Showing papers on "Cuneate nucleus published in 1988"

An immunohistochemical study of the nerve growth factor receptor in developing rats

Abstract: Nerve growth factor (NGF) receptor expression was studied in rats between embryonic day 11 (E11) to postnatal day 10 (PND10) by using a monoclonal antibody, 192-IgG, that specifically recognizes rat NGF receptor. Sympathetic ganglia were lightly stained by 192-IgG for NGF receptor immunoreactivity (NGFRI) (E11-PND10). Neural crest-derived sensory ganglia were moderately to densely stained (E11-PND10). Areas in CNS innervated by the central processes of these ganglia were also stained. Parasympathetic ciliary ganglion showed some detectable staining (E16-PND6). Placode-derived sensory ganglia were stained more densely than that of neural crest-derived sensory ganglia. The most densely stained tissue for NGFRI was found in all peripheral nerves. Basal forebrain cholinergic neurons were NGFRI positive from E15 throughout the period examined. Motoneurons in both spinal cord and brain stem were positive for NGFRI between E15 and PND10. NGFRI staining was seen in a variety of sensory pathways and related structures, such as olfactory tract and glomerular layer of olfactory bulb; retina, optic nerve and tract, lateral geniculate nucleus, medial terminal nucleus of the accessory optic tract, and olivary pretectal nucleus; ventral cochlear nucleus and to a lesser degree in dorsal cochlear nucleus, superior olive, and nucleus of lateral lemniscus; solitary tract; cuneate nucleus, gracile nucleus, and ventroposterior thalamic nucleus. The specific staining was also found in some other CNS structures, including brain-stem reticular formation; amygdala; medial nucleus of inferior olive but not the rest of inferior olive, external granule cell layer and Purkinje's cells of cerebellum, and deep cerebellar nuclei. Some non-neuronal tissues such as meninges and dental tissue showed very distinctive staining. Limb buds and somites were NGFRI positive starting at E11, and the staining on muscle tissue became very dense at E15-E18 and largely disappeared around PND10. Embryonic thymus was positive for NGFRI. The adventitia surrounding blood vessels was very densely stained. The changes in NGFRI staining seen in this study suggest that NGF may have broader effects during development than previously thought.

Central distribution of trigeminal and upper cervical primary afferents in the rat studied by anterograde transport of horseradish peroxidase conjugated to wheat germ agglutinin.

Abstract: Injections of WGA-HRP were made in the rat trigeminal ganglion and C1-3 dorsal root ganglia (DRGs) to study the central projection patterns and their relations to each other. Trigeminal ganglion injections resulted in heavy terminal labeling in all trigeminal sensory nuclei. Prominent labeling was also observed in the solitary tract nucleus and in the medial parts of the dorsal horn at C1-3 levels, but labeling could be followed caudally to the C7 segment. Contralateral trigeminal projections were found in the nucleus caudalis and in the dorsal horn at C1-3 levels. The C1 DRG was found to be inconstant in the rat. When it was present, small amounts of terminal labeling were found in the external cuneate nucleus (ECN) and the central cervical nucleus (CCN). No dorsal horn projections were seen from the C1 DRG. Injections in the C2 DRG resulted in heavy labeling in the ECN, nucleus X, CCN, and dorsal horn, where it was mainly located in lateral areas. Labeling could be followed caudally to the Th 7 segment. C2 DRG projections also appeared in the cuneate nucleus (Cun), in all the trigeminal sensory nuclei, and in the spinal, medial, and lateral vestibular nuclei. A small C2 DRG projection was observed in the ventral cochlear nucleus. C3 DRG injections resulted in heavy labeling in both medial middle and lateral parts of the dorsal horn, in the ECN, and in nucleus X, whereas the labeling in the CCN was somewhat weaker. Smaller projections were seen to trigeminal nuclei, Cun, and the column of Clarke. Comparisons of the central projection fields of trigeminal and upper cervical primary afferents indicated a somatotopic organization but with a certain degree of overlap.

Brain stem terminations of the trigeminal and upper spinal ganglia innervation of the cerebrovascular system: WGA-HRP transganglionic study.

Abstract: The central projections of the nerve fibers innervating the middle cerebral and basilar arteries were investigated by transganglionic tracing of wheat germ agglutinin conjugated with horseradish peroxidase (WGA-HRP) in the rat. WGA-HRP was applied to the exposed basilar and/or middle cerebral arteries. Sections of the brain, trigeminal and upper spinal ganglia were reacted with tetramethylbenzidine for detection of the tracer. The results demonstrate that trigeminal neurons that innervate the middle cerebral artery project to the trigeminal main sensory nucleus, pars oralis, and the dorsocaudal two-fifths of pars interpolaris of the trigeminal brain stem nuclear complex. Terminals were also visible in the ipsilateral nucleus motorius dorsalis nervi vagi (dmnX) and in the lateral nucleus tractus solitarius (nTs) bilaterally at the level of the obex. The ventral periaqueductal gray, including the dorsal raphe and C2 dorsal horn, were also innervated by nerve fibers from the middle cerebral artery. Ipsilateral trigeminal rhizotomy prior to WGA-HRP application over the middle cerebral artery impeded the visualization of nerve terminations throughout the brain stem. Pretreatment with capsaicin reduced the density of labeled neurons and terminals within the trigeminal ganglion and the brain stem, respectively, following WGA-HRP application over the middle cerebral artery. Basilar artery fibers terminate in the C2 dorsal horn, the cuneate nuclei, dmnX, and nTs bilaterally. A few projections were also labeled in the ventral periaqueductal gray. Unilateral upper two spinal dorsal rhizotomy prior to WGA-HRP application over the exposed basilar artery resulted in terminal labeling within the C2 dorsal horn, the cuneate nucleus, dmnX, and nTs contralateral to the rhizotomy, whereas the ipsilateral side was devoid of any labeling. Bilateral superior cervical ganglionectomy prior to WGA-HRP administration to the middle cerebral and basilar arteries did not alter the visualization of nerve terminations throughout the brain stem.

Projections of digit afferents to the cuneate nucleus in the raccoon before and after partial deafferentation.

Abstract: Within the cuneate nucleus of the raccoon, the representations of individual forepaw digits are anatomically separated by densely myelinated laminae. This unique arrangement was utilized to determine whether the terminations of cutaneous afferents from individual digits are precisely restricted to the appropriate region of the cuneate nucleus or overlap with afferents from adjacent digits. By using the transganglionic transport of horseradish peroxidase (HRP), it was found that, for each digit, the terminal labeling was restricted to the appropriate 150-250-micron-wide column that extended rostrocaudally throughout the nucleus. The topographical arrangement of digit input corresponded to the known electrophysiology, with the terminal column for the fifth digit located most medially within the nucleus and those for digits 4 to 1 successively more laterally. Within a column, the density of labeling was greater over cell clusters than between clusters. These results indicate that afferents from adjacent digits do not overlap in the cuneate nucleus. In six animals, the fifth digit was amputated, and 2-4 months later, HRP was injected into the nerves of the fourth digit to determine whether its afferents had sprouted into the denervated fifth-digit column. The projection pattern from the fourth digit in each of these animals was the same as in normal animals and the same as in the intact contralateral side. These results indicate that the reorganization seen in the cerebral cortex following peripheral deafferentation cannot be attributed to changes in the afferent fiber projections to the cuneate nucleus.

TRH analogue, RX 77368, injected into dorsal vagal complex stimulates gastric secretion in rats.

Abstract: Medullary sites inducing gastric acid secretion in response to microinjection of the stable analogue of thyrotropin-releasing hormone (TRH; RX 77368, pGlu-His-[3,3'-dimethyl]-Pro-NH2) were investigated in urethan-anesthetized rats. Gastric acid output was recorded every 2 min through a double gastric cannula constantly perfused with 0.9% saline solution maintained at pH 5.5 using an automatic titrator. Unilateral microinjection of RX 77368 (10-100 ng in 50-nl volume) into the dorsal vagal complex (DVC), the dorsal vagal nucleus and nucleus tractus solitarius, induced a significant dose-dependent stimulation of gastric acid secretion. The peak response occurred within 50 min and lasted over 1 h. Other medullary sites, including the lateral, dorsal, and parvocellular reticular nuclei; the medial longitudinal fasciculus; and the medial cuneate nucleus injected with RX 77368 (10-100 ng), were inactive. The TRH metabolites, TRH-OH and His-Pro diketopiperazine (100 ng), injected into the DVC did not influence gastric acid secretion. The stimulation of gastric acid secretion induced by DVC injection of TRH was abolished by vagotomy. These results demonstrate that 1) the DVC is an important site of action for TRH-induced stimulation of gastric acid secretion, 2) TRH action in the DVC is not secondary to the formation of TRH metabolites, and 3) the effect is expressed by vagal efferent pathways. These findings added to the high concentration of TRH-immunoreactivity and receptors in the DVC suggest a role for endogenous TRH in the regulation of vagal outflow to the stomach.

Cardiovascular responses to microinjection of ANF into dorsal medulla of rats.

Abstract: Atrial natriuretic factor (ANF) has been suggested as a putative neurotransmitter in central pathways involved in the control of the cardiovascular system. To investigate this possibility, 50 nl of 10(-7) M ANF were microinjected into discrete sites in the nucleus of the tractus solitarius (NTS) where baro- and chemoreceptor afferents terminate. Injections into 36 of a total of 66 sites in the NTS of paralyzed artificially ventilated Wistar rats under urethan anesthesia were found to produce a significant decline in heart rate [HR; -9.2 +/- 2.9 (SE) beats/min, P less than 0.05] and mean arterial pressure [MAP; -11.1 +/- 1.2 (SE) mmHg, P less than 0.01]. Similar responses were also present in anesthetized animals breathing spontaneously. Microinjection of an inactive peptide analogue or of saline did not produce cardiovascular changes. It was also found that ANF injection into the cuneate nucleus (20 of 38 sites) and the spinal trigeminal complex (28 of 42 sites) produced a decrease in MAP and HR that were of the same magnitude as those seen in the NTS. Injections of ANF into the medial longitudinal fasciculus (n = 22), hypoglossal nucleus (n = 9), area postrema (n = 16), and dorsal motor nucleus of the vagus (n = 11) did not change HR or MAP. These results suggest that ANF may serve as a neurotransmitter involved in cardiovascular reflexes mediated by specific nuclei in the dorsal medulla.

Representation of the forepaw in the feline cuneate nucleus: A transganglionic transport study

Abstract: The projection of forelimb nerves innervating the paw to the cuneate nucleus was studied in the cat by the transganglionic transport method. Exposure of a single digital nerve to the tracer (a conjugate of horseradish peroxidase to wheat-germ agglutinin) resulted in a longitudinal sequence of labeled patches throughout the extent of the nucleus. In the middle region the labeled patches coincided with the location of the cell clusters that are characteristic of this part of the nucleus. A very precise somatotopic termination pattern was found in the middle region of the nucleus. Afferent fibers from the palm were represented superficially close to the dorsal rim. The digits were represented in a mediolateral sequence, with the first digit in the dorsolateral part of the nucleus and the fifth digit in the dorsomedial part. The ventral surfaces of the digits were represented superficial to the dorsal surfaces. The dorsum of the paw was represented close to the center of the nucleus. A similar somatotopic organization, but much less detailed, was found in the rostral and caudal regions of the cuneate nucleus. These dissimilarities in somatotopic detail between the different cytoarchitectonic regions of the cuneate nucleus probably reflect differences in function between these regions.

Medullary sources of projections to the kinesthetic thalamus in raccoons: External and basal cuneate nuclei and cell groups x and z

Abstract: In raccoons and other mammals, a pathway for kinesthetic sensation (from muscles, fascia, tendons, and joints) reaches the anterodorsal cap of the ventrobasal thalamus and the anteriormost part of the somatic sensory cerebral cortex. To find the medullary component of this kinesthetic pathway in raccoons, small injections of horseradish peroxidase were made in the thalamus under guidance of simultaneous electrophysiological recording from kinesthetic projections. As determined by retrograde labeling following these injections, kinesthetic thalamic subregions receive projections as follows: caudomedial from cells in the external cuneate nucleus and its medial tongue, rostromedial from cells in basal cuneate nucleus, and rostrolateral from cells in cell group z and the reticular division of cell group x. Electro-physiological recording showed kinesthetic representations in each of these medullary regions. Labeled cells were also observed in the infratrigeminal subnucleus of the lateral reticular nucleus. Cats have kinesthetic projections to the thalamus from the basal cuneate and cell group z; raccoons (and monkeys) have these plus projections from the external cuneate and cell group x. This suggests that the kinesthetic projection system in raccoons and monkeys is expanded in correlation with their more dextrous use of the hand.

Degeneration of the primary snout sensory afferents in the cervical spinal cords following the infraorbital nerve transection in some mammals.

Abstract: To obtain the neuroanatomical information on the role of the snout sensory input in mastication, the present study was conducted on young and adult mice, young Wistar rats and adult Japanese shrew-moles. The animals were subjected to unilateral and bilateral infraorbital nerve transection. Transganglionic degeneration was studied by the Nauta method and electron microscopy including HRP application to the neck muscles. Transganglionic degeneration was found in every experimental case. 1. Transganglionic degeneration of the fibers was found not only in the main sensory nucleus and spinal tract nucleus of the trigeminal nerve but throughout the cervical and the upper part of the thoracic spinal cord. 2. These transganglionically degenerated fibers descended bilaterally through the cuneate nucleus and then caudally through the posterior funiculus at the obex level. They then entered the dorsal and ventral horns to make a synaptic contact with the degenerated synapses on the dorsal horn cells and with the multipolar cells in the ventral horns. This neuroanatomical information suggests: 1) that the trigemino-neck muscle reflex will be generated monosynaptically by the primary neurons arising from the snout sensory organs and 2) that these primary neurons may play a large role as a neuronal bridge in connecting the masticatory reflex system and the cranio-neck reflex system.

Antiepileptic drug phenytoin potentiates GABA in the rat cuneate nucleus.

Abstract: The putative amino acid neurotransmitter GABA appears to be a significant factor in seizure activity. Phenytoin (PHT) showed no significant effect on GABA metabolism in the mouse brain nor on the GABA mediated presynaptic inhibition in the rat brain,2 although PHT is one of the most effective antiepileptic drugs for the treatment of convulsive seizures. On the other hand, PHT interacts with the benzodiazepine (BZP) receptors' which proved to be coupled with the GABA receptors. The present study, therefore, was undertaken to clarify the site of action of PHT in the GABA system.

Afferent connections of the ventral magnocellular section of the cat red nucleus

Abstract: The location within the brain of labeled neurons giving rise to projections to the ventral magnocellular section of the red nucleus were investigated by means of microiontophoretically injected horseradish peroxidase Projections were identified from many cortical, thalamic, and hypothalamic structures and from the head of the caudate nucleus, septum, globus pallidus, anterior commissure nucleus, central amygdalar nucleus, field of Forel, Zona incerta, and a number of brainstem structures Findings in accordance with those found in the literature were obtained on projections to the red nucleus from the coronary and cruciate cortical sulci, the midbrain and dentate (lateral) cerebellar nuclei, subststantia nigra, nucleus gracilis, and the cuneate nucleus Trajectories of retrogradely labeled fiber systems of the red nucleus are described

Afferent connections of the dorsal magnocellularis area of the cat red nucleus

Abstract: Location within the brain of retrogradely labeled neurons putting out projections from the dorsal magnocellularis area of the red nucleus was investigated by means of microiontophoretic injection of horseradish peroxidase into the dorsal magnocellularis area of the cat red nucleus. Projections were found from a number of hypothalamic nuclei, the centrum medianum, parafascicular and subthalamic nuclei, zone incerta, Forel's field, nucleus medialis habenulae, pontine and bulbar reticular formation, and the following midbrain structures: the central gray matter, superior colliculus, Cajal's interstitial nucleus, reticular formation, and the contralateral red nucleus. Projections were also identified proceeding from more caudally located structures: the cerebellar fastigial nucleus, facial nucleus, medial vestibular and dorsal lateral vestibular nuclei, and ventral horns of the spinal cord cervical segments. Connections between the substantia nigra and the red nucleus were clarified. Projections to the red nucleus from the cerebral cortex, interstitial and dentate (lateral) cerebellar nuclei, the nucleus gracilis and cuneate nucleus were found, confirming data presented in the literature. Bilateral trajectories of retrogradely labeled fiber systems are described.

Participation of the brainstem visceral centers in the formation of emotional and behavioral reactions.

Abstract: The effect of electrical stimulation of the region of the medial parabrachial nucleus on the behavior of albino rats is studied in chronic experiments. Stimulation of this region is found to cause an increase in the rate of respiration and inhibition of natural behavioral reactions and reactions elicited by stimulation of the nuclei of the amygdala, lateral hypothalamus, and the zona incerta of the brain. Similar inhibitory effects are noted for stimulation of certain zones of the midbrain cuneate nucleus and regions of the pontine suture. The inhibitory influence of stimulation of the parabrachial nucleus on behavior is thought to be due to the switching-on of the central mechanisms of inhibition of motor activity in animals.