摘要:

AbstractThe three major classes of neurons in the paraventricular nucleus (PVH) provide a rich model for studying hormonal and neural influences on multiple neuropeptides expressed in individual cells. A great deal of previous work has examined this problem at the immunohistochemical level, where hormonal and neural influences on peptide levels have been established. In situ hybridization methods were used here to determine whether these effects are accompanied by measurable changes in neuropeptide mRNA levels. In the first series of experiments, the time‐course of corticosterone replacement effects on corticotropin‐releasing hormone (CRH) mRNA levels in parvicellular neuroendocrine cells of adrenalectomized animals were determined, and a doseresponse curve was established. CRH mRNA hybridization remains maximal with plasma levels of steroid up to about 50 ng/ml, then declines sharply between about 60–130 ng/ml, and is just detectable at higher levels. We confirmed that corticosterone decreases vasopressin mRNA levels in this cell group and showed that levels of preproenkephalin mRNA are also decreased, whereas no significant changes in cholecystokinin, β‐preprotachykinin, and angiotensinogen mRNA levels could be detected. Thus, corticosterone decreases some neuropeptide mRNA levels and has no influence on others in this cell group. Tyrosine hydroxylase mRNA hybridization is also unaffected in this part of the nucleus. In a second group of experiments, the cell‐type specificity of corticosterone influences was examined. It was found that while the hormone depresses CRH mRNA levels in parvicellular neurons, it increases such levels in PVH neurons with descending projections, in certain magnocellular neurosecretory neurons, and in a part of the central nucleus of the amygdala, whereas no influence was detected in the rostral lateral hypothalamic area. Furthermore, the stimulatory effects of corticosterone have different threshold levels in different cell groups. Thus, in different types of neurons, corticosterone may increase, decrease, or have no influence on CRH mRNA levels. In contrast, while corticosterone depresses vasopressin mRNA levels in parvicellular CRH neurons, it has no obvious effects on vasopressin mRNA levels in magnocellular or descending neurons; as with CRH, the effects of corticosterone on vasopressin mRNA levels are cell‐type specific. In a third series of experiments it was shown that glucocorticoid receptor and mineralocorticoid receptor mRNAs are found in all three cell types in the PVH and that corticosterone tends to produce modest increases in mRNA levels for both receptors. Finally, it was shown that unilateral catecholamine‐depleting knife cuts do not change mRNA levels for any of the neuropeptides (or steroid hormone receptors) examined here, although dramatic changes in neuropeptide levels themselves have been shown. The results indicate that corticosterone can alter the rations of neuropeptide mRNAs within individual cell type as well as alther the levels of a particular mRNA in the same or different directions in different cell types. The implications of these results for mechanisms underlying the stress response and for the concept of “biochemical switching” in anatomically fixed neural circu

ISSN:0092-7317    

DOI:10.1002/cne.902850402

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe cells of origin and projection fields of the descending afferents to the mammillary nuclei were studied in the rat with retrograde and anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase.The subiculum projects bilaterally to the entire medial mammillary nucleus (MM) in a topographic fashion along the two axes: (1) the proximal part of the subiculum along the presubiculo‐CA1 axis projects to the caudal and lateral regions of the MM whereas the more distal part of the subiculum projects to the medial region; (2) the septal part of the subiculum projects to the caudodorsal region of the MM whereas the more temporal part projects progressively to the more rostroventral regions. The ventral subiculum also projects ipsilaterally to the ventral and lateral margin of the lateral mammillary nucleus (LM). The presubiculum projects bilaterally to the dorsolateral region of the pars posterior of the MM and ipsilaterally to the LM. The infralimbic cortex projects bilaterally to the rostrodorsal region of the MM, whereas the retrosplenial cortex (areas 29a and 29b) projects bilaterally to the medial region at the midrostrocaudal and middorsoventral levels of the MM. The nucleus of the diagonal band projects bilaterally to the caudomedial region of the MM, whereas the lateral septal nucleus projects bilaterally to the pars mediana and the mammillary fiber capsule. A part of the anterior hypothalamic area ventromedial to the fornix projects predominantly ipsilaterally to the rostroventral part of the MM, whereas other basal forebrain regions such as the bed nucleus of the stria terminalis, the medial preoptic and anterior hypothalamic areas, and the area of the tuber cinereum send fibers predominantly ipsilaterally to the mammillary fiber capsule.The results reveal a complex organization of the descending projections to the mammillary nuclei, which may reflect the complex functions of these nuclei within the limbic circuitr

ISSN:0092-7317    

DOI:10.1002/cne.902850403

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe distribution of noradrenaline (NA) immunoreactivity in the forebrain and midbrain of the lizardGekko geckowas studied by means of recently developed antibodies against NA. Noradrenaline‐containing cell bodies are found in the hypothalamic periventricular organ and ependymal wall of the infundibular recess of the diencephalon. They are also present in the locus coeruleus and the nucleus of the solitary tract of the brainstem. Noradrenaline‐immunoreactive (NAi) fibers and varicosities are widely, but not uniformly, distributed throughout the forebrain and midbrain. In the telencephalon, dense plexuses of NAi fibers are found in the bed nucleus of the medial forebrain bundle, the vertical limb of the nucleus of the diagonal band of Broca, and the caudoventral part of the septal region. The diencephalon, the periventricular preoptic area, the supraoptic nucleus, and, in particular, the medial habenular nucleus are densely innervated by NAi fibers, whereas in the midbrain NAi plexuses are found in the ventral tegmental area, the substantia nigra and its dorsolateral extension (RA8), and in an area ventral to the nucleus interpeduncularis, pars ventralis. Moderately dense plexuses of NAi fibers are found in the small‐celled medial cortex, the dorsal cortex, and the midbrain tectum. The remaining forebrain and midbrain areas are generally not or only sparsely innervated by NAi fibers.The distribution of NAi cell bodies and fibers resembles the pattern revealed with antibodies against dopamine‐β‐hydroxylase (DBH). A remarkable exception is that the cells in the hypothalamic periventricular organ and ependymal wall of the infundibular recess are immunonegative for DBH. Possible explanations for this discrepancy are discussed. The present study on the distribution of NA immunoreactivity in the brain ofGekko geckocombined with the results of a previous report on the distribution of dopamine in the same species (Smeets et al., '86b) offer the opportunity to differentiate between the two catecholamines in the brain of this

ISSN:0092-7317    

DOI:10.1002/cne.902850404

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe synaptology of lamina I thalamic projection neurones in the spinal trigeminal nucleus of the rat was investigated by combining electron microscopic immunocytochemistry with the retrograde transport of horseradish peroxidase. Fifteen retrogradely labelled neurones were serially sectioned and their dendrites were traced for up to 160 μm in order to characterise the synaptic input to their cell bodies and proximal dendrites.Projection neurones receive synapses from dome‐shaped substance P and enkephalin immunoreactive terminals, which make simple axosomatic or axodendritic synapses. In addition, the cells receive synapses from numerous nonimmunoreactive terminals including a wide range of different domeshaped terminals and various scalloped or glomerular terminals. Domeshaped terminals synapse with small stubby spines in addition to cell bodies or dendritic shafts and they are probably derived from lamina II interneurones and from descending bulbospinal pathways. Glomerular terminals occur in two main classes: small type A terminals with dark axoplasm and larger type B terminals. Type B terminals participate in synaptic triads in which a peripheral terminal synapses both axoaxonically with the glomerular terminal and axodendritically with the projection neurone. Type A and type B terminals closely resemble the central terminals of spinal cord lamina II glomeruli and are probably derived from C and Aδ I° afferent fibers.The results indicate that lamina I projection neurones are under pre‐ and postsynaptic control from diverse sources. Their complex synaptic organisation highlights the key role that such cells play in the rostrad transmission of somatosensory infor

ISSN:0092-7317    

DOI:10.1002/cne.902850405

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

年代:1989

数据来源: WILEY

摘要:

AbstractConnections of primary auditory cortex (A‐I) were investigated in the tamarin (Saguinus fuscicollis), a New World monkey. In each case, A‐I was defined by multiunit recordings, and best frequencies were determined for neurons at different recording sites. Microlesions were placed to mark recording sites for correlation with cortical architecture. Following mapping, separate injections of up to three different tracers (HRP‐WGA and fluorescent dyes) were placed into the representations of different frequencies within A‐I. The results support several conclusions: (1) high to low frequencies are represented in a dorsocaudal to ventrorostral sequence in A‐I, (2) intrinsic connections in A‐I are more pronounced along isofrequency contours, (3) the pattern of connections between A‐I and adjoining cortex suggests that this surrounding auditory cortex contains at least two tonotopically organized fields and possibly one or more additional auditory fields, (4) callosal connections of A‐I are largely between parts of A‐I matched for frequency representation, (5) thalamic connections of A‐I include topographic connections with the ventral division of the medial geniculate complex (MGv) and more diffuse connections with the medial (MGm) and dorsal (MGd) divisions of the medial geniculate complex and the suprageniculate nucleus (Sg), and (6) A‐I projects bilaterally to the dorsal cortex of th

ISSN:0092-7317    

DOI:10.1002/cne.902850406

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe purpose of this study was to provide an ultrastructural description of the development of the olfactory nerve fiber layer (ONL) in the olfactory bulbs of mouse embryos. The developmental age of each embryo was determined by means of the Theiler staging system. During stages 17 and 18, the olfactory axons grew through the mesenchyme toward the cerebral vesicle; they were accompanied by a group of electron‐dense cells which were referred to as peripheral glial progenitor cells (GPCs) because they ensheathed the adjacent axons. In Theiler stage 19–21 embryos, the axons and the peripheral GPCs grew dorsocaudally along the external surface of the bulb primordium forming a presumptive ONL immediately superficial to its glia limitans. Through small breaks in this glia limitans, the axons, but not the peripheral GPCs, penetrated into the marginal zone of the bulb primordium. Even though by the first half of stage 21 there were only short stretches of glia limitans separating the presumptive ONL from the marginal zone, there was no intermingling of the perikarya between the two layers. A definitive ONL could be identified by the second half of Theiler stage 21, by which time the glia limitans of the bulb primordium had totally disappeared. However, up to Theiler stage 24 of development the only cells to be found in this definitive ONL were the peripheral GPCs. Although in Theiler stage 25 and 26 embryos there was an additional population of less‐electron‐dense GPCs within the definitive ONL, these cells were likely derived from the previous group of peripheral GPCs rather than from cells newly emigrated from the deeper layers of the developing bulb. This developmental data necessitated a reevaluation of the cell lineages of the two glial cell types that reside within the ONL of the adult olfacto

ISSN:0092-7317    

DOI:10.1002/cne.902850407

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

年代:1989

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902850401

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

年代:1989

数据来源: WILEY