摘要:

AbstractThe cholinergic innervation of the hippocampal formation is thought to play an important role in memory processes, but its organization in humans has not been described in detail. We studied the cholinergic innervation of the human hippocampal formation by means of immunohistochemistry with polyclonal antisera directed against acetyleholinesterase (AChE), choline acetyltransferase (ChAT), and the low‐affinity (p75) nerve growth factor receptor (NGFR). The density of ChAT‐like immunoreactive (ChAT‐li) fibers differed substantially among the various regions, in general paralleling the pattern of AChE‐li staining. One notable exception was the presence of AChE‐li cell bodies. In contrast, ChAT immunoreactivity was associated only with fibers and terminals. NGFR‐li staining corresponded closely to the ChAT‐li fiber pattern.ChAT‐li fibers in the CA fields diffusely filled the stratum pyramidale and extended into the stratum oriens and radiatum as well. The highest density was consistently observed in CA4 and CA3 subfields. Staining decreased from CA4 to CA1 and was substantially less dense in the subicular complex. In the entorhinal cortex, the ChAT‐ and NGFR‐li fiber innervation displayed a laminar pattern, most intense over the nests of cells in layer II.There was a trend towards an age‐related reduction in the density of ChAT‐ and AChE‐li fibers and terminals. Nonetheless, we also found a surprisingly conserved NGFR‐li innervation and the presence of occasional NGFR‐li pyramidal cells, providing evidence of a plastic response in the brains of the elderly pa

ISSN:0092-7317    

DOI:10.1002/cne.903450302

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThis study examined the synaptic terminal coverage of primate triceps surae (TS) motoneurons at the electron microscopic level. In three male pigtail macaques, motoneurons were labeled by retrograde transport of cholera toxin‐horseradish peroxidase that was injected into TS muscles bilaterally and visualized with tetramethylbenzidine stabilized with diamino‐benzidine. Somatic, proximal dendritic, and distal dendritic synaptic terminals were classified by standard criteria and measured. Overall and type‐specific synaptic terminal coverages and frequencies were determined.Labeled cells were located in caudal L5 to rostral S1 ventral horn and ranged from 40 to 74 μm in diameter (average, 54 μm). The range and unimodal distribution of diameters, the label used, and the presence of C terminals on almost all cells indicated that the 15 cell bodies and associated proximal dendrites analyzed here probably belonged to α‐motoneurons.Synaptic terminals covered 39% of the cell body membrane, 60% of the proximal dendritic membrane, and 40% of the distal dendritic membrane. At each of these three sites, F terminals (flattened or pleomorphic vesicles, usually symmetric active zones, average contact length 1.6 μm) were most common, averaging 52%, 56%, and 58% of total coverage and 56%, 57%, and 58% of total number on cell bodies, proximal dendrites, and distal dendrites respectively. S terminals (round vesicles, usually asymmetric active zones, average contact length 1.3 μm) averaged 24%, 29%, and 33% of coverage and 33%, 35%, and 36% of number at these three sites, respectively. Thus, S terminals were slightly more prominent relative to F terminals on distal dendrites, than on cell bodies. C terminals (spherical vesicles, subsynaptic cisterns associated with rough endoplasmic reticulum, average contact length 3.5 μm) constituted 24% and 11% of total terminal coverage on cell bodies and proximal dendrites, respectively, and averaged 11% and 6% of terminal number at these two locations. M terminals (spherical vesicles, postsynaptic Taxi bodies, some with presynaptic terminals, average contact length 2.7 μm) were absent on cell bodies and averaged 3% and 7% of total coverage and 2% and 5% of terminals on proximal and distal dendrites, respectively. Except for M terminals, which tended to be smaller distally, terminal contact length was not correlated with location. Total and type‐specific coverages and frequencies were not correlated with cell body diameter.Primate TS motoneurons are similar to cat TS motoneurons in synaptic terminal morphology, frequency, and distribution. However, primate terminals appear to be smaller, so that the fraction of menitrane covered by them is lower. © 199

ISSN:0092-7317    

DOI:10.1002/cne.903450303

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractLate fetal through postnatal development in sheep is a period of increasing convergence of afferent taste fibers onto second‐order neurons in the nucleus of the solitary tract (NST). To learn whether neuron morphology alters in concert with convergence and neurophysiological development in NST, three‐dimensional neuron reconstructions were made of cells in a functionally defined region of gustatory NST from Golgi preparations of the brainstem. Elongate, multipolar, and ovoid neurons were studied in fetuses from 85 days of gestation through the perinatal period (term = 147 days of gestation), to postnatal stages. Somal size and form, and dendritic complexity and extent, increased markedly from 85 to about 110 days of gestation in both of the proposed NST projection neurons, elongate and multipolar. From 130 days of gestation to postnatal ages, growth of dendrites of elongate neurons plateaued or declined, whereas dendrites of multipolar neurons apparently continued to increase in size and extent. In addition, spine density decreased on elongate neurons but remained stable on multipolar neurons. Morphological variables of ovoid cells, proposed interneurons in NST, did not alter over this later period. The data suggest that multipolar, not elongate or ovoid, neurons are logical candidates to receive the increasing afferent fiber input onto NST cells during late gestation. Also, neural activity from taste afferent fibers is more likely to have a role in altering NST neuron morphology at later, rather than earlier, developmental periods. © 1994 Wiley‐Lis

ISSN:0092-7317    

DOI:10.1002/cne.903450304

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe spatiotemporal distribution of cell death in the chick embryo neural tube and spinal cord (brachial region) was examined between stage (St.) 12 and 22, in plastic semithin sections. Between St. 12 and 16, the total number of pycnotic cells per segment was low, whereas after St. 16 the number of pycnotil cells was substantially increased. Between St. 17 and 19 three cell death foci or regions could be recognized. One region, the dorsal pycnotic zone, was located in the most dorsal part of the spinal cord, including the neural crest, with the highest number of pycnotic cells observed at St. 18. The second region, or ventral pyenotic zone, was located between motoneurons and the floor plate and had the highest number of dying cells at St. 17. The third region, the floor plate pycnotic zone, was located in the midportion of the floor plate and had the greatest amount of cell death at St. 19. Although low numbers of pycnotic cells were also observed in other regions between St. 17 and 19, no pycnotic cells were found in the ventrolateral region that gives rise to motoneurons. Ultrastructural observations as well as data from in situ nick end labeling indicate that the pycnotic cells observed in the neural tube die by apoptosis and that the debris from the dead cells is phagocytized primarily by adjacent healthy neuroepithelial cells.Although the spatiotem poral distribution of pycnotic cells suggests that cell death at these early stages could play a role in establishing the pioneer axonal pathway for spinal commissural neurons, preliminary observations following perturbations of cell death do not support this notion. Alternatively, early cell death may be involved in the regulation of cellular patterning along the dorsoventral axis of the neural tube by a kind of negative selection of specific progenitor cells. © 1994 Wiley‐Liss, I

ISSN:0092-7317    

DOI:10.1002/cne.903450305

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe sexually dimorphic nucleus of the preoptic area (SDN‐POA) is larger in male than in female rats, the male phenotype requiring the presence of circulating androgens perinatally. These experiments investigated the intracellular electrophysiology and morphology of SDN‐POA neurons and compared these properties with those of other medial preoptic area (MPOA) neurons. Biocytin‐injected cells in the SDN‐POA either had one or two primary dendrites, or they had multipolar dendritic arrays; dendrites were aspiny or sparsely spiny and displayed limited branching. Neurons in other parts of the MPOA were similar morphologically. Regardless of morphology, neurons situated in either the SDN‐POA or surrounding MPOA had low‐threshold potentials and linear or nearly linear current‐voltage relations. In most (73%) cells, stimulation of the dorsal preoptic region evoked a fast excitatory postsynaptic potential followed by a fast inhibitory postsynaptic potential (IPSP). Bicuculline blocked the fast IPSPs, which reversed near the Cl2equilibrium potential (‐71 ± 5mV), indicating their mediation by gamma‐aminobutyric acid (GABA)Areceptors.Neurons in the SDN‐POA have electrophysiological properties similar to those of other medial preoptic cells. When compared with the hypothalamic paraventricular nucleus, the MPOA appears relatively homogeneous electrophysiologically. This is despite the morphological variability within this population of neurons and heterogeneities that are also apparent at other levels of analysis. Finally, GABA‐mediated, inhibitory synaptic contacts are widespread among medial preoptic neurons, consistent with indications from earlier reports that GABA provides a link in the feedback actions of gonadal steroids on the release of gonadotropic hormones.

ISSN:0092-7317    

DOI:10.1002/cne.903450306

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractTo assess the possible role of trophic factors in lesion‐induced plasticity, we have used a sensitive immunohistochemical technique to evaluate changes in nerve growth factor (NGF) staining in the hippocampal formation 3, 8, 16, and 30 days following entorhinal cortex lesions. Our results indicate that a band of NGF immunoreactivity appears in the outer molecular layer of the ipsilateral dentate gyrus following entorhinal ablation. The distribution of the NGF‐immunoreactive band exactly coincides with the distribution of sprouting cholinergic terminals revealed by acetylcholinesterase histochemistry or NGF‐receptor immunostaining. Increased NGF‐immunoreactivity is detectable at 3 days postlesion, is most intense at 8 days, and decreases to near control levels by 30 days. Lesion‐induced increases in NGF immunostaining also occur in animals in which septohippocampal fibers had been removed by prior destruction of the fimbria‐fornix. Increases in NGF‐immunoreactivity, however, are substantially reduced in animals receiving intraventricular injections of colchicine, which presumably blocks NGF release. These results indicate that (1) increases in NGF immunostaining, which occur following entorhinal lesions, precede any changes in cholinergic sprouting parameters and are greatest during the period of maximal cholinergic sprouting; (2) increased NGF‐immunoreactivity is not due to NGF binding by septohippocampal fibers; and (3) increased NGF‐immunoreactivity appears to depend on the release of NGF by neurons that produce it. We hypothesize that, following entorhinal lesions, NGF immunostaining within the hippocampal formation may represent NGF “anchored” within the tissue and that NGF accumulation by such a mechanism may direct the sprouting response of NGF‐sensitive cholinergic neurons.

ISSN:0092-7317    

DOI:10.1002/cne.903450307

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractBony fishes add sensory hair cells to the saccule and lagena of the ear for at least several years after hatching. However, it is not known whether hair cell proliferation occurs for the whole lifetime of an animal, whether proliferation occurs in all endorgans of the ear, or whether the rate of proliferation is the same in all of the endorgans. To obtain answers to these questions, the extent of postembryonic hair‐cell proliferation was determined in the saccule, lagena, and utricle of the ear in the European hake,Merluccius merlaccius, for fish ranging from 7 to 75 cm in total length (6 months to 9 years of age). Results demonstrated that hair‐cell addition continued throughout this period in all three otic endorgans, although endorgan size was proportionally greatest in smaller animals. Of the three endorgans, cell addition was greatest in the saccule. Moreover, far more cells were added to the caudal end of the saccule than to the rostral end. Each saccule of the largest hake had over 900,000 hair cells. It is estimated that each saccule adds approximately 110,000 new hair cells each year (or 302 cells/day) over the life span of the fish studied. A significant number of small ciliary bundles, thought to represent newly proliferated hair cells, was found throughout each endorgan, and the number of such bundles declined as the rate of hair cell proliferation decreased. The results demonstrate that extensive proliferation occurs in all three otolithic endorgans of the ears in a fish and that such proliferation continues for virtually the whole life of the animal. The functional significance of this addition is not known. © 1994 Wiley‐Lis

ISSN:0092-7317    

DOI:10.1002/cne.903450308

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe possibility of GABAAreceptor heterogeneity in goldfish retina was studied with immunocytochemical and biochemical approaches: (1) immunoblotted membrane particulates of goldfish retina with mAb 62‐3G1; (2) immunoprecipitation of the detergent‐solubilized membrane proteins with mAb 62‐3G1 followed by the receptor binding assay; (3) photoaffinity labeling of the membrane particulates with3H‐flunitrazepam (FNZ) and visualization of the labeled receptors by SDS‐PAGE and fluorography; (4) dry autoradiography of3H‐muscimol and3H‐FNZ binding sites on frozen sections. Immunoblots showed that 62‐3G1 reacted with 55–57.5 kDa Mr polypeptides, similar to the muscimol‐binding subunit of the receptor complex in bovine brain; while3H‐FNZ photoaffinity labeled the 52.5 kDa and 41–43 kDa Mr polypeptides. Immunoprecipitated receptors bound only3H‐muscimol, not3H‐FNZ. An attempt to precipitate the3H‐FNZ photolabeled polypeptides failed. Dry autoradiography showed3H‐PNZ binding only in the inner plexiform layer (IPL); the binding was enhanced with γ‐aminobutyric acid (GABA) and blocked by clonazepam. In contrast,3H‐muscimol was bound in both the outer plexiform layer (OPL) and IPL, similar to that observed with 62‐3G1 immunocytochemistry. We suggest that there are two subtypes of GABAAreceptor in the goldfish retina: (1) GABAAreceptors that are not linked to a benzodiazepine (BZD) receptor are located in the OPL and at amacrine‐to‐amacrine and amacrine‐to‐ganglion cell synapses in the IPL and are recognized by 62‐3G1; (2) GABAAreceptors that are linked to a BZD receptor are located only in the IPL, largely at amacrine‐to‐bipolar cell synapses and are

ISSN:0092-7317    

DOI:10.1002/cne.903450309

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractCarotid body‐like organs, paraganglia, frequently occur in the superior and recurrent laryngeal nerves. The paraganglia are supplied with a rich innervation of unknown origin. In the present study, the origin of the innervation of the paraganglia of the rat was studied with two different techniques. One approach was anterograde tracing of wheat‐germ agglutinin‐horseradish peroxidase after injection into the nodose and jugular ganglia of the vagus and the superior cervical ganglion. The other approach was immunohistochemical staining for neuropeptides after excision of the superior cervical ganglion, or vagotomy. Antisera against neuropeptide Y, vasoactive intestinal polypeptide, and calcitonin gene‐related peptide were utilized. Both the tracing method and calcitonin gene‐related peptide immunohistochemistry after vagotomy showed that the paraganglia receive sensory innervation from the vagal ganglia. No labeling was detected in the paraganglia after injection of wheat‐germ agglutinin‐horseradish peroxidase in the superior cervical ganglion. Excision of this ganglion did not lead to a decrease in the neuropeptide‐Y innervation in the paraganglia, but most of this innervation in the surrounding blood vessels disappeared. The observations show that the superior cervical ganglion does not contribute to the innervation in the paraganglia and that the neuropeptide‐Y innervation of the blood vessels originates from the superior cervical ganglion whereas that of the paraganglia has another origin, most likely local ganglionic cells. The results also suggest that the vasoactive intestinal polypeptide innervation in the paraganglia arises from local ganglionic cells. The two approaches complemented each other in mapping the afferent and efferent nerve supply of the paraganglia. © 19

ISSN:0092-7317    

DOI:10.1002/cne.903450310

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractCorticothalamic connections of auditory areas of the superior temporal regions (STR) were investigated in the rhesus monkey. These connections are organized according to the recently described architectonic parcellation of the STR. The core line regions of the supratemporal plane (STP) project to the medial geniculate nucleus (MGN). All regions except the primary auditory area also have projections to additional thalamic nuclei. The rostral STP has strong connections with the caudal part of the ventral subdivision (MGv) of MGN as well as with medial pulvinar (PM). In contrast the primary auditory areaprojects mainly to rostral MGv. The caudalmost STP projects mainly to the dorsal subdivision (MGd) and to the magnocellular subdivision (MGmc) as well as to the PM and the lateral (PL) and oral (PO) pulvinar, nucleus limitans (Li), and mediodorsal (MD) nucleus. The belt line regions of the superior temporal gyrus (STG) project mainly to the pulvinar but also have projections to MGd and MGmc. Specifically, rostral STG projects to the caudal part of PM, to MGmc, and to the suprageniculate (SG) nucleus, whereas caudal STG projects to the rostral part of PM and to PL, PO, MGd, MGmc, SG‐Li and MD nuclei. The root line areas in the circular sulcus of the Sylvian fissure project mainly to MGmc but also to MGd, PM, and SG‐Li nuclei. These connections originate mainly from neurons in cortical layer VI, with some from layer Vb. It is suggested that these connections may be involved in different aspects of auditory information processing. © 1994 Wiley‐Lis

ISSN:0092-7317    

DOI:10.1002/cne.903450311

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY