摘要:

THE dynamics of intracellular calcium concentration ([Ca2+]i) following activation of low voltage-activated (LVA) and high voltage-activated (HVA) Ca2+currents were studied in identified relay neurons and interneurons of the rat dorsal lateral geniculate nucleus (LGNd)in situusing Ca2+imaging and patch-clamp techniques. In relay neurons, [Ca2+]itransients associated with the LVA Ca2+current showed a fairly homogeneous somatodendritic distribution, whereas HVA transients significantly decreased to 65% of the somatic value at 60 μm dendritic distance. In interneurons, LVA transients significantly increased to 239% of the somatic value at 60 μm dendritic distance, whereas HVA transients were not significantly different in the soma and dendrites. These results indicate differences in [Ca2+]idynamics, which may reflect a heterogeneous distribution of Ca2+channels contributing to subcellular compartmentation in the two types of thalamic neurons.

ISSN:0959-4965    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

STUDIES of the human visual cortex have demonstrated that an area for motion processing (V5) is located in the lateral occipito-temporal cortex. To study the timing of arrival of signals in V5 we recorded multi-channel visual evoked potentials (VEPs) to checkerboard stimuli. We then applied dipole source analysis which was computed on a grand average of 10 subjects, and on five individual subjects, respectively. We demonstrate an early VEP component with onset before 30 ms and with a peak around 45 ms, located in the vicinity of V5. This early component was independent of a second activity, which started around 50 ms and peaked around 70 ms, and was located within the striate cortex (V1). These results provide further evidence for a very fast input to V5 before activation of V1.

ISSN:0959-4965    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

ALTERATIONS of [3H]cyclic AMP (cAMP) binding, an indicator of the binding activity of particulate cyclic AMP-dependent protein kinase (PKA), were examined after 15 and 30 min of ischemia in the gerbil brain. Severe hemispheric cerebral ischemia was induced by occluding the right common carotid artery. Significant reductions in cAMP binding were noted only in the dendritic subfields of the hippocampus CA1 such as the strata oriens, radiatum and lacunosum-moleculare, on the ischemic side after 15 min of ischemia. After 30 min ischemia cAMP binding was significantly decreased not only in each dendritic subfield of the hippocampus CA1, but also in the layer of pyramidal cell bodies (stratum pyramidale) on the occluded side; other brain regions such as the hippocampus CA3, dentate gyrus and cerebral cortices revealed no significant changes in cAMP binding. These findings suggest that derangement of PKA may begin in the dendritic subfields of the hippocampus CA1 after as little as 15 min of severe ischemia, and proceed centrally to the neuronal cell bodies of the hippocampus CA1.

ISSN:0959-4965    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

NEURONAL destruction in the amygdala, hypothalamus and cerebellum provokes a diminution in anxiety and neophobia. In transgenic mice that express the human bcl-2 gene under the control of neuron specific enolase promotor (Hu-bcl-2), BCL-2 overexpression reduces the naturally occurring neuronal death, producing an increase of the number of neurons and brain size. Since BCL-2 over-expression has been observed in different parts of the brain and especially in the amygdaloid nuclei, the hypothalamus and the cerebellum, we studied the fear-related behavior of these transgenic mice. Hu-bcl-2 transgenic mice showed a decrease in anxiety and neophobia, indicating that, for this particular behavior, supernumerary neurons elicit the same modification as that observed after neuronal destruction.

ISSN:0959-4965    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

NACHRS heterologously expressed in human cells after transient transfection with α3β4α5or α3β4subunit cDNAs exhibited similar sensitivities to antagonists and comparable functional channel profiles. However, the sum of two Hill equations was required for best fitting the ACh dose—current response curves after co-expression of α5, α3and β4subunits. One component was comparable to that obtained in α3β4-transfected cells, while the additional component, putatively attributed to an α3β4α5nAChR population, showed a Hill coefficient > 2 and a nine-fold greater half-maximal ACh concentration (EC50). These results suggest that the α5subunit participates in the assembly of α3β4α5nAChRs complexes in human cells, adding a new member to the family of neuronal nicotinic receptors.

ISSN:0959-4965    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

USING differential display PCR, we identified a cDNA whose expression is altered in several brain regions in rats self-administering cocaine. The cDNA sequence corresponds to bases 13687–13723 of the rat NADH dehydrogenase subunit 6 gene. Northern analysis indicated a 26% decrease in nucleus accumbens, a 305% increase in the ventral midbrain and no changes in the caudate putamen mRNA levels; changes were also noted in the hypothalamus and cerebellum. This is the first demonstration of an effect of cocaine self-administration on mitochondrial gene expression and suggests that regional metabolic changes elicited by cocaine may be relevant to and involved in its reinforcing properties.

ISSN:0959-4965    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

BIPOLAR neurons of the vestibular ganglion (VG) are biochemically heterogeneous. The calcium-binding protein calbindin D-28k (Calb) is present only in a subset of particularly large neurons, and the amino acid glycine (Gly) has been immunocytochemically detected in a group of similarly sized cells. The close correspondence in size and number of cells in these two subgroups suggests that the Calb- and Gly-positive populations may be identical. In order to test this hypothesis, we performed direct and indirect double-labeling for Calb and Gly in the VG of the rat. The results confirm the existence of a distinct subpopulation of Calb-immuno-reactive neurons, consisting of the largest cells in the VG. In contrast, the vast majority of neurons in the VG display some degree of Gly immunoreactivity, which gradually decreases from intense to almost unlabeled. Direct evidence is provided that the fraction of cells most heavily labeled by Gly antibodies is not identical with the Calb-positive subpopulation. Although some correlation between soma diameter and labeling intensity exists, Gly immunoreactivity is clearly not restricted to large neurons. The findings imply that the functional mechanisms, in which Gly is potentially involved may be shared by a large spectrum of primary vestibular afferents with a broad range of physiological properties.

ISSN:0959-4965    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

SUBJECTS from four Mexican families at risk of inheriting Alzheimer's disease (AD) were studied using a complete neuropsychological battery. These tests were repeated and compared 1 year later. Some of the experimental subjects belong to an international protocol on molecular chromosomal study. A control group matched in age and schooling was included. The subjects at risk underwent a complete physical, neurological and neuropsychological assesment. A neuropsychological battery of cognitive domains designed for the the study of dementia syndromes was administered to all subjects. Six of the subjects showed abnormal performance in cognitive functions, memory, visuospatial functions or language which persisted 1 year later. The present work describes the initial findings of a long-term prospective study aimed at delineating the neuropsychological profile of subjects at risk and to validate subtle abnormalities which in some cases could be the incipient changes of AD.

ISSN:0959-4965    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

G protein activation of inwardly rectifying K+(Kir) channels by heptahelical receptors is an important signaling motif in slow synaptic transmission in the mammalian brain. To isolate candidate receptors responsive to the purine nucleoside adenosine, a cerebellar cDNA library was constructed in the vector pSGEM and transcripts were injected intoXenopus laevisoocytes co-expressing Kir3.1 and/or Kir3.2 subunits. Stepwise fractionation and functional characterization of the library using two-electrode voltage clamp measurements resulted in the identification of a single unique cDNA clone with an open reading frame of 326 amino acids. The pharmacological properties as determined from the responses to cyclopentyl-adenosine (CPA, EC50= 7 nM) and CGS21680 (EC50= 2.6 μM) were typical of adenosine A1 receptors. The differential receptor coupling to heteromeric Kir channels composed of Kir3.1–4 subunits provides a useful technique to isolate novel heptahelical receptors.

ISSN:0959-4965    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

WE used silver-enhanced immunogold electron microscopy to reveal synaptic localization of the glutamate transporter EAAT4 in mouse cerebellar Purkinje cells (PCs). Gold—silver particles representing the EAAT4 were densely localized on extra-junctional membrane, but not on junctional membrane of PC spines in contact with parallel fiber or climbing fiber terminals. No particle accumulations were observed at inhibitory synapses formed on cell body and dendritic shafts of PCs. Therefore, the EAAT4 is selectively targeted to the extra-junctional site of excitatory PC synapses. The finding suggests that the EAAT4 transports glutamate or its related amino acids from outside the synaptic cleft, which would facilitate glutamate diffusion from the synaptic cleft to the extrasynaptic space and restrict glutamate spillover to adjacent synapses.

ISSN:0959-4965    

出版商:OVID    

年代:1997

数据来源: OVID