ISSN:0092-7317    

DOI:10.1002/cne.903510102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractVisceral feedback circuits in lower brainstem were elucidated with retrograde tracers by mapping neurons that issue local projections to the general visceral afferent division of the nucleus tractus solitarii (NTS) and dorsomotor vagal nucleus (DMX) in adult male rats. In study 1, spinal and intramedullary afferents to the visceral‐sensorimotor complex (NTS‐X) were traced to contiguous populations of cell bodies arranged in cylindrical segmental organization. NTS‐X afferents derive from curvilinear arrays of neurons that parallel the efferent radiations of the solitariotegmental tract. Newly discovered afferents arise from circumscribed cell groups in the dorsal reticular formation and periventricular zone. Another source was traced to a paraambigual cell column in the apex of the rostral ventrolateral reticular nucleus (n.RVL). In study 2, catecholaminergic afferents were initially defined with combined retrograde transport‐immunocytochemical methods. Deposits of retrograde tracers into NTS‐X transported to neurons containing tyrosine hydroxylase (TH) in the A1, C1, and C3 areas or phenylethanolamine N‐methyltransferase (PNMT) in the C1 area of the n.RVL and C3 area. In study 3, it was revealed that NTS‐X afferents arise, in part, as collaterals of thoracic reticulospinal neurons. Deposits of the retrograde fluorescent tracer Fluorogold into the upper thoracic cord and rhodamine‐labeled microbeads into NTS‐X transported to the same neurons within a subambigual locus in n.RVL and parts of nucleus raphe magnus. In study 4, dual retrograde tracer‐immunocytochemical analysis demonstrated that catecholamines are synthesized by a subset of neurons in the n.RVL that issue collaterals to the NTS‐X and thoracic cord. Double retrogradely labeled TH‐or PNMT‐immunoreactive cell bodies were restricted to the C1 area within a 450‐μm column bordered rostrally by the facial nucleus and ventrally by the medullary subpial surface. We conclude that visceral reflex arcs are reciprocally organized. Targets of NTS projection are also sources of local NTS‐X afferent innervation. Catecholaminergic and other local afferents from reticular formation, periventricular, and spinal gray may, via collaterals, simultaneously modulate visceral reflex excitability at the level of NTS and the outflow of autonomic and respiratory moton

ISSN:0092-7317    

DOI:10.1002/cne.903510103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractClinical and animal data suggest that exposure of developing brain to cocaine has adverse consequences. One candidate mechanism for such effects is drug regulation of gene expression. In adult rats, cocaine induces expression of nuclear immediate early genes with specific spatial and temporal patterns. The products of such genes (e.g., c‐Fos, c‐Jun, and Zif/268) subserve the coupling of cell surface receptor stimulation to transcriptional regulation. Thus, activation of immediate early gene expression in developing brain by cocaine could alter programs of neural gene expression and, thereby, neuronal phenotype and function. We report that, during rat brain development, cocaine produced brain region‐specific and developmental age‐specific induction of c‐fos, c‐jun, and zif/268 mRNAs. At each age studied (P8, P15, P28, and adults), we found that acute cocaine administration resulted in a unique cell‐specific pattern of c‐fos mRNA induction and c‐Fos protein expression in striatum. We also observed cocaine‐induced activation of AP‐1 DNA binding activity in striatal extracts prepared at these different ages, suggesting that the observed induction of c‐fos and c‐jun may have biological consequences for the developing brain. These findings suggest a mechanism by which cocaine could alter patterns of gene expression during critical developmental periods with differential regional, temporal, and cellular vulnerabilities and, therefore, consequences for developing brai

ISSN:0092-7317    

DOI:10.1002/cne.903510104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractActivation of c‐fos, a member of the class of immediate early genes that act as transcription factors, may be one of the initial molecular mechanisms underlying plastic changes in gene expression in response to drugs of abuse. By combining c‐fos (radioactive) in situ hybridization histochemistry with nonradioactive in situ hybridization histochemistry for mRNAs encoding other striatal markers [preprotachykinin (substance P), proenkephalin, and D1 and D2 receptors], we have identified the cellular phenotype of striatal neurons activated by acute administration of cocaine to P8, P15, P28, and adult rats. At each age examined, substance P+, enkephalin−‐ striatal neurons were the predominant class of cells in which cocaine induced c‐fos gene expression. In addition, the topography of cellular activation at each age examined was distinct and reflected the topography of distribution of cells expressing high levels of substance P mRNA. We conclude that there is a marked specificity of cellular activation in striatum following acute cocaine administration restricted predominantly to subsets of substance P‐expressing cells, with age‐specific patterns in their topographic distribution. © 1995 W

ISSN:0092-7317    

DOI:10.1002/cne.903510105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractIn the brain of adult mice, cell division persists in the subventricular zone (SVZ) of the lateral ventricles. These SVZ cells migrate rostrally 3–5 mm to the olfactory bulb, where they differentiate into neurons. We have investigated the distribution of PSA‐N‐CAM in the adult mouse forebrain. Immunoreactivity for PSA‐N‐CAM precisely reveals the migratory pathway of SVZ cells. This pathway of PSA‐N‐CAM positive cells starts in the lateral wall of the lateral ventricle, where immunopositive cells form weblike patterns. The PSA‐N‐CAM positive pathway extends rostrally between the corpus callosum and the striatum into the anterior ventral telencephalon, and then into the core of the olfactory bulb. Experiments in which [3H]‐thymidine was injected systemically indicated that the majority of the dividing cells on the SVZ of the lateral ventricle and along the migratory pathway are positive to PSA‐N‐CAM or closly associated with PSA‐N‐CAM. Microinjection of [3H]‐thymidine into the SVZ of the lateral ventricle to label a small patch of dividing SVZ cells shows that neuroblasts that migrated away from the injection site are positive or are closely associated with other cells that are positive for PSA‐N‐CAM. Migrating cells are tethered together, forming long chains of immunopositive cells. The migratory pathway is formed by 30–40 of these immunopositive chains. Radially oriented individual PSA‐N‐CAM positive cells were observed in the olfactory bulb. These cells seem to have broken away from chains of immunopositive cells in the core of the olfactory bulb and to be migrating to more superficial layers. Little is known about the mechanisms of tangential migration during development and in adulthood. The cell‐cell arrangement revealed by PSA‐N‐CAM staining suggests new models for this form of neuronal migration. PSA‐N‐CAM staining suggests new models for this form of neuronal migration. PSA‐N‐CAM localization along the migratory pathway to the olfactory bulb suggests that in the adult brain this molecule plays a role in mig

ISSN:0092-7317    

DOI:10.1002/cne.903510106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractPreembedding immunoperoxidase staining methods were used to characterize tyrosine hydroxylase‐immunoreactive (TH‐ir) elements in the caudal ventrolateral medulla, and to determine the extent to which neurons of the A1 cell group are directly innervated by projections of the nucleus of the solitary tract (NTS). TH‐ir neurons in the A1 region were medium‐sized and multipolar. They possessed rounded nuclei with infrequent invaginations, well‐developed Golgi apparati, high cytoplasmic densities of mitochondria, and a low to moderate tendency for rough endoplasmic reticulum (RER) to align in parallel stacks. A1 cell bodies were commonly juxtaposed to TH‐positive and TH‐negative neurons, myelinated profiles, glia and /or vascular elements, but close membrane appositons were only seen with glial elements. Synaptic input to A1 neurons was predominantly asymmetric, provided virtually exclusively by non‐TH‐ir terminals, and directed principally to dendritic shafts; A1 somata are relatively sparsely innervated. In a second experiment, silver‐intensified immunogold localization of TH‐ir was combined with immunoperoxidase labeling for anterogradely transported Phaseolus vulgaris‐leucoagglutinin (PHA‐L), following tracer injections in the caudal aspect of the medial division of the NTS. These experiments revealed a small proportion of PHA‐L‐labeled axon terminals that made asymmetric contacts with dendritic shafts of TH‐ir neurons. These results suggest that the fine structure and synaptic input of A1 neurons are somewhat distinct from that of rostrally situated C1 catecholamine cells. In addition, while they document a direct NTS‐A1 projection that may participate in the interoceptive control of vasopressin secretion, the bulk of ventrolaterally directed projections from the caudomedial NTS contact noncatecholaminergic elements in the A1 region, some of which may correspond to so‐called depressor neurons implicated in the baroreflex control of sympathetic outflow and vasopressi

ISSN:0092-7317    

DOI:10.1002/cne.903510107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractTwo monoclonal antibodies and serial section analysis have been used to compare the sites and times at which hair and supporting‐cells differentiate in various sensory regions of the chick inner ear during its development. A monoclonal antibody recognising the 275 kD hair‐cell antigen, a protein that is specifically associated with the apical surface of hair cells, was used to identify immature hair cells. Another monoclonal antibody, gm‐2, which stains the gelatinous membranes of the cochlear duct, sacculus, and utriculus and the epithelial supporting cells of all vestibular structures in the inner ears of early posthatch chicks, was used to detect the onset of supporting‐cell differentiation. Although the antigens recognised by the two antibodies are first detected almost simultaneously during the development of each sensory region, their appearance is not always exactly temporally coincident, and their order of appearance, when not coincident, varies between the epithelia but is always the same within any one organ. Also, when the two antigens are first present in any one region, there is not always a very precise overlap in their spatial distribution. These results cannot be explained entirely by a previously proposed model for hair and supporting‐cell development in which hair cells differentiate first and prevent undetermined, surrounding cells from becoming hair cells via lateral inhibition. Modified forms of the original model that can accommodate some of these observations are considered and discussed. © 1995 Willy

ISSN:0092-7317    

DOI:10.1002/cne.903510108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractA putative choline transporter (CHOT1) has been cloned from rat brain and is reported to express a high‐affinity, sodium‐dependent, hemicholinium‐3‐insensitive choline transporter in oocytes. A second transporter (OCCREATRA) cloned from rabbit brain is 98% homologous to CHOT1 and is reported to transport creatine. We examined the distribution of CHOT1 mRNA in rat brain by in situ hybridization, using a 48 base oligonucleotide probe. In adult rats, the hybridization signal was widespread, but with a distinct pattern. High levels of expression were detectedin the cerebellum (Purkinje and granule cell layers), choroid plexus, medial habenula, pontine nuclei, several brainstem, nuclei, and hippocampus (pyramidal cell layer). Moderate signal was detected in cortex, globus pallidus, corpus callosum, and most other white matter tracts. Very low levels were present in striatum, nucleus accumbens, hippocampus molecular layer, and cerebellar molecular layer. Emulsion autoradiography indicated cellular localization to both neurons and glia. CHOT1 mRNA was relatively abundant in some cholinergic regions, including the medial habenula, the medial septum, and several brainstem nuclei. However, the overall pattern was distinctly different from that expected for cholinergic markers and correlated well with the localization of creatine kinase. The widespread distribution and poor correlation with cholinergic markers indicates that the CHOT1 gene does not encode the classical choline transporter known to be associated with acetylcholine synthesis. It is possible that CHOT1 is associated with cholinergic neurotransmission in some brain regions. However, it appears to encode the rat creatine transporter, and its widespread and heterogeneous distribution suggests regions where creatine phosphate is an important energy source. © 1995 Willy

ISSN:0092-7317    

DOI:10.1002/cne.903510109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe 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

ISSN:0092-7317    

DOI:10.1002/cne.903510110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe endogenous opioid peptide dynorphin is enriched in neurons in the nucleus accumbens, for which coexistence and synaptic interactions with substance P have been postulated. We examined the immunogold‐silver localization of dynorphin and immunoperoxidase labeling for substance P in single coronal sections through the core subregion of the nucleus accumbens of acrolein‐fixed rat brain tissue. Dynorphin‐immunoreactive somata were more prevalent than substance P‐containing neurons throughout the region sampled for ultrastructural analysis. Dynorphin‐labeled cells were spherical, contained unindented nuclei, and were closely apposed to other somata and dendrites, some of which also contained dynorphin immunoreactivity. The appositions were characterized by the absence of glial processes and contiguous contacts between the plasma membranes. Smooth endoplasmic reticulum and coated vesicles could also be identified in the cytoplasms on either side of the somatic or dendritic appositions. The dynorphin somata and dendrites received synaptic input from numerous unlabeled as well as dynorphin‐and/or substance P‐labeled axon terminals. Both types of terminals were morphologically similar in their content of small and large dense core vesicles and their formation of mainly symmetric synaptic specializations. In addition to dynorphin‐immunoreactive targets, numerous dynorphin‐and substance P‐labeled terminals also formed synapses with unlabeled somata and dendrites. In some cases, terminals separately labeled for dynorphin and substance P converged on common targets with or without detectable dynorphin immunoreactivity. Terminals colocalizing both peptides were also found to synapse on unlabeled or dynorphin‐labeled somata and dendrites. Additionally, presynaptic interactions were suggested by close appositions between dynorphin‐and/or substance P‐labeled terminals and other terminals that were unlabeled, dynorphin labeled, or substance P labeled. These results provide morphological data suggesting nonsynaptic communication between dynorphin‐immunoreactive neurons and other neurons possibly mediated through receptive sites or second messengers associated with smooth endoplasmic reticulum in the nucleus accumbens. They also indicate that, in this region, 1) the activity of dynorphin neurons may be dependent on activation of autoreceptors for dynorphin as well as substance P and 2) additional neurons lacking dynorphin immunoreactivity are most likely inhibited (symmetric junctions) by terminals containing either one or both peptides. The findings may have implications for motor and analgesic responses to aversive tonic pain transmitted through dynorphin and substance P pathways within the nucleus accumb

ISSN:0092-7317    

DOI:10.1002/cne.903510111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY