摘要:

AbstractSpiking local interneurones in the metathoracic ganglion of the locust have two fields of neuropilar branches linked by a single process. One, with numerous fine neurites of relatively uniform diameter, is in a ventral area of neuropile where the afferents from hairs on a hind leg also terminate. The other, with sparser and varicose neurites, is in a more dorsal area of neuropile where the motor neurones of the leg muscles have many neurites. Physiological studies have shown that these interneurones receive direct inputs from some hair afferents and in turn synapse directly upon some leg motor neurones (Burrows and Siegler, '82; Siegler and Burrows, '83). The distribution of synapses in these two fields was revealed by injecting HRP intracellularly into an interneurone following its physiological characterization. In theventralfield, the majority of synapses are input synapses. Many are from profiles with round agranular vesicles of similar diameter to those of known afferents. Other presynaptic profiles contain pleomorphic agranular, or large round granular, vesicles. There are also some output synapses, each with only a small population of vesicles. Most input synapses are made onto small‐diameter neurites, whereas the majority of outputs are made from the larger‐diameter neurites. In thedorsalfield, the majority of synapses are output synapses. They are made from vesicle‐filled varicosities onto postsynaptic profiles of small diameter. A single varicosity can be the site of many output synapses. Input synapses are few in number, but occur close to the output synapses. The absence of varicosities in the ventral field cannot therefore be correlated with a lack of output synapses and while the dorsal varicosities can be the sites of output, they can also receive input syn

ISSN:0092-7317    

DOI:10.1002/cne.902400302

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe morphology of eightnonspikinglocal interneurones in the metathoracic ganglion of the locust is described in relation to known tracts, commissures, regions of neuropile, and identified motor neurones. They are compared with thespikinglocal interneurones in the same ganglion. Each nonspiking local interneurone was injected intracellularly with cobalt, following characterization of its physiological effects on identified leg motor neurones. The shapes of the nonspiking interneurones are diverse, although all have processes restricted to one ganglion and lack an axon. Their cell bodies are distributed in the ventral and dorsal cortex of the ganglion. Interneurones with cell bodies in similar places have similar basic structures, with primary neurites in the same commissure or tract, and major branches in the same tracts. The fine branches of all the interneurones have the same texture throughout, and occur in the same lateral region of neuropile, dorsal to the prominent neurite of the fast extensor tibiae motor neurone. Some interneurones have branches that extend both to the midline and to the dorsal boundary of the neuropile, but none have branches in the ventral, medial neuropile. This distribution of branches corresponds with two known features of the physiology of these interneurones: (1) they make what appear physiologically to be direct connections with motor neurones, and have branches in the same region of the neuropile as the motor neurones. (2) They do not appear to receive direct inputs from hair afferents, and they have no branches in the ventral neuropile to which these afferents project.

ISSN:0092-7317    

DOI:10.1002/cne.902400303

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

年代:1985

数据来源: WILEY

摘要:

AbstractTwelve retrogradely horseradish peroxidase (HRP)‐labelled triceps surae motoneurons of gamma size (mean cell body diameter<38 μm) were studied ultrastructurally. The contours of the cell bodies, as observed in the transverse midnucleolus plane, were elongated to rounded. The axons identified all originated from the cell body. The mean diameter of the stem dendrites was 4.5 μm.A substantial part of the cell membrane was covered by glial extensions. The boutons and synaptic contacts apposing the γ‐motoneurons could be classified into two categories on the basis of the the type of synaptic vesicles: S‐type boutons with spherical synaptic vesicles and F‐type boutons with flattened vesicles. In each neuron, the values for mean length and mean area of apposition, percentage synaptic covering, and packing density of S‐type, F‐type, and S + F‐type boutons were estimated on the cell body and in two dendritic compartments. In comparison with α‐motoneurons and Renshaw cells, the cell bodies of the γ‐motoneurons were covered by smaller and strikingly fewer boutons of both the S‐ and F‐types. The values for percentage synaptic covering and packing density of boutons on the proximal dendrites were also lower for γ‐motoneurons than for both α‐motoneurons and Renshaw cells, although the differences were less pronounced than on the cell body. No boutons of the C‐, M‐, and T‐types described for α‐mo

ISSN:0092-7317    

DOI:10.1002/cne.902400304

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe present study delimits the relationship of primary trigeminal afferents to their targets, the brainstem trigeminal nuclei of the neonatal rat. Previously, the brainstem trigeminal complex of the rat has been subdivided on the basis of either cytoarchitectonics or patterns of succinic dehydrogenase activity into the principal sensory nucleus and the three subnuclei of the spinal trigeminal nucleus, oralis, interpolaris, and caudalis. In this paper, we demonstrate that each of these subdivisions can also be identified by its pattern of primary trigeminal afferents. In addition, we demonstrate that the terminations of these afferents are distributed in a punctate fashion which correlates with vibrissae‐related patterns of histochemical staining. Further, vibrissae removal in the neonatal rat at any age studied results in a corresponding deafferentation of both the principal sensory nucleus and all subnuclei of the spinal trigeminal nucleus. This same procedure has a graded, age‐dependent effect on the vibrissae‐related pattern of cytochrome oxidase staining in somatosensory cortex. On this basis, we conclude that vibrissae‐related pattern formation in the central trigeminal system can be best understood in terms of a single “sensitive” period for the entire system. We hypothesize that this is the period during which an interaction normally occurs between primary trigeminal afferents and target neurons of the principal sens

ISSN:0092-7317    

DOI:10.1002/cne.902400305

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

年代:1985

数据来源: WILEY

摘要:

AbstractSomatostatins are a brain peptide family centered on a 14‐amino acid cyclic peptide (SS‐14) and a 28‐amino acid N‐terminally extended form (SS‐28). Using radioiodinated analogs of SS‐14 and SS‐28, we have identified specific binding sites in rat and human brain sections that display pharmacological properties anticipated for somatostatin receptors and discrete patterns of anatomical localization. High binding densities are found in many forebrain regions, with special densities in infragranular cerebral cortical laminae in rat and human brain. In the rat, other densities lie in olfactory zones, lateral and triangular septal nuclei, the CA‐1 hippocampal region, and claustrum with moderate densities in the striatum. Discrete hypothalamic areas, especially the median preoptic, paraventricular, and periventricular nuclei, display elevated binding levels, while the thalamus shows only scattered areas of modest binding. Midbrain receptor concentrations are found in portions of the periaqueductal gray, interpeduncular nucleus, and the substantia nigra. Notable pontine and medullary densities lie in the locus coeruleus, fourth ventricular floor, parabrachial, solitary, prepositus hypoglossal, dorsal column, and caudal trigeminal zones. Although the cerebellar cortex shows unimpressive densities, each of the deep cerebellar nuclei is heavily labeled. Modest spinal cord receptor densities are concentrated in the substantia gelatinosa and central cord regions.These localizations show many parallels with the distributions of SS‐immunoreactive neurons, fibers, and terminals determined previously by immunohistochemistry. They provide plausible loci for several reported physiological or pharmacological activities of the SS‐peptides, and may improve understanding of the role of the SS alterations described in several human neurodeg

ISSN:0092-7317    

DOI:10.1002/cne.902400306

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

年代:1985

数据来源: WILEY

摘要:

AbstractNissl, Golgi and fibre preparations were made of the cerebral cortex of the lateral gyrus of the bottlenose dolphin (Tursiops truncatus)in the region where visual evoked potentials have been reported (Sokolov et al., '72; Ladygina et al., '78). In the adult the visual cortex is relatively thin (average about 1,300 μm) for so large a brain (fixed brain weight for a typical adult in our series was 1,330 g). Layers I, III, and VI are wide and represent three‐quarters of the total cortical thickness. Layer I contains few cell bodies, while III and VI have a variety of pyramidal and nonpyramidal neurons. Layers II and V are narrow and contain striking palisades of darkly staining pyramidal cells that are particularly large in layer V. No clearly demarcated layer IV is present in the adult dolphin visual cortex. Many of the neurons identified with the Golgi technique are typical of pyramids in other mammals, with a single apical dendrite and a bouquet of basal dendrites, mostly highly spiny. Others are unusual in having bifurcated or oblique apical dendrites. Typical large and small spiny and nonspiny stellates are also found, mainly in layers III and VI. In addition various forms of spindle‐shaped, bipolar and multipolar neurons are found in most layers.An 18‐day‐old brain shows signs of immaturity in its visual cortex. It is thinner (970 μm) and on average its neurons are smaller, paler, and more densely packed. Especially the pyramids of layer V are much smaller than in the adult. Also, a distinct “granular” band occurs between layers III and V and seems to be a rudimentary layer IV. At 3 years of age most of the adult features have developed, but layer IV is still detectable.No striking differences were observed in cell and fibre architecture between the cortex of the lateral gyrus and that of the so‐called “calcarine” area that has also been considered as “visual.”We conclude that, although different in many respects from other mammalian visual cortices, that of the dolphin is apparently well devel

ISSN:0092-7317    

DOI:10.1002/cne.902400307

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

年代:1985

数据来源: WILEY

摘要:

AbstractPairs of injections of different neuroanatomical tracers–peroxidase‐conjugated wheat‐germ agglutinin (WGA) and [3H]proline–were made into the lateral geniculate nucleus (LGN) of the cat, and the course of the labeled fibers in the optic radiation was reconstructed. When the two injections were widely separated in the rostrocaudal dimension of the LGN (i.e., one in the representation of the lower quadrant of the visual field and one in the upper quadrant), the two sets of labeled fibers also remained separated in the long (roughly rostrocaudal) axis of the optic radiation. When the injections were widely separated in the mediolateral dimension of the LGN (i.e., one at the representation of the area centralis and one on the horizontal meridian in the far periphery of the field), the two sets of labeled fibers were separated in the short (mediolateral) dimension of the radiation. Shortly before reaching area 17, however, the medially and laterally placed fibers exchanged positions. This crossing is the basis of the topological inversion in the optic radiation deduced previously by Connolly and Van Essen (J. Comp. Neurol.226:544–564, '84). The retinotopic organization of fibers in the radiation is less precise (in either dimension) than that of their terminal arborizations in visual cortex, but even injections as close as 1 mm to each other gave rise to spatially distinct fiber distributions. The WGA injections also labeled the corticogeniculate fibers by retrograde transport; these fibers traveled in a separate pathway medial to the optic

ISSN:0092-7317    

DOI:10.1002/cne.902400308

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

年代:1985

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902400301

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

年代:1985

数据来源: WILEY