摘要:

AbstractThe effect of neonatal deafferentation of the rat superior cervical ganglion (SCG) on the expression of two synaptic vesicle proteins was studied to assess the role of transsynaptic influences in the regulation of these neural antigens in the SCG. The two proteins studied were a 65 kilodalton integral membrane protein of synapatic vesicles (SV), and synapsin‐1 (S‐1), a synaptic vesicle phosphoprotein. Antigen levels were quantified by radioimmunoassay using antibodies directed against the proteins. Distribution of SV in control, deafferented and reinnervated ganglia from 30‐day‐old rats was visualized by immunohistochemical labeling. Levels of both antigens were reduced following deafferentation of the SCG on postnatal days 1–3. The reduction in S‐1 levels at 30 days was less than that observed for SV. The amount of S‐1 remaining in deafferented ganglia was consistent with estimates of the postsynaptic pool in the SCG reported previously. SV levels, in contrast, were reduced to 24% of control levels, suggesting that SV synthesis in principal ganglionic neurons might be affected. The time course of postnatal development of S‐1 in the SCG differed from previous studies of SV expression, with significant increases occurring after the second week after birth. The differences in response to deafferentation may reflect functional differences of the two vesicle‐associated proteins. These studies demonstrate that transsynaptic regulation of antigens other than those directly associated with neurotransmitters

ISSN:0887-4476    

DOI:10.1002/syn.890020102

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

年代:1988

数据来源: WILEY

摘要:

AbstractSpinal cord neurons form stable synapses on muscle cells in culture, whereas retinal neurons, an inappropriate presynaptic partner for muscle cells, form synapses that are transient. We have hypothesized that a trophic influence of neurons on muscle is involved in the stabilization of synapses. Because other neural tissues that form stable synapses on muscle cells contain factors that aggregate acetylcholine receptors (AChR) into clusters on the surface of muscle cells. It may be that these aggregation factors are necessary for stabilization of neuron‐muscle synapses. Therefore, we determined the AChR‐aggregating activity of retinal neurons. The results showed that cocultures of retinal neurons and muscle cells and retinal‐conditioned medium do not show increases in the number of AChR on muscle cells. Conversely, spinal cord‐muscle cocultures and spinal cord‐conditioned medium produce increases in the number of AChR clusters. These data, along with previous studies demonstrating that retinal neurons are unable to affect the electrical membrane properties of cultured muscle cells, whereas spinal cord neurons do elicit such changes, add support to the above hypothesis of a trophic influence of neurons in synapse stab

ISSN:0887-4476    

DOI:10.1002/syn.890020103

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe present study examined whether GABA treatments would affect the growth and development of embryonic chick cortical and retinal neurons in culture. Incubation of these cells in the presence of 10−−5M GABA produced several responses. It promoted the proliferation and the differentiation of the neurons studied by affecting the length and branching of the neurites as well as synaptogenesis, as revealed by morphometric measures. At the ultrastructural level, GABA treatment also led to an increased density of neurotubules, rough endoplasmic reticulum (RER), Golgi apparatus, coated vesicles, and other vesicles. These data support the hypothesis that GABA functions as a trophic or regulatory factor of at least certain neuron ty

ISSN:0887-4476    

DOI:10.1002/syn.890020104

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

年代:1988

数据来源: WILEY

摘要:

AbstractChronic treatment with iminodipropionitrile (IDPN) causes a behavioral syndrome characterized by lateral and vertical neck dyskinesias, hyperactivity, random circling, and increased startle response (the “ECC syndrome”). The effects of the neurotoxin on norepinephrine (NE), dopamine (DA), and their metabolites were evaluated in the hypothalamus and the striatum of IDPN‐treated animals. Urinary excretion of the amines was also measured. There was no significant persistent change in central metabolism of dopamine. There was a transient increase in NE metabolism in the hypothalamus after the third injection of IDPN that lasted until the development of the syndrome at 7 days of drug treatment. Urinary excretion of NE and its metabolites was increased on the day that the syndrome developed. Urinary excretion of homovanillic acid was persistently decreased throughout and after cessation of drug treatment. There was no change in the excretion of either dopamine or dihydroxyphenyl acetic acid. The ratio of total NE/total DA excreted by IDPN‐treated rats was the inverse of that of control animals. These results suggest that persistent dyskinesias may be associated with a relative increase in facilitatory NE‐dependent mechanisms at the cortical, subcortical, or spinal c

ISSN:0887-4476    

DOI:10.1002/syn.890020105

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

年代:1988

数据来源: WILEY

摘要:

AbstractGlutamate has been shown to be a neurotransmitter in the central nervous system of vertebrates, and it has been hypothesized that glutamate is functional as a neurotransmitter in the spinal cord dorsal horn. A monoclonal antibody to fixativemodified glutamate was used in this study to examine the light microscopic and ultrastructural profiles of glutamate‐like immunoreactivity in the superficial dorsal horn of the rat spinal cord. Glutamate‐like immunoreactivity was observed in neurons, fibers, and terminals of both laminae I and II. Marginal zone immunoreactive neurons ranged from 10 to 30 μm in diameter and received many nonimmunoreactive somatic synapses. In substantia gelatinosa, immunoreactive neurons were observed in both inner and outer layers, ranged 5 to 10 μm in diameter, and received few nonimmunoreactive somatic synapses. Glutamate‐like immunoreactive dendrites were observed in both laminae and were contacted primarily by nonimmunoreactive synaptic terminals that generally contained small clear vesicles. Both myelinated and unmyelinated immunoreactive axons were observed in Lissauer's tract. Immunoreactive terminals contained small (40 nm) clear vesicles and generally formed simple synaptic contacts with nonimmunoreactive dendrites in laminae I and II. The results of this study corroborate the importance of glutamate as a neurotransmitter in spinal sensory mec

ISSN:0887-4476    

DOI:10.1002/syn.890020106

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

年代:1988

数据来源: WILEY

摘要:

AbstractPhysiological and morphological properties of transplanted striatal neurons (TSNs) were examined in an in vitro slice preparation. Fetal striatal tissue (E13‐14) was implanted as a dissociated cellular suspension into the striatum of adult rats. Intracellular records were obtained from TSNs 2–6 weeks after transplantation. TSNs exhibited biophysical, morphological, and synaptic properties characteristic of normal striatal neurons, despite the disruption involved in processing of the fetal tissue. Differences were observed, however, between the TSNs and host striatal neurons. TSNs consistently had higher input resistance values than host striatal neurons as determined by neuronal responses to intracellular current injection. Stimulation of adjacent host striatum elicited both excitatory and inhibitory postsynaptic potentials in TSNs. By contrast, the same stimuli elicited only excitatory responses in host striatal neurons. Morphologically, TSNs resembled host medium‐size spiny neurons as demonstrated by intracellular injection of lucifer yellow. However, the complexity of dendritic branching and the density of spines on the dendrites were less than that observed for host striatal neurons. It was concluded that during the posttransplantation period studied, TSNs possess neuronal properties expected of developmentally immature striatal ne

ISSN:0887-4476    

DOI:10.1002/syn.890020107

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe actions of serotonin (5HT) on passive and active membrane properties of neurons in the rat dorsal lateral septal nucleus (LSN) were studied by using intracellular recordings in transverse, septal slices. Superfusion with 10 μm 5HT induced a hyperpolarization of the membrane in almost all neurons tested in the dorsolateral part of the LSN. The hyperpolarization was accompanied by a decrease in membrane resistance. These effects of 5HT persisted in a low‐Ca2+/high‐Mg2+‐containing medium or medium with tetrodotoxin, indicating a post‐synaptic site of action for 5HT. The reversal potential for the hyperpolarizing effect was ca. ‐95 mV. If the extracellular K+‐concentration was raised, the reversal potential became less negative. These data suggest that 5HT hyperpolarizes LSN neurons by increasing a K+‐conductance.Spontaneous, synaptically evoked action potentials and action potentials induced in LSN neurons by a depolarizing current step typically display a fast Na+‐spike with a subsequent K+‐afterhyperpolarization, followed by a much slower Ca2+‐dependent afterdepolarization. The amplitude of the K+‐afterhyperpolarization was decreased by 5HT, while at the same time the afterdepolarization became more pronounced. The Ca2+‐spike of LSN neurons was not affected by 5HT.Synaptic responses that were evoked in LSN neurons by stimulation of the dorsal part of the LSN consisted of a fast EPSP or spike, followed by a Cl−−‐dependent fast IPSP and a K+‐dependent late IPSP. Of these synaptic responses, 5HT suppressed particularly the late IPSP. The present data indicate that 5HT affects the conductance for active and passive K+‐channels in LSN neurons. While the increased conductance for passive K+‐channels directly hyperpolarizes and inhibits LSN neurons, the 5HT‐evoked changes in the shape of the action potential and IPSPs could facilitate transmi

ISSN:0887-4476    

DOI:10.1002/syn.890020108

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe present experiments studied the effects of cholinergic agonists and antagonists on the spontaneous and acoustic‐evoked discharge of auditory cortical neurons and examined whether these effects were mediated by muscarinic cholinergic receptors. A primary focus of this report is the analysis of specific effects of these agents on the spontaneous and tone‐evoked discharge and on different temporal components of the evoked discharge. Single neurons were recorded in the auditory cortex of chronically prepared, awake cats with multibarrel micropipette electrodes. The responses to acoustic stimuli were obtained before, during, and following continuous ejection of cholinergic agonist or antagonists by micropressure. The mean rate of discharge of the neurons was analyzed quantitatively for spontaneous discharge and for different peaks of the tone‐evoked PSTH corresponding to tone “on,” “through,” and “off” responses. Acetylcholine (ACh) and acetyl‐β‐methacholine (MCh) produced significant effects on spontaneous activity in 72% and 68% of neurons tested, respectively. Tone‐evoked responses were effected in 92% and 82% of cells tested, respectively. The ability of these agonists to modify spontaneous or evoked activity was dose‐dependent. Agonist effects on spontaneous and evoked activity were often different in the same cell; however, effects on spontaneous activity did predict effects on “through” responses. The most common effect of ACh or MCh on evoked activity was facilitation of the tone “on” responses. For neurons with multicomponent discharge patterns in response to tones, the agonists had nonuniform effects on different response components. However, the effects of ACh on the “on” and “off” responses covaried. Hence cholinergic agonists produce heterogenous, selective effects on different components of the responses of auditory cortical neurons rather than simple increases or decreases in discharge level. The effects of cholinergic agonists were modified in the presence of atropine. The effects of MCh were blocked by atropine in a hi

ISSN:0887-4476    

DOI:10.1002/syn.890020109

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

年代:1988

数据来源: WILEY

摘要:

AbstractBranching patterns of dendrites may be modulated by the way in which dendritic growth cone filopodia come into initial synaptic relationships with afferent axons. This synaptotropic hypothesis of dendritic branching predicts that dendritic growth will be directed preferentially into regions containing numerous prospective presynaptic elements. The developing mouse spinal cord provides a natural experiment to test this prediction, because synapses are found exclusively within the marginal zones bordering the motor columns during the early (E11–14) period of synaptogenesis. During this time, therefore, most motor dendritic growth would be expected to be directed laterally or ventrally into the marginal zones, whereas internally directed growth should become more prevalent later, when synaptogenesis begins to take place within the intermediate zone, i.e., the motor columns proper. A computer‐assisted three dimensional reconstruction system has been used to test these expectations in Golgi preparations of developing mouse (C57BL/6J) spinal cords ranging in age from E13 through P1. Mean dendritic lengths and branch densities are significantly greater for marginal zone dendrites than for intermediate zone dendrites at early ages (E13–14), but there are no significant differences in these measures at later stages of development (PO,1). These findings are interpreted as meaning that motor dendritic growth is initially biased into the marginal zone by synaptogenic afferents and that this oreferential distribution is progressively lost as synapses develop within the intermediate zone to attract or to stabilize internally directed dendritic growth. Thus the findings of this study are consistent with predictions of the synaptotropic hypothesis of dendritic bran

ISSN:0887-4476    

DOI:10.1002/syn.890020110

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

年代:1988

数据来源: WILEY

摘要:

AbstractCalpain I, a calcium‐activated neutral protease which degrades a number of cytoskeletal proteins, has been implicated in the rapid turnover of structural proteins that may participate in synaptic plasticity. In the present study, an antibody raised against purified erythrocyte calpain I was biochemically characterized and demonstrated to specifically bind the Mr=80,000 subunit of both rat erythrocyte and brain calpain I. This antibody was used to examine the cellular distribution of calpain I at the electron microscopic level in rat brain and spinal cord using the avidin‐biotin immunocytochemical technique. Reaction product was observed throughout neuronal perikarya, within both axonal and dendritic processes, and within spine heads and necks. Postsynaptic densities in both shaft and spine synapses were also immunoreactive. Glial cell bodies and processes were densely stained. In both neurons and glia, the reaction product was deposited along cytoskeletal elements. The localization of calpain I immunoreactivity to glial processes suggests this degradative enzyme may play a role in the glial hypertrophy and process retraction seen in brain. The presence of the enzyme in spines and postsynaptic densities is consistent with the hypothesis that it is involved in the turnover of synaptic cytoskeleton, thus providing a means through which transient physiological events effect lasting changes in the chemistry and morphology of spi

ISSN:0887-4476    

DOI:10.1002/syn.890020111

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

年代:1988

数据来源: WILEY