摘要:

THE present study was undertaken to examine the role of temperature on the ability of 7-nitroindazole (7-NI) to prevent methamphetamine-induced dopamine (DA) neurotoxicity. Male Swiss-Webster mice received methamphetamine alone or in combination with 7-NI at either room temperature (20 ± 1°C) or at 28 ± 1°C. At 20°C, 7-NI produced hypothermic effects and afforded total protection against methamphetamine-induced DA depletions in the striatum. At 28 ± 1°C, 7-NI produced minimal effects on body temperature and failed to prevent methamphetamine-induced DA reductions. These findings indicate that the neuroprotection afforded by 7-NI is likely related to its ability to produce hypothermia because agents that produce hypothermia and/or prevent hyperthermia are known to attenuate methamphetamine-induced neurotoxicity.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

IT has been shown recently in rat hippocampus that the synapse specificity of Hebbian long-term potentiation breaks down at short distances (< 100μm). Using a neural network model we show that this unspecific component of long-term potentiation can be responsible for the robust formation and maintainance of cortical organization during activity-driven development. When the model is applied to the formation of orientation and ocular dominance in visual cortex, addition of an unspecific component to standard Hebbian learning, in combination with a tendency of left-eye and right-eye driven synapses to initially group together on the postsynaptic neuron, induces the simultaneous emergence and stabilization of ocular dominance and of segregated, oriented ON/OFF subfields. Since standard Hebbian learning cannot account for the simultaneous stabilization of both structures, unspecific LTP thus induces a qualitatively new behaviour. Since unspecific LTP only acts between synapses which are locally clustered in space, our results imply that details of the local grouping of synapses on the dendritic arbors of postsynaptic cells can considerably influence the formation of the cortical functional organization at the systems level.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

NOCICEPTIN stimulation of the ORL1 receptor expressed in Chinese hamster ovary (CHO) cells results in the activation of the extracellular signal regulated kinases ERK1 and ERK2. ERK1/ERK2 activation is inhibited by pertussis toxin, the MEK inhibitor PD 98059 and by transient expression o α-transducin, indicating that ORL1 up-regulation of these kinases occurs as a consequence of the release of the G-protei n βγ complex following the activation of pertussis-toxin sensitive Gαi-family G-proteins. Using specific reporter genes we demonstrate that the transcription factors Elk-1 and Sap1a are activated in a pertussis toxin-sensitive manner as a consequence of ORL1 upregulation of ERK1/ERK2 to induce changes in gene expression. The activation of these transcription factors is also inhibited following treatment with PD 98059 and following coexpression of α-transducin.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

OUR recent study demonstrated with the brain's automatic change-detection response, the mismatch negativity (MMN) of the event-related potentials (ERPs), that the duration of auditory sensory memory is significantly shorter in school-age children with CATCH syndrome than in healthy age-matched controls. One of the haracteristic symptoms of this syndrome, caused by a microdelection in chromosome 22, is cleft palate. The most common problems in these children, however, are learning difficulties and, according to our results, it is likely that these problems are not due to the dysmorphology of peripheral speech mechanisms only but are also caused by CNS dysfunctions. In the present study we show with MMN that auditory sensory memory is also shortened in school-age children with cleft palate but without the ATCH syndrome. It has been shown in previous studies with neuropsychological tests that although children with cleft palate have language and learning-related problems these difficulties are usually less severe than those of CATCH children. Likewise the present study demonstrates that the auditory sensory memory trace seems to decay more rapidly in CATCH children than in children with cleft palate.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

WE have reported previously that the NPY Y1receptor antagonist BIBP3226 applied into the dorsal periaqueductal gray matter (DPAG) has an anxiogenic-like effect in the elevated plus-maze test in rats. In the present study the effects of neuropeptide Y (NPY) Y1receptor antagonists BIBP3226 (500 pmol) and 1229U91 (formerly also GR231118, GW1229 and EXBP68, 100 and 500 pmol) administered into the DPAG were investigated in the social interaction test in rats. BIBP3226 and 1229U91 (both 500 pmol) significantly decreased the time spent in active social interaction. These results provide additional evidence that NPY-ergic neurotransmission in the DPAG may be involved in the modulation of anxiety-related behaviour and suggest that endogenous NPY, released under stressful conditions in the DPAG, relieves anxiety via the NPY Y1receptors. This is the first report demonstrating the effect of NPY receptor active agent on social behaviour.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

INDrosophila melanogasteradult or larval rearing conditions influence brain structure. In particular, larval density affects the number of fibers forming the mushroom bodies, a neuropil structure involved in olfactory learning. The mushroom bodies receive chemosensory inputs from the antennal lobes at the level of the calyx. In this study we report that larval density affects calyx volume measured shortly after eclosion from the pupal case. We observe that in the memory mutantamnesiacthis form of experience-dependent structural plasticity is missing, whereas it is not affected in the learning mutantrutabagaand in the memory mutantradish. Independent of the plasticity effect, the calyces are on average slightly bigger than wild type inamnesiacand smaller inrutabagaflies.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

NON-INVASIVE brain temperature measurements using proton magnetic resonance spectroscopy were used to test the hypothesis that localized head cooling would reduce brain temperature in 10 normal adult humans. Temperature reductions of the head surface to 15.8 ± 3.5°C did not reduce brain temperature measured in the superficial cortex (36.8 ± 0.5°C) or thalamus (36.6 ± 0.7°C), as compared to measurements obtained with a head surface temperature of 34.7 ± 1.6°C (37.0 ± 0.6°C and 36.6 ± 0.4°C, respectively). There was no change in the temperature gradient from the superficial to deep brain locations in the presence or absence of head cooling, and brain temperature did not decrease as a function of the duration of head cooling for periods up to 50 min. There was no correlation between the scalp surface (range: 10–38°C) and brain temperature at either the deep or superficial locations.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE distribution and modulation of neural cell adhesion molecule polysialylation state (NCAM PSA) and the consequence of antisense inactivation of the Kv1.1 potassium channel was investigated following avoidance learning in mice. PSA immunoreactivity was most notable on cells at the inner denate border and in cortical layer II. Task acquisition resulted in a significant 30% transient increase in the frequency of dentate polysialylated neurons at the 1 2 h post-training time. In contrast, animals pretreated with the Kv1.1 antisense oligonucleotide exhibited both attenuated recall avoidance latencies and polysialylated cell frequency. As Kv1.1 is enriched on the dendrites of these granule-like cells, the attenuated polysialylation response is considered secondary to NCAM-mediated events during their transient synapse production in the 6–8 h post-training period.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

CELLULAR immediate early genes (IEG) such as c-foswere originally defined as rapid and transient inducible gene, but their products show a varying degree of basal expression in the brain of normal animals, suggesting that they also play a role in the transcriptional control under physiological conditions. In this study, we used an immunohistochemical method to investigate changes in the number of c-Fos-immunoreactive cells in the cerebral cortex and hippocampal formation of the aged rat. There was a remarkable decrease in the number of c-Fos -immunoreactive cells in the piriform and temporal cortex of aged rats compared with young adult rats. There was a slight decrease in the number of c-Fosimmunoreactive cells in the parietal cortex of aged rat. In the hippocampal complex, there were also decreases in the number of c-Fos-immunoreactive cells in aged rat; the degree of decrease was most prominent in the dentate gyrus. This report provides the first morphological evidence for decreased levels of basal c-Fos expression in some cerebral cortical areas and in the hippocampal complex of aged rats.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

TO investigate the functional organisation and information processing inLymnaeaneuronal networks, artificial spike trains were elicited in one of the main respiratory interneurons (RPeD1) and the modulation of the firing patterns of postsynaptic cells was examined. This was performed by precisely timing the action potential generation of the presynaptic cell using a computer-controlled voltage clamp amplifier (pattern clamp technique). Induced oscillation (0.1–0.4 Hz) in the firing pattern of RPeD1 spread to a large number of post-synaptic cells, as clearly demonstrated by Fourier power spectra. At the same time, no signs of precise (millisecond) spike timing was observed in the cells studied. The results confirm that the neurons used in our experiments process information as pure rate-coders.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID