bluuebunny/crossref_metadata_2025 huggingface dataset:
Morphology of rat spinal motoneurons with normal and hormonally altered specificity
Authors: Kurz Elizabeth M. , Bowers Christine A. , Sengelaub Dale R.
Published: January 2005

Potential determinants of motoneuronal morphology were examined by using a sexually dimorphic, steroid‐sensitive neuromuscular system in the rat spinal cord. In males, the spinal nucleus of the bulbocavernosus (SNB) innervates the perineal muscles bulbocavernosus (BC) and levator ani (LA), and the dorsolateral nucleus (DLN) innervates the ischiocavernosus muscle (IC). Adult females normally lack these motoneurons and the peripheral targets. Prenatal exposure of females to the androgen dihydrotestosterone propionate (DHTP) partially masculinizes this neuromuscular system and alters motoneuron‐to‐muscle specificity, resulting in retained SNB target muscles anomalously innervated by motoneurons in the DLN. Because the morphology of SNB and DLN motoneurons normally differs significantly, the influence of spinal cord location and peripheral target on motoneuron morphology can be directly compared.

Injection of cholera toxin conjugated to horseradish peroxidase (CTHRP) into the LA of DHTP‐treated females labeled motoneurons predominantly in the SNB. These (SNB‐LA) motoneurons in DHTP females were identical in all morphological measures to those of normal males. CTHRP injection into the BC of DHTP females labeled motoneurons in both the SNB and the DLN. SNB‐BC motoneurons in DHTP females resembled those of normal males in process number and orientation, but were significantly smaller in dendritic length per motoneuron and in soma size. The DLN motoneurons anomalously projecting to the BC in DHTP females differed significantly from SNB‐BC motoneurons in soma size and number and orientation of primary processes. However, these motoneurons were identical in all respects to DLN‐IC motoneurons in DHTP females; DLN‐IC motoneurons were similar to those of normal males in the orientation of their dendritic arbor, but were significantly smaller in dendritic length, soma size, and number of primary processes.

These comparisons make it clear that DHTP selectively affects motoneuronal specificity and morphology in specific motoneuron classes. Further, motoneuronal morphology in the SNB/DLN system appears to be influenced more by spinal cord location than by peripheral target.
Organization of adrenergic inputs to the paraventricular and supraoptic nuclei of the hypothalamus in the rat
Authors: Cunningham E. T. , Bohn M. C. , Sawchenko P. E.
Published: January 2005

Anterograde transport, retrograde transport, and immunohistochemical techniques were used to characterize the organization of neural inputs to the paraventricular (PVH) and supraoptic (SO) nuclei from the C1, C2, and C3 adrenergic cell groups in the rostral medulla. The results are as follows: (1) Phenylethanolamine‐N‐methyltransferase–immunoreactive (PNMT‐IR) fibers and terminals were distributed to all parts of the parvicellular division of the PVH; the dorsal and dorsal medial subdivisions received the most prominent inputs, the lateral and ventral medial parts the least. Sparse terminal fields were found consistently in the magnocellular division of the PVH and in the SO. (2) A combined retrograde transport–immunohistochemical method was used to estimate the number and proportion of cells in the regions of the C1, C2, and C3 cell groups that contribute to the PNMT‐IR innervation of the PVH. On average, 232 ± 37 retrogradely labeled cells in the C1 cell group, 73 ± 32 in the C2 cell group, and 96 ± 26 in the C3 group stained positively for PNMT‐IR. These values comprised 70%, 84%, and 89%, respectively, of all retrogradely labeled neurons in these regions. (3) Fibers and terminals arising from the regions of each of the three adrenergic cell gruops were labeled by local injections of the anterogradely transported plant lectin PHA‐L. Each component projection was found to distribute in a very similar fashion and to mimic the overall distribution of PNMT‐IR; differential projection patterns within the PVH or SO were not seen consistently following deposits in any of the individual adrenergic cell groups or at different rostrocaudal levels of any individual cell group. (4) A dual anterograde tracing (PHA‐L)–immunohistochemical (PNMT) labeling method revealed an appreciable number of varicosities arising from the regions of C1, C2, and C3 cell groups to contain PNMT‐IR. These results suggest that adrenergic inputs to the PVH and So, while arising from distinct medullary cell groups and presumably relaying different types of sensory information, are in a position to influence similar groups of parvicellular neurosecretory and/or autonomic‐related projection neurons.
Dorsomedial telencephalon of lungfishes: A pallial or subpallial structure? criteria based on histology, connectivity, and histochemistry
Authors: von Bartheld Christopher S. , Collin Shaun P. , Meyer Dietrich L.
Published: January 2005

The dorsomedial telencephalon of lepidosirenid lungfishes has been interpreted in two divergent ways: earlier investigators regarded it as a subpallial (septal) structure; more recently, it has been reinterpreted as the medial pallium (hippocampus). To resolve this question, we identified parameters that are conclusive in their association with either the medial pallium or the septum in anamniotes. The present study examines the position of ependymal thickenings and the distribution of acetylcholinesterase (AchE) in the cerebral hemispheres of the African lungfish Protopterus, the Australian lungfish Neoceratodus, and the amphibian species Xenopusand Ambystoma. In addition, projections from the hypothalamus (paraventricular organ) to the telencephalon are investigated in Protopterus.

Ependymal specializations are located dorsally and ventrally in the lateral ventricles of amphibians, but laterally and medially in lungfishes. In Protopterus, the paraventricular organ projects to the medial telencephalic hemisphere, but not to the dorsal roof. High levels of AchE are present in restricted neuropil regions of the medial hemisphere and in the ventral and ventrolateral telencephalon, but they are lacking in the dorsal roof. Intensely AchE‐stained neuronal cell bodies are located in the ventral telencephalon (rostrally) and the dorsomedial telencephalon (at mid‐level). In Neoceratodus, AchE staining is pronounced in the septal area, but absent in the pallium. The terminal nerve proper lacks AchE stain in Protopterus; nerve fibers of the preoptic nerve are AchE‐positive in both lungfish species. In Xenopus, AchE staining of fibers and terminals is restricted to the subpallium (medial septum, tuberculum olfactorium, striatum, nucleus accumbens, and medial amygdala); cell bodies are AchE positive in parts of the subpallium and rostral pallium.

Comparison of cytological, histochemical, and “connectional” parameters substantiates the interpretation that the dorsomedial telencephalon of lungfishes represents a subpallial, but not a “medial pallial” structure. The dorsomedial part of the lepidosirenid telencephalon corresponds to the septum in the most plesiomorphic living lungfish, Neoceratodus forsteri, but it differs considerably from the dorsomedial telencephalon (medial pallium) in amphibians.
Coexistence of corticotropin‐releasing factor and enkephalin in the paraventricular nucleus of the rat
Authors: Pretel S. , Piekut D.
Published: January 2005

Corticotropin‐releasing factor and enkephalin‐containing neurons are found in the paraventricular nucleus of the rat hypothalamus. Their immunocytochemical distribution suggests that a subpopulation of neurons of the paraventricular nucleus might contain both peptides. The present study describes the coexistence of corticotropin‐releasing factor and enkephalin in parvicellular neurons of the paraventricular nucleus. Immunocytochemical labeling of peptides was combined with in situ hybridization of mRNA to visualize peptide and mRNA labeling in the same tissue section. This resulted in several observations: (1) neurons labeling for the peptide corticotropin‐releasing factor also contain the mRNA to synthesize corticotropin‐releasing factor, (2) neurons labeling for the peptide enkephalin also contain the mRNA to synthesize the peptide enkephalin, (3) a subpopulation of corticotropin‐releasing factor neurons contains the mRNA to synthesize enkephalin, and (4) a subpopulation of enkephalin neurons contains the mRNA to synthesize corticotropin‐releasing factor. A large percentage of enkephalin immunoreactive neurons contains corticotropin‐releasing factor mRNA, where as a smaller percentage of corticotropin‐releasing factor immunoreactive neurons contains enkephalin mRNA. These double‐labeled neurons are present throughout the rostral‐caudal extent of the paraventricular nucleus; the majority of these neurons is present in the medial parvicellular paraventricular nucleus.
Subnuclear organization of the lateral tegmental field of the rat. II: Catecholamine neurons and ventral respiratory group
Authors: Ellenberger H. H. , Feldman J. L. , Zhan W.‐Z.
Published: January 2005

Bulbospinal and propriobulbar respiratory neurons of the ventral respiratory group and catecholamine neurons of the A1 and C1 cell groups were simultaneously labelled in the rat medulla by a combination of retrograde tracing and immunohistochemical identification. The ventral respiratory group and catecholamine cell groups form adjacent, parallel cell columns in the lateral tegmental field of the ventrolateral medulla. The ventral respiratory group is located immediately dorsal to the A1 and C1 groups, although some A1 neurons are intermingled with neurons of the rostral ventral respiratory group, and some C1 neurons are intermingled with those of the Bötzinger complex. The proximate populations of respiratory, catecholamine, and (presumptive) cardiovascular neurons identified in this study provide further support to the hypothesis that this regin of the lateral tegmental field of the ventrolateral medulla is a site of cardiorespiratory coordination.
Thyrotropin‐releasing hormone‐immunoreactive nerve terminals synapse on the dendrites of gastric vagal motoneurons in the rat
Authors: Rinaman Linda , Miselis Richard R.
Published: January 2005

Thyrotropin‐releasing hormone stimulates vagally mediated gastric acid secretion and motility by an undefined central mechanism in the rat. The present study sought to determine the anatomical basis for this stimulatory effect by examining the ultrastructural relationship of nerve terminals immunoreactive for thyrotropin‐releasing hormone with the dendrites of gastric vagal motoneurons. A light and electron microscopic double immunostaining technique was employed using the beta subunit of unconjugated cholera toxin as a neural tracer. Cholera toxin (50 μl, 0.25%) was injected into the ventral stomach musculature in five rats. After 72 hours' survival, animals were sacrificed by transcardiac perfusion fixation. Retrogradely transported choleratoxin was immunocytochemically localized in vagal gastric motoneurons and their dendrites in the dorsal motor nucleus of the vagus and nucleus of the solitary tract, alone or in combination with the immunocytochemical localization of thyrotropin‐releasing hormone.

Ultrastructural analysis of double‐labeled material revealed thyrotropin releasing hormone‐immunoreactive nerve terminals making asymmetric synaptic contacts on the retrogradely labeled dendrites of vagal gastric motoneurons. Nerve terminals immunoreactive for thyrotropin‐releasing hormone also made asymmetric and symmetric synaptic contacts with unlabeled dendrites of undetermined perikaryal origin. In addition, nonsynaptic varicosities immunoreactive for thyrotropin‐releasing hormone were frequently observed in the vagal nuclei. The synaptic contacts between thyrotropin‐releasing hormone‐immunoreactive nerve terminals and vagal gastric motoneuronal dendrites provide one possible basis for the profound stimulatory effect of central thyrotropin‐releasing hormone on gastric vagal motor activity.
Organization of the six motor nuclei innervating the ocular muscles in lamprey
Authors: Fritzsch B. , Sonntag R. , Dubuc R. , Ohta Y. , Grillner S.
Published: January 2005

The topography of motoneurons supplying each of the six ocular muscles of the lamprey, Lampetra fluviatilis, was studied by selective application of HRP to the cut nerves of identified muscles. In addition, the distributions of motoneuron populations to both eyes were studied simultaneously with fluoresceine and rhodamine coupled dextran‐amines (FDA and RDA) applied to cut ocular muscle nerves of either side. The motoneuron pool of the caudal oblique muscle is represented bilaterally in the trochlear (N IV) motor nucleus. The dorsal rectus muscle is innervated from a contralateral group of oculomotor (N III) motoneurons and the remaining four muscles exclusively from the ipsilateral side (N III and N VI). The inferior and posterior rectus muscles are both innervated by the abducens nerve. In contrast to all jawed vertebrates, only three eye muscles (the dorsal rectus, rostral rectus, and rostral oblique) are innervated by the oculomotor nerve in lampreys (N III). Lampreys have a motor nucleus similar to the accessory abducens nucleus previously described only in tetrapods. They lack the muscle homologous to the nasal rectus muscle of elasmobranchs and the medial rectus muscle of osteognathostomes. The distribution of the dendrites of different groups of motoneurons was studied and is considered in relation to inputs from tectum and the different cranial nerves.
Substance P antibody reveals homologous neurons with axon terminals among somata in the crayfish and crab brain
Authors: Sandeman R. E. , Sandeman D. C. , Watson A. H. D.
Published: January 2005

In the search for particular neurons that stain selectively and can be identified, the cerebral ganglia (brains) of the crayfish Cherax destructor and the crab Leptograpsus variegatus were immunocytochemically treated with a monoclonal antibody raised against substance P. Four large neurons in the cerebral ganglion of the crayfish and crab label selectively with a monoclonal antibody raised against substance P. Two of the large neurons have their cell bodies in the protocerebrum and two in the deutocerebrum in both animals. Each protocerebral cell in both animals projects through the ipsilateral and contralateral olfactory lobes to end among the lateral cell somata of the olfactory lobe and not in the neuropile. Electron micrographs show the presence of synapses within the cell somata area and on the cell somata themselves. Each deutocerebral cell in both animals projects only ipsilaterally and ends within the neuropile of the olfactory lobes. The immunoreactivity to substance P antibody and the shapes and the unique projections of the four cells suggest that they are homologous in the two species. Synaptic connections between axons and cell somata are rare in the arthropods but have been found on the Kenyon cells of the mushroom bodies of Limulus. This raises questions about homologies between the crustacean olfactory lobe and the mushroom bodies of Limulus and insects.
Afferent and efferent synaptic conncetions sof somatostatin‐immunoreactive neurons in the rat fascia dentata
Authors: Leranth Csaba , Malcolm Andrew J. , Frotscher Michael
Published: January 2005

The aim of this study was to determine whether somatostatin (SS)‐immunoreactive neurons of the rat fascia dentata are involved in specific excitatory circuitries that may result in their selective damage in modeis of epilepsy. Synaptic connections of SS‐immunoreactive neurons were determined at the electron microscopic level by using normal and colchicine pretreated rats. Vibratome sections prepared from both fascia dentata of control animals and from rats that had received an ipsilateral lesion of the entorhinal cortex cortex 30‐36 hours before sacrifice were immunostained for SS by using a monoclonal anatibody (SS8). Correlated light and electron microscopic analysis demonstrated that many SS‐immunoreactive neurons in the hilus send dendritic processes into the outer molecular layer of the fascia dentata, and dendrites of the same neurons occupy broad areas in the dentate hilar area. The majority of SS‐immunoreactive axon terminals form symmetric synapses with the granule cell dendrites in the outer molecular laayer and also innervate deep hilar neuronns. Via their dendrites in the outer molelcular layer, the SS‐immunoreactive neurons receive synaptic inputs from perforant pathway axons which were identified by their anaterograde degeneration following entorhinal lesions. The axons from the entorhinal cortex are the first segment of the main hippocampal excitatory loop. The hilar dendrites of the same SS‐immunoreactive cells establish synapses with the mossy axon collaterals which represent the second member in this excitatory neuronal chain. These observations suggest that SS‐immunoreactive neurons in the dentate hilar area amay be driven directly by their perforant path synapses and via the granule cells which are known to receive a dense innervation from the entorhinal cortex. These observations demonstrate that SS‐immunoreactive neurons in the hilar region of integerated in the main excitatory impulse flow of the hippocampal formation.
Cellular events associated with peripherally induced rejection of mature neural xenografts placed into neonatal rat brains
Authors: Backes M. G. , Lund Raymond D. , Lagenaur C. F. , Kunz H. W. , Gill T. J.
Published: January 2005

Various circumstances have brought about a dispute concerning the immunologically privileged status of the central nervous system (CNS). Using a transplantation paradigm, we have examined the cellular events associated with an experimentally induced focal assault on the CNS by the immune system. Chunks of embryonic mouse cortex were transplanted into neonatal rat brains and allowed to survive for 4 weeks. The adult rats then received a skin graft of donor origin to induce rejection of the transplanted tissue. Animals were sacrificed at various time points and examined histologically and immunocytochemically. Under these circumstances, the transplant is rejected via a first‐set rejection response, and astrocytes of donor origin appear to be the primary target of the host immune system. Expression of class I and class II major histocompatibility antigens is noted to correlate with lymphocytic invasion of the transplant.
Organization of cortical, basal forebrain, and hypothalamic afferents to the parabrachial nucleus in the rat
Authors: Moga Margaret M. , Herbert Horst , Hurley Karen M. , Yasui Yukihiko , Gray Thackery S. , Saper Clifford B.
Published: January 2005

In a previous study (Herbert et al., J. Comp. Neurol. [1990];293:540‐580), we demonstrated that the ascending afferent projections from the medulla to the parabrachial nucleus (PB) mark out functionally specific terminal domains within the PB. In this study, we examine the organization of the forebrain afferents to the PB. The PB was found to recive afferents from the infralimbic, the lateral prefrontal, and the insular cortical areas; the dorsomedial, the ventromedial, the median preoptic, and the paraventricualr hypothalamic nuclei; the dorsal, the retrochiasmatic, and the lateral hypothalamic areas; the central nucleus of the amygdala; the substantia innominata; and the bed nucleus of the stria terminalis. In general, forebrain areas tend to innervate the same PB subnuclei from which they receive their input. Three major patterns of afferent termination were noted in the PB; these corresponded to the three primary sources of forebrain input to the PB: the cerebral cortex, the hypothalamus, and the basal forebrain. Hypothalamic afferents innervate predominantly rostral portions of the PB, particularly the central lateral and dorsal lateral subnuclei. The basal forebrain projection to the PB ends densely in the external lateral and waist subnuclei. Cortical afferents terminate most heavily in the caudal half of the PB, particularly in the ventral lateral and medial subnuclei. In addition, considerable topography organization was found within the individual projections. For example, tuberal lateral hypothalamic neurons project heavily to the central lateral subnucleus and lightly to the waist area; in contrast, caudal lateral hypothalamic neurons send a moderately heavy projection to both the central lateral and waist subnuclei. Our results show that the forebrain afferents of the PB are topographically organized. These topographical differences may provide a substrate for the diversity of visceral functions associated with the PB.
Neuropeptide organization of the hypothalamic projection to the parabrachial nucleus in the rat
Authors: Moga Margaret M. , Saper Clifford B. , Gray Thackery S.
Published: January 2005

The hypothalamus is a major source of afferents to the parabrachial nucleus (PB), but the neurotransmitters in this pathway are largely unknown. In this study, we examine the neuropeptide immunoreactivities of neurons in the hypothalamus that project to the PB by using the combined retrograde fluorescence‐immunofluorescence method. After injections of the fluorescent tracer fast blue into the PB, retrogradely labeled neurons were observed in the paraventricular, dorsomedial, ventromedial, median preoptic, and anteroventral periventricular hypothalamic nuclei; in the dorsal, retrochiasmatic, and lateral hypothalamic areas; and in the medial and lateral preoptic areas. Our results show that at least five distinct neuropeptideimmunoreactive cell populations in the hypothalamus project to the PB. In the perifornical lateral hypothalamus, many neurotensin (NT)‐, corticotropin‐releasing factor‐, dynorphin (DYN)‐, angiotensin II (AII)‐, and galanin‐like immunoreactive (‐ir) neurons were retrogradely labeled. A cluster of retrogradely labeled neurons in the juxtacapsular lateral hypothalamus stained with an antiserum against α‐melanocyte stimulating hormone (αMSH). Over 50% of the retrogradely labeled cells in the arcuate nucleus were adrenocorticotropin (ACTH)‐or αMSH‐ir. Many αMSH‐ and ACTH‐ir, and a few DYN‐, NT‐ and AII‐ir neurons in the retrochiasmatic area were retrogradely labeled. Only small numbers of double‐labeled neurons were found in the paraventricular nucleus, and, of these, enkephalin‐ir and dynorphin‐ir neurons were the most common. Somatostatin‐ir cells in the hypothalamus were rarely double‐labeled. The chemical coding of these hypothalamic projections to the PB may provide important clues to the functional organization of these descending pathways.
Regeneration and soma size changes following axotomy of the trochlear nerve
Authors: Hazel Murphy E. , Brown Joyce , Iannuzzelli Pasquale G. , Baker Robert
Published: January 2005

The effects of CNS and PNS axotomy of the IVth nerve on cell death, soma size, axon size, and axon number were investigated. In adult cats, the IVth nerve was axotomised by using four surgical paradigms: (1) peripheral IVth nerve crush, (2) peripheral IVth nerve cut, (3) peripheral IVth nerve resection, and (4) a CNS IVth nerve cut in the velum. The extent of cell death resulting from each surgical paradigm was determined. Following axotomy distal to the decussation of the IVth nerves, cell death was least after nerve crush, intermediate after nerve cut, and maximal after resection of 5–7 mm of the nerve. Following axotomy at the decussationa CNS lesion‐most cells died but some successful regeneration was observed.

Soma size measurements following a short‐term survival (3 days to 4 weeks) before the regenerating axons reached their target muscle revealed that somas of axotomised cells underwent hypotrophy within 1 week of axotomy and then gradually increased in size. They re‐attained normal size by 4 weeks postoperative when regenerating axons first reach their target. Following a long‐term survival (>2 months), somas were significantly hypertrophied, and the degree of hypertrophy was inversely related to the extent of cell survival up to a limit of 40% soma size increase.

Counts and measurements of axons revealed that mean axon diameter of regenerated axons was much smaller than normal 3 months after axotomy, increased during the third to sixth postoperative months, but then showed no subsequent increase and remained below normal. In animals with cell death varying from 10% to 70%, the number of axons in the nerve was maintained constant at approximately 1,000. These data indicate that there is a mechanism for the production and maintenance of the appropriate number of regenerative axonal brabches following axotomy. In animals in which cell death exceeded 70%, the number of axons was controlled by a maximum ratio of 3 to 4 axon branches per surviving cell.

The results suggest that axon number is strongly influenced by the target muscle and that hypertrophy of regenerated cells is related to the number of axonal sprouts each cell has to produce and suppot in order to re‐establish the preoperative number of axons in the regenerated trochlear nerve.
Organization of the histaminergic system in the brain of the turtle Chinemys reevesii
Authors: Inagaki Naoyuki , Panula Pertti , Yamatodani Atsushi , Wada Hiroshi
Published: January 2005

To accumulate phylogenetic information on the central histaminergic system, we investigated the histaminergic system in the brain of the Reeves turtle, Chinemys reevesii, using the indirect immunofluorescent method with antiserum against histamine. Histaminergic neuronal cell bodies were found exclusively in the posterior part of the ventral hypothalamus. Histaminergic varicose fibers innervated almost all parts of the turtle brain, but tended to be concentrated in several areas. Very dense innervation was observed in the medial part of the telencephalon, ventrolateral part of the hypothalamus, nucleus habenularis lateralis, and ventromedial part of the tegmentum. Medium density of innervation was seen in the olfactory bulb, nucleus medialis amygdalae, and tectum. Only a few fibers were detected in the lateral part of the telencephalon, dorsal part of the hypothalamus, thalamus, rhombencephalon, and spinal cord. The main ascending fibers were observed in the lateral part of the hypothalamus, sending dense fiber bundles to the cortices dorsomedialis and medialis and nucleus habenularis lateralis. Descending fibers appeared to run in the ventral tegmental area, passing through the dorsal and ventral parts of the midline of the brain stem to the spinal cord. These findings indicate that the general morphological features of the histaminergic system in the turtle brain are similar to those in the mammalian and frog brains.
Retinal vasculature of the fovea of the squirrel monkey, Saimiri sciureus: Three‐dimensional architecture, visual screening, and relationships to the neuronal layers
Authors: Max Snodderly D. , Weinhaus Richard S.
Published: January 2005

The retinal vasculature of the fovea of squirrel monkeys was studied in retinal whole mounts and in sections of the same retinas. At the center of the fovea there is an approximately circular avascular zone surrounded by a set of terminal capillaries in the inner nuclear layer. Within the foveal depression, four capillary planes that bear a precise relationship to the neuronal organization appear in a specific sequence with increasing eccentricity. The first plane to be established is the dominant, most voluminous one, located closest to the photoreceptors at the deep (sclerad) border of the inner nuclear layer. A second major plane appears next at the sclerad border of the ganglion cell layer.

The two remaining, less voluminous planes occur at a slightly greater eccentricity. One of these, located at the shallow (vitread) border of the inner nuclear layer, often drains into the ganglion cell plane. The fourth plane is initially situated at the vitread border of the ganglion cell layer; with increasing eccentricity it moves into the nerve fiber layer. These capillaries are oriented like the nerve fibers with which they travel. Both the shallow inner nuclear and nerve fiber planes of capillaries show marked regional variations.

The capillary planes are within or adjacent to regions of high cytochrome oxidase activity.

The retinal vascular network is an unrecognized contributor to the optical filtering properties of the eye. In much of the central retina, a photon has a 40–50% chance of encountering one or more capillaries before it reaches a photoreceptor.
Motor neurons of grasshopper metathoracic ganglion occur in stereotypic anatomical groups
Authors: Siegler Melody V. S. , Pousman Cynthia A.
Published: January 2005

Anatomical groups containing identified motor neurons of the main muscles of the legs and the wings are described in a segmental ganglion of the adult grasshopper. The groups occur reproducibly in ganglia of different individuals and are a simplifying and organizing feature of ganglionic morphology. The motor neurons within each group have cell bodies near each other in the cortex of the ganglion and primary neurites that enter the ganglionic core as a discrete bundle. The primary neurite bundles are distinctive in shape and position and have the same composition in every individual, despite variations in the positions of the cell bodies of the contributing motor neurons. The primary neurite bundle of a group is separate from those of other groups and separate from bundles of motor axons that exit or sensory axons that enter the ganglion. Each group of cell bodies in the cortex appears from light microscope examination to be held separately within a glial surround. Areas of glial cell cytoplasm may extend considerably beyond the boundaries of the neuronal cell bodies, to give shape and structural integrity to the cortex. Similarities between the morphology of the adult groups reported here and the descriptions by others of embryonic and larval nervous systems suggest to us that the motor neurons of each group are the progeny of a single neuroblast.
Horseradish peroxidase labeling of the central pathways in the medulla of the ampullary nerves in the chicken, Gallus gallus
Authors: Cox Robert G. , Peusner Kenna D.
Published: January 2005

The purpose of the present study was to place horseradish peroxidase on the distal processes of the three ampullary nerves in 6–8‐week‐old chickens so that we could identify the ganglion cells associated with each nerve and trace the specific central pathways taken by each nerve in the brainstem. We are especially interested in the pathways of the colossal vestibular fibers, which may play a role in a fast reflex pathway as suggested by their large caliber and electrotonic mode of transmission in the tangential vestibular nucleus.

The cells of origin of each ampullary nerve occupy discrete portions of the vestibular ganglion. Those vestibular ganglion cells giving rise to the posterior ampullary nerve (PAN) occupy the posterior portion of Scarpa's ganglion; the ganglion cells producing the anterior (AAN) and lateral (LAN) ampullary nerves occupy the anterior ganglion, within the dorsal and ventral portions, respectively. Centrally the vestibular fibers occupy discrete portions of the tangential vestibular nucleus before bifurcating into ascending and descending tracts. The tangential nucleus receives afferents from the colossal fibers, which form spoon endings, and also from the fine vestibular fibers, which form small terminals. The ascending fibers of the posterior ampullary nerve are associated with the nucleus piriformis; the ascending fibers of the anterior and lateral ampullary nerves occupy discrete cell groups of the vestibulo‐cerebellar nucleus. All three ampullary nerves have descending branches that course through the retrotangential nucleus into the descending vestibular nucleus (DVN). Within the descending vestibular nucleus, the descending fibers of the posterior ampullary nerve run dorsally and centrally, whereas fibers of the anterior ampullary nerve course ventromedially, and the lateral ampullary nerve fibers take a ventrolateral course until all three fiber bundles converge in the posterior tip of the descending vestibular nucleus. The ascending and descending fibers of each ampullary nerve form collaterals that pass to the ventrolateral and dorsomedial parts of the medial vestibular nucleus. These collaterals are derived exclusively from the fine and medium diameter vestibular fibers. Some of these ascending fibers form a distinctive tract that courses posteriorly within medial regions of the dorsomedial part of the medial vestibular nucleus. The colossal vestibular fibers, which are found within all three ampullary nerves, conform to the ampullary pathways as described, excluding the innervation of the medial vestibular nucleus.
Distribution of neurotensin‐containing fibers in the frontal cortex of the macaque monkey
Authors: Satoh Keiji , Matsumura Hiroko
Published: January 2005

The distribution of neurotensin‐containing fibers was examined in the frontal cortex of the monkey Macaca fuscata using the immunoperoxidase histochemical technique. An extremely dense network of neurotensin‐containing fibers was observed in the medial prefrontal regions. The majority of cortical neurotensin fibers was observed in the anterior cingulate cortex (Walker's area 24) and adjacent medial prefrontal regions (areas 6 and 32). In area 24, the fiber density was similar to that in the nucleus accumbens. Immunoreactive fibers were particularly dense in two pyramidal layers (III, V). The medial prefrontal regions, areas 6 and 32, contained a moderate density of immunoreactive fibers. This regional distribution of neurotensin‐containing fibers was not observed in other cortical fiber systems that contained substance P, somatostatin, or tyrosine hydroxylase. No neurotensin‐containing cell bodies were observed in the frontal cortex.

The present study demonstrates that the laminar and regional distributions of neurotensin‐containing fibers are unique when compared to those of substance P‐ or somatostatin‐containing fibers, and also distinct from that of catecholaminergic fibers. The distribution of telencephalic neurotensin fibers points to a relationship with limbic structures.
Cerebellar nucleo‐olivary projections in the rat: An anterograde tracing study with Phaseolus vulgaris‐leucoagglutinin (PHA‐L)
Authors: Ruigrok T. J. H. , Voogd J.
Published: January 2005

In order to evaluate the reciprocity of olivo‐cerebellar and cerebello‐olivary connections, a detailed description of the cerebellar nucleo‐olivary projection in the rat is presented using small, iontophoretic injections of the anterograde tracer Phaseolus vulgaris‐leucoagglutinin.

Sparse projections were found to arise from the rostral part of the medial cerebellar nucleus toward the lateral part of the caudal medial accessory olive. Its medial parts receive a projection from the dorsolateral protuberance of the medial cerebellar nucleus. Caudal and lateral regions of the medial cerebellar nucleus project to the “beta” group and dorsomedial cell column.

Heavy olivary projections to circumscribed parts of the inferior olive were found after injections in the remaining cerebellar nuclei. The medial part of the posterior interposed nucleus connects to caudolateral areas of the rostral half of the medial accessory olive, whereas lateral areas project to more rostromedial parts. The most ventromedial part of the lateral cerebellar nucleus projects to the ventrolateral outgrowth. Adjacent medial, ventral, and caudal regions connect to the ventral leaf of the principal olive. The cerebellar origin of the projection to its dorsal leaf is located in lateral, dorsal, and rostral parts of the lateral cerebellar nucleus. The dorsolateral hump projects to the dorsomedial group of the rat inferior olive. Rostromedial projections to the dorsal accessory olive originate from the lateral part of the anterior interposed nucleus, whereas its medial parts project to more lateral and caudal regions of this olivary subnucleus. The dorsal fold of the dorsal accessory olive does not receive a projection from the cerebellar nuclei but from the lateral vestibular nucleus. No cerebellar projections were found to the dorsal cap. Relatively strong ipsilateral projections, which were the mirror images of the contralateral projections, were observed in the dorsomedial group, rostral medial accessory olive, and ventral leaf of the principal olive.

When both the inferior olive and the cerebellar nuclei are considered as folded but continuous sheets of grey matter, the complete nucleo‐olivary projection can be described as a simple transformation.
Localization and characterization of neuropeptide Y in the brain of Microcebus murinus (primate, lemurian)
Authors: Bons N. , Mestre N. , Petter A. , Danger J. M. , Pelletier G. , Vaudry H.
Published: January 2005

The distribution of neuropeptide Y (NPY) in the brain of the lemur Microcebus murinus was determined by immunocytochemistry with the aid of a highly specific antiserum against synthetic porcine NPY. When compared with previous immunohistochemical data obtained in primates and other mammalian species, the localization of NPY‐immunoreactive (IR) structures in the Microcebus murinus brain revealed particular features. (1) Numerous NPY‐IR perikarya and a dense network of IR nerve terminals were found in the supraoptic and suprachiasmatic nuclei, respectively. The occurrence of NPY‐IR perikarya in the supraoptic nucleus, also reported in the squirrel monkey, seems to be specific to primates. In the squirrel monkey, the suprachiasmatic nucleus exhibits only a moderate innervation, whereas in humans it appears totally devoid of NPY‐IR fibers. (2) IR perikarya and axon processes were observed in many upper brainstem areas, in particular in the interpeduncular, raphe pontine, dorsal tegmental, parabrachial, and dorsal raphe nuclei, in the locus coeruleus, the nucleus of the solitary tract, and the reticular formation; in this latter area, the occurrence of two categories of NPY‐IR neurons was demonstrated on the basis of their morphology and localization, suggesting that they may play distinct roles. (3) NPY‐IR nerve processes could be traced over a long distance. (4) For the first time, numerous NPY‐IR terminals were observed close to the lumen of the various cerebral ventricles. The immunoreactive NPY‐like peptide was characterized by combining high performance liquid chromatography (HPLC) analysis and radioimmunoassay quantification. The dilution curves obtained with synthetic porcine NPY and serial dilutions of occipital cortex, paraventricular and supraoptic hypothalamus, posterior hypothalamus, medulla oblongata, or preoptic area extracts were parallel. The highest amounts of NPY were measured in the hypothalamus and telencephalon. HPLC analysis resolved a single peak of NPY‐like immunoreactivity that exhibited the same retention time as synthetic porcine NPY. The distribution of NPY in the lemurian brain is discussed with respect to phylogeny and putative functions.
Projections from the lateral geniculate nucleus to the hypothalamus of the mongolian gerbil (Meriones unguiculatus): An anterograde and retrograde tracing study
Authors: Mikkelsen Jens D.
Published: January 2005

The lateral geniculate nucleus of the thalamus sends efferents to the hypothalamic suprachiasmatic nucleus, which is involved in generation and entrainment of several circadian rhythms. It seems reasonable to believe that the lateral geniculate conveys visual information about the length of the photoperiod to the circadian oscillator. In order to study in more detail the topographical relationship between the lateral geniculate and the suprachiasmatic nucleus, anterograde tracing with Phaseolus vulgaris leucoagglutinin (PHA‐L) and retrograde tracing with wheatgerm agglutinin coupled to horseradish peroxidase (WGA‐HRP) were performed in the gerbil.

After iontophoretic injections of PHA‐L in the lateral geniculate, a large number of PHA‐L‐immunoreactive fibers and nerve terminals were observed in the ventrolateral part of the suprachiasmatic nucleus. Nerve fibers were also present in the ventromedial and dorsolateral portions, particularly in the caudal half of the nucleus. PHA‐L‐immunoreactive nerve fibers continued outside the borders of the suprachiasmatic nucleus to the adjacent anterior hypothalamic, the periventricular, and the subparaventricular areas. A moderate number of fibers entered the lateral hypothalamic area and the tuber cinerum via the optic tract and chiasm. Moreover, the paraventricular nucleus, the supraoptic nucleus, the medial preoptic area, the lateral preoptic area, and the supramammillary nucleus contained a few labeled fibers. In all parts of the hypothalamus receiving an input from the lateral geniculate, fine beaded immunoreactive fibers with varicosities and nerve terminals were observed, some of which were found in close apposition to hypothalamic neurons. Only after labeling of neurons in the intergeniculate leaflet of the lateral geniculate nucleus, fibers were found in the hypothalamus. This topographical organization of the geniculohypothalamic pathway was supported by retrograde tracing after injections of WGA‐HRP in the suprachiasmatic area. In these experiments, retrograde labeled neurons were observed in the intergeniculate leaflet and, in agreement with the anterograde studies, most of labeling was observed in the ipsilateral side. These results confirm that the suprachiasmatic nucleus receives a substantial input from the intergeniculate leaflet of the lateral geniculate. Moreover, the present data demonstrate that the suprachiasmatic nucleus is not the only nucleus that receives a direct visual input. Thus other hypothalamic areas might be influenced by a direct rhythmic neuronal input as well.
Morphology of the octopus cell area of the cochlear nucleus in young and aging C57BL/6J and CBA/J mice
Authors: Willott James F. , Bross Lori Seegers
Published: January 2005

The influence of aging and age‐related cochlear impairment on the ventral cochlear nucleus was evaluated by measuring morphological properties of the octopus cell area (OCA) in five age groups of inbred C57BL/6J and CBA/J mice (young adult to very old). The former strain demonstrates progressive cochlear sensorineural pathology and hearing loss during middle age; the latter has only modest sensorineural pathology late in life. Histological sections of the OCA were evaluated with serial sections and several stains for neurons, glia, and fibers, and Golgi impregnations were also used. Aging was associated with a decrease in volume of the OCA, a loss of neurons, slight decrease in neuron size, increased packing density of glial cells, and changes in dendrites ranging from minor to total loss of primary branches. The greatest changes occurred in extreme old age, beyond the median lifespan. Age‐related changes were not exacerbated by sensorineural pathology in aging C57BL/6J mice. Individual octopus cells varied greatly in the extent of age‐related abnormality.
Single fiber studies of ascending input to the cuneate nucleus of cats: I. Morphometry of primary afferent fibers
Authors: Weinberg Richard J. , Pierce Joseph P. , Rustioni Aldo
Published: January 2005

The morphology of afferent fibers ascending to the cuneate nucleus has been examined in this and the subsequent paper in order to quantify the pattern of arborization and bouton arrangement of selected classes of primary afferents and to compare these data with data from postsynaptic fibers ascending to the cuneate nucleus.

Electrophysiologically identified G hair and la muscle afferent fibers in the cuneate fasciculus were intraaxonally injected with horseradish peroxidase. Cutaneous afferents terminated dorsal to proprioceptive afferents, especially at middle levels of the cuneate nucleus. The spacing of collaterals along G hair fibers was variable, but averaged 1.46 collaterals per mm; collateral density was higher at middle cuneate levels than in the rest of the nucleus. Collateral density of Ia fibers was lower than for G hair fibers and was lowest at caudal levels of the nucleus. Branches of G hair collaterals, though often initially diverging, usually converged to terminate in a single focus in the dorsal part of the nucleus. The probability of bifurcation of Ia collaterals decreased steadily at successive branch points. These collaterals branched less symmetrically than G hair collaterals, and terminated in the ventral cuneate with less dense arbors, stretched mediolaterally, but of comparable cross‐sectional area.

Individual G hair collaterals gave rise to more boutons than Ia collaterals; in both cases they were mostly of the en passant type. Boutons were restricted to distal branches of G hair collaterals, whereas boutons of Ia collaterals were also located on proximal branches. Bouton size was similar for the two classes of collaterals.

The data reported here, in combination with the published literature, suggest that the collaterals of roughly 300 G hair fibers overlap at any given point at middle levels of the cuneate nucleus. This high degree of anatomical convergence is not predicted by the functional segregation described with electrophysiological mapping, implying the presence of intrinsic nuclear mechanisms enhancing response specificity.
Light microscopic and ultrastructural analysis of GABA‐immunoreactive profiles in the monkey spinal cord
Authors: Carlton Susan M. , Hayes Elizabeth S.
Published: January 2005

It is hypothesized that terminals containing γ‐aminobutyric acid (GABA) participate in presynaptic inhibition of primary afferents. To date, few convincing GAB A‐immunoreactive (GABA‐IR) axo‐axonic synapses have been demonstrated in support of this theory. The goal of this study is to document the relationship between GABA‐IR profiles and central terminals in glomerular complexes in lumbar cord of the monkey (Macaca fascicularis). In addition, the relationship between GABA‐IR profiles and other neural elements are analyzed in order to better understand the processing of sensory input in the spinal cord.

GABA‐IR cell bodies were present in Lissauer's tract (LT) and in all laminae in the spinal gray matter except lamina IX, GABA‐IR fibers and terminals were heavily concentrated in LT: laminae I, II, and III; and present in moderate concentration in the deeper laminae of the dorsal horn, ventral horn (especially in association with presumed motor neurons), and lamina X. Electron microscopic analysis confined to LT and laminae I, II, and III demonstrated GABA‐IR cell bodies, dendrites, and myelinated and unmyelinated fibers. GABA‐IR cell bodies received sparse synaptic input, some of which was immunoreactive for GABA. The majority of the synaptic input to GABA‐IH neurons occurred at the dendritic level. Furthermore, the presence of numerous vesicle‐containing GABA‐IR dendrites making synaptic interactions indicated that GABA‐IR dendrites also provided a major site of output. Two consistent arrangements were observed in laminae I–III concerning vesicle‐containing GABA‐IR dendrites: (1) they were often postsynaptic to central terminals and (2) they participated in reciprocal synapses. The majority of GABA‐IR axon terminals observed contained round clear vesicles and varying numbers of dense core vesicles. Only on rare occasions were GABA‐IR terminals with flattened vesicles observed. GABA‐IR terminals were not observed as presynaptic elements in axo‐axonic synapses; however, on some occasions, GABA‐IR profiles presumed to be axon terminals were observed postsynaptic to large glomerular type terminals.

Our findings suggest that a frequent synaptic arrangement exists in which primary afferent terminals relay sensory information into a GABAergic system for further processing. Furthermore, GABA‐IR dendrites appear to be the major source of input and output for this inhibitory system. The implications of this GABAergic neurocircuitry are discussed in relation to the processing of sensory input in the superficial dorsal horn and in terms of mechanisms of primary afferent depolarization (PAD).