摘要:

AbstractNeurons containing gamma‐aminobutyric acid (GABA) in the medial portion of the adult rat nucleus accumbens were characterized with respect to their ultrastructure, sites of termination, and catecholaminergic input. Antisera against GABA‐conjugates and the catecholamine‐synthesizing enzyme, tyrosine hydroxylase (TH), were localized within single sections by means of peroxidase‐antiperoxidase (PAP) and immunoautoradiographic labeling methods. Peroxidase reaction product indicating GABA‐like immunoreactivity (GABA‐LI) was seen in medium‐size (15‐20 μm) perikarya containing either round and unindented or invaginated nuclear membranes. The cells with invaginated nuclei were few in number and usually exhibited more intense peroxidase reaction product in sections collected at the same distance from the surface of the tissue. Reaction product for GABA was also detected in proximal (1.5‐3.0 μm) dendrites, axons, and terminals. Terminals with GABA‐LI formed symmetric junctions on perikarya, proximal dendrites, and dendritic spines of neurons that usually lacked detectable immunoreactivity. Many of the GABAergic terminals also were apposed directly to other unlabeled terminals and to terminals exhibiting either peroxidase labeling for GABA or immunoautoradiographic labeling for TH. Many of the unlabeled terminals associated with the GABAergic axons formed asymmetric junctions on dendritic spines.From 138 TH‐labeled, principally dopaminergic terminals that were examined in the medial nucleus accumbens, 4% were associated with the somata of GABAergic neurons and another 14% formed symmetric junctions with proximal dendrites showing GABA‐LI. The remaining TH‐immunoreactive terminals either lacked recognizable densities or formed symmetric synapses on unlabeled dendrites and spines. A few of the unlabeled dendrites, as well as those containing GABA‐LI, received symmetric synapses from both catecholaminergic and GABAergic terminals.We conclude that in the medial portion of the rat nucleus accumbens, GABA is localized to two morphologically distinct types of neurons, one or both of which receive monosynaptic input from catecholaminergic afferents, and that GABAergic terminals form symmetric synapses on other princi‐pally non‐GABAergic neurons. The results also support earlier physiological evidence showing that GABA may modulate the output of other GABAergic and non‐GABAergic neuro

ISSN:0092-7317    

DOI:10.1002/cne.902720102

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe feline posterior ectosylvian gyrus contains a broad band of association cortex that is bounded anteriorly by tonotopic auditory areas and posteriorly by retinotopic visual areas. To characterize the possible functions of this cortex and to throw light on its pattern of internal divisions, we have carried out an analysis of its thalamic afferents. Deposits of differentiable retrograde tracers were placed at 17 cortical sites in nine cats. The deposit sites spanned the crown of the posterior ectosylvian gyrus and adjacent cortex in the suprasylvian sulcus. We compiled counts of retrogradely labeled neurons in 12 thalamic nuclei delineated by use of Nissl and acetylcholinesterase stains. We then employed a statistical clustering algorithm to identify groups of injections that gave rise to similar patterns of thalamic labeling.The results suggest that the posterior ectosylvian gyrus contains 3 fundamentally different cortical districts that have the form of parallel vertical bands. Very anterior cortex, overlapping previously identified tonotopic auditory areas (AI, P and VP) receives a dense projection from the laminated division of the medial geniculate body (MGl). An intermediate strip, to which we refer as the auditory belt, is innervated by axons from nontonotopic divisions of the medial geniculate body (MGds, MGvl, MGm, and MGd), from the lateral division of the posterior group (Pol), and from the posterior suprageniculate nucleus (SGp). A posterior strip, to which we refer as EPp, receives strong projections from the LM‐SG complex (LM‐SGa and LMp), and lighter projections from the intralaminar and lateroposterior (LPm and LPl) nuclei. On grounds of thalamic connectivity, EPp is not obviously distinguishable from adjacent retinotopic visual areas (PLLS, DLS, and VLS), and may be regarded as forming, together with these areas, a connectionally homogeneous visual b

ISSN:0092-7317    

DOI:10.1002/cne.902720103

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

年代:1988

数据来源: WILEY

摘要:

AbstractIn a preceding report, we described patterns of thalamic retrograde labeling following 17 tracer deposits on the cat's posterior ectosylvian gyrus and concluded, on the basis of patterns of thalamic connectivity, that the posterior ectosylvian gyrus is composed of three major divisions: a tonotopic auditory zone located anteriorly, a belt of auditory association cortex occupying the gyral crown, and a visual belt located posteriorly. We describe here patterns of transcortical retrograde labeling obtained from tracer deposits in the three zones so defined. Our results indicate that the tonotopic auditory strip is innervated primarily by axons from low‐order auditory areas (AAF, AI, P, VP, and V), that the auditory belt receives its strongest input from nontonotopic auditory fields (AII, temporal cortex, and other parts of the auditory belt), and that projections to the visual belt derive primarily from extrastriate visual areas (ALLS, PLLS, DLS, 19, 20, and 21) and from association areas affiliated with the visual system (insular cortex, posterior cingulate gyrus, area 7p, and frontal cortex). We discuss the results in relation to previous systems for parcellating the posterior ectosylvian gyrus of the cat and consider the possibility that divisions of the feline posterior ectosylvian gyrus correspond directly to areas making up the superior temporal gyrus in primate

ISSN:0092-7317    

DOI:10.1002/cne.902720104

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe distribution and sources of putative cholinergic fibers within the lateral geniculate nucleus (GL) of the tree shrew have been examined by using the immunocytochemical localization of choline acetyltransferase (ChAT). ChAT‐immunoreactive fibers are found throughout the thalamus but are particularly abundant in the GL as compared to other principal sensory thalamic nuclei (medial geniculate nucleus, ventral posterior nucleus). Individual ChAT‐immunoreactive fibers are extremely fine in caliber and display numerous small swellings along their lengths. Within the GL, ChAT‐immunoreactive fibers are more numerous in the layers than in the interlaminar zones and, in most cases, the greatest density is found in layers 4 and 5. Two sources for the ChAT‐immunoreactive fibers in the GL have been identified–the parabigeminal nucleus (Pbg) and the pedunculopontine tegmental nucleus (PPT)–and the contribution that each makes to the distribution of ChAT‐immunoreactive fibers in GL was determined by combining immunocytochemical, axonal transport, and lesion methods. The projection from the Pbg is strictly contralateral, travels via the optic tract, and terminates in layers 1, 3, 5, and 6 as well as the interlaminar zones on either side of layer 5. The projection from PPT is bilateral (ipsilateral dominant) and terminates throughout the GL as well as in other thalamic nuclei. Lesions of the Pbg eliminate the ChAT‐immunoreactive fibers normally found in the optic tract but have no obvious effect on the density of ChAT‐immunoreactive fibers in the contralateral GL. In contrast, lesions of PPT produce a conspicuous decrease in the number of ChAT‐immunoreactive fibers in the GL and in other thalamic nuclei on the side of the lesion but have no obvious effect on the number of ChAT‐immunoreactive fibers in the optic tract. These results suggest that there are two sources of cholinergic projections to the GL in the tree shrew which are likely to play different roles in modulating the transmission of visual activity to the cortex. The Pbg is recognized as a part of the visual system by virtue of its reciprocal connections with the superficial layers of the superior colliculus, while the PPT is a part of the midbrain reticular formation and is thought to play a non‐modality‐specific role in modulating the activity of neurons throughout the thalamus and in other

ISSN:0092-7317    

DOI:10.1002/cne.902720105

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

年代:1988

数据来源: WILEY

摘要:

AbstractWe have examined the anatomical features of ipsilateral transient cortical projections to areas 17, 18, and 19 in the kitten with the use of axonal tracers Fast Blue and WGA‐HRP. Injections of tracers in any of the three primary visual areas led to retrograde labeling in frontal, parietal, and temporal cortices. Retrogradely labeled cells were not randomly distributed, but instead occurred preferentially at certain loci. The pattern of retrograde labeling was not influenced by the area injected. The main locus of transiently projecting neurons was an isolated region in the ectosylvian gyrus, probably corresponding to auditory area A1. Other groups of transiently projecting neurons had more variable locations in the frontoparietal cortex.The laminar distribution of neurons sending a transient projection to the visual cortex is characteristic and different from that of parent neurons of other cortical pathways at the same age. In the frontoparietal cortex, transiently projecting neurons were located mainly in layer 1 and the upper part of layers 2 and 3. In the ectosylvian gyrus, nearly all the neurons are located in layers 2 and 3. In addition, a few transiently projecting neurons are found in layer 6 and in the white matter. Transiently projecting neurons have a pyramidal morphology except for the occasional spindle‐shaped cell of layer 1 and multipolar cells observed in the white matter.Anterograde studies were used to investigate the location of transient fibers in the visual cortex. Injections of WGA‐HRP at the site of origin of transient projections gave rise to few retrogradely labeled cells in areas 17, 18, and 19, demonstrating that transient projections to these areas are not reciprocal. Although labeled axons were found over a wide area of the posterior cortex, they were more numerous over certain regions, including areas 17, 18, and 19, and absent from other more lateral cortical regions. Transient projecting fibers were present in all cortical layers at birth. Plotting the location of transient fibers in numerous sections and at all ages showed that these fibers are not more plentiful in the white matter than they are in the gray matter. We found no evidence that the white/gray matter border constituted a physical barrier to the growth of transient axons.Comparison of the organization of this transient pathway to that of other transient connections is discussed with respect to the development of the c

ISSN:0092-7317    

DOI:10.1002/cne.902720106

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe family of tachykinins includes the neuropeptides substance P, neurokinin A, and neurokinin B. The distribution of substance P in the central nervous system has been studied immunohistochemically but the lack of specific antibodies has prevented similar studies of neurokinin B. Recent molecular genetics techniques have revealed the sequences for the complementary DNAs that code for the substance P and neurokinin B precursors. These results have permitted the design of specific probes to differentiate between substance P and neurokinin B transcripts by using in situ hybridization histochemistry. Our probes, 48‐base synthetic oligodeoxynucleotides labeled with35S revealed extensive and distinct patterns of cell labeling for both substance P and neurokinin B throughout the rat central nervous system.The distribution of substance‐P‐mRNA‐containing cells that we observed confirmed and extended previous immunocytochemical descriptions. Cells containing transcripts for either tachykinin were present in the neocortex, hippocampus, olfactory bulb and associated areas, caudate‐putamen, hypothalamus, medial habenula, superior colliculus, central gray, and dorsal horn of the spinal cord. However, their distributions within these areas were usually quite different. Other areas contained only one tachykinin cell type: e.g., the nucleus of the lateral olfactory tract contained only neurokinin B cells whereas the raphe nuclei had only substance P cells. This study demonstrates the sensitivity and specificity of in situ hybridization histochemistry for mapping peptidergic neurons and lays the foundation for further investigations of the roles of these two tachykinins in the central nervo

ISSN:0092-7317    

DOI:10.1002/cne.902720107

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

年代:1988

数据来源: WILEY

摘要:

AbstractImmunocytochemistry was used to localize the populations of tyrosinehydroxylase‐like (TH)‐immunoreactive cells in the tiger salamander retina. Ninety percent of these cells possessed somas that were situated in the innermost cell row of the inner nuclear layer and were classified as amacrine cells. Ten percent of TH‐immunoreactive somas were located in the ganglion cell layer and were tentatively designated as those of displaced amacrine cells. The processes of TH‐immunoreactive cells ramified most heavily in sublayer 1 of the inner plexiform layer, while a relatively small number of TH‐labelled processes distributed in sublayers 3 and 5. Less than 1% of TH‐immunoreactive cells in the amacrine cell layer exhibited a short process of somal origin that extended distally toward the outer plexiform layer. However, these processes did not cross the whole of the inner nuclear layer, and no immunolabelling was observed in the outer plexiform layer.An examination of retinal whole‐mounts revealed that TH‐immunoreactive amacrine and displaced amacrine cells were distributed throughout the center and periphery of the retina. The density of TH‐immunolabelled amacrine cells was calculated to be 49 ± 13 (mean ± standard error) cells per mm2. The vast majority of TH‐immunoreactive amacrine and displaced amacrine cells exhibited a stellate appearance and gave rise to three or more primary dendrites. A few TH‐amacrine and displaced amacrine cells possessed two primary dendrites that emerged from opposite sides of their somas. The processes of TH‐immunoreactive cells were generally poorly branched and varicose with terminal branches sometimes appearing thin and beaded. Because some TH‐immunolabelled processes were very long, there was considerable overlap between the dendritic fields of neighboring TH‐cells. Lastly, individual TH‐immunoreactive amacrine and displaced amacrine cells were often observed in whole‐mounts to provide processes that ramified at more than one l

ISSN:0092-7317    

DOI:10.1002/cne.902720108

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe distribution and morphologic characteristics of choline acetyltransferase (ChAT)‐containing neurons were studied throughout the rostrocaudal extent of the rat hippocampus and in a midline area just dorsal to the dorsal hippocampus. Peroxidase reaction product was observed with the aid of immunohistochemical methods and a high‐titer polyclonal antibody against ChAT, the acetylcholine biosynthetic enzyme. ChAT‐positive cells in the hippocampus were characterized by small, round or oval perikarya with two or more proximal processes. They were located within the caudal and temporal hippocampal formation, predominantly within the subiculum, in the stratum lacunosum moleculare, at the border of the stratum lacunosum moleculare and the stratum radiatum, and in the molecular layer of the dentate gyrus. The cells resembled in morphology the small, bipolar and multipolar neocortical ChAT‐immunoreactive cells. In addition to the hippocampus, ChAT‐positive neurons were observed caudally in a region just above the dorsal hippocampal commissure and rostrally in the columns of the fornix. These cells were large with an oval perikarya and darkly labeled compared to neurons in the hippocampus. They more closely resembled the ChAT‐positive neurons in the midline raphe of the medial septal nucleus.Examination of the rat hippocampus 2 and 8 weeks following unilateral lesioning of the fimbria‐fornix and supracallosal striae revealed a sparse innervation of ChAT‐positive fibers in the hippocampus ipsilateral to the lesion. ChAT‐labeled neurons in the hippocampus did not appear to sprout in response to the lesion. In contrast, ChAT‐positive cells in the midline did appear to sprout into the medial dorsal subiculum and dorsal medial hippocampus. We conclude that these two populations of cells are distinct with respect to their response to hippocampal denervation and, furthermore, that this distinction may be attributed to a differential response to

ISSN:0092-7317    

DOI:10.1002/cne.902720109

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe present work was undertaken to determine what proportion of all nerve fibers in the circular muscle of the guinea pig small intestine contain the neuropeptides enkephalin, substance P, and vasoactive intestinal peptide and in which combinations these peptides occur in the fibers. It was envisaged that such an analysis would provide insights into the chemical identity of excitatory and inhibitory nerve fibers that innervate the muscle. Whole‐mount preparations from normal and extrinsically denervated gut were labelled with antiserum to the individual peptides or with combinations of antipeptide antisera and processed for electron microscopy. Reactive and nonreactive vesicle‐containing nerve fiber profiles were examined and counted in ultrathin sections.Vesicle‐containing nerve fiber profiles immunoreactive for enkephalin, substance P, or vasoactive intestinal peptide had similar morphologies in that they all contained variable proportions of small clear and large granular vesicles. In all samples stained for single peptides or combinations of peptides, a small proportion of immunoreactive profiles approached smooth muscle cells to within 15‐20 nm with no intervening basal lamina.A total of 14,694 vesiculated nerve fiber profiles from three control and three extrinsically denervated animals were scored for the presence of immunoreactivity to enkephalin, substance P, vasoactive intestinal peptide, or combinations of these peptides. Analysis of variance showed that the number of profiles labelled for substance P was not different from the number of profiles labelled for vasoactive intestinal peptide and that the number labelled with the substance P and vasoactive intestinal peptide antisera simultaneously were not different from the sum of the numbers obtained with each alone. The number of profiles labelled for substance P plus enkephalin was greater than the number labelled for substance P alone and the number labelled with vasoactive intestinal peptide plus enkephalin was greater than that with vasoactive intestinal peptide alone. Simultaneous labelling for substance P and vasoactive intestinal peptide resulted in immunoreactivity in the same number of profiles as did reaction for all three peptides at the same time. In both cases, about 95% of the profiles were labelled. The results from extrinsically denervated muscle were not different from control circular muscle.These results indicate that nearly all the intrinsic nerve fibers supplying the circular muscle of the guinea pig small intestine contain either substance P or vasoactive intestinal peptide but not both. Enkephalin is not found alone in intrinsic nerve fibers in the circular muscle but always occurs with either substance P or vasoactive intestinal peptide. Enkephalin is absent from about one‐third of the nerve fibers that contain substance P and a similar number that contain vasoactive intestinal peptide. These findings, along with data from physiological experiments, imply that both excitatory nerve fibers to the circular muscle, which are cholinergic, and inhibitory nerve fibers, which are neither noradrenergic nor cholinergic, contain one or more neuropeptides. Substance P is probably present in some, possibly all, of the excitatory nerve fibers whereas vasoactive intestinal peptide is probably present in some, if not all, of the inhibitory ner

ISSN:0092-7317    

DOI:10.1002/cne.902720110

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

年代:1988

数据来源: WILEY

摘要:

AbstractRecent evidence indicates that corticotectal neurons belong to only one of the three morphological classes of pyramidal cells in layer V. The present study compares the dendritic morphology and axon collaterals of corticotectal, corticopontine, and layer V callosal neurons by using techniques based on the retrograde transport of horseradish peroxidase and fluorescent dyes as well as in vitro intracellular dye injections. Our results indicate that corticotectal and corticopontine neurons are located predominantly in the upper middle part of layer V. These neurons have medium to large somas with 5 or 6 primary basal dendrites and a single apical dendrite ascending to layer I. Approximately 60% of these cells send axon collaterals to both the superior colliculus and the pons. In contrast, callosal neurons form a heterogeneous group. In general, they have small pyramidal or ovoid cell bodies which give rise to 3 or 4 primary basal dendrites. Many cells have an apical dendrite that bifurcates and terminates in layer V or IV. We find that callosal neurons do not send an axon collateral to either the superior colliculus or the pons.We conclude that the corticotectal and corticopontine systems are similar in their intralaminar distribution, dendritic morphology, and pattern of axon collaterals, whereas the callosal system differs in these characteristics.

ISSN:0092-7317    

DOI:10.1002/cne.902720111

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

年代:1988

数据来源: WILEY