionectomy did produce a 25% decrease in [3H]quinuclidinyl benzilate (muscarinic cholinergic) binding in the subnucleus gelatinosus of the solitary nucleus, and a marked decrease in [3H][D-Pen5]enkephalin (delta opioid) binding in the dorsomedial subnucleus of the nucleus tractus solitarii, ipsilateral to the lesion. These data suggest that muscarinic cholinergic and delta opioid receptors may be present on terminals of vagal afferent neurons that project to these specific brainstem regions. Since these vagal afferent neurons are known to arise, at least in part, from the gastrointestinal tract, it is possible that cholinergic and/or opioid receptors modulate specific autonomic functions associated with gastric sensory information such as satiety or nausea and emesis.     

Galanin inhibits gut-related vagal neurons in rats

Galanin plays an important role in the regulation of food intake, energy balance, and body weight. Many galanin-positive fibers as well as galanin-positive neurons were seen in the dorsal vagal complex, suggesting that galanin produces its effects by actions involving vagal neurons. In the present experiment, we used tract-tracing and neurophysiological techniques to evaluate the origin of the galaninergic fibers and the effect of galanin on neurons in the dorsal vagal complex. Our results reveal that the nucleus of the solitary tract is the major source of the galanin terminals in the dorsal vagal complex. In vivo experiments demonstrated that galanin inhibited the majority of gut-related neurons in the dorsal motor nucleus of the vagus. In vitro experiments demonstrated that galanin inhibited the majority of stomach-projecting neurons in the dorsal motor nucleus of the vagus by suppressing spontaneous activity and/or producing a fully reversible dose-dependent membrane hyperpolarization and outward current. The galanin-induced hyperpolarization and outward current persisted after synaptic input was blocked, suggesting that galanin acts directly on receptors of neurons in the dorsal motor nucleus of the vagus. The reversal potential induced by galanin was close to the potassium ion potentials of the Nernst equation and was prevented by the potassium channel blocker tetraethylammonium, indicating that the inhibitory effect of galanin was mediated by a potassium channel. These results indicate that the dorsal motor nucleus of the vagus is inhibited by galanin derived predominantly from neurons in the nucleus of the solitary tract projecting to the dorsal motor nucleus of the vagus nerve. Galanin is one of the neurotransmitters involved in the vago-vagal reflex.     

P2X(2) receptor immunoreactivity in the dorsal vagal complex and area postrema of the rat

Adenosine 5'-triphosphate (ATP) can function as a fast synaptic transmitter through its actions on ionotropic (P2X) and metabotropic (P2Y) receptors in neuronal tissue. The ionotropic receptors have been classified into seven subtypes (P2X(1)-P2X(7)) by molecular cloning. However, they are difficult to distinguish pharmacologically owing to an absence of specific agonists and antagonists. In this study we used neuroanatomical methods to determine the origin and neurochemical phenotype of the P2X(2) subtype of purinoceptor in the dorsal medulla of the rat. Using immunohistochemistry we observed dense networks of P2X(2) receptor immunoreactive labelled fibres and terminals in the dorsal vagal complex and area postrema, as well as labelled cell bodies in the dorsal vagal nucleus and the area postrema. The P2X(2) receptor was localized presynaptically in vagal afferent fibres and terminals in the nucleus tractus solitarius at the ultrastructural level by combining injections of an anterograde tracer (biotin dextran amine) into the nodose ganglion with pre-embedding immunogold visualization of P2X(2) immunoreactivity. Terminals immunoreactive for the P2X(2) receptor in the nucleus tractus solitarius were found to contain glutamate, but not GABA immunoreactivity by post-embedding immunogold-labelling techniques. In cell bodies in the area postrema, dual immunofluorescence also indicated that P2X(2) receptor immunoreactive cells are glutamatergic but not GABAergic. The P2X(2) receptor was localized to vagal preganglionic neurons in the dorsal vagal nucleus that were identified by prior intraperitoneal injections of the retrograde tracer FluoroGold. No cells immunoreactive for the P2X(2) receptor were observed in the nucleus tractus solitarius.The localization of P2X(2) receptor immunoreactivity presynaptically in vagal afferent terminals indicates that the receptor may be involved in modulating transmitter release from vagal afferent fibres. Furthermore, the presence of the P2X(2) receptor in vagal preganglionic cells and in glutamatergic cells of the area postrema implies that it may, respectively, play a role in regulation of vagal efferent cell activity and modulation of excitatory outputs from the area postrema to other brain regions.     

大鼠孤束迷走复合体儿茶酚胺能神经元向杏仁核的直接投射—HRP与免疫组织化学双标记研究

将HRP注入大鼠杏仁中央核(Ce)和基底外侧核(BL),发现在孤束迷走复合体(Sol/dmnx)尾段出现较多的逆行标记细胞。将WGA-HRP注入Sol/dmnx,在Ce和BL见到标记终末。用HRP逆行追踪和抗酪氨酸羟化酶(TH)抗体进行的免疫组化染色相结合的双重标记方法,发现从锥体交叉平面到最后区(AP)吻端平面,Sol/dmnx内有恒定的HRP逆行标记、TH样阳性和HRP/TH样双重标记的三种阳性神经元。双标记细胞主要分布于连合核(solC)、内侧亚核(solM),少量的位于间位核(solI)、背侧亚核(solD)及dmnx的背侧缘等。闩至最后区平面较多。阳性细胞皆以小型为主,多为圆形、三角形,soll中的则为长梭形。双重标记细胞占TH样免疫阳性细胞总数的18.8%,占HRP逆标细胞总数的90%,同侧为主,对侧偶见。本文对其功能意义作了探讨分析。     

Cellular and subcellular distribution of the amino-3-hydroxy-5-methyl-4-isoxazole propionate receptor subunit GluR2 in the rat dorsal vagal complex

Amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) type glutamate receptors are ligand gated ion channels made up of various combinations of four subunits termed GluR1-4. The GluR2 subunit controls several key features of the receptor including calcium permeability and inward rectification. In the present study, we analysed by immunocytochemistry the cellular and subcellular distribution of the GluR2 subunit in neurons of the dorsal vagal complex of the rat. GluR2 immunoreactivity was found both in the neuropile and in neuronal cell bodies. Perikaryal staining was strong in the dorsal motor nucleus of the vagus nerve and moderate in the medial part of the nucleus tractus solitarii as well as in the area postrema. The lateral part of the nucleus tractus solitarii was almost devoid of immunoreactivity except for the interstitial subnucleus which was filled with numerous strongly immunoreactive perikarya and large cell processes. Ultrastructural examination was carried out in the interstitial subnucleus. Peroxidase staining indicative of GluR2 immunoreactivity was observed in neuronal cell bodies and dendrites. No labeled axon terminal or glial cell body was found. Additional experiments performed using pre-embedding immunogold showed that most of the labeling in immunoreactive dendrites was intracytoplasmic.These results indicate that GluR2 immunoreactivity is differentially distributed among neurons in the dorsal vagal complex, thereby suggesting differences in the functional properties of AMPA receptors between neuronal populations. These results also suggest that AMPA receptors, at least those containing the GluR2 subunit, have no major role as presynaptic receptors within this region. Finally, they indicate the existence of large intracellular pools of GluR2 subunits within dendrites of immunoreactive neurons.     

The Central Nucleus of the Amygdala Modulates Gut-Related Neurons in the Dorsal Vagal Complex in Rats

Using retrograde tract-tracing and electrophysiological methods, we characterized the anatomical and functional relationship between the central nucleus of the amygdala and the dorsal vagal complex. Retrograde tract-tracing techniques revealed that the central nucleus of the amygdala projects to the dorsal vagal complex with a topographic distribution. Following injection of retrograde tracer into the vagal complex, retrogradely labelled neurons in the central nucleus of the amygdala were clustered in the central portion at the rostral level and in the medial part at the middle level of the nucleus. Few labelled neurons were seen at the caudal level. Electrical stimulation of the central nucleus of the amygdala altered the basal firing rates of 65 % of gut-related neurons in the nucleus of the solitary tract and in the dorsal motor nucleus of the vagus. Eighty-one percent of the neurons in the nucleus of the solitary tract and 47 % of the neurons in the dorsal motor nucleus were inhibited. Electrical stimulation of the central nucleus of the amygdala also modulated the response of neurons in the dorsal vagal complex to gastrointestinal stimuli. The predominant effect on the neurons of the nucleus of the solitary tract was inhibition. These results suggest that the central nucleus of the amygdala influences gut-related neurons in the dorsal vagal complex and provides a neuronal circuitry that explains the regulation of gastrointestinal activity by the amygdala.     

Atropine methyl nitrate increases myenteric but not dorsal vagal complex Fos-like immunoreactivity in the rat

Atropine methyl nitrate (AMN, 0.05, 0.5 and 25 mg/kg) intraperitoneally increased Fos-like immunoreactivity (Fos-LI) in the myenteric plexus, but not the dorsal vagal complex (DVC, the area postrema (AP), nucleus of the solitary tract (NTS) and the dorsal motor nucleus of the vagus (DMV)) in adult, male Sprague-Dawley rats. A 3 mg/kg AMN dose decreased intake of 15% sucrose, but failed to increase Fos-LI in both locations. In conclusion, the myenteric plexus may play a local role in the behavioral response evoked by AMN.     

Adrenergic neurons in human brain demonstrated by immunohistochemistry with antibodies to phenylethanolamine-N-methyltransferase (PNMT): discovery of a new group in the nucleus tractus solitarius

Adrenaline neurons in human brain were demonstrated by immunohistochemistry using antibody to phenylethanolamine-N-methyltransferase (PNMT), the final enzyme in the pathway of adrenaline synthesis, using fixed frozen sections and a highly sensitive free floating technique which utilizes metallization. Small densely packed PNMT-immunoreactive neurons were observed to form a nucleus lying just ventrolateral to the area postrema and in the dorsal part of the nucleus tractus solitarius. Larger adrenergic neurons were also present in and around the lateral reticular nucleus and in relationship with the dorsal motor nucleus of the vagus in regions equivalent to the C1 and C2 groups in rats. Longitudinally oriented PNMT-positive axons constitute a subset of tyrosine hydroxylase-immunoreactive axons in the dorsomedial reticular formation.     

Lesion of vagal afferent terminals impairs glucagon-induced suppression of food intake

Selective hepatic branch vagotomy impairs glucagon-induced inhibition of food intake. However, the relative importance of afferent and efferent neurons in glucagon satiety has not been directly investigated. In this experiment, lesions were placed in the area postrema (AP) and immediately subjacent nucleus of the solitary tract (NTS) where hepatic vagal afferents have been reported to terminate. We found that these lesions impaired glucagon-induced satiety under testing conditions similar to those that reveal a glucagon satiety deficit in rats with selective hepatic branch vagotomies. Since these lesions did not damage the underlying dorsal motor nucleus of the vagus, our results suggest that our AP/NTS lesions impaired glucagon satiety by damaging terminal fields of vagal afferent neurons. Finally, our lesions did not impair satiety induced by cholecystokinin (CCK), a response mediated by gastric vagal afferent neurons. This latter result suggests that the vagal afferent terminal fields required for glucagon- and CCK-induced satiety are not coextensive.     

Neurons in the rat medulla oblongata containing neuropeptide Y-, angiotensin II-, or galanin-like immunoreactivity project to the parabrachial nucleus.

Projections from the medulla to the parabrachial complex of the rat were examined for their content of neuropeptide Y-, angiotensin II- or galanin-like immunoreactivity using combined retrograde tracing and immunohistochemical techniques. Rhodamine-labelled latex microspheres were stereotaxically injected into discrete nuclei of the parabrachial complex. After survival of two to five days, colchicine (100 micrograms in 10 microliters saline) was injected into the cisterna magna. One day later, rats were perfused and the brainstems were prepared for visualization of the retrograde tracer and immunoreactivity of one of the three peptides. Retrograde labelling verified that the area postrema, nucleus of the tractus solitarius, caudal spinal nucleus of the trigeminal nerve, parvocellular reticular nucleus, and ventrolateral medulla including the rostral ventrolateral medulla and nucleus paragigantocellularis project to the lateral parabrachial and K?lliker-Fuse nuclei. While most projections were primarily ipsilateral, a small proportion of the projections from the ventrolateral medulla was bilateral. Neurons containing neuropeptide Y-like immunoreactivity were found in the caudal and intermediate nucleus of the tractus solitarius, dorsal to the lateral reticular nucleus and in the nucleus paragigantocellularis. After bilateral microsphere injections into the lateral parabrachial and K?lliker-Fuse nuclei, double-labelled neurons were found dorsal to the lateral reticular nucleus of caudal and intermediate medullary levels, at the ventral surface of the medulla at intermediate levels and in the nucleus paragigantocellularis at rostral levels. Neurons with angiotensin II-like immunoreactivity were observed at the dorsomedial border of the caudal and intermediate nucleus of the tractus solitarius, in the area postrema and in the lateral reticular nucleus and nucleus paragigantocellularis. Of these neurons, small numbers in the nucleus of the tractus solitarius and ventrolateral medulla also projected to the lateral parabrachial and K?lliker-Fuse nuclei. Neurons containing galanin-like immunoreactivity were found in the caudal nucleus of the tractus solitarius, the area postrema, the spinal trigeminal nucleus, the raphe nuclei (pallidus and obscurus), the nucleus paragigantocellularis and dorsal to the lateral reticular nucleus. Of these cells, double-labelled neurons were found in the commissural and medial subdivisions of the caudal nucleus of the tractus solitarius and in the rostral ventrolateral medulla including the ventral surface and the nucleus paragigantocellularis. The results suggest that neuropeptide Y, angiotensin II and galanin may serve as neurochemical messengers in pathways from the medulla to the parabrachial complex. The location of double-labelled neurons suggests that the information relayed by these neurons is related to autonomic activity.     

Distribution of type B monoamine oxidase immunoreactivity in the cat brain with reference to enzyme histochemistry.

We studied the detailed distributions and morphology of structures immunoreactive to type B monoamine oxidase, and compared them with those stained by monoamine oxidase enzyme histochemistry in the brain of cats treated with or without colchicine. By means of the indirect immunohistochemical method in conjunction with type B monoamine oxidase monoclonal antibody, we demonstrated type B monoamine oxidase immunoreactivity in neuronal cell bodies, fibers and astroglial cells in the cat brain. As expected, the distribution of type B monoamine oxidase-immunoreactive cell bodies overlapped that of serotonin-containing ones in the lower brainstem and midbrain, as well as that of histaminergic ones in the posterior hypothalamus. We found novel cell groups containing type B monoamine oxidase in the areas described below. Intense type B monoamine oxidase-immunopositive and enzymatically active neurons, corresponding to liquor-contact ones, were discovered in the wall of the central canal of the spinomedullary junction. Weak immunoreactivity was identified in neurons of the dorsal motor nucleus of the vagus, parvocellular reticular formation and locus coeruleus complex, which have been reported to contain type A monoamine oxidase enzymatic activity. Type B monoamine oxidase-immunostaining in these structures was enhanced by treatment with colchicine. In addition, lightly immunostained cells were distinguished in the caudal portion of the hypothalamic arcuate nucleus, area of tuber cinereum, retrochiasmatic area, and rostral portion of the paraventricular thalamic nucleus after colchicine treatment. These cells also displayed monoamine oxidase activity; however, it was difficult to enzymatically characterize their nature due to its weak activity and sensitivity to inhibitors of both A and B. Distinct type B monoamine oxidase-immunoreactive fibers and terminal-like dots were abundant in the whole brain, particularly in the central gray, dorsal pontine tegmentum, interpeduncular and pontine nuclei, nucleus of the solitary tract and dorsal motor nucleus of vagus, where dense innervations of serotonergic fibers have been reported. Their immunoreactive density increased after colchicine treatment, but monoamine oxidase enzymatic reaction did not. An intense immunoreactivity could be seen in many glial cells in parts of the brain including myelinated axon pathways. The densest accumulation of such labeled glial cells was found in the central gray, inferior olive, medial geniculate body, substantia nigra, ventral tegmental area of Tsai, retrorubral area, hypothalamus, thalamus and bed nucleus of the stria terminalis. In contrast, the striatum contained less numerous type B monoamine oxidase-immunoreactive and enzymatically active astroglial cells in comparison with the other structures.(ABSTRACT TRUNCATED AT 400 WORDS)     

Glycine receptor (gephyrin) immunoreactivity is present on cholinergic neurons in the dorsal vagal complex

We previously demonstrated that microinjection of exogenous glycine into the nucleus tractus solitarii of anesthetized rats elicits responses that are qualitatively like those elicited by microinjection of acetylcholine at the same site. The responses to glycine, like those to acetylcholine, are blocked by administration of a muscarinic receptor antagonist and prolonged by administration of an acetylcholinesterase inhibitor. Furthermore, glycine leads to release of acetylcholine from the nucleus tractus solitarii and surrounding dorsal vagal complex. An anatomical framework for interactions between glycinergic and cholinergic neurons was established by studies that identified glycine terminals and receptors in the dorsal vagal complex. The current study investigated the relationship between glycine receptors and neuronal elements that were immunoreactive for choline acetyltransferase in the dorsal vagal complex. Neurons that were immunoreactive for choline acetyltransferase were located in the dorsal motor nucleus of the vagus, hypoglossal nucleus and nucleus ambiguus, and stained cells were also present in medial, intermediate, and ventrolateral subnuclei of the nucleus tractus solitarii. We found that glycine receptors, immunolabeled with an antibody to gephyrin, were present on cholinergic dendrites in the nucleus tractus solitarii. Gephyrin immunoreactivity was also present on dendrites that did not stain for choline acetyltransferase. These data further support the contribution of cholinergic neurons in mediating cardiovascular responses to glycine in the nucleus tractus solitarii.     

Glycine receptor (gephyrin) immunoreactivity is present on cholinergic neurons in the dorsal vagal complex

We previously demonstrated that microinjection of exogenous glycine into the nucleus tractus solitarii of anesthetized rats elicits responses that are qualitatively like those elicited by microinjection of acetylcholine at the same site. The responses to glycine, like those to acetylcholine, are blocked by administration of a muscarinic receptor antagonist and prolonged by administration of an acetylcholinesterase inhibitor. Furthermore, glycine leads to release of acetylcholine from the nucleus tractus solitarii and surrounding dorsal vagal complex. An anatomical framework for interactions between glycinergic and cholinergic neurons was established by studies that identified glycine terminals and receptors in the dorsal vagal complex. The current study investigated the relationship between glycine receptors and neuronal elements that were immunoreactive for choline acetyltransferase in the dorsal vagal complex. Neurons that were immunoreactive for choline acetyltransferase were located in the dorsal motor nucleus of the vagus, hypoglossal nucleus and nucleus ambiguus, and stained cells were also present in medial, intermediate, and ventrolateral subnuclei of the nucleus tractus solitarii. We found that glycine receptors, immunolabeled with an antibody to gephyrin, were present on cholinergic dendrites in the nucleus tractus solitarii. Gephyrin immunoreactivity was also present on dendrites that did not stain for choline acetyltransferase.These data further support the contribution of cholinergic neurons in mediating cardiovascular responses to glycine in the nucleus tractus solitarii.     

Transneuronal labelling of nerve cells in the CNS of female rat from the mammary gland by viral tracing technique.

Using the viral transneuronal tracing technique, the cell groups in the CNS transneuronally connected with the female mammary gland were detected. Lactating and non-lactating female rats were infected with pseudorabies virus injected into the mammary gland. The other group of animals was subjected to virus injection into the skin of the back. Four days after virus injection, infected neurons detected by immunocytochemistry, were present in the dorsal root ganglia ipsilateral to inoculation and in the intermediolateral cell column of the spinal cord. In addition, a few labelled cells could be detected in the dorsal horn and in the central autonomic nucleus (lamina X) of the spinal cord. At this survival time several brain stem nuclei including the A5 noradrenergic cell group, the caudal raphe nuclei (raphe obscurus, raphe pallidus, raphe magnus), the A1/C1 noradrenergic and adrenergic cell group, the nucleus of the solitary tract, the area postrema, the gigantocellular reticular nucleus, and the locus coeruleus contained virus-infected neurons. In some animals, additional cell groups, among others the periaqueductal gray and the red nucleus displayed labelling. In the diencephalon, a significant number of virus-infected neurons could be detected in the hypothalamic paraventricular nucleus. In most cases, virus-labelled neurons were present also in the lateral hypothalamus, in the retrochiasmatic area, and in the anterior hypothalamus. In the telencephalon, in some animals a few virus-infected neurons could be found in the preoptic area, in the bed nucleus of the stria terminalis, in the central amygdala, and in the somatosensory cortex. At the longer (5 days) survival time each cell group mentioned displayed immunopositive neurons, and the number of infected cells increased. The pattern of labelling was similar in animals subjected to virus inoculation into the mammary gland and into the skin. The distribution and density of labelling was similar in lactating and non-lactating rats.The present findings provide the first morphological data on the localization of CNS structures connected with the preganglionic neurons of the sympathetic motor system innervating the mammary gland. It may be assumed that the structures found virus-infected belong to the neuronal circuitry involved in the control of the sympathetic motor innervation of the mammary gland.     

Neurons in the nucleus of the solitary tract mediating inputs from emetic vagal afferents and the area postrema to the pattern generator for the emetic act in dogs.

Roles of neurons in the nucleus of the solitary tract corresponding to the area subpostrema (mNST) for the retching reflex were investigated in decerebrate, paralyzed dogs. Retching was defined as rhythmic coactivation of the phrenic and abdominal muscle nerves. Retching which had been induced by stimulation of the left and right abdominal vagus nerves was impaired by cooling the left and right mNSTs, respectively. This result indicates that the mNST neurons mediate activities of emetic vagal afferents. All 40 non-respiratory neurons in the mNST, which had excitatory response to pulse train stimulation of the vagus nerve, were also activated by continuous stimulation of the vagus nerve to provoke retching. During provoked retching, however, these neurons did not exhibit any activities modulated in association with retching. The average latency of responses of these neurons to the pulse train stimulation (306.5 ms) was significantly shorter than that of the inspiratory neurons in the lateral NST and the adjacent reticular formation. Discharge frequencies of these neurons in the mNST gradually increased after administration of apomorphine (6/10) and glutamate (14/14) to the 4th ventricle. Antidromic responses to stimulation of the B?tzinger complex were observed in some (20/289) of the mNST neurons. These findings suggest that neurons in the mNST mediate the information from both the abdominal vagal afferents and the area postrema and drive the pattern generator for retching and vomiting, which is assumed to be located in the B?tzinger complex.