摘要:

A CASE of apperceptive visual agnosia, revealing difficulties only in the performance on a standard overlapping-figures test, has been studied. Unusually, the patient demonstrated difficulties only with two semantic categories of the overlapped figures (clothes and school accessories); preserving, however, the knowledge of the same figures when presented isolated. We propose that the underlying deficit is only of a pseudo-semantic nature and is actually due to certain similarities of the two overlapping combinations, creating difficulties still on the apperception level only.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

NORIBOGAINE is formedin vivoby theO-demethylation of the indole alkaloid ibogaine. We report here that noribogaine acts as a full agonist at the μ-opioid receptor. Noribogaine-stimulated guanylyl 5′γ-[35S]thio]triphosphate ([35S]GTPγS) was studied in rat thalamic membranes to measure activation of guanine nucleotide binding proteins (G-proteins) in the presence of excess GDP. Noribogaine caused a 170% increase above basal [35S]GTPγS binding at sub-micromolar effective concentrations (EC50) in a naloxone-sensitive manner, confirming that this effect was an opioid receptor-mediated process. The level of intrinsic activity for noribogaine in these assays was comparable to the full agonists DAMGO and morphine. In contrast, ibogaine had no significant effect on [35S]GTPγS binding over a similar concentration range. The efficacy of noribogaine as a full μ-opioid agonist may explain ibogaine's ability to block the acute signs of opiate withdrawal and its suppressive effects on morphine self-administration.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE role of G proteins in glucose uptake was investigated using C6 glioma cells. Carbachol (an agonist acting via G protein coupled receptors) and 5′-guanylylimido diphosphate (Gpp(NH)p; a nonhydrolysable guanine nucleotide analog which bypasses the receptors and directly activates G proteins) stimulated [3H]2-deoxy-D-glucose (2DG) uptake by C6 cells, suggesting that hexose uptake is a G protein-mediated process. To identify the G protein involved in glucose uptake by C6 cells, the effect of carbachol on 2DG uptake was examined in the presence of pertussis toxin. Pertussis toxin treatment did not alter the ability of C6 cells to respond to carbachol, ruling out the involvement of Giαin 2DG uptake. C6 cells were transfected with Gqαor GLUT1 cDNA for 48 h, exposed to 1 mM carbachol for 2 h, and processed for 2DG uptake. Carbachol stimulated 2DG uptake in both Gqαand GLUT1-transfected cells. Gpp(NH)p, also stimulated 2DG uptake in Gqαand GLUT1-transfected cells. These results suggest that muscarinic receptor coupling to Gqαregulates hexose uptake in C6 cells.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

PREVIOUS functional neuroimaging studies of attention have emphasized the visual modality. We developed an auditory version of the continuous performance test (CPT) that included simple, focused and divided attention conditions. Positron emission tomographic (PET) scans were acquired during CPT performance in normal young adults and then submitted to statistical parametric mapping. Simple attention brought about a large region of activation involving the anterior cingulate gyrus and the right anterior/mesial frontal lobe. Focused and divided attention CPT conditions were compared but there were few significant differences. The findings are consistent with activation of an anterior attention network during auditory attention, without involvement of posterior attention structures which are more likely to vary in accordance with sensory modality.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

LAYER III pyramidal neurones were injected with Lucifer Yellow in cortical slices taken from the medial subdivision of the frontal eye field (FEF) of the macaque monkey. The average area covered by basal dendritic fields, in the dimension parallel to the cortical layers, was 115.1 ± 2.9 × 103μm2, significantly larger than that observed among layer III cells in eye movement-related visual areas of the parietal lobe. Furthermore, the dendritic fields of pyramidal cells in the FEF were considerably more complex than those of their counterparts in the parietal lobe, as evaluated by Sholl analysis. Spine density varied along the basal dendritic tree, reaching a maximum of 8.5 ± 0.8 spines/10 μm at a distance of 70–90 μm from the centre of the cell body. Such highly complex basal dendritic fields of layer III pyramidal neurones in the FEF may enable the integration of a diverse set of inputs from visual, motor, polysensory and memory-related periprincipal cortical areas.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

RECENT reports have shown that typical neuroleptics may enhance glutamatergic neurotransmission and that these effects might in part underlie motor side effects of chronic neuroleptic treatment. Since glutamate reuptake is the primary mechanism for controlling extracellular glutamate levels, the present study was conducted to examine whether chronic neuroleptic exposure alters gene expression for the glutamate transporter GLT-1 in the striatum. Although both haloperidol and clozapine treatment for 30 days significantly decreased GLT-1 expression from normal, the effects of haloperidol treatment were consistently, and in the dorsal striatum, significantly greater than those of clozapine. These findings suggest that a deficiency in glutamate transport may underlie the pathogenesis of neuroleptic-induced movement disorders.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

TEMPORAL patterns of release of aspartate, glutamate and glycine, which are related to excitatory amino acidergic transmission, were examined in organotypic slice cultures of rat suprachiasmatic nucleus over a 60 h period. Vasopressin release in the same culture was measured simultaneously to compare the temporal pattern with that of the amino acids. Amino acids and vasopressin were measured by high performance liquid chromatography and enzyme immunoassay, respectively. Robust circadian rhythms were detected in release of aspartate, glutamate and glycine. Glycine levels were about 10 times higher than those of aspartate and glutamate in the culture. Vasopressin also showed a clear circadian rhythm and the phase angle difference between each amino acid and AVP was not significantly different. The results indicate that cultured SCN cells release these amino acids and the release is under the control of the circadian pacemaker.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

WE have previously characterized the expression of the cystic fibrosis transmembrane conductance regulator protein (CFTR) gene, mRNA and protein in rat brain with reverse transcriptase (RT)-PCR amplification,in situhybridization and immunocytochemistry. We now report that the CFTR mRNA is expressed in the human anterior hypothalamus, an area involved in regulation of appetite, resting energy expenditure and sexual differentiation. Expression of CFTR in neurons localized to this region may elucidate the pathogenesis of other non-pulmonary manifestations of cystic fibrosis which commonly are observed in children with CF, including congenital absence of the vas deferens. Neuron-specific expression of CFTR in brain may be involved in the regulation of homeostatic functions including reproductive function and fertility through effects on neurosecretion, i.e. GnRH release. Dysregulation of normal neuropeptide vesicle trafficking by mutant CFTR in brain my lead to alteration in physiological function.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

WE investigated the role of retinotectal projections on the distribution of nitric oxide synthase (NOS) in the retinoceptive layers of the rat superior colliculus (SC) using histochemical methods. Rats enucleated at birth showed no alteration in the temporal pattern of NOS expression. There was, however, a dramatic change in the NADPH-diaphorase staining pattern of NOS-positive cells. NOS was absent from the distal portions of the dendritic trees of the deafferented SC. Nevertheless, staining the dendritic trees of these cells with Lucifer yellow showed that they were not morphologically different from those of the ipsilateral SC of monoenucleated animals. The same results were obtained when enucleation was performed in adult rats. We conclude that NOS intracellular distribution in the SC cells can be regulated by retinotectal projections in both developing and adult animals.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE effect of L-arginine (L-ARG; 10–100 mM) on dopamine efflux from rat striatum was investigated usingin vivomicrodialysis. L-ARG (50 mM–100 mM), but not D-arginine (100 mM) nor L-citrulline (100 mM), produced a biphasic effect on dopamine efflux with an initial small reduction, followed by a large sustained increase. The effect of L-ARG was not prevented by nitric oxide synthase inhibition with NG-nitro-L-arginine methyl ester or 7-nitroindazole monosodium salt. Efflux of 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) was reduced by L-ARG (10–100 mM), D-arginine (100 mM) and L-citrulline (100 mM). These data suggest that changes in dopamine, DOPAC and HVA efflux produced by high concentrations of L-ARG occur independently of NO, and that the use of high L-ARG concentrations are inappropriate when investigating the role of NO in striatum.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID