摘要:

THE various components which together make up the complex state of consciousness require neural support involving a connected network of many brain areas at differing levels. At the lowest level is non-aware processing, of which there is not direct awareness. There are also modules involved in processing with awareness but without focussed attention. Finally there must be a set of modules involved in directing attention in a controlled manner. We expect to be able to dissociate the various components of the three-stage network by using different levels of attention. The results of an auditory experiment performed under three different levels of awareness and attention are analysed to show support for the three-stage model of awareness. The relevant auditory areas are delineated.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

SWALLOWING-RELATED neurons (SRNs) were recorded systematically in the medulla oblongata of urethane-anesthetized cats. The SRNs received orthodromic inputs from the superior laryngeal nerve (SLN) and showed transient changes in their activity synchronous with swallowing. These neurons could be divided into three types. Type I SRNs are sensory-relay neurons from the SLN in the nucleus of the tractus solitarius (NTS), type II are interneurons located diffusely in the parvo-cellular reticular formation ventral to the NTS, which received oligosynaptic inputs from the SLN, and type III are motoneurons in the nucleus ambiguus. Some type II neurons still showed the swallowing activity after the animals were paralysed, which suggests that they could be involved in the generation of swallowing outputs.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

ACETYLCHOLINE is well established as the neurotransmitter of starburst amacrine cells in the vertebrate retina but their function is poorly understood. We compared the distribution of muscarinic m2 receptors in the rat retina with the localization of the starburst cell processes. mAChR2 immunoreactivity appeared in a central band in the inner plexiform layer, which did not co-localize with the processes of the cholinergic amacrine cells. We found co-labelling of VAChT and ChAT making it highly unlikely that there are undetected cholinergic neurons in rat retina. Most mAChR2 receptors were located far from the cholinergic neurons, suggesting that most of them are unlikely to be associated with conventional cholinergic synapses.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

MOTOR effects mediated through adenosine A2Areceptors within the caudate-putamen were investigated in rats using bilateral microinfusions of MSX-3 (9 μg in 1 μl per side), a water-soluble phosphate prodrug of the selective A2Areceptor antagonist MSX-2. Blockade of striatal A2Areceptors produced a significant motor stimulation measured by an enhanced sniffing activity. Furthermore, catalepsy induced by systemic dopamine D1(0.75 mg/kg SCH23390, i.p.) or dopamine D2receptor blockade (1.5 mg/kg raclopride, i.p.) was potently reversed. These findings suggest that A2Areceptors within the caudate-putamen are tonically activated by endogenous adenosine and that a striatal A2Areceptor blockade produces motor stimulant effects, in particular in animals with dopamine hypofunction. The present results support the view that A2Areceptor antagonists may be potentially useful therapeutics for the treatment of Parkinson's disease.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

VISUAL motion perception of a single object, moving with a constant angular velocity of 40 min of arc/s in four orthogonal directions, was measured in eight patients with chronic bilateral vestibular failure (BVF) with the head stationary. Perception of object motion was more severely impaired for horizontal than for vertical directions and the impairment was more pronounced in the dominant eye than the nondominant eye. Impaired motion perception in patients with BVF is best explained by a central visual mechanism that suppresses oscillopsia due to the involuntary retinal slip caused by the defective vestibulo-ocular reflex (VOR). This mechanism cannot be switched off with the head stationary (inactive VOR) and thus causes a measurable deficit of motion perception.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

IN order to characterize how the dopamine (DA) and serotonin (5HT) systems may be interacting in medial prefrontal cortex (mPFC) during postnatal development, the specific toxin 5,7-dihydroxytryptamine (5,7-DHT) was used to induce lesions of the nucleus raphe dorsalis (NRD) in neonatal rats and the density of tyrosine hydroxylase-immunoreactive varicosities (TH-IRv) was assessed. During the early adult period, lesioned rats showed a significant increase in the density of the THIR fibers in layers V and VI when compared with sham-treated animals. These results suggest that postnatal development in medial prefrontal cortex may be associated with a competitive interaction between cortical monoaminergic systems, such that an early disturbance in the development of the 5HT innervation can potentially induce a hyperinnervation of DA fibres.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

TO determine whether neurturin (NTN), a recently identified homologue of glial cell line-derived neurotrophic factor (GDNF), is able to preserve tyrosine hydroxylase immunoreactivity (TH-IR) in a rat model of Parkinson's disease, polymer encapsulated cells genetically engineered to release NTN were implanted near the substantia nigra 1 week before a unilateral medial forebrain bundle axotomy. Animals were allowed to survive for 1 week post-axotomy. Upon sacrifice, animals that received a NTN capsule had a significantly higher percentage of TH-IR (lesioned sidevsnon-lesioned side) than animals that had received a capsule containing nontransfected parent cells. However, in contrast to GDNF, no reduction of turning was observed upon amphetamine rotation with NTN. Nevertheless, these results suggest that NTN might have a therapeutic value for the treatment of Parkinson's disease.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

NEURONAL intranuclear inclusions were recently found in the brain of patients with inherited neurodegenerative disorders characterized by the expansion of a polyglutamine stretch in the mutated protein. These inclusions are ubiquitinated and, for some of these diseases, the presence of the mutated protein could be also identified. Using immunohistochemistry, we show here that ubiquitinated intranuclear inclusions are also observed postmortem in the brain of patients suffering from Huntington's disease characterized by small polyglutamine expansions and adult onset. We were, however, unable to detect the mutated form of huntingtin in these inclusions. These intranuclear inclusions were detected only in the affected cerebral regions, suggesting that their presence is probably linked to the neurodegenerative process.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

WE examined the effects of puff application of endothelin (ET)-1 on the induction of long-term potentiation (LTP) and heterosynaptic long-term depression (LTD) in hippocampal CA1 slices. ET-1 applied 2 min prior to tetanus blocked the induction of LTP, but facilitated the induction of heterosynaptic LTD. These ET-1 effects on synaptic plasticity were dose-dependent, and not due to a generalized depression of baseline responses. ET-1 did not alter NMDA receptor-mediated responses. These data provide the first evidence that endothelin modulates activity-dependent synaptic plasticity, and the potency of these effects suggests that endogenous ET-1 may play an important role in regulating memory storage processes.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

EFFECTS of adrenalectomy on the 5-HT1Areceptor agonist 8-hydroxy-2-di-n-(propylamino)tetralin (8-OHDPAT)-and 2-deoxy-D-glucose (2-DG)-induced hyper-phagia were investigated in rats. Prior adrenalectomy completely inhibited 2-DG-induced hyperphagia, although it did not affect increases in food intake elicited by 8-OH-DPAT. These results suggest that 8-OH-DPAT-induced hyperphagia is independent of the adrenal hormone, corticosterone while 2-DG-induced hyperphagia is closely related to corticosterone.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID