摘要:

AbstractThe enkephalinergic afferent system in the rat habenula was examined by the indirect immunofluorescence method with antibodies against leucine‐enkephalin.Leucine‐enkephalin‐like immunoreactive (L‐ENKI) fibers were observed in the dorsal portion of the medial habenular nucleus (MHb), the intermediate portion of the lateral habenular nucleus (LHb), and the border zone between the MHb and the LHb (BZHb).Knife‐cut studies demonstrated that almost all the fibers were supplied via the stria medullaris. Also two discrete ENKergic afferents to the MHb and the LHb were found by several kinds of lesion studies: (1) the MHb was ipsilaterally innervated from L‐ENKI neurons in “septoperiventricular area,” which is the junctional area between the ventral supracommissural septum and the rostral thalamic periventricular region. (2) The LHb was ipsilaterally innervated from L‐ENKI neurons in the rostral portion of the lateral hypothalamus. Our findings also suggested that the L‐ENKI fibers in the BZHb are supplied via the stria medullaris with an ipsilateral predominance and that, at the most caudal level, they arise not only from the ipsilateral stria medullaris but also from the contralateral stria medullaris via the h

ISSN:0092-7317    

DOI:10.1002/cne.902550402

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe distribution of enkephalin and dynorphin immunoreactivity in the hippocampus of four rodent species (gray squirrel, guinea pig, rat, and hamster) is compared with the pattern of opiate receptor subtypes (mu, delta, and kappa). The distribution of opioid peptides is fairly consistent in the anterior hippocampus of these four species. Intense immunoreactivity for dynorphin and enkephalin is found in the hilus of the dentate gyrus and in the mossy fiber system. Occasional immunoreactive processes are seen in the dentate molecular layer and scattered throughout the CA1 and CA3 fields. In the rat and hamster, an additional plexus of enkephalinergic fibers straddles both sides of the hippocampal fissure. Cells immunoreactive for both opioid peptides are located in and just superficial to the dentate granule cell layer.Opiate receptors are variably distributed in these rodent species. In the squirrel, guinea pig, and hamster, mu and kappa binding is dense in the stratum lucidum of CA3 and the molecular layer of the dentate gyrus. In the rat, dense mu and kappa binding is localized within and adjacent to the pyramidal and granule cell layers. Delta receptor patterns show additional species differences. In the rat, the delta distribution is similar to the mu and kappa patterns. In the other species, the delta binding pattern is generally the inverse of the mu/kappa pattern: most areas of the hippocampus are enriched in delta sites, whereas the stratum lucidum and the pyramidal cell layer are receptor‐sparse. Thus, the stratum lucidum–site of dense terminations of mossy fibers containing opioid peptides–is characterized by selectively sparse delta receptors in four species and by selectively dense kappa receptors in three species. The three receptor subtypes, taken either individually or together and compared to the peptides, are more variably and more widely distributed throughout the hippocampus and fail to show a correspondence with opioid‐peptide‐containing terminals. The mismatches suggest that receptor locations and densities are organized without relation to the sites of relevant transmitte

ISSN:0092-7317    

DOI:10.1002/cne.902550403

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractExperiments were designed to determine if neurons of the ranid optic tectum, a major target of the optic nerve, possess the same regenerative potential as optic axons. Normal tectal efferent (TE) projections were reexamined by using the anterograde transport of3H‐proline and autoradiography (n = 18), bulk‐filling damaged TE axons with horseradish peroxidase (HRP; n = 18) and anterogradely transporting wheat germ agglutinin‐HRP (n = 8) to label TE axons. Results were similar to reports that used degeneration methods (Rubinson:Brain Behav. Evol. 1:529–561, '68; Lazar:Acta. Biol. Hung. 20:171–183, '69). Following a brainstem hemisection just caudal to the nucleus isthmi (1–20 weeks), the ipsilateral descending TE pathway was autoradiographically examined (n = 20). While all other TE projections appeared normal, there was no detectable ipsilateral descending projection beyond the lesion site. Ascending TE axons were cut at the anterior tectal border by hemisecting the left diencephalon (LDH)–a lesion that also cuts optic axons projecting to the left tectum. There was no indication of TE axonal regeneration with the aid of autoradiography or HRP histochemistry 1–30 weeks postlesion (n = 48) even when the medial diencephalon was intentionally left intact (n = 4). However, in all four cases examined, optic axons regenerated following the same LDH where TE axonal regeneration failed (also see Stelzner, Lyon, and Strauss:Anat. Rec. 205:191A–192A, '83). Local effects of LDH should be similar for both the cut optic and cut TE axons. Other factors were tested that may contribute to the lack of TE axonal regeneration. Our results indicate that optic regeneration itself (n = 8), postaxotomy retrograde cell death of TE neurons (n = 6), deafferentation of the tectum of optic axons, and potential sprouting within tectal targets by intact contralateral TE axons (n = 10) are not critical factors aborting TE axonal regeneration. TE axons filled with HRP at chronic periods after LDH (n = 4) terminate anomalously near the LDH border. Many of these endings are similar to reactive endings or terminal clubs seen after axonal injury in the mammalian CNS. Our results suggest that this disparity in regenerative ability of optic and TE axons may be related to a difference in the responsive ability of these cell types to initiate or maintain axonal elongation after axotomy within the amphibia

ISSN:0092-7317    

DOI:10.1002/cne.902550404

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractEigenmanniais a weakly electric fish that emits a constant‐frequency electric organ discharge (EOD). Probability coder (P unit) and phase coder (T unit) electroreceptive afferents differentially encode changes in EOD amplitude and phase, respectively. physiologically identified T and P units were intracellularly labelled with HRP and their terminals were examined with electron microscopy to determine their postsynaptic targets. This technique reveals that phase and amplitude are relayed to first‐order electrosensory neurons by two parallel but not independent pathways. P‐type afferents terminate on granular interneurons, basilar pyramidals, and polymorphic cells, electrosensory lateral line lobe targets that monitor amplitude modulations, but P‐type afferents do not contact spherical cells. T‐type afferents relay phase information to spherical cells and thus form a separate afferent pathway. T unit terminals do not synapse directly on basilar pyramidal cells. Collateral branches from T‐type afferents, however, were also found to terminate on granule and polymorphic cells, thereby adding phase information into the amplitude channel. P‐ and T‐type afferents exhibit cellular specificity by forming synaptic junctions with different subsets of post synaptic targets in the deep neuropil. The afferent terminals make either asymmetric chemical or gap junction synapses depending on the identity of the post synaptic target.T units contacting granule cells or polymorphic cells had not been previously described. Two possible roles of adding phase to amplitude information are discussed in terms of

ISSN:0092-7317    

DOI:10.1002/cne.902550405

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe anatomical development of muscle sensory arbors and dendrites of brachial motoneurons in the spinal cord of the bullfrog was studied by labeling both types of cells with horseradish peroxidase. Sensory and motoneurons were labeled in tadpoles (stages XV‐XVIII) by backfilling the triceps nervein vivowith HRP throughout the stages in development when functional monosynaptic connections between these cells are first being formed. Individual triceps motoneurons were injected with HRP in other tadpoles at the same developmental stages. By stage XV, triceps sensory afferents already projected to and arborized in the ventral sensory neuropil region of the spinal cord where sensory‐motor connections are made. In contrast, the dendrites of triceps motoneurons rarely were present in this region until stage XVI. By stage XVII, triceps dendrites in this region were common and they intermingled with the collaterals of muscle sensory axons. Thus, sensory axons supplying limb muscles grow into the future neuropil region well in advance of the arrival of motoneuronal dendrites.Electrophysiological studies have shown that the connections between triceps sensory and motor neurons are already specific at stage XVII, as soon as monosynaptic potentials between these cells can be detected (Frank and Westerfield:J. Physiol (Lond.) 343:593–610, '83). The present anatomical results demonstrate that the processes of sensory and motor cells are not in close anatomical proximity before this time; thus the selection of appropriate synaptic partners must occur from the o

ISSN:0092-7317    

DOI:10.1002/cne.902550406

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe tobacco hornwormManduca sextaexhibits dramatic changes in its body morphology and behavior as it is transformed from a larva into an adult during metamorphosis. Accompanying these changes is an extensive reorganization of this moth's central nervous system (CNS), which involves both the death and remodeling of subsets of larval neurons. We report here that the segmental ganglia of the larvae also contain a stereotyped array of identifiable neuronal stem cells (neuroblasts) that contribute over 2,000 cells to each thoracic ganglion and about 40–80 cells to each abdominal ganglion. The distribution of these neuroblasts varies in a segment specific manner. Dormant neuroblasts are found adjacent to the neuropil in late embryos and early first instar larvae. After the molt to the second instar, these cells enlarge and begin to divide. Through a series of asymmetrical divisions, each neuroblast generates a discrete nest of 10–90 progeny by the end of larval life. These progeny (the imaginal nest cells) are developmentally arrested at an early stage of differentiation and remain so until metamorphosis. At the onset of metamorphosis, a wave of cell death sweeps through the nests, the extent of the death being much greater within the abdominal nests than in the thoracic nests. The surviving imaginal nest cells then differentiate to become functional neurons that are incorporated into the adult

ISSN:0092-7317    

DOI:10.1002/cne.902550407

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractHorseradish peroxidase (HRP) was injected extracellularly into the auditory nerve of adult mice so that the enzyme could infuse individual spiral ganglion neurons. Forty‐two well‐stained neurons were reconstructed through serial sections from their cell bodies to peripheral terminations in the organ of Corti with the aid of a light microscope and drawing tube. No neuron was observed to innervate both inner and outer hair cells (IHCs and OHCs). Previous observations from neonatal mammals that reported that IHCs and OHCs were innervated by the same neuron are thus presumed to describe a transient developmental phenomenon.Two populations of spiral ganglion neurons were determined on the basis of the differences in receptor innervation. The type I neurons innervated exclusively IHCs by way of thick (1–2 μm) radial fibers, whereas the type II neurons innervated only OHCs by way of thin (∼0.5 μm) outer spiral fibers. Certain features of the peripheral process in the vicinity of the cell body were highly correlated with fiber type. This pattern of separate innervation of IHCs and OHCs by type I and type II neurons, respectively, may represent the general plan of afferent organization for the adult mammalia

ISSN:0092-7317    

DOI:10.1002/cne.902550408

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe projections from the striatal part of the olfactory tubercle were examined in rats, both with the aid of experimental silver impregnation methods following superficial laminar heat lesions of the tubercle and by the use of anterograde transport ofPhaseolus vulgaris‐leucoagglutinin (PHA‐L) following injections of the lectin in the dense cell layer of the tubercle. Retrograde transport of fluorescent substances following injections of the tracer in the multiform layer of the tubercle were used to corroborate the results obtained by the anterograde transport and degeneration methods. The main and apparently only significant termination from the striatal cells in the olfactory tubercle is located immediately deep to the dense cell layer in areas that could be identified as part of the ventral pallidum on the basis of either the Nissl method or glutamate decarboxylase immunocytochemistry. Whereas a mediolateral topography is generally maintained by the ventral striatopallidal pathway originating in the dense cell layer, there is a considerable spread of the projection in the rostrocaudal direction. The dense projection field of the olfactory tubercle component of the ventral striatopallidal pathway permeates the ventrolateral part of the ventral pallidum, thereby complementing the termination of the accumbens projection to the more mediodorsal parts of the ventral palli

ISSN:0092-7317    

DOI:10.1002/cne.902550409

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe projection of ventral pallidal neurons to the mediodorsal nucleus of the thalamus (MD) was examined in rats by combined retrograde transport of horseradish peroxidase (HRP) after injections in the MD and glutamate decarboxylase (GAD) immunocytochemistry at light and electron microscopic levels, with and without prior exposure of the brains to colchicine. HRP was transported Lo the soma of medium‐sized and large ventral pallidum neurons, which along with their long, large dendrites were contacted by many glutamate decarboxylase immunoreactive synaptic boutons. The retrograde tracer positive neurons bore a remarkable resemblance to the projecting cells of the globus pallidus and entopeduncular nucleus. When colchine exposure was included in the tissue preparation, some but not all tracer positive cells also exhibited cytoplasmic GAD immunoreactivit

ISSN:0092-7317    

DOI:10.1002/cne.902550410

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractWe have previously shown that perfusion of the gerbil cochlea with probe concentrations of3H‐D‐aspartic acid (D‐ASP) results in immediate, selective labeling of 50–60% of the efferent terminals under the inner hair cells, presumably by high‐affinity uptake. The present study was undertaken to determine the origin of these endings. Twenty‐four hours after cochlear perfusion with D‐ASP, labeled neurons were observed in the ipsilateral, and to a much lesser extent in the centralateral, lateral superior olivary nucleus (LSO). The cells were small, primarily fusiform, and showed fewer synaptic contacts than other LSO cells. Combined transport of D‐ASP and horseradish peroxidase indicated that all olivocochlear neurons within the LSO that projected to the injected cochlea were labeled by D‐ASP.Labeled fibers coursed dorsally from the LSO, joined contralateral fibers that had passed under the floor of the fourth ventricle, and entered the VIIIth nerve root at its ventromedial edge. Adjacent to the ventral cochlear nucleus (VCN), densely labeled collateral fibers crossed the nerve root to enter the VCN. Labeled fibers and terminals were prominent in the central VCN.Neither retrograde transport of D‐ASP by medial olivocochlear and vestibular efferents nor anterograde transport by VIIIth nerve afferents was observed.The D‐ASP‐labeled cells and fibers are clearly lateral olivocochlear efferents. Retrograde transport of D‐ASP thus allows the cells, axons, and collaterals of the lateral olivocochlear system to be studied, morphologically, in isolation from other cells that project to the cochlea. Since the olivocochlear neurons are almost certainly cholinergic, retrograde amino acid transport does not necessarily identify the primary neurotransmitter of a neuron. Rather, it indicates the presence of selective uptake by the processes of that neuron at the site of amino acid injection. Retrograde labeling appears to be markedly enhanced by the use of metabolically inert compounds suc

ISSN:0092-7317    

DOI:10.1002/cne.902550411

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY