摘要:

AbstractA monoclonal antibody raised against the receptor for nerve growth factor (NGF) was used to examine the distribution and morphology of NGF receptor‐containing neurons within the central nervous system ofCebus apellamonkeys. Most somata demonstrating positive immunoreactivity were localized within the Ch1–4 regions of the basal forebrain. Neurons in the Ch1 region displayed morphological features typical of cholinergic medial septal neurons. These perikarya were primarily vertically oriented (40–50 μm along the vertical axis) with both apical and basal neuritic processes. Magnocellular (40–50 μm) neurons within the Ch2 (vertical limb of the diagonal band), Ch3 (horizontal limb of the diagonal band) and Ch4 (nucleus basalis of Meynert) regions were multipolar and had rounded perikarya that often displayed an eccentric nucleus. Fibers presumably originating from the Ch1–2 regions were observed throughout the fimbria‐fornix system and were found to terminate preferentially within the CA1 and CA3 regions of the hippocampal formation and within the dentate gyrus of the hippocampus. An intense fiber network was also observed in the olfactory tubercle and other rhinencephalic structures, presumably originating from the Ch3 region of the basal forebrain. Beaded processes emanating from the Ch4 region primarily coursed within the external capsule and terminated preferentially within layers I, II, and IV of the cerebral cortex. In a pattern similar to that of cortical acetylcholinesterase (AChE) staining, NGF receptor immunopositive fibers were oriented in a tangential plane within the molecular layer of the cortex and in both a radial and tangential fashion within the cortical granular cell layers. In addition to neural innervation, there was an extensive vascular apposition by NGF receptor‐containing neurites on both large caliber vessels and microcapillaries. NGF receptor immunoreactivity was extensively, but not exclusively, colocalized with choline acetyltransferase (ChAT) and AChE in the basal forebrain. A small population of cholinergic neurons were observed that were not NGF receptor‐immunoreactive. Conversely, a few NGF receptor‐containing neurons that were noncholinergic were also observed in this brain region.NGF receptor‐containing somata were also identified in the putamen. The number of immunoreactive neurons observed in this structure, however, would not appear to be sufficient to account for the homologous NGF receptor binding densities described in rodents. NGF receptor immunoreactive neurons were also observed within the dorsal columns of the fornix, bed nucleus of the stria terminalis, and within the mesencephalic nucleus of the trigeminal nerve. Specific fiber immunoreactivity was also observed within the hypothalamic median eminence and the subfornical organ. These data are discussed in terms of the putative roles that NGF may play in modulating and supporting central ne

ISSN:0092-7317    

DOI:10.1002/cne.902770402

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractThe enteric nervous system (ENS) can mediate reflex activity without input from the brain or spinal cord. The ENS thus contains intrinsic primary afferent neurons that link mucosal sensory receptors with motor neurons in the myenteric plexus. The intrinsic primary afferent neurons of the gut have not yet been identified. Although the submucosal plexus is known to innervate the mucosa, where enteric sensory receptors are located, no submucosal to myenteric projections have previously been found. In order to detemine whether such projections exist, the submucosal plexus was examined following the microinjection of a retrograde tracer (Fluoro‐Gold or 4‐acetoamido, 4′‐isothiocyanostilbene‐2,2′‐disulphonic acid [SITS]) into single myenteric ganglia. In addition, the myenteric plexus was studied following the iontophoretic injection of an anterograde tracer (Phaseolus vulgarisleucoagglutinin; [PHA‐L]) into single submucosal ganglia. Ganglia were visualized by use of differential interference contrast optics and were injected from the beveled tip of a glass micropipette; 2.5–3.0 hours were allotted for retrograde and 20–24 hours (under culture conditions) for anterograde transport. In the myenteric plexus, a small number of the neurons of each injected ganglion were fluorescent and additional neurons in distant myenteric ganglia (predominantly orad) were also retrogradely labeled. About five to six submucosal neurons deep to but not directly underneath the injected myenteric ganglion were labeled by Fluoro‐Gold or SITS and only rarely was there more than one labeled neuron in a submucosal ganglion. When control injections of Fluoro‐Gold were placed into the muscle instead of a ganglion, some myenteric neurons near the injection site became labeled indicating an innervation of the circular muscle by myenteric neurons; however, there was no labeling of neurons in the submucosal plexus. Similarly, if connections between the myenteric and submucosal plexuses were severed before injecting Fluoro‐Gold, no submucosal neurons were labeled. Following injection of PHA‐L into a single submucosal ganglion, small‐diameter axons were labeled in ∼︁2 myenteric ganglia as well as in several distant submucosal ganglia (mainly anal and circumferential to the injection site). Additional labeled fibers traveled with blood vessels or surrounded mucosal crypts. It is concluded that submucosal neurons project to the myenteric plexus as well as to the mucosa and to one another. These observations are consistent with the hypothesis that at least some intrinsic enteric primary afferent neuron

ISSN:0092-7317    

DOI:10.1002/cne.902770403

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractThis study was undertaken to determine how increasing ploidy inXenopus laevisaffected the size of the lumbar lateral motor column (L‐LMC) motoneuron population, the size of representative hindlimb muscles, and the relationship between these features in animals at the completion of metamorphosis. Triploids were produced by exposing fertilized diploid eggs to increased hydrostatic pressure. In the triploids, L‐LMC motoneuron number was significantly reduced and motoneuron nuclear cross‐sectional area was significantly increased. Both L‐LMC length and the total L‐LMC size (neuron number × mean nuclear size) were roughly equal in diploids and triploids. No ploidy‐related differences in fiber number were observed in two representative thigh muscles.In diploid animals, motoneuron number is significantly correlated with both muscle fiber number and with body size. The latter two variables are also significantly correlated with one another, making it possible that a feature related to muscle fiber number or one related to body size or both are significant in determining motoneuron number. In triploid animals, motoneuron number was significantly correlated with body size but not with muscle fiber number. This suggests that the feature significant in determining motoneuron number may be one related to body size rather than to muscle fiber number. If a feature related to muscle fiber number were the primary determinant of motoneuron number, one would have expected in addition similar average changes in the two variables in comparing diploids and triploids. That this was not observed provides further reason to suspect muscle fiber numbers may not be a primary determinant of motoneuron number.In both diploids and triploids, total L‐LMC size (a value combining neuron number and neuron size) was highly correlated with body size, but again, not with muscle fiber number. The average total L‐LMC size and the average body size were equal in diploids and triploids while average motoneuron number was significantly different. What this suggests is that in discussing possible mechanisms to account for correspondences between central and peripheral sizes, the relevant variable for the former may be total L‐LMC size rather than

ISSN:0092-7317    

DOI:10.1002/cne.902770404

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractThe present investigation was carried out to clarify the topographical details of both the origin and terminal site of the thalamic projections and the commissural connections of the ventral lateral geniculate nucleus (LGNv) in the cat by using bidirectional transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA‐HRP).Thalamic projections: Unilateral injections of WGA‐HRP into the LGNv produced orthograde labeling in the intralaminar nuclei bilaterally and in the lateralis posterior (LP) and the pulvinar (Pul) nucleus ipsilaterally. In the intralaminar nuclei the rostral part of the nucleus centralis lateralis (CL) was most densely labeled by orthogradely transported material, particularly in its dorsal and lateral large‐celled portion. Other intralaminar nuclei—such as the nucleus paracentralis, centralis medialis, and centralis dorsalis—also were labeled bilaterally with ipsilateral predominance, but no labeling was detected in the caudal portion of the CL and the centromedian and parafascicular nuclei. In the Pul, labeling of terminal ramifications was found to be concentrated in a region just medial to th so‐called retinorecipient zone of the Pul as a slim band of labeling inclining dorsoventrally. In the LP, fine labeled fibers were located in the lateral portion of the LP.Commissural connections: Commissural fibers crossed in the dorsal part of the posterior commissure and reached the most caudal part of the contralateral LGNv. Labeling in the contralateral LGNv was concentrated in the dorsomedial part of the medial zone that extends medially to the middle portion of the cerebral peduncle. Origins of the commissural connections arose mostly from the medial zone that roughly corresponds to the commissural terminal zone and partly from aberrant cells dispersed among optic tract fibers.From these results, together with the previous studies, it is concluded that although the cat's LGNv has connections with diverse structures in the central nervous system, the origin and terminal site of the connections are partially segregated within the nucleus, which suggests that the LGNv may contain functional

ISSN:0092-7317    

DOI:10.1002/cne.902770405

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractCholine acetyltransferase (ChAT) immunocytochemistry and lectin‐conjugated horseradish peroxidase (WGA‐HRP) histochemistry were combined at the electron microscopic level to examine the morphology of cholinergic terminals in the canine centrum medianum—parafascicular complex (CM‐Pf) and to localize cholinergic terminals making synaptic contact with retrogradely labeled CM‐Pf thalamostriatal projection neurons. Following WGA‐HRP injections into the caudate nucleus, CM‐Pf neurons were heavily labeled with WGA‐HRP reaction product. Examination with the electron microscope revealed retrogradely labeled neurons characterized by a large nucleus with deep infoldings of the nuclear envelope. ChAT‐positive terminals were observed arising from small‐diameter nonmyelinated axonal profiles. These terminals varied in size from 0.5 to 1.4 μm in long diameter. The smaller terminals (0.5–0.7 μm) were seen most frequently and established symmetrical or slightly asymmetrical synaptic contacts with small dendritic profiles. The larger ChAT‐positive terminals (1.0–1.4 μm) were less frequently observed, contained several mitochondria and small clusters of pleomorphic vesicles, and contacted large dendritic shafts and cell somata. Some of the postsynaptic targets of both smaller and larger ChAT‐positive terminals were identified as belonging to retrogradely HRP‐labeled thalamostriatal neurons.These observations indicate that at least some thalamostriatal neurons within the CM‐Pf complex are innervated by cholinergic terminals which probably arise from ChAT‐positive cell bodies located within the pontomesencephalic tegmentum, particularly within the nucleus tegmenti pedunculopontinus and the laterodorsal tegmental nucleus. These findings provide evidence for direct influence by cholinergic brainstem nuclei over a

ISSN:0092-7317    

DOI:10.1002/cne.902770406

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractA conjugate of alpha‐bungarotoxin and a fluorescent marker (fluorescein isothiocyanate) has been used to localize “nicotinic” acetylcholine receptors on neurons in the outer plexiform layer of marine teleost retina. Toxin binding was confined to bipolar cell dendrites and to intermediate horizontal cells. The arrangement of labeled horizontal cells appears irregular inthe whole retina, with a peak density in the ventral and dorsal quandrants. Alpha‐bungarotoxin receptors on horizontal cells differ from those on bipolar cells and from those on dendrites in the inner plexiform layer in their sensitivity to agonists and antagonists such as d‐tubocurarine and nicotine. They consistute a different type of “nicotinic” receptor that probably has a diffe

ISSN:0092-7317    

DOI:10.1002/cne.902770407

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractWithin the cuneate nucleus of the raccoon, the representations of individual forepaw digits are anatomically separated by densely myelinated laminae. This unique arrangement was utilized to determine whether the terminations of cutaneous afferents from individual digits are precisely restricted to the appropriate region of the cuneate nucleus or overlap with afferents from adjacent digits. By using the transganglionic transport of horseradish peroxidase (HRP), it was found that, for each digit, the terminal labeling was restricted to the appropriate 150–250‐μm‐wide column that extended rostrocaudally throughout the nucleus. The topographical arrangement of digit input corresponded to the known electrophysiology, with the terminal column for the fifth digit located most medially within the nucleus and those for digits 4 to 1 successively more laterally. Within a column, the density of labeling was greater over cell clusters than between clusters. These results indicate that afferents from adjacent digits do not overlap in the cuneate nucleus. In six animals, the fifth digit was amputated, and 2–4 months later, HRP was injected into the nerves of the fourth digit to determine whether its afferents had sprouted into the denervated fifth‐digit column. The projection pattern from the fourth digit in each of these animals was the same as in normal animals and the same as in the intact contralateral side. These results indicate that the reorganization seen in the cerebral cortex following peripheral deafferentation cannot be attributed to changes in the afferent fiber projections to the cunea

ISSN:0092-7317    

DOI:10.1002/cne.902770408

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractAcetylcholinesterase (AChE)‐containing axons are the only extrinsic fibers projecting to the adult cortex that readily innervate embryonic cortical grafts up to normal densities without prior manipulation of the host brain. In the present paper we compare the time course of AChE‐positive fiber innervation in the normal mouse cortex with that seen in neocortical grafts by using AChE histochemistry as a marker for presumed cholinergic fibers. Donor tissue was taken at two different stages of gestation; before (embryonic days 12–14, or El2–14) and after (El7–19) the cortical plate is formed. Three features are analyzed: (1) the distribution and density of AChE‐containing fibers, (2) the presence of AChE‐positive cells, and (3) the distribution of butyrylcholinesterase (BuChE)‐positive elements.The modification of Koelle's method used for AChE localization showed AChE‐positive fibers in developing parietal neocortex as early as El8–19. The distribution of AChE‐labeled fibers in the normal cortex achieves the mature pattern by the end of the third postnatal week. The rate of innervation of transplants takes longer and depends on the age of the donor tissue. Tissue from both donor ages first showed AChE‐positive fibers crossing the host‐transplant interface by 7 days postsurgery. El7–19 tissue approaches the density of AChE‐positive fibers in the normal adult cortex by 15 weeks after grafting, whereas the El2–14 donor tissue does not approach normal innervation densities until after 20 weeks. While the degree of innervation in the El2–14 donor tissue never equalled the surrounding adult cortex within our range of survival times, a few of the El7–19 transplants did develop densities equal to that of the host cortex.AChE‐positive cells are first detectable in the normal parietal cortex on the day of birth, peak by the end of the first postnatal week, and then decline in number to the low levels of the mature cortex after the second postnatal week. Grafted cells in El2–14 tissue stain lightly for AChE by 7 days postsurgery, achieve maximal densities by 3 weeks, and become markedly reduced in number and density by 10 weeks. Cells in El7–19 tissue are lightly reactive by 7 days postsurgery, reach maximal numbers by 2 weeks postsurgery, and become similar in number and density to those seen in the mature cortex after 4 weeks. The appearance of BuChE‐reactive blood vessels, neurons, and glia in both normal development and in the transplants is described and discussed.These findings indicate that embryonic neocortical tissue implanted into adult neocortex becomes innervated by AChE‐positive fibers from the host brain at different rates depending on the age of the donor tissue. Cells within the transplants express AChE transiently, similar to cortical neurons during normal development. Possible roles for the cholinergic inputs to

ISSN:0092-7317    

DOI:10.1002/cne.902770409

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractThe present study was designed to assess whether cortical changes after peripheral nerve damage are related to the degree of death of primary sensory neurons in the damaged nerve. The cytotoxin ricin was injected into the sciatic nerves of adult rats to kill primary sensory neurons with axons through the injection site. Following periods of 6–101 days, the S‐I hindpaw map was evaluated with neurophysiological techniques and compared with the hindpaw maps of previously studied normal adult rats and adult rats that had undergone adult or neonatal sciatic section at a comparable level of the nerve. These comparisons allowed evaluation of cortical functional organization following different degrees of sensory neuron loss after sciatic nerve injury.There were three main results. 1) The comparison ofricin‐treatedandnormaladult rats indicated that ricin treatment interrupted inputs from the sciatic skin territory on the hindpaw and caused a limited increase in the size of the cortical area that was activated by stimulation of hindpaw skin innervated by the remaining saphenous nerve. 2) The cortical maps of rats that had undergone adultricin treatment(relatively large primary neuron loss) orsection during adulthood(small to moderate primary neuron loss) were similar. In both groups, only the saphenous hindpaw skin was represented in cortex, and the cortical area that was activated by stimulation of the saphenous hindpaw skin had undergone a comparable limited enlargement. 3) The comparison ofricin‐treatedadult rats (relatively large primary neuron loss) and adult rats that had undergoneneonatal section(relatively large primary neuron loss) indicated that cortical organization differed after these treatments. In particular, after ricin treatment the cortical area that was activated by stimulation of the saphenous hindpaw skin was larger than the comparable area in neonatal denervates, and the topographical progressions between the hindpaw and adjacent body representations were not as variable as after neonatal section.These findings indicate that cortical maps are altered after injection of ricin into a nerve. Thesimilarityin cortical organization after ricin treatment (relativelylargesensory neuron loss) and nerve section in adults (relativelysmallsensory neuron loss) and thedifferencesin cortical organization after ricin treatment and nerve section in neonates (both relativelylargesensory neuron loss) indicate cortical changes do not covary as a simple function of the degree of peripheral neuro

ISSN:0092-7317    

DOI:10.1002/cne.902770410

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY

摘要:

AbstractDuring specification of orderly neural maps, axons correctly navigate to their targets and form terminal arbors in topographically correct positions. To learn more about this mapping process, the patterns of geniculocortical topography were correlated with growth of axon arbors in the hamster visual cortex. Topography was studied by retrograde transport of WGA‐HRP from area 17 to the dorsal lateral geniculate nucleus (LGd) and visualized with TMB histochemistry. In separate experiments, geniculocortical axon arbors were filled with HRP deposited extracellularly into the optic radiations and stained with cobalt‐intensified DAB.On the day of birth (P0) and on P1–2, a crude topography was detected in the geniculocortical system. At these ages, geniculocortical axons coursed in the embryonic white matter of the visual cortex, parallel to the pia. During their passage, multiple short collaterals, with no terminal arbors, were extended into the subplate and deeper portions of the cortical plate. By P3–5, the topography was more precise and simple axonal arbors had now begun to be formed on some branches within the cortical plate. During the second postnatal week, branches in the white matter without terminals were eliminated and the ramifications of branches in the gray matter became more elaborate. The arbors continued to increase in complexity and resembled adult forms

ISSN:0092-7317    

DOI:10.1002/cne.902770411

出版商:Alan R. Liss, Inc.    

年代:1988

数据来源: WILEY