摘要:

The effect of chronic alcohol drinking on maze behaviour was studied in laboratory rats. Thirteen animals received 20% alcohol for 15 weeksad libitum, and 18 were kept under identical conditions drinking tap water. Both groups were then tested twice within one day for performance in an 8 arm radial maze after 48 h fluid deprivation. Reinforcing fluid droplets were placed at the end of each arm only at the beginning of the test. Total and erroneous entries to the arms, total time spent until reaching the criterion, and strategy of arm choice was recorded for each animal. Activity of the groups did not differ significantly, nor were differences in choosing strategy found. Alcoholic rats, however, showed a significant loss of performance in the second test: they frequently entered arms already visited, and in a number of cases were unable to complete the test within time. These and earlier findings suggest no impairment of learning ability or short term memory, but rather some kind of rigidity and invariability of behaviour.

ISSN:0959-4965    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

The ability of NBQX, a potent antagonist of AMPA glutamatergic receptors, to prevent or stop seizures induced by the organophosphate soman, an irreversible inhibitor of AChE, was studied in rats. NBQX administered concomitantly with soman prevents the onset of seizures (ED50: 29.2 mg kg−1, i.p.). Administered 5 min after the onset of seizures, NBQX greatly reduces the intensity of the epileptic activity. The same decrease of epileptic activity is observed, in the presence of atropine, when the administration of NBQX is delayed 15 min after the onset of seizures. NBQX thus appears as a promising antiepileptic candidate against soman-induced seizures. The roles of AMPA and muscarinic receptors in the onset and propagation of soman-induced epileptic activity are discussed.

ISSN:0959-4965    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Expression of brain-derived neurotrophic factor (BDNF) in the ventral mesencephalon has been assayed by mRNAin situhybridization in adult rats with unilateral injections of 6-hydroxydopamine in the substantia nigra. On contralateral control sides, a specific hybridization signal was detected in the substantia nigra pars compacta (A9), ventral tegmental area (A10) and substantia nigra pars lateralis (A8). Cellular levels of BDNF mRNA were lower than those in BDNF expressing cortical and hippocampal neurons. The 6-hydroxydopamine injections completely abolished BDNF mRNA labeling in the pars compacta of the substantia nigra, whereas many labeled neurons remained in the ventral tegmental area and pars lateralis. The results strongly suggest that BDNF is expressed by nigral dopaminergic neurons.

ISSN:0959-4965    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

There is evidence that the cholinergic system modulates, in a circadian and asymmetric way, the neural activity involved in the regulation of ovulation. In the present study we measured choline acetyltransferase (ChAT) activity during the oestrous cycle in both sides of the preoptic-anterior hypothalamic area (POA-AHA) of the rat. The right side of POA-AHA showed significant changes in ChAT activity during the oestrous cycle. The activity of the enzyme was higher in the right side on the day of oestrous (47.3 ± 3.2 nmol mg−1protein 1 h−1vs25.8 ± 2.4,p< 0.05), whilst on the second day of dioestrous the activity was higher in the left one (30.6 ± 3.4vs20.0 ± 1.5). The differences in the activity of ChAT observed support the idea of the existence of asymmetry in the POA-AHA cholinergic system which varies during the oestrous cycle.

ISSN:0959-4965    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

We examined the effect of kynurenic acid, a broad spectrum antagonist of excitatory amino acid receptors, on striatal extracellular glutamate and aspartate accumulation induced by a 30 min forebrain ischaemia in rats. Kynurenic acid, given systemically (500 mg kg−1, i.p.) or administeredin situthrough the dialysis probe (10 mM), markedly depressed the ischaemia-induced increase in glutamate and aspartate concentrations. These results indicate that, during forebrain ischaemia, local glutamate receptors play a major role in glutamate and aspartate accumulation in the striatum. Ischaemia-induced increase in extracellular concentrations of these excitatory amino acids may be due in part to a positive glutamatergic feedback loop via activation of NMDA and/or non-NMDA receptors.

ISSN:0959-4965    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

In order to investigate GABA uptake into Müller glial cells electrophysiologically, we used the whole-cell voltage-clamp technique. Since Müller cells were insensitive to application of muscimol and baclofen, the expression of GABAAand GABABreceptors can be excluded. Therefore, the observed GABA current must be due to an electrogenic GABA transporter. This transporter is driven by the transmembrane Na+gradient, as replacement of the extracellular Na+by choline inhibits the GABA current. Currents evoked by cis-4-aminocrotonic acid, a GABACspecific agonist, are also inhibited by replacement of extracellular Na+, indicating that this compound is a substrate for the uptake. The competitive GABA uptake blockersβ-alanine and nipecotic acid are substrates of the transporter as well, and produce 42% and 65% of the currents elicited by the same GABA concentration, respectively. Affinity of the transporter for GABA is high, the Kmvalue being 5μM at −80 mV.

ISSN:0959-4965    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

A full-length cDNA clone encoding theα-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)/kainate (KA) receptor subunit 2 (HBGR2) was isolated from a human brain cDNA library. The HBGR2 cDNA has an open reading frame ≊2.7 kb that codes for an 883-residue protein. At the amino acid level, HBGR2 is 98% identical to its rat counterpart GluR2, and 69% to the AMPA/KA receptor subunit 1 from human brain (HBGR1). Injection of cRNA transcripts from the HBGR2 into oocytes produces barely detectable kainateactivated ionic currents, indicating that the HBGR2 subunit alone weakly expresses homomeric receptor channels. Coexpression of HBGR2 and HBGR1 transcripts, however, evokes kainate-dependent currents which activate at higher agonist concentration than those required by homomeric HBGR1 receptor channels. Coexpressed receptors display a linear current-to-voltage relationship at variance with the inwardly rectifying profile exhibited by HBGR1 homomers. Hence, the HBGR2 subunit co-assembles with the HBGR1 subunit to form heteromeric receptor channels akin to the glutamate receptors from rodent brain.

ISSN:0959-4965    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Mechanism of Ca2+mobilization from caffeine- and inositol-1,4,5-trisphosphate (IPA3) -sensitive internal Ca2+stores were studied in embryonic chick sensory neurones. Caffeine transiently increased [Ca]iin one-quarter of all cells tested. For non-responsive cells caffeine elicited [Ca]itransients at elevated [Ca]ilevel indicating the operation of Ca2+-induced Ca2+release. Injections of IP3and GTPγS-induced [Ca]itransients but IP3mobilizing agonists, carbachol and bradykinin, were either ineffective or produced weak responses. Pre-treatment with staurosporine and H-7 increased both the peak [Ca]iand the percentage of cells responsive to agonists. The effects were abolished by phorbol esters indicating that down-modulation is mediated by protein kinase C.

ISSN:0959-4965    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

A pilot study was carried out to test the feasibility of an adjustable computerized brain atlas, adapted to the individual anatomy for localizing current dipoles by means of magnetoencephalography (MEG). The atlas can be adapted to individual computed tomography (CT) or magnetic resonance (MR) images. Position information is transferred between these imaging methods and MEG using a stereotactic technique. For this purpose, a special non-magnetic helmet was designed to be used together with the ordinary head fixation system. It seems likely that the proposed combination of the brain atlas with MEG, CT and MRI methods will become a powerful tool in exploring different brain functions.

ISSN:0959-4965    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Visuo-kinesthetic matching of the orientation of an object in three-dimensional space has been studied by asking normal human subjects to align their unseen hand in parallel to the perceived orientation of a virtual stereoscopic object. Systematic errors were found for all three degrees of freedom of object orientation. These errors were much reduced when vision of the hand was allowed. The analysis of the distribution of the directional components of the errors revealed that matching performance without view of the hand was biased in a preferred direction that coincides with neither anatomical axes of the hand nor earth-fixed axes of visual space, but is intermediate between hand space and visual space. This suggests that a hybrid frame of reference is constructed by combining parallel multisensory information.

ISSN:0959-4965    

出版商:OVID    

年代:1994

数据来源: OVID