bluuebunny/crossref_metadata_2025 huggingface dataset:
Distribution and origin of serotoninergic afferents to guinea pig cochlear nucleus
Authors: Thompson Ann M. , Moore Kyle R. , Thompson Glenn C.
Published: January 2005

The distribution of serotoninergic fibers in the guinea pig cochlear nucleus was studied with serotonin immunohistochemistry. In addition, the origin of the serotoninergic fibers was determined by combining the retrograde transport of wheat germ agglutinin‐apohorseradish peroxidase (gold conjugated) with serotonin immunohistochemistry.

Immunoreactivity was present in varicose and nonvaricose fibers that were unevenly distributed throughout the cochlear nucleus. The fibers were most prominent in the superficial layers of the dorsal cochlear nucleus and the anterior spherical cell area of the anteroventral cochlear nucleus. Although less prominent, serotonin‐positive fibers were also present in the remaining part of the anteroventral cochlear nucleus and the posteroventral cochlear nucleus. A few positive fibers were present in the auditory nerve root and the dorsal and intermediate acoustic stiae. Double‐labeled cells were found throughout the rostral‐ caudal extent of the serotoninergic system from the caudal linear nucleus to the nucleus raphe pallidus. However, most were confined to the dorsal (52%) and median (18%) raphe nuclei. Some serotoninergic cell groups contained retrogradely labeled cells that were not serotonin immunoreactive, indicating nonauditory afferents to cochlear nucleus containing other neurotransmitter substances.

Serotonin may tonically modulate auditory processing within the cochlear nucleus as well as influence certain ascending auditory pathways. Most of the serotonin in the cochlear nucleus comes from superior raphe nuclei that also project to basal ganglia motor systems and limbic strctures. Therefore, the effect of serotonin on the cochlear nucleus may be related to level of arousal or behavioral state. © 1995 Willy‐Liss, Inc.
Axonal regeneration into Schwann cell‐seeded guidance channels grafted into transected adult rat spinal cord
Authors: Xu Xiao Ming , Guénard Véronique , Kleitman Naomi , Bunge Mary Bartlett
Published: January 2005

Schwann cells (SC) have been shown to promote regeneration in both the peripheral and central nervous systems. In this study we tested the ability of SC to enhance axonal regeneration in adult rat spinal cord by grafting SC‐seeded guidance channels into transected cords. SC were purified in culture from adult inbred rat sciatic nerves, suspended in Matrigel, and seeded into semipermeable PAN/PVC channels (2.6 mm I.D. X 10 mm long) at a final density of 120 × 106 cells/ml. Channels filled with Matrigel alone served as controls. Adult isologous rat spinal cords were transected at the T8 level, and segments T9–T11 were removed. The rostral stump was inserted 1 mm into channels with capped distal ends. One month after grafting, a vascularized tissue cable was present within the channel in all animals. In SC‐seeded channels (n = 14), a mean of 501 myelinated axons was found in the cable, and many axons extended 9–10 mm. Electron microscopy revealed typical SC ensheathment and myelination of axons with four times more unmyelinated than myelinated axons. Control channels (n = 8) contained fewer myelinated axons (mean = 71). When SC were prelabeled in culture with a nuclear dye, labeled nuclei were observed at 30 days, confirming SC survival. Astrocytes identified by glial fibrillary acidic protein staining did not migrate far into the cable, and prelabeled SC did not enter the cord. Lack of immunostaining for serotonin and dopamine β‐hydroxylase indicated that supraspinal axons did not regenerate into the cable. Fast Blue injections into the middle of the cable (n = 3) marked spinal cord interneurons (mean = 306) as far as nine segments rostral (25 mm, C7) extending axons into the graft; fewer dorsal root ganglion neurons were retrogradely labeled. In conclusion, purified populations of SC transplanted within channels promote both propriospinal and sensory axonal regeneration in the adult rat thoracic spinal cord. © 1995 Willy‐Liss, Inc.
Dendritic reorganisation in the basal forebrain under degenerative conditions and its defects in Alzheimer's disease. III. The basal forebrain compared with other subcortical areas
Authors: Arendt Thomas , Brückner Martina K. , Bigl Volker , Marcova Lena
Published: January 2005

The distribution of the reticular neuronal type in the human brain and its involvement in both degeneration and dendritic reorganisation under the conditions of ageing, Korsakoff's disease (KD), Alzheimer's disease (AD), and Parkinson's disease (PD) was comparatively investigated after Golgi impregnation. Reticular neurones are distributed throughout different areas along the brain axis. The cholinergic basal forebrain nuclei, i.e., the basal nucleus of Meynert, the nucleus of the diagonal band, and the medial septal nucleus form the most rostral part of this network of “open nuclei,” which is collectively referred to as the “reticular core.” Reticular neurones of the following areas were quantitatively investigated by a computer‐based three‐dimensional analysis: caudate nucleus, globus pallidus, medial septal nucleus, nucleus of the vertical limb of the diagonal band, basal nucleus, medial amygdaloid nucleus, reticular thalamic nucleus, lateral hypothalamic area, subthalamic nucleus, substantia nigra, locus coeruleus, pedunculopontine tegmental nucleus, and raphe magnus nucleus. There are three major findings. First, neurones that were found to be susceptible to degeneration in AD were largely part of the same neuronal populations prone to degeneration during ageing, in KD and PD. Thus, areas could be classified according to their overall degree of vulnerability under the present degenerative conditions as being highly vulnerable (basal forebrain nuclei, caudate nucleus, locus coeruleus), moderately vulnerable (medial amygdaloid nucleus, raphe magnus nucleus, lateral hypothalamic area, substantia nigra, pedunculopontine tegmental nucleus), or marginally vulnerable (globus pallidus, subthalamic nucleus, reticular thalamic nucleus). Second, neuronal populations that are particularly vulnerable to degenerative changes show a high degree of structural plasticity. Third, the degree of this dendritic plasticity is inversely related to the complexity of dendritic arborisation of the neurone. It is concluded that the sparsely ramified reticular type of neurone forms a pool of pluripotent neurones that have retained their plastic capacity throughout life, which makes them vulnerable to a variety of perturbations. © 1995 Willy‐Liss, Inc.
Specific cell types in cat retina express different forms of glutamic acid decarboxylase
Authors: Vardi Noga , Auerbach Peter
Published: January 2005

We studied the expression of glutamate decarboxylase (GAD), GAD65 and GAD67, in cat retina by immunocytochemistry. About 10% of GABAergic amacrime cells express only GAD65 and 30% express only GAD67. Rougly 60% contain both forms of the enzyme, but GAD67 is present only at low levels in the majority of these double‐labeled amacrine cells. The staining pattern in the inner plexiform layer (IPL) for the two GAD forms was also different. GAD65 was restricted to strata 1–4, and GAD67 was apparent throughout the IPL but was strongest in strata 1 and 5. This indicates that soams, as well as their processes, are differentially stained for the two forms of GAD. Cell types expressing only GAD65 include interplexiform cells, one type of cone bipolar cell, and at least one type of serotonin‐accumulating amacrine cell. Cell types expressing only GAD67 include amacrine cells synthesizing dopamine, amacrine cells synthesizing nitric oxide (NO), and amacrine cells accumulating serotonin. Cholinergic amacrine cells express a low level of both GAD forms. Our findings in the retina are consistent with previous observations in the brain that GAD65 expression is greater in terminals than in somas. In addition, in retina most neurons expressing GAD67 also contain a second neurotransmitter as well as GABA, and they tend to be larger than neurons expressing GAD65. We propose that large cells have a greater demand for GABA than small cells, and thus require the constant, relatively unmodulated level of GABA that is provided by GAD67. © 1995 Willy‐Liss, Inc.
Fine structure of the medullary lateral line area of Chelon labrosus (order perciformes), a nonelectroreceptive teleost
Authors: Diaz‐Regurira Sof́ia M. , Anadon Ramón
Published: January 2005

The ultrastructure and synaptic organization of the nucleus medialis and cerebellar crest of the teleost Chelon labrosus have been investigated. The nucleus medialis receives projections from the anterior and posterior lateral line nerves. This nucleus consists of oval neurons and large crest cells (“Purkinje‐like” cells) whose apical dendrites branch in the overlying molecular layer, the cerebellar crest. In the dorsal region of the nucleus medialis, the perikarya and smooth primary dendrites of the crest cells are interspersed among myelinated fibers and nerve boutons. The ventral layer of the nucleus medialis contains crest cell perikarya and dendrites as well as oval neurons. The cerebellar crest lacks neuronal bodies, but the apical dendrites of crest cells receive synapses from unmyelinated and myelinated fibers. In the cerebellar crest, two types of terminals are presynaptic to the crest cell dendrites: boutons with spherical vesicles that from asymmetric synapses with dendritic spines and boutons containing pleomorphic vesicles that from symmetric synapses with dendritic spines and boutons containing pleomorphic vesicles that from symmetric synapses directly on the dendritic shaft. Most axon terminals found on the somata and primary dedrites of crest cells in the nucleus medialis have pleomorphic vesicles and form symmetric contacts, though asymmetric with spherical vesicles and mixed synapses can be observed; these mixed synapses exhibit gap junctions and contain spherical vesicles. Unlike crest cells, the oval neuron perikarya receive three types of contacts (symmetric, asymmetric, and mixed). The origins and functions of these different bouton types in the nucleus medialis are discussed. © 1995 Willy‐Liss, Inc.
Seven protein tyrosine phosphatases are differentially expressed in the developing rat brain
Authors: Sahin Mustafa , Dowling James J. , Hockfield Susan
Published: January 2005

Regulation of protein function through tyrosine phosphorylation is critical in the control of many developmental processes, such as cellular proliferation and differentiation. Growing evidence suggests that tyrosine phosphorylation also regulates key events in neural development. Although a large body of data has demonstrated that protein tyrosine kinases play an important role in neural development, much less is known about their counterparts, protein tyrosine phosphatases (PTPases). Using polymerase chain reaction (PCR) with degenerate primers and a neonatal rat cortex cDNA library, we have identified seven PTPases expressed in the developing rat brain. Four of these are transmembrane PTPases: LAR, LRP, RPTPγ, and CPTP1. Three are nonreceptor PTPases: PTP‐1, P19‐PTP, and SHP. Northern hybridization analysis demonstrates that only CPTP1 is preferentially expressed in neural tissues, whereas the others are found abundantly in nonneural tissues as well as in the brain.

Within the embryonic and early postnatal brain, the seven PTPases have overlapping, yet unique, distributions. For example, LAR mRNA is highly expressed by both proliferating and postmitotic cells in the cerebral cortex at embryonic day 17 and in all layers of the cortex at postnatal day 4. In contrast, RPTPγ mRNA is expressed by postmitotic neurons in the embryo and predominantly by neurons in the superficial layers of the postnatal cortex.

Several of the PTPases examined here are expressed at very high levels in the embryonic cortical plate and postnatal neocortex, including the subplate and subventricular zone. The spatial and temporal regulation of PTPase agene expression suggests that these PTPases have important roles in signal transduction during early neuronal differentiation and neural development. © 1995 Willy‐Liss, Inc.
Distribution of spinal cord projections from the medullary subnucleus reticularis dorsalis and the adjacent cuneate nucleus: A phaseolus vulgaris‐ leucoagglutinin study in the rat
Authors: Villanueva Luis , Bernard Jean Franiçois , Le Bars Daniel
Published: January 2005

The distribution and organization of descending spinal projections from the dorsal part of the caudal medulla were studied in the rat following injections of Phaseolus vulgaris leucoagglutinin into small areas of the subnucleus reticularis dorsalis (SRD) and the adjacent cuneate nucleus (Cu). The caudal aspect of the Cu projected only to the dorsal horn of the ipsilateral cervical cord via the dorsal funiculus. These projections were mainly to laminae I, IV, and V. More ventrally located reticular structures projected to the full length of the cord. Fibers originating from the SRD travelled through the ipsilateral dorsolateral funiculus and terminated within the deep dorsal horn and upper layers of the ventral horn, mainly in laminae V–VII. Fibers originating from subnucleus reticularis ventralis (SRV) travelled ipsilaterally through the lateral and ventrolateral funiculi and bilaterally through the ventromedial funiculus. These fibers terminated within the ventral horn. The density of labeling within the gray matter varied at different levels of the cord was as follows: cervical > sacral > thoracic > lumbar. The reciprocal connections between the caudal medulla and the spinal cord suggest that the former is an important link in feedback loops that regulate spinal outflow. © 1995 Wiley‐Liss, Inc.
Cardiovascular responses to electrical stimulation of the bed nucleus of the stria terminalis
Authors: Dunn J.D. , Williams T.J.
Published: January 2005

To determine whether the influence of the bed nucleus of the stria terminalis (BST) on cardiovascular function can be localized to specific cytoarchitectural areas within the BST, urethane (1.3 g/kg)‐anesthetized male Sprague‐Dawley rats were probed for cardiovascular reactive sites. Electrical stimuli (50 μa, 50 Hz, and a 0.5 ms pulse duration), delivered through stereotaxically placed glass semimicroelectrodes, were localized to the BST. Sham‐stimulated animals served as controls. Stimulation sites were correlated with cytoarchitecturally distinct areas within the BST, and changes in mean arterial pressure (MAP) were subjected to statistical analysis.

Systematically probing the BST for cardiovascular reactive sites showed a correlation between evoked responses and distinct cytoarchitectural areas. Stimulation of the me dial BST produced increases in MAP; stimulation of the lateral aspect of the BST produced decreases in MAP. Both pressor and depressor responses were evoked from the area ventral to the anterior commissure. Pressor responses were elicited from the area immediatley ventral to the anterior commissure, and depressor responses followed stimulation of an area more ventral. All subnuclei showed corroborating cardiovascular responses to 20–30 n1 microinjection of sodium glutamate. Taken together, these data provide substantial evidence to indicate that the BST, particularly at more rostral areas, consists of a medial pressor area, a lateral depressor area, and a ventral area with both pressor and depressor zone. © 1995 Wiley‐Liss, Inc.
Crayfish brain interneurons that converge with serotonin giant cells in accessory lobe glomeruli
Authors: Sandeman David , Beltz Barbara , Sandeman Renate
Published: January 2005

Freshwater crayfish have well‐developed olfactory systems with an array of receptors that project exclusively to areas in the brain that are functionally specialized for the processing of odors. The accessory lobes are large bilateral areas of neuropil that are anatomically associated with the olfactory lobes. The accessory lobes receive no primary afferents and do not contain the endings of motor efferents; thus, their role in olfaction is still obscure. Intracellular dye filling of interneurons in the deutocerebral commissure in the crayfish brain has shown that they end bilaterally in glomeruli in the accessory lobes, have cell somata in a dorsal cluster medial to the olfactory lobes, and have unilateral projections to the deutocerebral commissure neuropil. Each deutocerebral commissure interneuron has only 6 to 15 output glomeruli in each accessory lobe and does not share glomeruli with other deutocerebral commissure interneurons. The deutocerebral commissure interneurons converge with the dorsal giant serotonin neurons in the accessory lobe glomeruli. Deutocerebral commissure interneurons can be separated into classes according to their projections to the protocerebrum, central body, and deutocerebrum. Physiological responses of the deutocerebral commissure interneurons following photic stimulation of the eyes and electrical stimulation of the second antennae lead to the conclusion that the deutocerebral commissure represents an input to the accessory lobes from the protocerebral neuropils and that visual and tactile inputs are included in the processing performed in the accessory lobes. © 1995 Wiley‐Liss, Inc.
The annexins: Specific markers of midline structures and sensory neurons in the developing murine central nervous system
Authors: Hamre Kristin M. , Chepenik Kenneth P. , Goldowitz Dan
Published: January 2005

The annexins are a family of cytoplasmic proteins that have been shown to have numerous actions within a cell. Recent evidence suggests that at least one of these proteins plays a role in the development of the central nervous system (CNS). The present study examines the temporal expression and spatial distribution of annexins I, II, IV, V, and VI during development and at maturity in the murine CNS by immunocytochemical analysis. The results demonstrate that annexins I, II and IV exhibit clear immunolabeling in the murine CNS with distinct patterns of temporal and spatial expression. Annexin IV is the first annexin to be expressed on embryonic day (E) 9.5 while annexin I is the last to be expressed (Ell. 5). Annexins I, II and IV are found in the floor plate region, but to differing rostrocaudal extents. Annexin I has a very restricted distribution, only present in the midline raphe of the brainstem. Annexin II is present in the spinal cord, brainstem and mesencephalon. Annexin IV has the widest midline distribution, being observed in the floor and roof plates of the developing CNS. Additionally, antibodies against annexin II and IV immunolabel most dorsal root and sensory ganglion cells and their axons. During early postnatal development, immunolabeling with each antibody gradually disappears in many structures, and only first order sensory neurons and their fibers are immunopositive for annexins II and IV at weaning. Three functions of the annexins are suggested by the present findings: (1) to help establish the midline structures of the floor and roof plates, (2) to help direct the decussation of sensory fibers, and (3) to regulate some aspect of sensory neuron processing, such as signal transduction. © 1995 Wiley‐Liss, Inc.
Physiological regulation of peptide messenger RNA colocalization in rat hypothalamic paraventricular medial parvicellular neurons
Authors: Watts Alan G. , Sanchez‐Watts Graciela
Published: January 2005

In the present study, we used subcutaneous polyethylene glycol injections to show that a physiologically relevant stimulus, hypovolemia, will selectively increase the expression of neuropeptide genes in a restricted population of parvicellular corticotropin‐releasing hormonecontaining neurons in the hypothalamic paraventricular nucleus. Our results show that a large reduction in extracellular fluid maintained over approximately 20 hours is associated with a significant increase in the level of corticotropin‐releasing hormone mRNA in the medial parvicellular division of the paraventricular nucleus. Additionally, there are concomitant increases in cellular levels of both neurotensin/neuromedin N and proenkephalin mRNAs. Our colocalization results show that the increases in neurotensin/neuromedin N and proenkephalin mRNAs after polyethylene glycol injection occur to a significant degree in cells that also contain corticotropin‐releasing hormone mRNA. Furthermore, significant numbers of cells containing proenkephalin mRNA also contain neurotensin/neuromedin N mRNA, raising the possibility that some neurons have increased levels of all three mRNAs. Finally, in the medial parvicellular division of the paraventricular nucleus, the number of identified corticotropin‐releasing hormone neurons also containing vasopressin mRNA is very low in control animals and is not increased by polyethylene glycol injections, suggesting that, within this period, activation of the vasopressin gene may not be a critical event in the neuroendocrine response of corticotropinreleasing hormone neurosecretory neurons to extracellular dehydration. Considered together with the effects of adrenalectomy on peptide colocalization, our results suggest the existence of several phenotypically distinct sets of neurons within the medial parvicellular division of the paraventricular nucleus, each characterized by its ability to regulate the expression of neuropeptide genes in a stimulus‐specific manner. © 1995 Wiley‐Liss, Inc.
Afferent connections of the medial frontal cortex of the rat. II. Cortical and subcortical afferents
Authors: Condé Françoise , Maire‐lepoivre Evelyne , Audinat Etienne , Crépel Francis
Published: January 2005

In order to compare the frontal cortex of rat and macaque monkey, cortical and subcortical afferents to subdivisions of the medial frontal cortex (MFC) in the rat were analyzed with fluorescent retrograde tracers. In addition to afferent inputs common to the whole MFC, each subdivision of the MFC has a specific pattern of afferent connections. The dorsally situated precentral medial area (PrCm) was the only area to receive inputs from the somatosensory cortex. The specific pattern of afferents common to the ventrally situated prelimbic (PL) and infralimbic (IL) areas included projections from the agranular insular cortex, the entorhinal and piriform cortices, the CA1–CA2 fields of the hippocampus, the subiculum, the endopiriform nucleus, the amygdalopiriform transition, the amygdalohippocampal area, the lateral tegmentum, and the parabrachial nucleus. In all these structures, the number of retrogradely labeled cells was larger when the injection site was located in area IL. The dorsal part of the anterior cingulate area (ACd) seemed to be connectionally intermediate between the adjacent areas PrCm and PL; it receives neither the somatosensory inputs characteristic of area PrCm nor the afferents characteristic of areas PL and IL, with the exception of the afferents from the caudal part of the retrosplenial cortex.

A comparison of the pattern of afferent and efferent connections of the rat MFC with the pattern of macaque prefrontal cortex suggests that PrCm and ACd areas share some properties with the macaque premotor cortex, whereas PL and IL areas may have characteristics in common with the cingulate or with medial areas 24, 25, and 32 and with orbital areas 12, 13, and 14 of macaques. © 1995 Wiley‐Liss, Inc.
Topography of projections to posterior cortical areas from the macaque frontal eye fields
Authors: Stanton G. B. , Bruce C. J. , Goldberg M. E.
Published: January 2005

Frontal eye field (FEF) projections to posterior cortical areas were mapped by autoradiography of tritiated amino acids (Leu, Pro) in six macaque monkeys. In three monkeys, the large saccade part of the FEF (IFEF) was identified by microstimulation and injected with tracers. In a fourth monkey, the small saccade part of the FEF (sFEF) was identified by microstimulation and injected with tracer. Tracer injections were placed into the sFEF region of two other monkeys using anatomical landmarks. The IFEF and sFEF generally had distinct and largely segregated projections to posterior cortical areas, and the overall pattern of labeling in visual areas with established topology indicates that IFEF neurons preferentially project to areas having large and eccentric receptive fields, whereas sFEF neurons project to areas having smaller, more centrally located fields. The terminal fields from the sFEF were more widespread than those from IFEF. Projections from sFEF terminated in the lateral intraparietal area (LIP), the ventral intraparietal area (VIP), and the parietal part of visual area V3A, in the fundus of the superior temporal visual area (TST), the middle temporal area (MT), the medial superior temporal area (MST), the temporal part of visual area V4, the inferior temporal area (IT), and the temporal‐occipital area (TEO) and in occipital visual areas V2, V3, and V4. Projections from IFEF terminated in parietal areas 7a, LIP, and VIP and the medial part of parietal area PE; in temporal areas MST and the superior temporal polysensory area (STP); and in occipital area V2 and posterior cingulate area 23b. Projections from IFEF and sFEF appeared to terminate in different parts of common target areas in MST, LIP, and V2. The topography of IFEF and sFEF projections to LIP suggests that this posterior eye field may also be organized by saccade amplitude. Most terminal labeling from FEF injections was bilaminar to layers I and V/VI, but labeling in area LIP, area MT, the medial part of area PE, and area 23b was columnar‐form to all layers. © 1995 Wiley‐Liss, Inc.
Transient expression of NADPH‐diaphorase in the lateral geniculate nucleus of the ferret during early postnatal development
Authors: Cramer Karina S. , Moore Christopher I. , Sur Mriganka
Published: January 2005

Retinogeniculate projections in the ferret are refined during postnatal development so that inputs from the two eyes become segregated into eye‐specific laminae, and each eye‐specific lamina is further divided into sublaminae containing inputs from on‐center or off‐center afferents. Segregation into eye‐specific laminae and on/off sublaminae is dependent on neuronal activity; sublamination depends on activation of N‐methyl‐d‐aspartate (NMDA) receptors. By analogy with the suggested role of nitric oxide in NMDA‐mediated long‐term potentiation in the hippocampus, we investigated a possible role for nitric oxide in ferret retinogeniculate development. The expression of NADPH‐diaphorase, a nitric oxide synthase, was examined histologically in the lateral geniculate nucleus of ferrets at several postnatal ages. At birth, neuropil is labeled in the nucleus, although no cell bodies are visible. After the first postnatal week, some labeled cells appear, predominantly in the C laminae. By three postnatal weeks, cell bodies are clearly labeled in all geniculate laminae. Staining reaches a peak in density at about four postnatal weeks, then declines such that by six postnatal weeks labeled cells are no longer visible. This transient expression of NADPH‐diaphorase activity is consistent with a role for nitric oxide in the development of mature connections within the ferret lateral geniculate nucleus. © 1995 Wiley‐Liss, Inc.
Localization of serotonin in taste buds: A comparative study in four vertebrates
Authors: Kim Dae‐Joong , Roper Stephen D.
Published: January 2005

To investigate monoaminergic synaptic mechanisms in taste buds, we examined taste buds of mice, rats, rabbits, and mudpuppies for the presence of the neurotransmitter candidate, serotonin. Immunocytochemistry revealed serotonin‐like immunostaining in cells in mammalian taste buds and Merkel‐like basal cells in taste buds of mudpuppies. In untreated mudpuppies and in mammals injected with the precursor to serotonin, L‐tryptophan, certain taste cells showed serotonin‐like immunoreactivity, although in mammalian taste buds the immunostaining was relatively weak. After pretreating mammals with 5‐hydroxytryptophan (5‐HTP), the intermediate precursor between L‐tryptophan and serotonin, several taste cells showed strong immunoreactivity for serotonin. These findings indicate that mammalian taste cells normally contain serotonin and that taste cells can take up 5‐HTP and convert it to serotonin. Immunocytochemistry on wholemount preparations demonstrated that serotonergic cells of mudpuppies (i.e., Merkel‐like basal cells) were disposed in a ring at the periphery of taste buds. Similarly, serotonergic cells in mammalian taste buds tended to be located at the periphery of taste buds. Based on the position of serotonergic cells in the taste bud and on recent physiological studies on the actions of serotonin in taste buds, we postulate that serotonin functions as a neuromodulator or neurotransmitter in vertebrate taste buds. © 1995 Wiley‐Liss, Inc.
Topographical organization of the rat suprachiasmatic‐paraventriocular projection
Authors: Vrang Niels , Larsen Philip J. , Moller Morten , Mikkelsen Jens D.
Published: January 2005

The suprachiasmatic nucleus (SCN) is a dominant pacemaker involved in the generation of circadian rhythms in mammals. Surprisingly, the expression of the many rhythms appears to be mediated via a limited efferent projection system of the pacemaker, of which the largest pathway terminates in the subparaventricular area and in the paraventricular nucleus of the hypothalamus. In order to investigate a possible topographical organization of this major outflow pathway of the SCN, microiontophoretic injections of the anterograde tracer Phaseolus vulgaris‐leucoagglutinin (PHA‐L) or the retrograde tracer cholera toxin subunit B (ChB) were centered in distinct subparts of the SCN (PHA‐L) or in the subparaventricular areaparaventricular nucleus (ChB), respectively. PHA‐L injections involving the entire SCN revealed not only a major projection to the subparaventricular area, but also one directed towards the medial and dorsal parvicellular subnuclei of the paraventricular nucleus. As opposed to injections involving the entire nucleus, injections of PHA‐L centered in the dorsomedial subdivision of the SCN resulted in a relatively larger number of PHA‐Limmunoreactive fibers in the parvicellular subdivisions of the PVN, whereas the terminal field in the subparaventricular area was less substantial. A topography of the SCN efferent output system was also revealed by the retrograde tracing with ChB. Injections of ChB in the dorsal part of the paraventricular hypothalamic nucleus, not involving the underlying subparaventricular area, gave rise to a population of retrogradely labeled cells in the dorsomedial part of the SCN. In contrast, ChB injections in the subparaventricular area resulted in labeling of neurons clustered in a more ventrolateral aspect of the SCN. The present data provide evidence for a topography in the major efferent, projection system from the SCN, implying that different subparts of the rat SCN, presumably containing partly different potential neurotransmitter substances, may regulate different circadian rhythms. © 1995 Wiley‐Liss, Inc.
Development of the primary afferent projection in human spinal cord
Authors: Konstantinidou Aphrodite D. , Silos‐Santiago Inmaculada , Flaris Nicolaos , Snider William D.
Published: January 2005

The development of spinal cord circuitry in humans is poorly characterized, primarily because standard anatomical tracers must be actively transported, which requires living tissue. Intensely fluorescent lipid‐soluble tracers have largely eliminated this problem, at least for circuits that can be traced over short distances. We have, therefore, used the carbocyanine dye DiI (1, 1‐dioctadecyl‐3, 3, 3, 3‐tetramethyl‐indocarbocyanine perchlorate) to study the development of the dorsal root afferent projection to fetal human spinal cord between 8 and 19 weeks of gestation.

We show here that the dorsal root afferents enter the gray matter of the spinal cord very early in gestation. By 8 weeks, a few axons have already reached the motor pools. These axons, presumably spindle afferents, traverse the length of the spinal gray matter in fascicles to reach different groups of motor neurons. As development progresses, these axons project to the ventral horn and branch in a restricted area in the intermediate zone as well as in the motor pools. Between 11 and 19 weeks of gestation, axons in the ventral horn elaborate boutons that appear to be in proximity to the motor neuron somata and their proximal dendrites.

Other groups of axons penetrate the gray matter of the spinal cord all along the mediolateral extent of the dorsal horn. These axons descend to lamina IV, and then turn upward to terminate in laminae III and IV, arborizing primarily rostrocaudally. The time course of the development of these axons parallels that of the axons projecting to the ventral horn. On the basis of their laminar termination and patterns of distribution, we suggest that these are the central axons from dorsal root ganglion neurons that innervate low‐threshold mechanoreceptors in the periphery. Axon arborizations in laminae I and II were sparse, even at the latest developmental stages examined. It is unclear whether their specific connections have not yet developed or whether DiI does not diffuse well along these small‐caliber axons.

This characterization of the development of the laminar specific projections of dorsal root ganglion neurons provides a foundation for studies of the expression of genes that may be implicated in dorsal root axon growth and branching in humans. © 1995 Wiley‐Liss, Inc.
Taurine immunoreactivity in the rat supraoptic nucleus: Prominent localization in glial cells
Authors: Decavel Chantal , Hatton Glenn I.
Published: January 2005

Taurine is an inhibitory amino acid that hyperpolarizes magnocellular neurosecretory neurons. To determine which cell types in the rat supraoptic nucleus contain taurine, we used a monoclonal antibody raised against a taurine conjugate. Preembedding immunocytochemistry was carried out at the light and electron microscopic levels using diaminobenzidine and gold‐substituted silver‐intensified peroxidase as markers. We report the presence of taurine in all cellular compartments of the supraoptic nucleus, except axons, with variable labeling intensities among the different compartments. Few cell bodies of magnocellular neurons were immunoreactive, but many distal dendrites and some proximal ones showed weak‐to‐moderate levels of immunoreactivity. Strong immunoreactivity was found over glial cell bodies and their processes, in particular in the ventral glial lamina of the supraoptic nucleus. Large astrocytic processes labeled with the taurine antibody included the endfeet participating in the glial limitans around capillaries and at the ventral surface of the hypothalamus. Other types of immunoreactive astropytic profiles were found scattered within the neuropil where these processes participated in different interactions with the neuronal elements of the supraoptic nucleus. Immunoreactive glial expansions, sometimes even the main process of the glial cell, engulfed axonal boutons. Other labeled glial processes were found between two magnocellular perikarya or closely apposed to the membrane of axonal boutons contacting the neuronal cell bodies. The frequent finding of closely apposed glial and dendritic elements bearing different levels of taurine‐like immunoreactivity suggests that exchange of taurine between those two compartments may occur. We propose that taurine could be released from supraoptic glia by a small decrease in osmolarity or by receptor‐mediated mechanisms during conditions of low hormonal (vasopressin and/or oxytocin) needs. Such released taurine could then act on presynaptic or postsynaptic sites, or both, to exert its neuromodulatory actions. © 1995 Wiley‐Liss, Inc.
Decrease and long‐term recovery of choline acetyltransferase immunoreactivity in adult cat somatosensory cortex after peripheral nerve transections
Authors: Avendaño Carlos , Umbriaco Denis , Dykes Robert W. , Descarries Laurent
Published: January 2005

The functional reorganization of cerebral cortex following peripheral deafferentation is associated with changes in a number of neurotransmitters and related molecules. Acetylcholine (ACh) enhances neuronal responsiveness and could play a role in activity‐dependent cortical plasticity. In this study, choline acetyltransferase (ChAT) immunohistochemistry was used to investigate ACh innervation of the primary somatosensory cortex in cats sustaining complete unilateral forearm and paw denervations. Survival times of 2–52 weeks were examined. The deafferented contralateral cortex was defined electrophysiologically, and quantitative estimates of ChAT‐immunoreactive fiber density were obtained from the forelimb and hindlimb sectors of area 3b in both hemispheres. In the 3b forelimb sector contralateral to the deafferentation, a decrease in density of ChAT‐positive fibers relative to the ipsilateral hemisphere was apparent at 2 weeks and most pronounced at 13 weeks, involving all cortical layers except layer I. There was no such decrease in the hindlimb sector, but the loss of ChAT immunoreactivity extended to sectors representing proximal forelimb and trunk. Changes in ChAT immunoreactivity were no longer found after 1 year of survival. This long‐lasting but reversible lowering of ChAT immunoreactivity could result from a loss of afferent activity in basalis neurons and/or trophic influences retrogradely exerted by cortex on these cells. Reduced ACh transmission might then contribute to the loss of gamma aminobutyric acid (GABA) inhibition in the deafferented cortex by decreasing the activation of inhibitory interneurons. The long‐term recovery of a normal ChAT immunoreactivity in cortex could be a consequence of its functional reorganization. © 1995 Wiley‐Liss, Inc.
Evolution of cortical responsiveness subsequent to multiple forelimb nerve transections: An electrophysiological study in adult cat somatosensory cortex
Authors: Dykes Robert W. , Avendaño Carlos , Leclerc Serge S.
Published: January 2005

Multiunit recordings along mediolateral rows in the primary somatosensory cortex of the animals described by C. Avendafio, D. Umbriaco, R. W. Dykes, and L. Descarries (1995, J. Comp. Neurol. 354:321–332) provided information about the functional status of the regions in and near the deafferented cortex. Responses changed along this axis from normally organized receptive fields in the hindlimb representation through a transition zone of unusually small receptive fields into the clearly deafferented forelimb representation, where receptive fields were uncommon and often had unusual characteristics.

The most abrupt change along this axis was the appearance of a repetitive, bursting discharge pattern in the multiunit activity near the border of the deprived cortex. The appearance of this pattern was used as a reference to describe differences between normal and deprived cortices. The nature of these differences evolved with time. Much of the deprived cortex lacked identifiable receptive fields for months after the nerve transections and, 1 year later, still only about half of the recording sites within the deprived region displayed organized receptive fields. Some sites within the deprived region lacking definable receptive fields could be excited at long latencies by somatic stimuli anywhere on the body. With time, regions of normal cortex near the border with the deprived zone became more involved in these processes. Spontaneous activity and thresholds also changed with time in both normal and deprived cortices.

These electrophysiological responses occurred during a time when choline acetyltransferase staining was reduced in and around the deprived cortex (Avendaño et al., 1995); the effects of nerve transections were most pronounced between the 8th and 13th weeks, as was the reduction in immunostaining; however, although immunostaining had returned to normal levels at 1 year, many parts of the deprived cortex remained without new afferent drive, some being unresponsive to any somatic stimuli. © 1995 Wiley‐Liss, Inc.
AII amacrine cell population in the rabbit retina: Identification by parvalbumin immunoreactivity
Authors: Casini Giovanni , Rickman Dennis W. , Brecha Nicholas C.
Published: January 2005

Parvalbumin (PV) is a calcium‐binding protein localized to selected neurons in the nervous system, including the retina. This investigation evaluated the distribution of PV immunoreactivity in the rabbit retina using immunohistochemistry with a monoclonal antibody directed to carp PV. In the inner nuclear layer (INL), PV immunoreactivity was present in horizontal and amacrine cells. In the ganglion cell layer, PV immunostaining was confined to somata that are likely to be both displaced amacrine cells and ganglion cells. PV‐immunoreactive (IR) amacrine cells were positioned in the proximal INL adjacent to the inner plexiform layer (IPL). These cells usually gave rise to a single primary process, which arborized into two distinct bands in the IPL. In sublamina a, the processes were thin and had large, irregular endings. In sublamina b, multiple processes branched from the primary process and were characterized by varicosities and spines. PV‐IR amacrine cell bodies measured from 8 to 10 μm in diameter. Their density was highest in the visual streak and lowest in the periphery of the superior retina. The average number of PV‐IR amacrine cells was 464,045 cells per retina (N = 3), and the average regularity index of the PV‐IR cell mosaic was 3.23. PV‐IR amacrine cells were further characterized by double‐label immunofluorescence experiments using antibodies to PV and tyrosine hydroxylase (TH). Varicose TH‐IR processes were in close apposition to many PV‐IR amacrine cells and often formed “ring structures” around them. Together, these morphological, quantitative, and histochemical observations indicate that PV immunoreactivity in the INL is localized predominantly to AII amacrine cells, and therefore it is a valuable marker for the identification of this cell type. © 1995 Wiley‐Liss, Inc.
Expression of trk receptors in the developing and adult human central and peripheral nervous system
Authors: Muragaki Yoshihiro , Timothy Nigel , Leight Susan , Hempstead Barbara L. , Chao Moses V. , Trojanowski John Q. , Lee Virginia M.‐Y.
Published: January 2005

A family of tyrosine receptor kinases known collectively as trk receptors plays an essential role in signal transduction mediated by nerve growth factor and related neurotrophins. To localize the major trk receptors (trkA, B and C) in the developing and adult central (CNS) and peripheral (PNS) nervous system, we generated monoclonal antibodies (MAbs) to extracellular (MAbs E7, E13, E16, E21, E29) and intracellular (MAb I2) domains of human trkA fused to glutathione S‐transferase. Several MAbs (E7, E13, E16) recognized glycosylated trkA (gp 140trk and gp110trk) in Western blots, one MAb (E7) recognized non‐glycosylated (p80trk) and glycosylated trkA in immunoprecipitation assays, and two MAbs (E13, E29) detected trkA on the cell surface of NIH3T3 cells transfected with a trkA cDNA. Although generated to trkA fusion proteins, this panel of MAbs also recognized trkB and trkC in flow cytometric studies of NIH3T3 cells transfected with trkB or trkC cDNAs. Thus, we used these pan‐trk MAbs to probe selected regions of the CNS and PNS including the hippocampus, nucleus basalis of Meynert, cerebellum, spinal cord, and dorsal root ganglion (DRG) to localize trkA, B, and C receptors in the developing and adult human nervous system. These studies showed that trk receptors are expressed primarily by neurons and are detectable very early in the developing hippocampus, cerebellum, spinal cord, and DRG. Although the distribution and intensity of trk immunoreactivity changed with the progressive maturation of the CNS and PNS, immunoreactive trk receptors were detected in neurons of the adult human hippocampus, nucleus basalis of Meynert, cerebellum, spinal cord, and DRG. This first study of trk receptor proteins in the developing and adult human CNS and PNS documents the expression of these receptors in subsets of neurons throughout the developing and adult nervous system. Thus, although the expression of trk receptor proteins is developmentally regulated, the constitutive expression of these neurotrophin receptors by neurons in many regions of the adult human CNS and PNS implies that mature trk receptor‐bearing neurons retain the ability to respond to neurotrophins long after terminal neuronal differentiation is complete. © 1995 Wiley‐Liss, Inc.
Substance P‐immunoreactive neurons in the human retina
Authors: Cuenca Nicolás , De Juan Joaquín , Kolb Helga
Published: January 2005

Substance P (SP) is a neuropeptide that acts as a neurotransmitter or a neuromodulator in the retina. The aim of this study was to identify the type(s) and the distribution of the SP‐immunoreactive (SP‐IR) cells in the human retina. We have used an antiserum to SP to immunostain neurons in postmortem human retinae. Immunostained retinae were processedwith the avidin‐biotin complex (ABC) to visualize the cells either whole mounted in glycerol or embedded in plastic. Some retinae were also sectioned at 20 μm in order to obtain radial views of stained cells. SP‐IR amacrine cells stain intensely and appear to be of a single type in the human retina. They are large‐field cells with large cell bodies (16 μm diameter) lying in normal or displaced positions on either side of the inner plexiform layer (IPL). Their sturdy, spiny, and appendage‐bearing dendrites stratify in stratum 3 (S3) of the IPL, where many overlapping, fine dendrites intermingle to form a plexus of stained processes. Either cell bodies or primary dendrites emit an “axon‐like” process that, typically, divides into two long, fine processes, which run in opposite directions for hundreds of micrometers in S5 and S3 before disappearing as distinct entities in the stained plexus in S3. Long, fine dendrites also pass from the dendritic plexus to run in S5 and down to the nerve fiber layer to end as large varicosities at blood vessel walls. In addition, fine processes are emitted from the dendritic plexus that runs in S1, and some pass up to the outer plexiform layer (OPL) to run therein for short distances. The SP‐IR amacrine cell has many similaritiesto the thorny, type 2 amacrine cells described from Golgi studies.

In addition to the SP‐IR amacrine cells, a presumed ganglion cell type is faintly immunoreactive. Its 20–22 μpm cell body gives rise to a radiate, sparsely branched, widespreading dendritic tree running in S3. Its dendrites and cell body become enveloped by the more intensely SP‐IR processes and boutons from the SP‐IR amacrine cell type. The SP‐IR ganglion cell type most resembles G21 from a Golgi study. © 1995 Wiley‐Liss, Inc.