摘要:

AbstractThe neuronal cell types and their morphology in the nucleus basalis (NB), in the horizontal and vertical limbs of the diagonal band of Broca (NHL and NVL), and in the medial septal nucleus (MSN) were examined in Golgi‐impregnated material. Cells appeared as multipolar or oligopolar and displayed a variable dendritic morphology; their somata varied considerably both in shape and size. The dendrites of most cells were restricted within nuclear boundaries, although occasionally neurons located near boundaries, particularly cells in NHL, extended dendritic arbors into neighboring areas. Axons were rarely seen, but when they were found they were generally not impregnated beyond the initial segment and displayed no apparent preferential direction.Three types of cells common to each of the 4 nuclear groups could be identified on the basis of soma shape and dendritic form. The first type included large multipolar neurons with triangular or polygonal perikarya and typically 3–5 dendrites emerging from the poles of each cell. These cells were especially numerous in NB, NHL, and NVL, but were much less frequent in MSN. The second type comprised medium‐sized cells with round or oval somata and a small number, usually 2–3, of dendrites. They constituted a large percentage of the cell population in MSN, but were also encountered in NHL and NVL as well as in NB. The third type consisted of cells with fusiform or spindle‐shaped somata with usually single dendrites emanating from each pole of the cell. A rare but distinct type of spindleshaped neuron with dendrites bearing a rich complement of long and thin appendages was observed mainly in the ventral border of NHL.The present observations suggest that although the proportions and sizes of the 3 types of neurons vary between the 4 nuclei, neurons throughout the basal forebrain share common morphological charac

ISSN:0092-7317    

DOI:10.1002/cne.902720402

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

年代:1988

数据来源: WILEY

摘要:

AbstractAll neuronal cells in the dwarf male of the dimorphic polychaete speciesDinophilus gyrociliatuswere individually identified by means of serial ultrathin sections. Altogether 68 neural cells–including 40 sensory neurons and 2 glial cells–constitute a small but complex nervous system. Fifty‐three neural cells are located in three pairs of ganglia and connected by paired nerve cords. The prominent frontal ganglia, each consisting of a well‐developed neuropile and surrounded by 20 or 21 neural cells, represent the animal's brain. The ventral ganglia contain only 2 neurons each. The penis ganglia–four cells each–are associated with the copulatory organ. A conspicuous circumpenial fiber mass surrounds the basal part of the penis. The effector cells–22 multiciliated epidermal cells, 34 muscle cells, and different gland cells (?)–were also reconstructed and their innervation was partly elucidated. Sensory‐motor neurons were unambigously identified. They are discussed in regard to the small body size of the animal. The male's nervous organization resembles a very simple rope ladder and may represent a reduced derivative of a nervous system in normal‐sized males of monomorphic species. Similarities, however, also occur with the developing nervous system of a planktotrophic metatrochophore. The neuronal organization, with its two centers (frontal ganglia and ventral ganglia vs. penis ganglia and circumpenial fiber mass), accords well with the bipartite behavioral pattern, which is entirely devoted to locomotion and copul

ISSN:0092-7317    

DOI:10.1002/cne.902720403

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

年代:1988

数据来源: WILEY

摘要:

AbstractOur objective was to determine whether GABAergic and cholinergic basal forebrain neurons project to the neocortex. The retrograde connectivity marker wheat germ agglutinin lectin‐bound horseradish peroxidase was injected into the neocortex of adult cats. Histo‐ and immunohistochemical methods were combined to label sequentially connectivity and transmitter markers (glutamic acid decarboxylase; choline acetyltransferase) in forebrain neurons. The labels of each marker were identified by correlative light and electron microscopy.Two principal types of doubly labeled neurons were demonstrated. The connectivity marker was colocalized with glutamic acid decarboxylase or choline acetyltransferase. The neurons were located in the basal forebrain. Their ultrastructural, cellular, and regional organization supported 2 conclusions. (1) GABAergic basal forebrain neurons project to the neocortex. This is important new morphological evidence for the origin of inhibitory neocortical afferents from a subcortical brain site. (2) The GABAergic and cholinergic basal forebrain neurons projecting to the neocortex exhibit remarkable structural similarities. The transmitter diversity of these intertwined neocortical afferents may be significant for the pathology and treatment of human neurological disorders such as Alzheimer's dise

ISSN:0092-7317    

DOI:10.1002/cne.902720404

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

年代:1988

数据来源: WILEY

摘要:

AbstractUnilateral lesions of the right cochlea were made in ferrets aged postnatal day (P)12 to P93. The extent of the lesions was assessed by counting remaining hair cells and ganglion cells in midmodiolar sections through the lesioned cochleas and by comparison with a sample of unlesioned cochleas. The neural effects of the lesions were assessed by measuring the volume of each cochlear nucleus (CN) and by counting the number of neurons in each CN that were retrogradely labeled following injections of WGA‐HRP in the left inferior colliculus (IC). Survival times between lesioning and injection of the tracer ranged from 11 to 98 days. CN volume and projections to the IC were also measured in a sample of normal adult ferrets and in normal infants aged P39 to P80.Cochlear lesions resulted in a reduction of the volume of the CN on the lesioned side, relative to the other CN, in animals of all ages and survival times. The extent of the CN volume reduction was negatively correlated with the number of remaining cochlear ganglion cells. However, even where the number of ganglion cells was within the normal range, significant volume reductions occurred. The ventral CN was more severely affected by the lesions than the dorsal CN, but no difference was found between the anteroventral and posteroventral divisions of the nucleus. There was no significant difference in the extent of CN volume reductions between animals of different ages or survival times.Lesions of the right cochlea in younger animals (P14 to P24) resulted, after 90 days survival, in an increase in the number of left CN neurons projecting to the left IC. No significant increase was seen following lesions in older (P90) ferrets or following short (11 or 30 days) survival times in young (P14 to P24) ferrets. The extent of the increase in the ipsilateral CN‐IC projection was not related to the number of remaining ganglion cells or to the division of the CN examined. Lesions did not affect the contralateral CN‐IC projection.We conclude that cochlear lesions in infant ferrets can alter auditory brainstem morphology and connectivity. The dependence of these alterations on the age of the animal, survival time following lesion, and extent of the lesion varies markedly with the index exa

ISSN:0092-7317    

DOI:10.1002/cne.902720405

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe distribution of neurotensin immunoreactivity in the basal ganglia of the adult rat was evaluated by studying alternate serial vibratome sections that were exposed to antiserum against neurotensin, substance P, or cholecystokinin. It was observed that a heterogeneous distribution of neurotensin‐immunoreactive fibers and terminals contributes to the neurochemical compartmentation of the ventral pallidum and ventral striatum, and that significant numbers of neurotensin‐immunoreactive neurons occupy striatal districts of the olfactory tubercle, nucleus accumbens, and ventromedial caudate‐putamen. An intense band of pallidal neurotensin immunoreactivity characterizes the medial part of the ventral pallidumadjacentto the nucleus accumbens, whose medial boundary is conveniently defined in sections incubated with cholecystokinin antiserum. Electron microscopic studies showed that the pallidal plexus of neurotensin‐immunoreactive elements consists primarily of boutons, which contact large dendrites in arrangements that in all respects appear to be of the classical striatopallidal variety. A gradual decrese in immunolabel was observed approaching the lateral parts of the ventral pallidum, which display sparse neurotensin immunoreactivity. The results thus indicate the existence of a significant neurotensinergic striatopallidal pathway confined primarily, if not exclusively, to the medial part of the ventral striatopallidal system. The contribution of neurotensin‐immunoreactive fibers and terminals to the compartmentation of ventral striatum is expressed most vividly in their exclusion from clusters of tightly packed medium‐sized neurons, many of which are intensely substance P immunoreactive. Such clusters appear identical with those previously described as rich in opiate receptors and poor in acetylcholinesterase activity. In the ventral striatal region where the nucleus accumbens and ventromedial caudate‐putamen merge, neurotensin‐immunoreactive neurons are organized in clusters. Further rostral in the nucleus accumbens, they are more evenly distributed. Few were found in the dorsolateral quadrant of

ISSN:0092-7317    

DOI:10.1002/cne.902720406

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

年代:1988

数据来源: WILEY

摘要:

AbstractEmbryonic neocortical tissue survives and differentiates when grafted to injured adult neocortex. While these transplants are readily innervated by the host cholinergic fibers, specific thalamic fibers fail to innervate them. The present study was designed to test whether changing the activity levels of the thalamic ventrobasal projection neurons would promote sprouting of their axons into the embryonic cortical implants placed in the barrel field cortex. To achieve this the main input to the these thalamic neurons was eliminated two synapses away, by blocking the peripheral sensory input to the barrel field cortex. Adult hosts underwent unilateral transection of the infraorbital nerve and two days later the contralateral barrel field cortex was lesioned enough to insert an embryonic neocortical graft. Following a one month post‐transplantation period we examined the amount of specific thalamic axon ingrowth into the transplants by injecting the ventrobasal nucleus with horseradish peroxidase. The control cases without prior nerve damage confirmed previous observations that ventrobasal nucleus neurons fail to innervate the implanted neocortex. Transection of the infraorbital nerve prior to transplantation resulted in an unprecedented ingrowth of specific thalamic axons into the transplants. There was no significant difference in the amount of thalamic fiber ingrowth into the transplants when the peripheral nerve was (transection) or was not (cautery) allowed to regenerate. However, transection of the infraorbital nerve permits the nerve to regenerate and at least partially reconnect the sensory periphery, thus leading to the possibility of functional integration of the neocortical transplants into the host trigeminal system.The morphology and distribution of host acetylcholinesterase‐positive fibers that grow into the transplants under both experimental and control conditions were distinctly different from those of thalamic axons. These results provide the first demonstration of peripheral sensory nerve induction of regenerative propensity in specific thalamocortical projection neurons. The thalamic fiber ingrowth should lead to enhanced functional innervation of the neocortical implants and better incorporation of the graft into the adult host brain circui

ISSN:0092-7317    

DOI:10.1002/cne.902720407

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe monoamine innervation of the organum vasculosum laminae terminalis (OVLT) was examined in the adult rat by light and electron microscope radioautography after intraventricular administration of tritiated serotonin ([3H]5‐HT) or dopamine ([3H]DA). Radioautographic and biochemical controls after 5,7‐dihydroxytryptamine or 6‐hydroxydopamine lesioning established the respective serotonin (5‐HT) and catecholamine (CA) identities of the axonal varicosities labeled under the conditions of the present experiments. For descriptive purposes, the OVLT was subdivided in three parts: two parenchymal zones, one juxtaventricular, the other juxtavascular, and the vascular core. Almost 10% of all axonal varicosities in the OVLT were found to be labeled with [3H]5‐HT. This 5‐HT innervation was most prominent in the rostrocaudal and ventrodorsal portions of the juxtaventricular zone and the dorsal aspect of the juxtavascular zone; there was none in the vascular core. [3H]DA‐labeled varicosities were much less abundant and yet more numerous than earlier histofluorescent and immunohistochemical studies would have predicted. They predominated in the juxtavascular zone, where a majority presumably had a dopamine (DA) rather than a noradrenaline identity. Some were also found in the vascular core, where they most likely corresponded to peripheral autonomic noradrenaline endings. In the juxtaventricular zone of the OVLT, a significant proportion of the [3H]5‐HT‐labeled varicosity profiles could be observed to form axodendritic synapses, but in the juxtavascular zone no 5‐HT or any [3H]DA‐labeled ones were ever seen in synaptic junction. In the juxtavascular zone, the 5‐HT and the presumed DA endings established close relationships with neurosecretory axons, and with astrocytic or tanycytic processes on which they occasionally formed “synaptoid contacts.” A few endings of either type were also seen to abut directly on the outer basement membrane of the perivascular space. It therefore appears probable that in OVLT monoamines influence neural and nonneural elements. At a proximal level of regulation (juxtaventricular zone), 5‐HT could act both synaptically and nonsynaptically as an interneuronal transmitter or modulator. In contrast, distally (juxtavascular zone), both DA and 5‐HT could be released as neurohormones in addition to modulating neurosecretion. 5‐HT and DA varicosities in the OVLT could also behave as sensors for circulating factors that do

ISSN:0092-7317    

DOI:10.1002/cne.902720408

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe tree shrewTupaia belangerihas three functional pathways (ON‐center, OFF‐center, and W‐like cells) that arise in the retina and proceed through separate LGN laminae to separate cortical targets. To determine whether these pathways have consistent differences in activity, cytochrome oxidase (C.O.) patterns were examined in the retina, LGN, and striate cortex. In six normal tree shrews the outer and inner plexiform layers of the retina were highly reactive for C.O. A pale, vascularized cleft zone separated the a (OFF) and b (ON) inner plexiform sublaminae, which seemed about equally reactive for C.O. In the LGN, laminae 1 and 2 (ON‐center cells) and laminae 4 and 5 (mostly OFF‐center cells) were highly reactive for C.O. LGN lamina 3 and 6 are part of an W‐like afferent pathway. Lamina 3 was distinctly paler than laminae 1, 2, 4, and 5 while lamina 6 was intermediate. In the striate cortex, layer IV was the most reactive layer. Sublayer IVb (predominantly an OFF region) was consistently more reactive than sublayer IVa (predominantly ON). The middle portion, layer IVm, was paler than either IVa or IVb. This pale region includes, but extends above and below, the cell‐sparse “cleft” region. Thus, considering all three levels of the retinogeniculostriate pathway, the ON and OFF systems were equally active until they reached the striate cortex, where the OFF system appeared to be more active than the ON. The W‐cell laminae in the LGN exhibited the lowest level of activity.The contribution of ganglion cell activity to these patterns was assessed by intravitreal administration of tetrodotoxin (TTX) blockade either monocularly (three animals) or binocularly (two animals). In the TTX‐treated retinae, the inner plexiform a and b sublaminae were paler for C.O., although visible, and were still separated by the pale cleft. The ganglion cell layer was very pale in comparison to the normal. In the LGN, monocular TTX blockade reduced the C.O. reactivity in the ON and OFF laminae that received input from the treated eye but had little effect on the W‐like cell laminae. The ipsilaterally innervated ON and OFF laminae were more affected than were the contralaterally innervated laminae. Binocular TTX treatment resulted in a decrease of C.O. activity in the binocular segment of the ON and OFF LGN laminae.In the striate cortex, the most marked changes following TTX treatment occurred in layer IV. As in the LGN, the effects of monocular TTX were greater ipsilaterally than contralaterally. In the hemisphere contralateral to the treated eye, sublayers IVa and IVb were paler than the normal but the general pattern remained the same. Ipsilateral to the TTX‐treated eye, the decrease in C.O. reactivity was especially marked in lower IVa and upper IVb adjacent to IVm, giving the appearance that the middle pale zone had widened. Bilateral TTX also reduced the reactivity in layer IV. However, the pattern resembled that seen ipsilateral to monocular TTX treatment. In all cases, whether monocular or binocular TTX, sublayer IVb remained slightly more reactive than IVa. Four saline control animals showed basically normal C.O. patterns throughout the visual system, as did three animals that recovered for 2 months after 2 weeks of TTX administration.The TTX‐produced reduction in C.O. activity in the striate cortex suggests a model of geniculocortical input in which (1) ipsilateral eye inputs to layer IVa and IVb produce a greater postsynaptic C.O. activity level in the lower portion of IVa and the upper portion of IVb adjacent to IVm; (2) contralateral‐eye inputs predominate in producing the C.O. activity in upper IVa and lower IVb; and (3) the ipsilateral pathway suffers a greater decrease in activity following retinal impulse blockade than d

ISSN:0092-7317    

DOI:10.1002/cne.902720409

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe hypothalamus provides a major projection to the spinal cord that innervates primarily lamina I of the dorsal horn and the sympathetic and parasympathetic preganglionic cell columns. We have examined the chemical organization of the neurons that contribute to this pathway by using combined retrograde transport of fluorescent dyes and immunohistochemistry for 15 different putative neurotransmitters or their synthetic enzymes. Our results demonstrate that 5 cytoarchitectonically distinct cell groups in the hypothalamus contribute to the spinal projection and that each has its own predominant chemical types. In the paraventricular nucleus, substantial numbers of hypothalamo‐spinal neurons stain with antisera against arginine vasopressin (25‐35%), oxytocin (20‐25%), and metenkephalin (10%). About 25% of the neurons with spinal projections in the retrochiasmatic area stain with an antiserum against α‐melanocyte‐stimulating hormone. Nearly 100% of the hypothalamo‐spinal neurons in the tuberal lateral hypothalamic area stain with this same antiserum, but these cells do not stain for other proopiomelanocortin‐derived peptides, and so probably contain a cross‐reacting peptide. This population must be distinguished from an adjacent cell group, in the perifornical region, where many spinal projection neurons stain with antisera against dynorphin (25%) or atrial natriuretic peptide (20%). Finally, in the dorsal hypothalamic area as many as 55‐75% of the neurons with spinal projections are dopaminergic, on the basis of their staining with an antiserum against tyrosine hydroxylase.These 5 neurochemically distinct projections from the hypothalamus to the spinal cord are discussed in the context of their possible funct

ISSN:0092-7317    

DOI:10.1002/cne.902720410

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe structure and distribution of synapses on nonspiking local interneurones in the metathoracic ganglion of the locust was revealed by electron microscopy following intracellular injection of horseradish peroxidase (HRP). Before staining, each interneurone was characterized physiologically as nonspiking and its output effects on motor neurones innervating muscles in a hindleg were investigated. Three nonspiking interneurones of different morphologies, each typical of a previously described population, were selected for detailed study. The first has a dorsal soma and ipsilateral neuropilar branches, the second a ventral soma and ipsilateral branches, and the third a ventral soma and contralateral branches. The somata have few trophospongial invaginations, and most of their volume is occupied by the nucleus. The initial parts of the primary neurites are either wrapped in glia or isolated in tracts from the neuropile and thus do not participte in synaptic interactions. Some of the larger secondary neurites are also wrapped in glia, but others both make and receive synaptic contacts. Output synapses have an array of some 500–1,600 round, agranular vesicles (diameter 47.0 ± 5.7 nm; mean ± S.D., n = 97) associated with a bar‐shaped presynaptic density up to 0.3 μm long. Two postsynaptic processes, whose diameter can vary greatly, are usually associated with each presynaptic density. Processes making input synapses onto nonspiking local interneurones typically contain round, agranular vesicles and often make several contacts within a few microns. Serial reconstructions from one of the interneurones revealed input and output synapses intermingled on the larger processes with outputs dominating by a factor of 3:1, whereas on some of the thinner processes only input synapses are present. In the other two interneurones, however, both input and output synapses are present on the fine branches. No feature of the structure or distribution of synapses observed here on the nonspiking local interneurones distinguishes them from spiking neurones in the same g

ISSN:0092-7317    

DOI:10.1002/cne.902720411

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

年代:1988

数据来源: WILEY