摘要:

THE brain angiotensin (Ang) system plays an important role in the central control of vasopressin release. Using EC33, a selective aminopeptidase A inhibitor which blocks the metabolism of Ang II in Ang III, we previously reported that vasopressin release was under the control of Ang III and not Ang II. To determine accurately the action of EC33, the effects of intracerebroventricular injection of Ang peptides or EC33 on extracellular unit activity of vasopressinergic neurons in the supraoptic nucleus of urethane-anaesthetized rats were examined. Angiotensin II (15–30 ng) or Ang III (15 ng) increased the firing rate of all neurons tested. Conversely, EC33 (10 μg) reduced or completely abolished (30–60μg) the basal firing rate for 4–6 min in all eight neurons tested. EC33 (30 μg) also inhibited the activity induced by 30 ng Ang II. It was concluded that the observed activity of Ang II required its conversion to Ang III and that endogenous Ang III may exert a tonic control on the basal firing level of vasopressinergic neurons.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE relationship between anatomical asymmetry of the planum temporale (PT) and functional lateralization for language comprehension was studied in 14 normal volunteers, including five left-handers (LH). PT surfaces and asymmetry were measured in each subject using structural MRI, while functional lateralization was assessed on individual regional cerebral blood flow (rCBF) difference images of a PET-H215O activation protocol in which a story listening condition was contrasted with a control state. Significant positive correlations were found between the left PT surface and the amount of NrCBF increase during the story listening in the left superior temporal gyrus as well as with the left-right activation index in the superior temporal and the temporal pole. Functional imaging data were correlated neither with the right PT surface nor with the right–left PT surface asymmetry index. However the latter index was correlated with handedness scores. The present results indicate that the size of the left PT is the relevant anatomical landmark for language dominance, and demonstrate that anatomical asymmetries are part of the functional variability for language.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

STUDIES of normal behaviour have shown that the process of selection takes a finite time, one measure of which is the attentional dwell time, that is the period of interference produced by one attended stimulus on a subsequent one. Here we investigated the time for selection in FB, a neurological patient suffering from a visuospatial disorder of attention (unilateral extinction). FB was asked to identify two letters displayed in rapid succession either to the left (damaged), or to the right (intact) visual hemifield. By varying the interval between stimuli, we measured how long the first letter continued to interfere with accuracy on the second–that is the first letter's attentional demand over time. The results showed that the process of selection has an abnormal duration in the affected visual field, being at least twice as long as in the intact field. We suggest that the slowed visual processing for the contralesional object may contribute to the competitive bias against that object which is the hallmark of unilateral extinction.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

HERE we report that macrophages in the rat superior cervical ganglia (SCG) respond differently to pre- and postganglionic axotomy. Postganglionic axotomy results in a rapid activation of resident macrophages, as measured by inducible nitric oxide synthase (iNOS) immunoreactivity, and a massive invasion by macrophages. Following preganglionic lesion there was no such rapid activation and the macrophage invasion was of much lower magnitude. A subpopulation of the macrophages also expressed haem oxygenase-1 (HO-1). The results are compatible with a model in which macrophages or their products, including nitric oxide (NO) and carbon monoxide (CO) could be important for induction of early changes in the nerve cell body, like an altered neuropeptide synthesis, which has been shown to accompany the regenerative response in peripheral ganglia.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

LONG-TERM potentiation (LTP) is a popular model of the synaptic plasticity which may be engaged by the biological processes underlying learning and memory. Most available studies of LTP have concentrated on the analysis of LTP occurring in ‘early’ components of the hippocampal circuit (for example, dentate gyrus and area CA1). We examine here, for the first time, LTP as it occurs in the massive, unidirectional projection from CA1 to the subiculumin vivo. We show that this projection sustains high-frequency stimulus-induced LTP (10 trains of 20 stimuli at 20 0 Hz; intertrain interval 2 s; LTP 181 ± 9% at 30 min post-LTP induction). In addition, input-output (I/O) curves show a leftward shift for all stimulation values.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Brn-3a, Brn-3b and Brn-3c are closely related POU family transcription factors which are expressed predominantly in neuronal cells. Previously Brn-3a has been shown to activate a number of gene promoters in cotransfections carried out in different cell types, while Brn-3b inhibits the basal activity of these promoters. We show here that Brn-3c activates the same promoters as Brn-3a but only in co-transfections into neuronal cells and not in other cell types. This effect is dependent upon an N-terminal region of Brn-3c which acts as a neuronal cell specific activation domain when linked to a heterologous DNA binding domain. To our knowledge this is the first report of an activation domain with apparently neuronal specific activity.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

WE performed a quantitative electron microscopic analysis of the middle third of the molecular layer in the dentate gyrus of rat, using material processed with postembedding gold labeling for the glutamate receptor subunits GluR1, GluR2/3, or NMDAR1. Perforated axospinous synapses were at least twice as likely as nonperforated ones to express detectable levels of AMPA receptor subunits, whereas no significant differences in NMDA receptor expression were observed. These data imply that perforated synapses may be especially potent, and are consistent with the hypothesis that insertion of AMPA receptor protein into the postsynaptic membrane of previously silent synapses contributes to long-term potentiation.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

AXONS from central neurons can regenerate into the tissue matrix formed within a silicone tube capped with two pieces of peripheral nerve, one of which had been sutured to a lesion in the spinal cord. Such axons can grow through a transversely positioned microchip in the tube. These observations suggest that it is feasible to establish functional contact between external electronic equipment and regenerating central nervous axons making it possible to monitor and control their electrical activity. The findings open new perspectives for restoration of motor and sensory functions following spinal cord lesions.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

PREVIOUS research has implicated the striatum in implicit sequence learning. However, imaging findings have been inconsistent with regard to activity within the thalamus during performance of such tasks. Contemporary models of cortico-striato-thalamic circuitry suggest opposing influences on thalamic activity; suppression of thalamic activity is mediated by theindirectpathway and enhancement is mediated by thedirectpathway. Using functional magnetic resonance imaging, we studied activity within human thalamus during early and late phases of an implicit sequence learning task known to reliably recruit the striatum. Significant deactivation (decreased signal relative to a baseline condition) was observed within the thalamus during early implicit learning. This finding is consistent with models of cortico-striato-thalamic function and specifically supports a profile of early ‘thalamic gating’ via the indirect pathway.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

TO test whether mitogen-activated protein kinases (MAPKs) are involved in microglial activation, pure microglia prepared from 1- to 3-day-old rat brains were activated with either 10 0 ng/ml lipopolysaccharide (LPS) or 5 nM synthetic β-amyloid (Aβ) (25-35). The patterns of MAPK activation following LPS and Aβ treatment were very similar. Three MAPK subtypes, p38, extracellular signal-regulated kinase (ERK) and c-Jun N- terminal kinase/stress-activated protein kinase (JNK/SAPK) were activated within 1 5 min and the activities of p38 and ERK were rapidly reduced to background level within 3 0 min while that of JNK was maintained for over 1 h. Both inhibitors of p38 (SB203580) and ERK pathway (PD098059) reduced LPS-induced nitric oxide (NO) release and A β-induced tumor necrosis factor α-(TNF-α) release. Furthermore, co-treatment of SB203580 and PD098059 additively reduced NO and TNF α-release. These results suggest that MAPK, at least p38 and ERK, mediate LPS-, and Aβ-induced microglial activation.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID