摘要:

WE selectively imaged the neural correlates of tinnitus, by contrasting a condition with no phantom auditory sensation with a condition during which tinnitus is present, using a rare form of tinnitus elicited by eye movements. Using positron emission tomography (PET), we demonstrate that phantom auditory sensation increases regional cerebral blood flow bilaterally in temporo-parietal association auditory areas but not in the primary auditory cortex. These results confirm that conscious perception does not necessarily require activation in primary areas and suggest that the perceptual qualities of tinnitus, e.g. intensity, frequency and spatial localization, are represented in temporo-parietal regions. Activation in these regions is compatible with cortical processing of ascending auditory messages generated at subcortical levels.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

IN an effort to define human cortical gustatory areas we reviewed functional neuroimaging data for which coordinates standardized in Talairach proportional space were available. We observed a wide distribution of peaks within the insula and parietal and frontal opercula, suggesting multiple gustatory regions within this cortical area. Multiple peaks also emerged in the orbitofrontal cortex. However, only two peaks, both in the right hemisphere, were observed in the caudolateral orbitofrontal cortex, the region likely homologous to the secondary taste area described in monkeys. Overall significantly more peaks originated from the right hemisphere suggesting asymmetrical cortical representation of taste favoring the right hemisphere

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

TO characterize the behavioral consequences of OMP gene deletion on odor processing we assessed the ability of OMP-null animals to acquire an airvsodor discrimination for five odorants, and determined whether OMP-null animals differed from controls in their threshold sensitivity to the odorant propanol. On average, control and OMP-null animals did not differ in the number of testing sessions needed to achieve criterion performance on each discrimination problem (2.04vs1.68, respectively; t=0.83,p= 0.41). However, null animals were significantly less sensitive to the odorant propanol (3.01 × 10−8vs1.06 × 10−5, respectively; t=4.09,p= 0.015). These invivobehavioral results provide support for the hypothesis that OMP plays a modulatory role in the odor detection/signal transduction process.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

VISUAL evoked potentials (VEPs) were recorded to probes presented to the dominant and suppressed eyes in a binocular rivalry paradigm. Probes presented to the suppressed eye interrupted the current dominance phase and produced a P300-like deflection (400–700 ms). Probes delivered to the dominant eye increased the duration of the current dominance phase. VEPs to these probes included an endogenous component that overlapped the early exogenous components. The early endogenous component (rivalry-related potential, RRP) started as early as 70 ms and had a broad centroparieto-occipital distribution.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

IN view of the key role exerted by neurotransmitter transporters in the synaptic transmission, the expression of GABA transporter GAT-1 was analysed during cerebellar development, when relevant processes of synapse maturation take place. GAT-1-immunoreactive (IR) structures started to be detected on PD 8–9, at the low molecular and Purkinje cell layer, coincident with the onset of functional inhibitory synapses on Purkinje neurons. By PD 18, GAT-1-IR structures completely ensheathed the Purkinje cell somata thus outlining the characteristic perisomatic formation, whereas GAT-1 wrapping on the axon initial segment started to be detected only at PD 15, and the mature form of the pinceau was fully developed from PD 23 on. These results, when compared with the functional maturation of the GABAergic input to Purkinje cells, indicate that GAT-1 may play a significant role in the differentiation of basket interneuron-Purkinje cell circuit.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

ENDOTHELINS (ETs) elicit a diversity of cellular responses in cultured astrocytes that suggest an important role of these peptides in glial cell function. Stimulation of astroglial ET receptors induces phosphoinositide (PI) hydrolysis and intracellular calcium mobilization, but little is known about the signalling events that occur downstream of this system. Here we show that in rat cerebellar astroglia in culture ETs produce a receptor-mediated stimulation of cyclic GMP (cGMP) formation that is rapid and totally dependent on nitric oxide synthase (NOS) activity. The effect is blocked by an inhibitor of PI phospholipase C, compound U73122, and by depletion of intracellular calcium stores with thapsygargin. These results indicate that calcium released by inositol trisphosphate is responsible for NOS activation and subsequent cGMP formation.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

THE β-amyloid peptide (Aβ) has been known to activate microglia and to induce release of nitric oxide (NO). In this study, we examined the effect of cAMP on Aβ-induced microglial activation using cultured rat brain microglia. Dibutyryl-cAMP (dbcAMP) and 3-isobutyl-1-methylxanthine (IBMX) significantly potentiated Aβ(25–35)- or Aβ(1–42)-induced NO release in a dose-dependent manner. The increase in NO release was due to the increased expression of inducible nitric oxide synthase (iNOS). However, forskolin, an adenylate cyclase activator, weakly increased NO release at 10–50 μM but caused a decrease at 100 μM. These results suggest that increase in intracellular cAMP could potentiate microglial activation induced by Aβ.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

METABOLIC hypofunction is a common finding in a number of neurodegenerative diseases, including Alzheimer's disease (AD). The strong linkage between the amyloid precursor protein (APP) and AD led us to examine whether over-expression of this protein in CNS-type cells had an effect on mitochondria. We found abnormal morphology in mitochondria of the neuroectodermal progeny of P19 cells stably transfected with human APP751. In addition, the mitochondria of APP-transfected clones had a decreased mitochondrial membrane potential. These changes were independent of Aβ toxicity and distinct from complex I inhibition. Our results have important implications for the earliest events in the pathophysiology of AD and, by extrapolation, for intervention therapies.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

NEUROPROTECTIVE drugs such asGinkgo bilobaextract (EGb 761) could prevent the ischemia-induced impairment of the Na, K-ATPase activity. In this study, Na, K-ATPase activity and expression, contents in fatty acids and malondialdehyde, an index of lipoperoxidation, were compared in the ipsilateral (ischemic) and the contralateral (unlesioned) cortices after 1 h of unilateral focal cortices cerebral ischemia in the mouse. EGb 761 (100 mg/kg) was administered daily to half of the animals for 10 days before ischemia. Ischemia significantly reduced Na, K-ATPase activity by about 40% and increased malondialdehyde content; EGb 761 pretreatment abolished these effects. The free radical scavenger properties of EGb 761 are a potential mechanism by which Na, K-ATPase injury and lipoperoxidation are prevented.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

VIRAL entry through the blood-brain barrier (BBB) has not been fully defined and identification of coreceptors that can facilitate this phenomenon is crucial in understanding disease progression. Using a RNAse protection assay to examine chemokine receptor families simultaneously, we analyzed the total RNA ofin vitroBBB cultures treated with purified preparations of HIV gp120, gp41, TAT proteins and TNF-α. HIV tat protein affected CCR1 and CCR3 mRNA expression whereas the other viral by-products had no effect. Interestingly, TNF-α was able to induce CCR1, CCR3 as well as CXCR1, CXCR2, CXCR4 receptors and Burkitt's lymphoma receptor BLR2. These results suggest that HIV-induced molecules can manipulate the surface receptor expression of the BBB to allow for their preferential entry into brain.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID