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.

Estudio de las neuronas del núcleo supraóptico del hipotálamo en ambos hemisferios de ratas después del parto / Study of the neurons of the hypothalamic supraoptic nucleus in both hemispheres in rats after delivery

Se estudiaron las características morfológicas (volumen nuclear y cantidad de material neurosecretor presentes en el ciplasma celular) que son índices del estado funcional de las neuronas del núcleo supraóptico del hipotálamo, en ambos hemisferios de ratas después del parto. Se compararon los resultados de ambos hemisferios mediante la prueba de la t de Student, que indica asimetría hemisférica en esta área del sistema nervioso central. El volumen nuclear es mayor y la cantidad de material neurosecretor más escaso en las neuronas del núcleo supraóptico del hemisferio izquierdo, lo que indica un aumento de la síntesis y liberación de las neurohormonas oxitocina y principalmente vasopresina

Estudio de las neuronas del núcleo supraóptico del hipotálamo en ambos hemisferios de ratas después del parto / Study of the neurons of the hypothalaic supraoptic nucleus in both hemispheres in rats after delivery

Se estudiaron las características morfológicas (volumen nuclear y cantidad de material neurosecretor presentes en el ciplasma celular) que son índices del estado funcional de las neuronas del núcleo supraóptico del hipotálamo, en ambos hemisferios de ratas después del parto. Se compararon los resultados de ambos hemisferios mediante la prueba de la t de Student, que indica asimetría hemisférica en esta área del sistema nervioso central. El volumen nuclear es mayor y la cantidad de material neurosecretor más escaso en las neuronas del núcleo supraóptico del hemisferio izquierdo, lo que indica un aumento de la síntesis y liberación de las neurohormonas oxitocina y principalmente vasopresina

Transient increase in the number of cholinergic neurons in the developing rat dentate gyrus.

Using a monoclonal antibody against choline acetyltransferase (ChAT), we have examined the distribution of cholinergic neurons in the rat dentate gyrus during development. ChAT-positive neurons were occasionally detected in the hilus on postnatal day 2 (P2). There was a transient abrupt increase in the number and density of ChAT-positive neurons between P15 and P20 and then a decline to the adult level with few ChAT-immunoreactive neurons. A few ChAT-positive varicose fibers and punctae were first seen at P5. They increased in number and density until P20 when they reached the adult level and distribution. These observations suggest the occurrence of a transient expression of cholinergic markers in the hippocampus.

The morphology of cat spinal neurons projecting to both the lateral cervical nucleus and the dorsal column nuclei.

Morphological features of physiologically characterized doubly projecting spinocervical tract-dorsal column postsynaptic (SCT-DCPS) neurons were examined following intracellular injections of horseradish peroxidase. Their cell bodies and majority of dendrites were located in laminae III-IV. The SCT-DCPS neurons have rostrocaudally elongated dendritic trees with spiny fine caliber dendrites, and issue local axon collaterals that are studded with varicosities. The results show that the doubly projecting SCT-DCPS neurons do not represent a morphologically distinct subset of the spinocervical tract (SCT) or dorsal column postsynaptic (DCPS) cells.

Interstitial cells of the adult neocortical white matter are the remnant of the early generated subplate neuron population.

The postnatal fate of the first-generated neurons of the cat cerebral cortex was examined. These neurons can be identified uniquely by 3H-thymidine exposure during the week preceding the neurogenesis of cortical layer 6. Previous studies in which 3H-thymidine birthdating at embryonic day 27 (E27) was combined with immunohistochemistry have shown that these neurons are present in large numbers during fetal and early postnatal life within the subplate (future white matter), that they are immunoreactive for the neuron-specific protein MAP2 and for the putative neurotransmitters GABA, NPY, SRIF, and CCK. Here, the same techniques were used to follow the postnatal location and disappearance of the early generated subplate neuron population. At birth (P0), subplate neurons showing immunoreactivity for GABA, NPY, SRIF, or CCK are present in large numbers and at high density within the white matter throughout the neocortex, and the entire population can be observed as a dense MAP2-immunoreactive band situated beneath cortical layer 6. Between P0 and P401 (adulthood), the MAP2-immunostained band disappears so that comparatively few MAP2-immunoreactive neurons remain within the white matter. There is a corresponding decrease in the number and density of neurons stained with antibodies against neurotransmitters. In each instance, these neurons could be double-labeled by the administration of 3H-thymidine at E27, indicating that they are the remnants of the early generated subplate neuron population. The major period of decrease occurs during the first 4 postnatal weeks, and adult values are attained by 5 months. Within the white matter of the lateral gyrus (visual cortex), the density of immunostained neurons decreases dramatically: MAP2, 82%, SRIF, 81%, and NPY, 96%. While SRIF-immunoreactive neurons compose a nearly constant percentage of MAP2-immunoreactive neurons in the white matter between P0 (22%) and P401 (23%), those immunoreactive for NPY decline from 18 to 4%. These changes occur during the same period in which there is less than a twofold increase in white matter area. These observations indicate that the interstitial neurons of the adult neocortical white matter are the oldest neurons of the cerebral cortex since most if not all are derived from the subplate neuron population. In addition, a quantitative analysis suggests that the postnatal decline in subplate neuron density cannot be accounted for solely through dilution by differential growth of the white matter and most likely reflects an absolute decrease in subplate neuron number.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent connections of the oculomotor nucleus in the chick.

Horseradish peroxidase was injected into the oculomotor nucleus of the chick in order to locate and characterize the neurons projecting to this nucleus. In the rostral mesencephalon, 120-180 neurons were labelled in the medial area of the ipsilateral nucleus campi Foreli; 190-220 in the interstitial nucleus of Cajal (most of them contralateral); and smaller numbers bilaterally in the medial mesencephalic reticular formation, the nucleus of the basal optic root complex, and the central grey matter. More caudally, numerous neurons were labelled in the contralateral abducens nucleus and the vestibular complex and a few in the nucleus reticularis pontis caudalis. Labelled neurons appeared ipsilaterally in the caudal region of the nucleus vestibularis superior and in the rostral tip of the nucleus descendens just lateral to the tractus lamino-olivaris. In the contralateral vestibular complex, a group of labelled cells observed in the dorsolateral area may be homologous to the mammalian cell group Y. At the level of the contralateral abducens nucleus, the most numerous group of cells (625-700) projecting to the oculomotor nucleus formed a lateromedial fringe that affected the nucleus tangentialis, the rostral tip of the nucleus descendens, and the ventrolateral region of the nucleus medialis. Only a few labelled neurons were seen in the contralateral nucleus vestibularis superior, the ipsilateral cell group A, and the ipsilateral nucleus vestibularis medialis.

Structure and histogenesis of the principal sensory nucleus of the trigeminal nerve: effects of prenatal exposure to ethanol.

Clinical and experimental evidence shows that prenatal exposure to ethanol causes craniofacial malformations, microcephaly, and abnormal development of the central nervous system. This study describes the effects of ethanol on the development of the principal sensory nucleus of the trigeminal nerve (PSN). The offspring of two groups of rats were examined. Pregnant females in one group were fed a liquid diet containing 6.7% (v/v) ethanol (Et) and rats in the other group were fed an isocaloric liquid control diet (Ct). Each pregnant rat was administered [3H]thymidine on one day during the period from gestational day (G) 10 to G22. After pups grew to 30 days of age, they were killed and their brains were processed by an autoradiographic procedure. Qualitatively, the PSN of Ct- and Et-treated rats appeared similar; they were composed chiefly of small neurons and a few scattered large neurons. On the other hand, quantitative analyses revealed significant differences between both groups. Although the volume of the PSN of Et-treated rats was not significantly different (-3.2%) than that for Ct-treated rats, the PSN of Et-treated rats had significantly (P less than 0.01) fewer (30.0%) neurons than did the PSN of Ct-treated rats. The number of the small neurons, but not of the large neurons, was affected most by the ethanol exposure. Prenatal exposure to ethanol also altered the generation of PSN neurons. Most neurons in the PSN of Ct-treated rats were born between G12 and G15, the small neurons being generated before the large neurons. In Et-treated rats, too, small neurons were born before the large neurons; however, the time frame of neuronogenesis was delayed as it occurred between G13 and G16. Thus, prenatal exposure to ethanol produces profound developmental abnormalities that lead to permanent alterations in the structure of the mature central nervous system.

Survey of noncortical afferent projections to the basilar pontine nuclei: a retrograde tracing study in the rat.

The retrograde transport of the conjugate wheat germ agglutinin-horseradish peroxidase (WGA-HRP) was used in the rat to identify the cell bodies of origin for all subcortical projections to the basilar pontine nuclei (BPN). A parapharyngeal surgical approach was used to allow the injection micropipette to enter the BPN from the ventral aspect of the brainstem and thus avoid any potential for false-positive labeling due to transection and injury-filling of axonal systems located dorsal to the basilar pontine gray. A surprisingly large number of BPN afferent cell groups were identified in the present study. Included were labeled somata in the lumbar spinal cord and a large variety of nuclei in the medulla, pons, and midbrain, as well as labeled cells in diencephalic and telencephalic nuclei such as the zona incerta, ventral lateral geniculate, hypothalamus, amygdala, nucleus basalis of Meynert, and the horizontal nucleus of the diagonal band of Broca. Quite a number of cell groups known to project directly to the cerebellum also exhibited labeled somata in the present study. To explore the possibility that such neurons were labeled because their axons were transected and injury-filled as they coursed through the BPN injection site to enter the cerebellum via the brachium pontis, a series of rats received complete, bilateral lesions of the brachium pontis followed 30-60 minutes later with multiple, diffuse injections of WGA-HRP (12-16 placements per animal) throughout the cerebellar cortex. In another series of animals, the massive cerebellar WGA-HRP injections were not preceded by brachium pontis lesions. In the latter cases, each of the cell groups in question that were known to project directly to the cerebellum exhibited labeled somata. However, when the cerebellar HRP injections were preceded by brachium pontis lesions, each of the cell groups in question continued to exhibit labeled somata in numbers comparable to that observed in the nonlesion cases. This implies that such neurons project to the BPN and the cerebellar cortex and that the axons of these particular neurons do not project to the cerebellum via the brachium pontis.

The interstitial system of the spinal trigeminal tract in the rat: anatomical evidence for morphological and functional heterogeneity.

Utilizing cyto-, myelo-, and chemoarchitecture as well as connectional criteria, the present study reveals the interstitial system of the spinal trigeminal tract (InSy-SVT) in the rat to be composed of five morphologically and functionally distinct components that are distributed within spatially restricted regions of the lateral medulla. The first component is represented by scattered interstitial cells and neuropil, which extend laterally into SVT from the superficial laminae of the medullary dorsal horn (MDH). The second component, the dorsal paramarginal nucleus (PaMd), consists of a small group of marginal (lamina I)-like neurons and neuropil situated within the dorsolateral part of SVT at the rostral pole of MDH. The third component represents a trigeminal extension of the parvocellular reticular formation (V-Rpc) into the ventromedial aspect of SVT at levels extending from rostral MDH to the caudal part of trigeminal nucleus interpolaris (Vi). The fourth component, the paratrigeminal nucleus (PaV), consists of a large accumulation of neurons and neuropil situated within the dorsal part of SVT throughout the caudal half of Vi. The fifth component is the insular trigeminal-cuneatus lateralis nucleus (iV-Cul), which is a discontinuous collection of neurons and neuropil interspersed among fibers of SVT as well as wedged between it and the spinocerebellar tract. Thalamic projection neurons are located in PaMd and V-Rpc, whereas cerebellar projecting neurons are confined to iV-Cul.

Computer software for development and simulation of compartmental models of neurons.

A software package 'Nodus' for simulation and development of compartmental models of neurons is described. Passive or excitable membranes with voltage dependent ion conductances or synaptic conductances can be modeled. Detailed simulations of morphology and electrophysiology of neurons are possible. Neurophysiological experiments like voltage clamps and complex current injections can be simulated. Two integration methods are available: a fast hybrid method and an accurate fifth order Runge-Kutta method, with variable time steps. Nodus is implemented on Apple Macintosh microcomputers, with the standard user interface and interactive graphics. Simulations of simple test models demonstrate the accuracy and computation speed of the application.

The distribution of luteinizing hormone-releasing hormone (LHRH) neurons and fibers in the Formosan rock-monkey.

The anatomical distribution of neurons and fibers containing Luteinizing Hormone Releasing Hormone-Immunoreactivity (LHRH-IR) in the brain of the Formosan Rock-Monkey was investigated employing immunohistochemical techniques. LHRH-IR neurons were observed in an area demarcated rostrally by the diagonal band of Broca and caudally by the mammillary area. The majority of these neurons were principally localized in the preoptic area, periventricular zone, and the arcuate nucleus. The supraoptic nucleus, septal area, triangular septal nucleus, nucleus of the diagonal band of Broca, suprachiasmatic nucleus, retrochiasmatic area, mammillary area, and the amygdala also exhibited neuronal LHRH immunoreactivity. LHRH-IR fibers appeared to originate in all of the above areas of the hypothalamus, project caudally, and subsequently terminate in the median eminence (ME). In addition to the above, LHRH-IR fibers were also detected in the organum vasculosum of the lamina terminalis (OVLT). A scattering of LHRH-IR fibers were also observed in several extrahypothalamic regions, notably the subfornical organ, indusium griseum, habenular complex, septohypothalamic nucleus, and amygdala.

Nucleolar eccentricity in trigeminal ganglion neurons.

The aim of this study was to determine if measuring trigeminal ganglion neuron profiles containing nucleoli in histological sections gave a reasonable estimation of cell size. Serial sections of ferret trigeminal ganglia were prepared, and neuron profiles traced with the aid of a camera lucida. The cross sectional area of the profiles was measured. Profiles containing nucleoli formed the upper part of the size spectrum and were significantly larger than the profiles that did not contain nucleoli. When serial profiles of individual neurons were examined the largest profile contained the nucleolus in 20 of 27 cases, and the mean sizes of 'largest' and 'nucleolus-containing' profiles did not differ significantly. Computer reconstructions of individual cells show the nucleolus to be central in almost all cells viewed from almost every projection. It is concluded that the nucleolus lies at, or very near to, the centre of the neuron and at its widest dimension. Measuring the size of profiles containing nucleoli gives a satisfactory representation of cell size.

Neurons of the inferior medullary velum in the cerebellopontine angle.

The edge of the inferior medullary velum (tenia) is attached in part to the surface of several structures localized in the cerebellopontine angle, including the cochlear nuclear complex and the pontobulbar body. Since superficial layers of these structures contain numerous neurons, we examined the possibility that neurons are also present within the velum. On light microscopy, we found groups of neurons accumulated immediately under the pia mater covering the tenia. The number of groups in different specimens varied from one to three, and the groups were rounded or oval in shape. A bundle of fibers running from the main mass of the brain stem toward these groups was revealed with a myelin-staining technique. The majority of neurons in the groups were angular in shape. These findings may contribute to our understanding of the general and surgical anatomy of the cerebellopontine angle.

[Neurotransmitters of giant neurons in the African giant snail, Achatina fulica Férussac. IV. Supplemental results]. / Neurotransmetteurs des neurones géants chez l'Escargot géant africain, Achatina fulica Férussac. IV. Résultats complémentaires.

Following the previous works, we identified recently the twelve giant neurones in the ganglia of an African giant snail (Achatina fulica Férussac), by the pharmacological study of their sensitivities to putative neurotransmitters and derivatives, and by the morphological investigation of their axonal pathways due to the intracellular injection of Lucifer Yellow. The neurones studied were: TAN-2, TAN-3, BAPN, LPPN, LBPN and LAPN in the right parietal ganglion; RPeNLN and LPeNLN in the pedal ganglia; and d-LBAN, d-LBMN, d-LBCN and d-LBPN in the left buccal ganglion.

Somatostatin-14-like immunoreactive neurons and fibres in the human olfactory bulb.

This study describes the morphological features and the distribution pattern of neurons in the human olfactory bulb which are immunoreactive for an antiserum against the neuropeptide somatostatin-14. Immunoreactive nerve cell bodies were mainly found in the white matter surrounding the cell clusters of the anterior olfactory nucleus. Some immunoreactive neurons were also found scattered throughout the anterior olfactory nucleus and the deeper parts of the inner granule cell layer. Only a few immunoreactive neurons were localized in the glomerular layer and the outer granule cell layer. Immunoreactive fibres were found in all layers of the olfactory bulb. In addition, an impressive number of coiled and kinked immunoreactive fibres were localized within the anterior olfactory nucleus forming a dense plexus. Accumulations of twisted and coiled branches of immunoreactive fibres were rarely found either surrounding or within the olfactory glomerula. The characteristics of somatostatin-14 immunoreactive neurons as seen in the combined pigment-Nissl preparation were studied after decolourizing the chromogen and restaining the preparations with aldehydefuchsin in order to demonstrate the lipofuscin pigment and gallocyanin chrome alum for Nissl material. About 90% of the immunoreactive neurons studied in this manner turned out to be devoid of lipofuscin granules. The remaining 10% displayed different patterns of pigmentation. These findings suggest the presence of different types of somatostatin-14-like immunoreactive neurons in the olfactory bulb of the human adult.