Showing papers on "Solitary tract published in 1983"

Central connections of the sensory and motor nuclei of the vagus nerve

Abstract: Recent morphological and immunohistochemical studies bearing on the central pathways involved in processing vagal afferent information and in modulating the activity of vagal preganglionic neurons are summarized. The nucleus of the solitary tract (NTS), the principal recipient of first order vagal afferent inputs, projects to preganglionic cell groups of both divisions of the autonomic nervous system, to motor nuclei of cranial nerves that supply the face and tongue, to a series of 'relay' nuclei in the brainstem, and to a number of cell groups in the hypothalamus and the limbic region of the telencephalon that integrate autonomic, neuroendocrine and regulatory behavioral responses. With the exception of the cranial nerve motor nuclei, each cell group in receipt of direct inputs from the NTS projects back to this region and/or to the vagal motor nuclei, and is thereby in a position to influence vagal motor outflow. This central vagal system is further characterized by the presence of neurons that contain an impressive diversity of neuropeptides and monoamines. Examples are cited to illustrate how biochemically specified projections within this system are organized, and how they provide potential substrates for encoding information transfer between its components.

Anatomy of the gustatory system in the hamster: central projections of the chorda tympani and the lingual nerve

Abstract: The sensory modalities of taste and touch, for the anterior tongue, are relegated to separate cranial nerves. The lingual branch of the trigeminal nerve mediates touch: the chorda tympani branch of the facial nerve mediates taste. The chorda tympani also contains efferent axons which originate in the superior salivatory nucleus. The central projections of these two nerves have been visualized in the hamster by anterograde labelling with horseradish peroxidase (HRP). Afferent fibers of the chorda tympani distribute to all rostral-caudal levels of the solitary nucleus. They synapse heavily in the dorsal half of the nucleus at its rostral extreme; synaptic endings are sparser and located laterally in caudal regions. These taste afferents travel caudally in the solitary tract and reach different levels by a series of collateral branches which extend medially in the the solitary nucleus, where they exhibit preterminal and terminal swellings. Taste afferent axons range in diameter from 0.2 micrometer to 1.5 micrometers. The thickest axons project exclusively to the rostral and intermediate subdivisions of the solitary nucleus; the find ones may distribute predominantly to the caudal subdivision. Afferent fibers of the lingual nerve terminate heavily in the dorsal one-third of the spinal nucleus of the trigeminal nerve and also as a dense patch in the lateral solitary nucleus at the midpoint between its rostral and caudal poles. This latter projection overlaps that of the chorda tympani. Thus the two sensory nerves which subserve taste and touch from coincident peripheral fields on the tongue converge centrally on the intermediate subdivision of the solitary nucleus. Efferent neurons of the superior salivatory nucleus were labelled retrogradely following application of HRP to the chorda tympani. These cells are located ipsilaterally in the medullary reticular formation ventral to the rostral pole of the solitary nucleus; their dendrites are oriented dorsoventrally. The efferent axons course dorsally, form a genu lateral to the facial somatomotor genu, and course ventrolaterally through the spinal nucleus of the trigeminal nerve to exit the brain ventral to the entering facial afferents.

Effects of area postrema/caudal medial nucleus of solitary tract lesions on food intake and body weight

Abstract: Lesions of the area postrema/caudal medial nucleus of the solitary tract (AP/cmNTS), located on the surface of the dorsal medulla of the rat, cause a transient syndrome of hypophagia and body weight loss, with the establishment of a new growth curve at a lower body weight set point. The regulatory responses to prolonged food deprivation, glucoprivic stimulation, and chronic access to a palatable diet are left largely intact. However, there is an overconsumption of highly palatable foods during acute exposure to supermarket and high-fat diets. Intestinal transit and gastric retention are unaffected by the lesion, indicating normal motor function within the gastrointestinal system. The hypophagia and chronic depression of body weight by the AP/cmNTS lesion demonstrate that this area is an important part of the larger neurocircuitry subserving feeding behavior and energy balance.

Visceral representation within the nucleus of the tractus solitarius in the pigeon, Columba livia.

Abstract: This study describes the distribution of organ-specific populations of vagal afferent fibers within the nucleus of the solitary tract (nTS) in the pigeon. The central projections of vagal sensory neurons were visualized by the centripetal and trans-ganglionic transport of horseradish peroxidase from either the central cut ends of peripheral vagal branches or from HRP injection sites in peripheral vagal target tissues. This paper also includes a detailed description of the cytoarchitectural organization of the nTS in the pigeon based on studies of Nissl-stained material. Vagal afferent fibers that innervate different peripheral target organs are partially segregated within cytoarchitecturally distinct subnuclei of the nTS. Gastrointestinal afferents, for example, project primarily to medial subnuclei. On the other hand, pulmonary, and on the basis of earlier studies, cardiovascular afferents, project primarily to lateral subnuclei, Moreover, the rostral to caudal distribution of gastrointestinal afferents corresponds to the rostrocaudal topography of the gastrointestinal tract. In addition, our data demonstrate a projection of gastrointestinal afferents to the lateral descending tract of the trigeminal nerve that appears to terminate in the external cuneate nucleus. The cytoarchitectural organization of visceral representations within the pigeon nTS corresponds closely to recent descriptions of this cell group in mammals. Comparison of our results with studies of the central connections of nTS neurons suggests that the subnuclear distribution of organ-specific vagal afferents within nTS plays a critical role in the organization of ascending and descending visceral afferent pathways.

Development of taste responses in rat nucleus of solitary tract.

Abstract: Extracellular responses from neurons in the nucleus of the solitary tract (NST) were studied in rats aged 5 days to adulthood during chemical stimulation of the tongue with monochloride salts, citr...

Long descending projections of the hypothalamus in the pigeon, Columba livia

Abstract: An autoradiographic analysis was performed on the descending projections of nucleus periventricularis magnocellularis (PVM) of the hypothala-mus in the pigeon. A PVM-medullospinal pathway was observed coursing posteriorly through the lateral hypotlialamus, ventrolateral midbrain teg-mentum, and into the spinal lemniscus (ls) in the ventrolateral pons and medulla. In the pons, some fibers course dorsomedially from ls and terminate at the lateral border of 1 he locus coeruleus. At medullary levels, fibers from ls sweep dorsomedially in the plexus of Horsley and project to certain regions of the nucleus of the solitary tract (NTS) and the dorsal motor nucleus of the vagus (NX). Specifically, PVM fibers project heavily into NTS subnuclei medialis superficialis, medialis ventralis, and lateralis (sulcalis) dorsalis as well as into the ventral parvocellular subnucleus of NX. Fibers in ls were traced caudally into the lateral funiculus as far as upper cervical levels of the spinal cord. Although autoradiographs of lower cervical or thoracic spinal cord sections were not available, PVM fibers do descend to thoracic spinal cord levels, as evidenced by the retrograde transport of horseradish peroxidase. In addition to the medullospinal pathway, the autoradiographs demonstrated PVM projections to septum, diencephalon, and midbrain. Labeled PVM fibers are found in the lateral septal nucleus, nucleus of the anterior pallial commisure, dorsomedial thalamic nucleus, dorsolateral anterior tha-lamic nucleus (pars ventralis), median eminence, medial and lateral hypo-thalamus, medial mammillary area, and nucleus intercollicularis and central gray of the midbrain. The projection of fibers to medullospinal regions and median eminence suggests that PVM is homologous to the mammalian par a ventricular nucleus. These projections to specific subnuclei of NTS and NX denote hypo-thalamic control over certain autonomic functions.

Projection of single pulmonary stretch receptors to solitary tract region.

Abstract: 1. Central projections of single slowly adapting pulmonary stretch receptors were mapped in the medulla by the technique of spike-triggered averaging of extracellular field potentials. Discharge of...

Aortic baroreceptor reflex pathway: a functional mapping using [3H]2-deoxyglucose autoradiography in the rat

Abstract: The organization of pathways within the central nervous system which are activated by aortic baroreceptor input was studied in the urethane anesthetized rat using the 2-deoxyglucose method. [3H]2-deoxyglucose was administered i.v. while either the aortic nerve was electrically stimulated or aortic baroreceptors were physiologically activated by pulse increases in arterial pressure in animals with bilateral denervation of the carotid sinus. Autoradiographs of transverse sections of the central nervous system were developed and analyzed for changes in metabolic activity in discrete regions compared to control animals, as indicated by the density of the photographic emulsion. Electrical stimulation of the aortic nerve resulted in all animals in an increase in the uptake of deoxyglucose in a number of sites throughout the central nervous system, primarily ipsilateral to the site of stimulation. In the brainstem, structures previously implicated in cardiovascular reflexes were labeled. These included the nucleus of the solitary tract, the solitary tract, the dorsal motor nucleus of the vagus, and the nucleus ambiguus. In addition, the inferior olivary nucleus, the parabrachial nuclei and the ventrolateral reticular formation showed increased labeling. In the hypothalamus, increased labeling was observed only in the paraventricular and supraoptic nuclei.

Ipsilateral disturbance of taste due to pontine haemorrhage.

Abstract: A patient with haemorrhage in the right tegmentum of the pons demonstrated ipsilateral disturbance of taste on both the anterior two-thirds and posterior one-third of the tongue. The contralateral medial lemniscus was not disturbed, contrary to the early descriptions that the secondary gustatory neurons from the nucleus of the solitary tract cross and turn upwards in the pons through the contralateral medial lemniscus. This finding would accord with the concept of the pontine taste area which receives ipsilaterally the secondary gustatory neurons from the anterior pole of the nucleus of the solitary tract.

Effects of clonidine on the rate of noradrenaline turnover in discrete areas of the rat central nervous system

Abstract: Turnover of noradrenaline in various regions of the rat brain was estimated by the decrease in noradrenaline content and/or formaldehyde-induced catecholamine fluorescence after inhibition of noradrenaline biosynthesis with α-methyl-p-tyrosine. Clonidine (0.1 and 0.3 mg/kg p.o.) decelerated the decrease in noradrenaline content of the locus coeruleus, the nucleus of the solitary tract, the intermediolateral cell column and the ventral horn of the thoracic spinal cord, as measured in tissue punches of the respective regions with a sensitive radioenzymatic method. In all these central regions the clonidine-induced decrease in noradrenaline turnover was antagonized by yohimbine, but not by phenoxybenzamine, indicating mediation through central α2-adrenoceptors, similar to the cardiovascular effects clonidine. When given alone, both yohimbine and phenoxybenzamine accelerated the disappearance of noradrenaline after inhibition of its biosynthesis. The combined results of radioenzymatic assay and fluorescence histochemistry determinations demonstrated that clonidine markedly reduced noradrenaline turnover in central noradrenaline-containing nerve terminals, but had no effect on the cell bodies of the A1 and A2 cell groups. Noradrenaline turnover was, however, decreased in projection areas of the A1 and A2 cell groups, namely the intermediolateral cell column of the spinal cord and nucleus of the solitary tract, respectively. This observation argues against the existence of a neuronal feedback loop running from the projection areas to the cell bodies of the A1 and A2 cell groups and mediating inhibition of noradrenaline turnover. The effect of clonidine on noradrenaline turnover is, therefore, most likely the result of a local feedback inhibition through presynaptic α-adrenoceptors. Since the nucleus of the solitary tract and the intermediolateral cell column of the spinal cord are prime candidates for the site of the cardiovascular action of clonidine and since the cardiovascular effects of clonidine can be elicited in the virtual absence of neuronal noradrenaline (Haeusler 1974), the present results suggest that the decrease in central noradrenaline turnover and the cardiovascular effects of clonidine are not interrelated phenomena.

Ganglioradiculitis in the dog

Abstract: Facial hypalgesia, sensory ataxia, depression of tendon reflexes, and masticatory muscle wasting developed acutely to subacutely in three adult dogs. These deficits were correlated with craniospinal sensory ganglioradiculitis. CNS degeneration in the dorsal funiculus, spinal tract of the trigeminal nerve, and solitary tract was secondary to loss of primary sensory neurons. Megaesophagus, which occurred in two dogs appeared to be associated with loss of vagal primary afferent neurons; however, esophageal and gastric myenteric ganglionitis was also observed in one of these animals. In the three dogs changes in the sensory ganglia and roots included non-suppurative inflammation and degeneration and loss of neurons. Perivenular and perineuronal mononuclear infiltrates were prominent. EM study revealed that the satellite cells around degenerating and necrotic cell bodies were commonly invaded and displaced by lymphocytes and macrophages. It was not clear whether these mononuclear cells effected neuronal degeneration or merely responded to it. Although the pathogenesis remained undefined, the similarity of the clinical and pathologic findings in these dogs indicated a nosologic entity that had not been reported previously. This canine ganglioradiculitis was compared with inflammatory disorders of the cranial and spinal ganglia in man.