ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Satiety signals from the gastrointestinal tract travel via vagal afferents to the nucleus of the solitary tract (NTS) in the brain stem, the first central relay in a neural network which controls food intake. The non-competitive NMDA antagonist MK-801 faciliates food intake in rats by acting on the NTS. Here we report that hepatic portal vein infusion of MK-801 (25 or 50 μg/kg) increases intake of an intraorally infused IM solution of sucrose (by 113 ± 9 and 132 ± 11%, respectively) and that this effect is prevented by hepatic vagotomy. By contrast, jugular vein infusion of MK-801 fails to increase sucrose intake but induces forward locomotion, indicating activation of a central mechanism. These data suggest that MK-801 can stimulate food intake by acting peripherally on hepatic vagal afferents.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The i.v. self-administration by rats of a polydrug combination of methamphetamine and heroin was explored. The rewarding efficacy of a range of methamphetamine doses (0.0625–2.0 mg/kg/injection) alone or in combination with heroin (12.5 μg/kg/injection) was compared using a progressive-ratio (PR) schedule of reinforcement. Breaking points (BP) for one group of rats were determined at each dose of methamphetamine-alone and for another group at each of the same methamphetamine doses plus the heroin dose. The methamphetamine–heroin combination was associated with higher BPs than methamphetamine alone at all doses of methamphetamine. These data demonstrate that methamphetamine-heroin combinations (speedballs) produce a greater rewarding effect than the identical doses of methamphetamine alone and suggest that enhanced reward may underlie the popularity of speedball abuse.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Pharmacological data suggest that opioids exert their excitatory action in brain indirectly, by inhibiting release of the inhibitory neurotransmitter GABA. However, it is also possible that single neuron may interact with both opioids and GABA. In the present study, we investigated whether neurons in rat midbrain and medulla express both opioid and GABAAreceptors. Coronal sections through rat brain were double-stained using antibodies against the alpha 1 subunit of GABAAreceptor that were combined with antibodies either against the cloned muopioid receptor (MORI) or the cloned kappa-opioid receptor (KORI). Neurons double-labeled for GABAAreceptors and either MORI or KORI were found in many brain regions including inferior colliculus, mesencephalic trigeminal nuclei, pontine reticular nuclei and raphe interpositus nucleus. Neurons double-labeled for GABAAand MORI were observed less frequently than those labeled for GABAAand KORI. Our findings provide anatomical evidence that GABAergic and opioidergic systems are closely linked and activity of the same neuron may be regulated directly by both GABA and opioids.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Brief tetanic stimulation (eight pulses at 100 Hz) of afferent fibers innervating area CAI of the hippocampus produce gamma oscillations. When delivered every minute the oscillation habituated markedly after the first stimulus. This habituation could be transiently reversed by stimulating a different pathway to the recorded area. Gamma oscillation-induced beta frequency oscillations were only seen in response to the first (novel) stimulus and the gamma oscillation itself was markedly attenuated by on-going, non-oscillogenic, synaptic activity. The NMDA receptor antagonist ketamine abolished the response to novel stimuli but left the habituated response relatively unaffected. The pattern of habituation parallelled that seen for sensory induced gamma and beta oscillations in the clinical EEG.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Mutations in the parkin gene cause autosomal recessive juvenile parkinsonism. Immunostaining of substantia nigra sections from sporadic Parkinson's disease (PD) cases shows that Parkin accumulates in axonal spheroids and in some Lewy bodies. Because ubiquitin is a major component of Lewy bodies and axonal spheroids, we investigated whether Parkin is metabolized via the ubiquitin/proteosomal pathway. Treatment of BEM17 neuroblastoma cells with the proteosomal inhibitor, MG132, produced a band corresponding to di-ubiquitinated Parkin that was apparent by immunoblot using two different anti-Parkin antibodies. This higher mol. wt band also coimmunoprecipitated with Parkin. These data suggest that Parkin plays a role in the pathophysiology of sporadic PD, and that Parkin is a substrate for ubiquitination that is degraded by the proteosomal complex.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

A patient with a lesion of the posterior half of the corpus callosum correctly named simple (e.g. colors) and complex (e.g. faces) stimuli whether presented to one or both hemi-fields. Although proficient at these tasks, and also able to make same/different judgements for stimuli within an hemifield, he failed dramatically when required to compare stimuli between the two hemifields. These results indicate that, while the posterior portion of the corpus callosum may not be essential for naming visual stimuli, it is essential for comparing stimuli between the two visual fields.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The lack of subtype-selective compounds for AMPA receptors (AMPA-R) led us to search for compounds with such selectivity. Homoibotenic acid analogues were investigated at recombinant GluR1o, GluR2o(R), GluR3oand GluR1o+ 3oreceptors expressed in Sf9 insect cells and affinities determined in [3H]AMPA radioligand binding experiments. (S)-4-bromohomoibotenic acid (BrHIBO) exhibited a 126-fold selectivity for GluR1ocompared to GluR3o.Xenopus laevisoocytes were used to express functional homomeric and heteromeric recombinant AMPA-R and to determine BrHIBO potency (EC50) at these channels. (R,S)-BrHIBO exhibited a 37-fold selectivity range amongst the AMPA-R. It is hoped that BrHIBO can be used as a lead structure for the development of other subtype-selective compounds.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Two abnormal SOD1mRNAs, exon 2-skipping and exon 2 and 3-skipping species, were identified from occipital brain tissue of sporadic amyotrophic lateral sclerosis (ALS) patients carrying no mutations in the SOD1 gene. Both transcripts were ubiquitously expressed in non-neuronal as well as neuronal tissues from a subject without neurological diseases. The expression pattern did not show disease specificity or lesional selectivity associated with ALS. Transient expression studies revealed weak expression of the proteins derived from the exon 2-skipping SOD1 cDNA in a cell-free translation system but not in cells. The putative abnormal SOD1 protein may accumulate and exert toxic effects on motor neurons in ALS when the proteolytic system is disturbed by aging or some causal factors.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Processing of somatosensory input in rhesus monkey is known to involve unimodal and polymodal association cortex within the the first superior temporal sulcus (STS) Of the temporal lobe. The present study provides evidence for the activation of homologous structures in normal human subjects. Neuromagnetic evoked responses to intermittent unilateral median nerves stimulation were generated within the temporal lobe at 72–96 ms, with responses in the contralateral hemisphere leading those in ipsilateral cortex by 18ms. The latency of these responses suggests that somatosensory information is available for integration with input from other sensory modalities in temporal cortex quite early in the processing stage.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID