摘要:

AbstractAn understanding of the organization of cholinergic neurons in the central nervous system has been an important objective for many years. By developing and applying a new electronic method for mapping tissue sections, we have generated original graphic and quantitative findings on forebrain cholinergic neurons that provide new insight into their distribution and organization. Satoh, Armstrong, and Fibiger (Brain Res. Bull. 11:693–720, 1983) have proposed that in the basal forebrain cholinergic neurons with long axons form a continuum rather than being arranged as a series of discrete nuclear groups. It has been difficult, however, by conventional methods of data analysis and display, to test this hypothesis. By using a digital microscopy system, the position of every cholinergic neuron was marked with 1‐μm resolution in tissue sections taken at 90‐μm or 180‐μm intervals through the entire distribution of these neurons in the forebrain. The three‐dimensional reconstruction of these neurons in context shows them to be distributed as a continuous cell column. The column twists and changes position as it is deformed by adjacent neuronal structures, such that its shape and continuity would not be apparent without reconstruction into a computer graphics model. Complementary analyses of the distribution of cholinergic interneurons in dopamine‐rich regions of the forebrain indicated that there are regional differences between striatal and olfactory tubercle neurons. Cellular morphometry analyses show the population of cholinergic neurons in the rat to be surprisingly homogenous in size, but not in shape. Graphic and quantitative analyses indicated that there is a striking relationship between the distributions of projection and interneuronal cell groups.We conclude that the basal forebrain cholinergic neurons form a continuum. The chemoarchitecture of this cell group does not conform to the usual cytoarchitectural divisions. The present, results, however, taken together with the findings based on Nissl‐stained sections and connectional and biochemical data, suggest that the region of this neurochemically defined continuum should be reexamined for consideration as a single functional entity or nucleus: a cholinergic basal

ISSN:0092-7317    

DOI:10.1002/cne.902630302

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractCorticocortical connections within the primary somatosensory (SI) cortex of rat were investigated by using discrete injections of retro‐ and orthogradely transported neuroanatomical tracers (including HRP, WGA, PHAL, and3H‐leucine). Tangential and vertical connections were defined with respect to the cytoarchitectonic divisions within the rat SI, specifically: (1) the “granular zones” (GZs), characterized by their dense layer IV granular aggregates, which receive the majority of direct ventroposterior (VP) thalamocortical terminations, (2) the “perigranular zones” (PGZs), the less‐granular cortical matrix just surrounding the GZs, and (3) the “dysgranular zones” (DZs), the larger dysgranular regions lying centrally within and just lateral to the SI. Receptive fields recorded in the granular zones are small and discrete, whereas in the perigranular zones and especially in dysgranular zones they exhibit complex sensory convergence. A major aim of this study was to determine whether the pattern of intracortical connectivity within the SI is compatible with these observed physiological differences.In general, the perigranular and dysgranular zones contained more profuse systems of corticocortical connections than did the granular zones. For example, discrete tracer injections in the perigranular zones produced “walls” of labelling throughout the adjacent perigranular zones, while adjacent granular zones were relatively empty. Nevertheless, the granular zones were filled with dendritic branches of neurons in adjacent perigranular zones. Since these dendrites could presumably receive direct VP thalamocortical contacts, they represent one path through which this thalamic sensory information might be transmitted to the perigranular zones. Further transmission to the dysgranular zones might be subserved by a topographically organized system of reciprocal interconnections that was found between the perigranular zones and dysgranular zones.In coronal sections, labelling produced by relatively distant injections of either retro or orthograde tracers generally appeared in a columnar distribution, and was localized in perigranular zones and dysgranular zones. Within these zones, orthograde labelling consisted of vertically oriented axons emitting collateral sprays of terminals in all layers. Retrograde neuronal labelling (composed almost exclusively of pyramidal cells) was greatest in supragranular layers. Proximal to the injection site, labelling tended to spread out from these columns into supra‐ and infragranular layers in adjacent granular zones. The cellular basis for these connections was assessed by following single axons (filled by extracellular HRP or PHA‐L injections) for long distances through thick sections. Axons of layer III pyramids travelled in a U‐shaped trajectory, first ramifying locally, then descending to the deep cortical layers and ramifying further before coursing through deep cortical layers or white matter to their termination zones.It was concluded that neurons in the perigranular zones as well as the granular zones may receive VP thalamocortical information projecting to layer IV in the granular zones, and that this may be transmitted (I) to deep layers of adjacent granular zones and (3) to topographically more distant dysgranular zones. This is consistent with neurophysiological findinge that receptive fields are smallest in granular zone layer IV, and largest in layerV, and in all layers in perigranular zon

ISSN:0092-7317    

DOI:10.1002/cne.902630303

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe distribution of vasotocin (VT)‐immunoreactive neuronal perikarya and fibers in the canary (Serinus canaria) was investigated with immunohistological techniques. The results suggest that most VT‐stained cell bodies are located in three diencephalic regions. First, a large number of densely packed neurons are found in the paraventricular nucleus (PVN) and the anterior preoptic nucleus. Neurons here vary widely in size and shape. Small‐size rounded neurons and large‐size multipolar neurons appear to concentrate in separate subdivisions. Second, a series of loosely organized cell groups of medium‐ to large‐size cells occurs in the lateral parts of the hypothalamus. Those aggregates of neurons apparently correspond to subdivisions of the supraoptic nucleus (SON). Third, diffusely distributed, lightly stained cells are found dorsal to the paraventricular nucleus in the dorsal diencephalons. A number of cells of this group seem to be located in the basal septal area and bed nucleus of the stria terminalis. Immunoreactive fibers and varicosities concentrate in brain regions that are associated with neuroendocrine, autonomic, and limbic functions. Axons from the PVN and SON form compact bundles of the hypothalamohypophysial tract in the lateral hypothalamus and then funnel into the internal zone of the medium eminence (ME). Furthermore, a heavy innervation seems to be present in the pulisadal, external zone of the ME. A substantial number of fibers appear to leave the PVN toward extrahypothalamic areas. Most extrahypothalamic VT fibers innervate telencephalic and brainstem regions that are thought to be involved in mediation of limbic and autonomic functions. These areas include the lateral and medial septum, the lateral habenula, the subtantia grisea centralis, the area ventralis (Tsai), the locus coeruleus, raphe nuclei, the nucleus tractus solitarii, and lateral medulla. In addition, fibers with immunoreactivity for VT innervate structures such as the optic tectum and the nucleus ovoidalis that have been implicated in sensory processing of visual and auditory information. Finally, VT fibers and varicosities occur in centers including the nucleus robustus archistriatalis and nucleus intercollicularis that have been implicated in vo

ISSN:0092-7317    

DOI:10.1002/cne.902630304

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractA new method for determining the number of neurons in sectioned tissue is presented. The method does not involve identification of subcellular structures; rather, it uses estimates of the mean diameters of sections of the neuronal somata (with or without nuclei). All such sections are termed profiles. A mathematical model is developed to reconstruct the cell population from a size histogram of the profiles. Although the model is simple, the calculations are numerous and best done on a computer. A program that performs these calculations is provided. We discuss the idealizations on which the model is based and test the method in various ways: on hand‐ and computer‐generated data in which imaginary spheres of known size were sectioned; on two small samples of real cells for which both cell and profile size histograms were available; and on a sample of potatoes, sliced by hand. In every case the estimate was within 10% of the actual number of cells (or potatoes). The method is robust in that it is relatively insensitive to section thickness, sample size, somal morphology, and observer error with respect to missing the small or thin profiles from any given cell. Results from the present model are compared to those obtained by using other cell count correction schemes that are currently employed. We call our methodrecursive translat

ISSN:0092-7317    

DOI:10.1002/cne.902630305

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe retrograde and anterograde capabilities of the horseradish peroxidase (HRP) technique were employed to study frontal projections to the perioculomotor region in the rat. Following HRP microinjections or trans‐cannular HRP gel implants into the oculomotor complex (OMC), the majority of retrogradely labeled pyramidal cells were located in lamina V of the dorsomedial frontal shoulder cortex, i.e., medial precentral and anterior cingulate (PrCm/AC) cortices, the proposed frontal eye field (FEF) in the rat. A smaller number of labeled cells were present in the frontal polar cortex, agranular insular (AI), and lateral precentral (PrCl) cortices. Following HRP gel implants into the PrCM/Ac, anterogradely labeled projections were observed to the dorsal medial subthalamic region (nucleus campi Foreli, NCF) and medial accessory nucleus of Bechterew (MAB), and to other subcortical nuclei known to receive inputs from cortical area 8 in the monkey. These results, taken together with previous anatomical and physiological studies, support the conclusion that the PrCm/AC cortex contains the rat FEF. Its homo logy with the primate FEF is discusse

ISSN:0092-7317    

DOI:10.1002/cne.902630306

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe olfactory system of the frogRana esculentawas studied by using horseradish peroxidase (HRP) tracing of axonal pathways. Injections of HRP were made in the main olfactory bulb (MOB), accessory olfactory bulb (AOB), anterior olfactory nucleus (AON), the amygdala (AMY), and in a zone of the leteral wall of the telencephalic hemisphere immediately posterior to the AOB. Projections from these sites are described and are generally similar to those obtained by degeneration methods. However, HRP reveals more extensive olfactory connections than previously reported. Ipsilateral, contralateral, and bilateral projections arc described. The MOB, AOB, and AON have ipsilateral connections to each other. The MOB and AOB have very different projections. The MOB and AON project via the habenular commissure (HC) to the contralateral medial wall of the telencephalon. Ipsilateral MOB fibers also terminate in this cell‐free zone where the medial forebrain bundle (MFB) originates. The AOB projects to the lateral cortex of the contralateral telencephalic hemisphere via the HC and also to the ipsilateral AMY and lateral forebrain bundle (LFB) from where some fibers project contralaterally. HRP injections in the AMY retrogradely fill cells in the ipsilateral AOB, two nuclei of the ipsilateral hypothalamus and a nucleus of cells caudal to the ipsilateral nucleus isthmi. Fibers are also labeled that project to the contralateral AMY. Few fibers were observed to decussate in the interpeduncular nucleus or optic chiasma. No olfactory fibers were found to project to the habenular nuclei, and no labeled neurons were found to project to the olfactory bulbs. No morphological asymmetry was observed qualitatively in the distribution of olfactory fibers in the two halves of the brai

ISSN:0092-7317    

DOI:10.1002/cne.902630307

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractCholecystokinin (CCK) is a putative peptide neurotransmitter present in high concentration in the cerebral cortex. By using techniques ofin vitroreceptor autoradiography, CCK binding sites in primate cortex were labeled with125I‐Bolton‐Hunter‐labeled CCK‐33 (the 33‐amino‐acid C‐terminal peptide) and3H‐CCK‐8 (the C‐terminal octapeptide). Biochemical studies performed on homogenized and slide‐mounted tissue sections showed that the two ligands labeled a high‐affinity, apparently single, saturable site.Autoradiography revealed that binding sites labeled by both ligands were anatomically indistinguishable and were distributed in two basic patterns. A faint and diffuse label characterized portions of medial prefrontal cortex, premotor and motor cortices, the superior parietal lobule, and the temporal pole. In other cortical areas the pattern of binding was layer‐specific i.e., binding sites were concentrated within particular cortical layers and were superimposed upon the background of diffuse label. Layer‐specific label was found in the prefrontal cortex, anterior and posterior cingulate gyrus, somatosensory cortex, inferior parietal lobule, retrosplenial cortex, insula, temporal lobe cortices, and in the primary visual and adjacent visual association cortices.The areal and laminar localization of layer‐specific CCK binding sites consistently coincided with the cortical projections of thalamic nuclei. In prefrontal cortex, CCK binding sites were present in layers III and IV, precisely paralleling the terminal fields of thalamocortical projections from the mediodorsal and medial pulvinar nucleus of the thalamus. In somatosensory cortex, the pattern of CCK binding in layer IV coincided with thalamic inputs arising from the ventrobasal complex, while in the posterior cingulate gyrus, insular cortex, and retrosplenial cortex, layer IV and lower III binding mirrored the laminar distribution of cortical afferents of the medial pulvinar. CCK binding in layers IVa, IVc alpha, IVc beta, and VI of primary visual cortex corresponded to the terminal field disposition of lateral geniculate neurons, whereas in adjacent visual association cortex, binding in layers III, IV, and VI faithfully followed the cortical distribution of projections from the inferior and lateral divisions of the pulvinar nucleus of the thalamus.We interpret the diffusely labeled binding sites in primate cortex as being associated with the intrinsic system of CCK‐containing interneurons that are distributed throughout all layers and areas of the cortex. The stratified binding sites, however, appear to be associated with specific extrinsic peptidergic projections. The anatomical coincidence of layer‐specific CCK binding sited and thalamocortical terminal fields suggests that certain thalamocortical projection fibres either contain CCK or inte

ISSN:0092-7317    

DOI:10.1002/cne.902630308

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe development and distribution of substance P(SP) immunoreactivity were studied in the spinal cord and ganglia of embryonic and newly hatched chick by using the indirect immunofluorescence method. Substance P immunoreactivity was first detected in the spinal cord at embryonic stages 18–20 (incubation day 3). Before stage 32 (day 7), it was mainly found in regions corresponding to the dorsolateral funiculus and Lissauer's tract. Subsequently, SP fibers appeared in the dorsal horn. By stage 38 (day 11), they were demonstrated almost throughout the gray matter, but mostly in laminae I and II. During this period, however, many SP‐positive cells were found just ventral to the central canal at the thoracic level, although a few were also detected in other areas throughout the cord. In the white matter, very dense longitudinal SP fibers were observed in Lissauer's tract and the dorsolateral funiculus, where extremely dense plexuses of SP immunoreactivity were also detected around a group of nonimmunoreactive cell bodies. At later stages, no remarkable differences were noticed in the distribution of SP fibers, but the SP‐positive cells decreased gradually in number and disappeared after hatching. However, they reappeared following colchicine treatment. In the spinal ganglia, SP immunoreactivity appeared initially at stage 25 (day 4). It was mostly located in small neurons of the mediodorsal region. These cells also decreased in number from later stages but increased by colchicine treatment after hatching. The development and distribution of SP immunoreactivity in the spinal cord and ganglia were generally comparable at all levels examined, except where indi

ISSN:0092-7317    

DOI:10.1002/cne.902630309

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractIn the present investigation we have examined whether retinal axons can be directed to the superior colliculus via an alternate route when they do not have access to their normal substrates along the optic tract. To address this issue we transplanted embryonic mouse retinae into the mid‐brain parenchyma and to various positions around the outer surface of the midbrain of newborn rats and then examined the development of projections from the transplanted tissue. The projections from cortical grafts placed in the midbrain were studied to determine whether axons from different classes of neurons respond to the same cues for outgrowth.When retinae were placed within the midbrain close to the cerebral aqueduct, axons projected dorsally to the superficial layers of the superior colliculus. Directed outgrowth was seen from the earliest time a projection could be detected and was independent of whether the superior colliculus still received host optic afferents. In contrast, the major projection from similarly placed cortical transplants was directed toward the ventral part of the midbrain. Deafferentation of midbrain corticorecipient areas did not affect the projection patterns from either type of graft. Projections from retinae placed more ventrally in the midbrain tegmentum could not be detected. However, retinae placed on the surface of the midbrain, even as far ventral as the cerebral peduncle at the level of the inferior colliculus, always had a projection to the superior colliculus that ran along the brain‐stem surface.These observations, suggest that the superior colliculus exerts a positive influence on the growth of optic axons to the midbrain. However, while target cues appear to be able to support retinal axon growth through the midbrain parenchyma, their range appears to be limited, and at distances beyond the extent of their influence, optic fiber outgrowth occurs only over the surface of the brain. It is suggested, therefore, that there are both local surface‐related and target‐derived surface‐independent cues that guide optic axons to the tectum in developin

ISSN:0092-7317    

DOI:10.1002/cne.902630310

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902630301

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY