摘要:

AbstractDifferent subpopulations of GABA neurons containing the neuropeptides somatostatin and neuropeptide Y, and the calcium binding protein parvalbumin were studied by immunocytochemistry using light and electron microscopy in the dorsomedial cortex of the lizardPsammodromus algirusto investigate the connectivity of different subsets of GABA neurons in the lizard dorsomedial cortical circuitry and to compare cortical regions of reptiles and mammals. GABA neurons were classified into different subsets by using the peroxidase anti‐peroxidase immunohistochemical method on adjacent Araldite‐embedded semithin sections. GABA neurons in the dorsomedial cortex fall into three major subsets: (1) neurons with somatostatin (and neuropeptide Y), which accounted for about 44% of the GABA population; (2) neurons with parvalbumin, which accounted for about 13% of the GABA neurons; and (3) neurons without parvalbumin or neuropeptides, which represented 40% of all GABA cells. This division of GABA neurons in non‐overlapping subpopulations of neuropeptide‐ and parvalbumin‐containing cells is similar to that found in the mammalian hippocampal formation. On the basis of the nerve terminal fields, somatostatin‐ and parvalbumin‐immunoreactive neuronal populations appear to be functionally different, acting on different portions of the projection neurons. Parvalbumin‐immunoreactive neurons inhibit the pyramidal neurons at the cell body level, whereas somatostatin‐immunoreactive neurons inhibit them on distal dendrites. The results of the present study add more similarities between the lizard dorsomedial cortex and parts of the mammalian hippocampus. © 19

ISSN:0092-7317    

DOI:10.1002/cne.903360202

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractPostembedding immunocytochemistry was used to determine the cellular localization of the amino acid neurotransmitters glutamate, aspartate, gamma‐aminobutyric acid (GABA), and glycine in the avian retina. The through retinal pathway was glutamatergic, with all photoreceptors, bipolar cells, and ganglion cells being immunoreactive for glutamate. Bipolar cells displayed the highest level of glutamate immunoreactivity, with the cell bodies terminating just below the middle of the inner nuclear layer. All lateral elements, horizontal cells, amacrine cells, and interplexiform cells were immunoreactive for glycine or GABA. The GABAergic neurons consisted of two classes of horizontal cells and amacrine cells located in the lower part of the inner nuclear layer. GABA was also localized in displaced amacrine cells in the ganglion cell layer, and a population of ganglion cells that co‐localize glutamate and GABA. Both the horizontal cells and GABAergic amacrine cells had high levels of glutamate immunoreactivity, which probably reflects a metabolic pool. At least two types of horizontal cells in the avian retina could be discriminated on the basis of the presence of aspartate immunoreactivity in the H2 horizontal cells. Glycine was contained in a subclass of amacrine cells, with their cell bodies located between the bipolar cells and GABAergic amacrine cells, two subclasses of bipolar cells, displaced amacrine cells in the ganglion cell layer, and ganglion cells that colocalize glutamate and glycine. Glycinergic amacrine cells had low levels of glutamate. We have also identified a new class of glycinergic interplexiform cell, with its stellate cell body located in the middle of the inner nuclear layer among the cell bodies of bipolar cells. Neurochemical signatures obtained by analyzing data from serial sections allowed the classification of subclasses of horizontal cells, bipolar cells, amacrine cells, and ganglion cells. © 1993 Wiley‐Lis

ISSN:0092-7317    

DOI:10.1002/cne.903360203

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe descending spinal projecting system of the lamprey is of interest because it includes axons that activate swimming pattern generatorsand because regeneration of this system is involved in the behavioral recovery of lampreys following spinal transection. However, little is known about the true size of this projection and of the distribution of its terminations along the spinal cord. Brain neurons with spinal projections were studied in larval sea lampreys by using wholemount preparations labeled retrogradely with horseradish peroxidase (HRP) from spinal injections at 10%, 15%, 25%, 50%, 70%, and 75% of body length from the anterior end. Neurons projecting to different levels of the spinal cord were mapped. A large number of descending axons terminated within nine segments caudal to the last gill. The spinal projection system was divided into 10 bilateral groups based on cytoarchitectural landmarks. All of the lateral nuclear groups had contralateral spinal projections. In addition to the 12 pairs of Müller cells, the pair of Mauthner cells, and the pair of auxiliary Mauthner cells described by previous authors, the study revealed four pairs of smaller neurons that were individually identifiable. © 1993 Wiley‐Liss,

ISSN:0092-7317    

DOI:10.1002/cne.903360204

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractSeveral areas on the medial surface of the frontal lobe in both monkeys and humans, including the supplementary motor area and specific areas within the ventral bank of the cingulate sulcus called the cingulate motor areas, have been implicated in the initiation and execution of skiled movements. These areas project directly to the motor cortex and spinal cord, and, on this basis alone, can be considered premotor areas. The present study investigated whether these premotor areas are specific targets of prefrontal cortical projections in the rhesus monkey and thereby provide links between this association cortex and motor effector pathways. Circumscribed injections of wheat germ agglutinin‐conjugated horseradish peroxidase were placed into different cytoarchitectonic subdivisions of prefrontal cortex, and resultant retrograde and anterograde labeling examined with respect to designated premotor targets. Conversely, injections were also made in the supplementary and cingulate motor areas and labeled cells and terminals charted in the prefrontal cortex.A principal finding in this study is the identification of multiple prefrontal regions that project to the supplementary motor area, the cingulate motor areas, or both. Areas 46, 8a, 9, 11, and 12 are reciprocally connected with an area of the superior frontal gyrus in or near the supplementary motor area at its rostral margin. A smaller constellation of prefrontal areas, areas 46, 8a, and 11, is reciprocally connected with portions of cingulate cortex that have been classified as premotor arm and/or leg representations (Hutchins et al., Exp Brain Res 71:667–672, 1988). In accordance with numerous previous reports, prefrontal areas 46, 8a, 9, 10, 11, and 12 are reciprocally connected with “nonmotor” subdivisions of cingulate cortex.The results presented here specify the corticocortical connections by which prefrontal cortex may influence motor output. © 1993 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903360205

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe intracortical synaptic relationships of pyramidal neurons in the cat motor cortex were studied by intracellular recording and labeling techniques. Neurons that responded with monosynaptic excitatory postsynaptic potentials (EPSPs) to microstimulation in the somatosensory cortex were identified by intracellular recordings. Long‐term potentiation (LTP) was evoked in all of these neurons (n = 15), following tetanic stimulation (50 Hz, 5 s) of their afferents from the somatosensory cortex. Three of these cells (cells A‐C) were identified as pyramidal neurons, following intracellular injections of Neurobiotin. The intracortical axon collaterals of these labeled cells arborized extensively, forming terminal clusters both in clse proximity to the parent soma and along their long, horizontal branches. Terminal clusters in both the proximal and in the distal termination zones of each of the cells were studied by electron microscopy. In their proximal arborization zones, the axon collaterals of the labeled pyramidal neurons synapsed preferentially with dendritic spines belonging to other pyramidal cells. In contrast, in their distal terminal clusters, the axon collateals of each of the cells formed synapses in different proportions with different postsynaptic targets. The distal axon collaterals of cell A formed 86% of their synapses with pyramidal neurons; those of cell B formed 64% of their synapses with pyramidal cells, the remaining synapses with the dendritic shafts and somata of nonpyramidal neurons, and those of cell C provided most of their output (68%) to nonpyramidal, presumably inhibitory neurons. These findings suggest a high selectivity of intrinsic axon collaterals to form specific patterns of synapses. The patterns of synaptic interactions formed by these intrinsic axon collaterals may be a substrate for shaping and modulating representation maps in the motor cortex. © 1993 Wiley‐Lis

ISSN:0092-7317    

DOI:10.1002/cne.903360206

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractPrior studies indicate that neonatal nerve injury kills many trigeminal (V) first‐ and second‐order cells, and interrupts pattern formation in the brainstem and cerebral cortex. Yet it is not known whether effects upon cell survival and pattern formation are causally related. To determine whether axotomized V ganglion cells can be rescued by an exogenous trophic agent, rats received 5 mg/kg of nerve growth factor (NGF) prior to, and every day after, infraorbital nerve section on the day of birth until sacrifice on postnatal day (PND) 1, 3, 5, 7, or 14. Other animals received identical lesions without NGF. Ganglion cell numbers were significantly reduced by PNDl in pups not given NGF, while NGF‐treated rats displayed no significant cell loss through PND7. However, NGF did not permanently rescue V neurons because ganglion cell numbers were reliably reduced by PND14.Cell numbers in V nucleus principalis were reduced by PNDl in pups not given NGF, while NGF‐treated animals displayed no cell loss through PND14. NGF's rescue of second‐order cells is probably an indirect effect of NGF actions upon V ganglion cells because, in other newborns, NGF failed to maintain principalis cells after direct lesion of the left V ganglion.To determine whether preventing cell death permits whisker‐related pattern formation, other rats also received NGF prior to and after infraorbital nerve section at birth. After 3–14 days, patterns were assessed in the brainstem and cortex with cytochrome oxidase histochemistry and serotonin immunocytochemistry. Whisker‐related patterns failed to develop as in cases not given NGF.These data indicate that communication with the periphery is necessary for the maintenance of central whisker‐related patterns. They also suggest that V ganglion cells can be rescued, albeit temporarily, from rapid injury‐induced death by NGF, thereby delaying injury‐induced cell death in nucleus principalis. However, the mechanism(s) responsible for injury‐induced pattern alterations in the developing V system remains to be elucidated.

ISSN:0092-7317    

DOI:10.1002/cne.903360207

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe three inhibitory motoneurons supplying crayfish thoracic limbs were identified, stained, and compared structurally. The inhibitors to the walking leg muscles (inOrconectes) were identified anatomically by a combination of immunocytochemical staining for gammaaminobutyric acid (GABA) or glutamate decarboxylase and differential backfill staining with nickel and cobalt ions. The cheliped inhibitors were identified intracellularly and injected with Lucifer Yellow (Pucifustucus) or cobalt (Procumbarus). The common inhibitor (CI) in each thoracic segment has a medial or slightly contralateral soma near the ganglion's posterior boundary, a gently curving primary neurite, an extensive ipsilateral dendritic tree, and an axon emerging through the anterior root. The stretcher‐closer inhibitor (SI) has a soma slightly anterior and ipsilateral to the CI's, a sharply bent proximal neurite, a smaller dendritic tree, and an axon in the posterior root. The opener inhibitor (OI) lies more laterally and often posterior to the CI; its diagonally directed neurite enters the posterior root. The inhibitors' structures were related to major neuroanatomical landmarks within the ganglion, to soma positions of excitatory motoneurons revealed by backfilling, and to soma locations of inhibitory interneurons revealed by GABA‐like immunoreactivity.In their peripheral distributions to the leg muscles and in their central structures, these crayfish limb inhibitors show striking similarities with those of the locust. Crayfish and locust thoracic ganglia also show more general neuroanatomical similarities. These observations suggest that the crayfish CI, SI, and 01 are, respectively, homologous with the locust CI1CI2, and CI3. The implications of such a homology for arthropod phylogeny are discussed. © 1993 Wiley‐Lis

ISSN:0092-7317    

DOI:10.1002/cne.903360208

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe ultrastructural organization of cholinergic afferents to the rat olfactory bulb (OBI) was studied with the aid of choline acetyltransferase (ChAT) immunocytochemistry in electron microscopy. Particular attention has been paid to a subset of glomeruli characterized by a remarkably high density of cholinergic afferents. Numerous cholinergic terminals making symmetric or asymmetric synaptic contacts were observed in the periglomerular area. ChAT‐labelled terminals have a diameter ranging from 0.3 to 1.5 μm and contain numerous clear agranular vesicles. Axo‐somatic and axo‐dendritic contacts were both observed in contact with several types of target neurons. Three types of cholinoceptive, noncholinergic neurons could be identified: periglomerular cells, superficial short‐axon cells, and external tufted cells. Our results provide an anatomical substrate for the hypotheses concerning the complex effects of acetylcholine in the processing of sensory information in the olfactory bulb. © 1993 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903360209

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractWe have previously shown that the density of dendritic spines on hippocampal CA1 pyramidal cells is dependent on circulating estradiol and progesterone and fluctuates naturally during the 5 day estrous cycle in the adult rat. To date, however, no detailed characterization of the roles that these hormones play in regulation of spine density has been made. In order to determine the time courses and extent of the effects of estradiol and progesterone on dendritic spine density, we have analyzed the density of dendritic spines on the lateral branches of the apical dendritic tree of Golgi‐impregnated CA1 hippocampal pyramidal cells in several experiments. In summary, our findings included the following: (1) Following ovariectomy, circulating estradiol is undetectable within 24 hours; however, spine density decreases gradually over a 6 day period. (2) Spine density does not decrease any further up to 40 days following ovariectomy. (3) Treatment with estradiol alone can reverse the ovariectomy‐induced decrease in spine density. (4) Spine density begins to increase within 24 hours following estradiol benzoate injection in an ovariectomized animal, peaks at 2 and 3 days, then gradually decreases over the next 7 day period. (5) Although free estradiol is metabolized more rapidly than estradiol benzoate, there is no difference in the rate of decrease in spine density following injection of either form. (6) Progesterone has a biphasic effect on spine density in that progesterone treatment following estradiol initially increases spine density for a period of 2 to 6 hours but then results in a much sharper decrease than is observed following estradiol alone. By 18 hours following progesterone treatment, spine density is decreased nearly to 6 day ovariectomy values. (7) Treatment of intact rats with the progesterone receptor antagonist, RU 486, during the proestrus phase of the estrous cycle inhibits the proestrus to estrus drop in spine density. These findings account for both the gradual increase and rapid decrease in spine density which we have previously observed during the estrous cycle and indicate that progesterone in particular may be an important factor in the regulation of rapid morphologic changes which occur naturally in the adult brain. © 1993 Wiley‐Lis

ISSN:0092-7317    

DOI:10.1002/cne.903360210

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractCorticotropin‐releasing factor (CRF) has been implicated by both anatomical and physiological techniques as a potential cerebellar transmitter or modulator. In the present experiment, with the aid of immunohistochemistry, we have described specific cerebellar afferent pathways in the rabbit in which CRF is located. CRF‐immunoreactive climbing fibers were present in the molecular layer throughout the cerebellum, but especially in lobules 8–9a. All inferior olivary neurons were CRF‐immunoreactive.In lobules 8–9a, CRF‐immunoreactive mossy fibers were organized in sagittal bands. The highest density of CRF‐immunoreactive mossy fiber terminals was observed in the granule cell layer of lobules 8–9a and the flocculus. No CRF‐immunoreactive perikarya were located in rabbit cerebellum. The brainstem origin of CRF‐immunoreactive mossy fiber terminals was suggested by numerous CRF‐immunoreactive perikarya located in the medial, lateral and descending vestibular nuclei, nucleus prepositus hypoglossi, nucleus x, paramedian reticular nucleus, gigantocellular reticular nucleus, lateral reticular nucleus, and raphe nuclei.Using double label experiments, we investigated the specific CRF afferent projection to the flocculus and posterior vermis. Horseradish peroxidase (HRP) injections into the posterior vermis double labeled CRF‐immunoreactive neurons in the caudal medial and descending vestibular nuclei and nucleus prepositus hypoglossi. HRP injections into the flocculus double labeled more CRF‐immunoreactive neurons in the nucleus prepositus hypoglossi than in the vestibular nuclei. HRP injections into either the posterior vermis or flocculus double labeled CRF‐immunoreactive neurons in the paramedian reticular nucleus, nucleus reticularis gigantocellularis, and raphe nuclei. These data suggest that CRF may play an important role in vestibularly related functions of the cerebel

ISSN:0092-7317    

DOI:10.1002/cne.903360211

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY