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Shigenaga, Yoshio; Okamoto, T.; Nishimori, T.; Suemune, S.; Nasution, I. D.; Chen, I. C.; Tsuru, K.; Yoshida, A.; Tabuchi, K.; Hosoi, M.; Tsuru, H.
doi: 10.1002/cne.902440102pmid: 3950088
Transganglionic transport of horseradish peroxidase (HRP) was used to study the patterns of termination of somatic afferent fibers innervating oral and facial structures within the principal nucleus (Vp), nucleus oralis (Vo), and nucleus interpolaris (Vi). The primary trigeminal afferent fibers that innervate the oral cavity supplied by the pterygopalatine, superior alveolar, lingual, buccal, and inferior alveolar branches, as well as the facial skin sunnlied by the frontal, corneal, zygomatic, infraorbital, auriculotemporal, mylohyoid, and mental branches, were traced in this experiment. The results show that trigeminal afferent nerves that innervate the oral cavity project mainly to the principal nucleus, the rostrodorsomedial part (Vo.r) and dorsomedial division (Vo.dm) of pars oralis, and the dorsomedial region of pars interpolaris, while an extensive overlap of projections is found in the Vo.r, Vo.dm, and rostral Vi. The central processes of fibers innervating the anterior face (i.e., mental, infraorbital, and frontal nerves) terminate in the ventral division of principalis (Vpv), caudal region pars oralis (Vo.c), and ventrolateral Vi, with the largest numbers of terminals being found in the Vpv and Vi. In contrast, the central projection patterns of the corneal, zygomatic, mylohyoid, and auriculotemporal afferents are different from those of other afferent nerves examined, and present a discrete projection to the trigeminal sensory nuclear complex (TSNC). The corneal, mylohyoid, and auriculotemporal afferents mainly project to the restricted regions of principalis and caudal Vi, while zygomatic afferent nerve fibers project to the caudal third of pars interpolaris. The typical somatotopic organization with the face of the mouth open inverted is represented in the rostrocaudal midlevels of the Vpv and caudal pars interpolaris. The Vpd receives topographical projection from primary afferent nerves that innervate the oral structure only, while this projection was organized in a complicated manner. The relationship between the functional segregation and the cytoarchitectonic differentiation of the TSNC is discussed, particularly with respect to this somatotopic organization, combined with the characteristics of projecting cells in the TSNC.
Lehman, Michael N.; Robinson, Jane E.; Karsch, Fred J.; Silverman, Ann‐Judith
doi: 10.1002/cne.902440103pmid: 3512631
The luteinizing hormone‐releasing hormone (LHRH) system of the sheep brain was examined by light microscopic immunocytochemistry with thick, unembedded sections. We compared the distribution and morphology of LHRH cells and their fibers in intact and ovariectomized anestrous ewes, and in breeding season ewes during the mid‐luteal phase of their estrous cycle. In all animals, a majority of LHRH neurons were found in the medial preoptic area adjacent to the organum vasculosum of the lamina terminalis. These cells formed a continuum rostrally with immunoreactive neurons in the diagonal band of Broca and medial septum and caudally with cells in the ventrolateral anterior hypothalamus and lateral hypothalamus. Relatively few cells (1–2%) were seen in the arcuate nucleus or its vicinity. Preoptic LHRH neurons project to the tubero‐infundibular sulcus of the median eminence by at least two routes: a major ventrolateral projection above the optic tract in the anterior and lateral hypothalamus, and a less prominent periventricular pathway along the third ventricle. LHRH fibers were also observed in a number of extrahypothalamic regions, including the medial amygdala and the accessory olfactory bulb.
DiFiglia, Marian; Carey, Janice
doi: 10.1002/cne.902440104pmid: 3950089
Large neurons in the monkey neostriatum were examined in the electron microscope in tissue treated with the rapid‐Golgi impregnation method followed by the gold‐toning procedure. Two types of large neurons were investigated: an aspiny neuron (aspiny type II; N = 5) with numerous varicose dendrites and a spiny cell (spiny type II; N = 1) with few sparsely spined dendrites. The large aspiny neurons had variably shaped somata, an eccentric highly invaginated nucleus, and a cytoplasm rich in organelles. Mitochondria were distributed unevenly in dendrites and were localized primarily in varicosities. Some mitochondria exhibited dense hodies 80–300 nm in size. Most synapses (84%) onto large aspiny neurons occurred 20 μm or more from the cell body and contacted dendritic varicosities (63%). A smaller proportion of boutons (21%) contacted constricted portions of varicose segments. A low incidence of synaptic boutons was observed on smooth primary and secondary dendrites (11%), cell bodies (3%), and branch points (2%). Seven percent of the axons that synapsed with large aspiny neurons also contacted nearby dendrites or spines of medium‐sized spiny neurons. At least eight morphologically distinct types of axons making synapses with large aspiny neurons were identified and included both symmetric and asymmetric types.
Lima, Deolinda; Coimbra, Antonio
doi: 10.1002/cne.902440105pmid: 3950090
On the basis of dendroarchitecture and cell body shape, complemented with morphometry of dendritic ramification, four major neuronal types were distinguished in lamina I of the spinal cord of the rat. (I) Fusiform spiny cells (39% of impregnated neurons) have longitudinal spindle‐shaped perikarya with bipolar, less frequently unipolar, dendritic trees rich in pedicled spines and a thin, beaded longitudinal axon; such neurons occur mainly in the lateral marginal zone. In type IA cells (33% of the total), the dendritic domain occupies a narrow longitudinal area, while in type lb cells (6%) the polar dendritic trees partly arborize ventrally. Fusiform neurons are considered intrinsic cells connected with the longitudinal afferent plexus in lateral lamina I, and in type IB cells also receiving primary input in the substantia gelatinosa. (II) Multipolar cells (23%) have a dense dendritic arbor originating from numerous primary trunks and they predominate in the medial marginal zone. The dendritic arbor is moderately extended dorsoventrally in type IIA cells and reaches lamina III in the larger type JIB cells. The former possess a variety of spines, axonlike processes and sometimes an unmyelinated axon, and are presumably interneuron's, while type IIB cells show a thick tapering axon that is probably myelinated. (III) Flattened aspiny neurons (13%) with a polygonal body flattened in the horizontal plane, and a horizontal dendritic arbor confined to lamina I; these cells predominate in middle lamina I. (IV) Pyramidal neurons (25%) have longitudinally elongated perikarya that bulge into the white matter. The arbor has a large longitudinal and lateromedial spread and includes branches which ramify in the white matter. Types III and IV show the classical lateromedially elongated orientation of the marginal cells of the old literature; they show thick tapering axons and probably make up the bulk of the projection neurons of rat lamina I.
doi: 10.1002/cne.902440106pmid: 3950091
The solitary nucleus is the first level of the central nervous system where processing of taste information can occur. A structural basis for that processing was investigated. Facial taste afferent axons were labelled by application of horseradish peroxidase to either the chorda tympani or the geniculate ganglion. The labelled afferent fibers in the rostral solitary nucleus were studied with light and electron microscopy. Preterminal facial taste afferent axons enter the nucleus from the solitary tract with a pronounced lateral to medial trajectory. The axons bear numerous preterminal and terminal swellings that, with the electron microscope, were identified as synaptic endings located in glomeruli. The endings are ovoid or scalloped, indented by structures that surround them. The primary afferent endings contain large, round vesicles and synapse, by means of slightly asymmetrical junctional complexes, on small dendrites and spines. Two types of unlabelled endings, surrounding the labelled ones, contact the dendrites receiving taste afferent input or contact the endings of taste afferent axons themselves. One type is variable in size and contains scattered large round vesicles. It resembles a presynaptic dendrite. The other is a small axonal ending packed with small, pleomorphic vesicles, that engages in symmetrical junctions. The synaptic milieu of the taste endings allows for the possibility of modulation of taste‐elicited activity in afferent endings or secondorder neurons by other, possibly interneuronal, inputs.
Bregman, Barbara S.; Reier, Paul J.
doi: 10.1002/cne.902440107pmid: 3950092
Rubrospinal tract cells undergo massive retrograde degeneration following spinal cord damage in newborn rats (Prendergast and Stelzner, J. Comp. Neurol. 166:163–172, '76b). In the current study, fetal spinal cord tissue (E12–14) was grafted into midthoracic spinal cord lesions in newborn rats (<72 hours old) in order to determine whether such transplants could modify the response of the immature host central nervous system (CNS) to axotomy. These transplants grew, differentiated, and formed extensive areas of apposition with the recipient spinal cords. Counts of red nucleus (RN) neurons indicated a significant loss of RN neurons in animals with lesion alone, but a rescuing of most of these cells if a transplant was placed into the lesion site. In fact, the number of neurons in animals with lesions and transplants was not significantly different from control animals. Horseradish peroxidase injected 10–15 mm caudal to the transplant (at 1–12 months post‐transplantation) labeled neurons within the transplant and RN neurons contralateral to the spinal cord lesions and transplant. In animals with spinal cord lesion but no transplant, only the unaxotomized RN was labeled. Thus, spinal cord transplants prevented the massive retrograde cell death of immature axotomized rubrospinal neurons. Some of these rescued neurons projected to the host spinal cord caudal to the transplant.
doi: 10.1002/cne.902440108pmid: 3950093
Neurons in the ventrolateral (VL) subdivision of rat trigeminal nucleus oralis (Vo) have most of their dendritic arbors confined within this region. This study examines the morphology and synaptic connections of a population of myelinated primary trigeminal axons that arborize within VL and are in a position to provide input directly to VL neurons. Primary axons were visualized for light and electron microscopic analysis by injecting 30% horseradish peroxidase (HRP) in 2% dimethylsulfoxide (DMSO) into the sensory root of the trigeminal nerve and allowing 24–36 hours for the anterograde transport of HRP into the terminal axonal arbors. This population is characterized by its cone‐shaped terminal arbors, which generate many axonal endings (2–8 μm in diameter) along unmyelinated terminal strands. These arbor s arise from collaterals emanating from thinly myelinated (2–5 μm in diameter) parent branches descending in the spinal V tract, which, on the basis of their size, are considered to be small myelinated (As) primary trigeminal axons.
doi: 10.1002/cne.902440109pmid: 3081602
Giant medullary neurons were revealed in adult Xenopus laevis and Rana esculenta following HRP injections to the spinal cord. These neurons were identified as Mauthner neurons because (1) they have the same position and orientation as the larval Mauthner neurons, i.e., they lie at the level of the VIIIth nerve root. (2) they have two large dendritic trees that for each species are similar to those of the larval Mauthner neurons, (3) they are clearly distinguishable from other large reticular neurons, (4) they have close connections with the VIIIth nerve afferents, (5) they have a decussating descending axon, the largest of the adult brainstem, and (6) they have a reduced axon cap, i.e., a dense neuropil without cap dendrites.
Carlsen, Jørn; Heimer, Lennart
doi: 10.1002/cne.902440110pmid: 3512630
The cholinergic innervation of the rat basolateral amygdaloid nucleus (BL) was determined by the immunocytochemical localization of the acetylcholine biosynthetic enzyme, choline acetyltransferase (ChAT).
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