摘要:

Several enzymes hydrolyze ATP, producing ADP which is hydrolyzed to AMP. Ecto-5′-nucleotidase produces adenosine from AMP. Glutamate (Glu) is an excitatory neurotransmitter and increases extracellular adenosine levels, which is considered an important inhibitory neuromodulator. Here we show that Glu activates ADP and AMP hydrolysis. NMDA and kainic acid (KA) also increased these enzymatic activities, but 1-aminocyclopentane-1S, 3R-dicarboxylic acid (ACPD) had no effect. Dihydrokainate (DHK), an inhibitor of glutamate uptake, also blocked glutamate-evoked activation of ecto-nucleotidases, suggesting that this activation was also Glu transporters dependent. Therefore, we suggest that the Glu-evoked stimulation of ecto-nucleotidases might contribute to the increase of adenosine in extracellular space induced by Glu.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The view that light affects the mammalian circadian clock only through the eyes was recently challenged by a study in which the phases of human circadian rhythms were shifted by extraocular light exposure. This finding has not been confirmed, however. We studied the effects of light exposure (3 h, broad spectrum fluorescent white light, 13 000 lux) on abdomen and chest on the circadian rhythms of serum melatonin, cortisol and thyrotropin in six subjects. The protocol consisted of two 3-day sessions in a dimly lit (< 10 lux) experimental unit. In both sessions hourly serum samples were collected for hormone analysis on days 1 and 3. The skin light exposure was delivered on day 2 from 22.00 to 01.00 h in one of the two sessions in a randomized order. In both sessions all three rhythms tended to delay, presumably due to the endogenous circadian cycle length being slightly longer than 24 h. However, the phase shifts did not differ significantly between the sessions. Thus, the present study does not support the existence of extraocular photic regulation of the circadian rhythms in humans.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

We report here a modified mRNA differential display method and its application for the analysis of differential gene expression in NGF-treated PC12 cells and in embryonic rat spinal cord. The optimized protocol is based on low fidelity priming of multiple cDNAs followed by high fidelity amplification. In PC12 cells induction by nerve growth factor (NGF) altered the expression of 4% of the 466 transcripts evaluated. During neurogenesis of the spinal cord we found that 30% of the 288 examinedproducts changed. The differential expression of the characterized genes was confirmed by independent quantitative PCR. We conclude this method is suitable for the identification of increases and decreases of mRNA levels and allows the discovery of differentially expressed unknown transcripts.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The responses to neurotrophic factors may be modulated by changes in the levels of expression of their receptors. The aim of this study was to determine whether neural precursorsin vivoshow cell cycle phase-dependent changes in expression of p75NTRand Ret. Preparations of embryonic mouse gut were processed for Ret or p75NTRimmunohistochemistry to identify neural crest-derivedcells, and cells undergoing mitosis were identified using a fluorescent nucleic acid stain. Neural crest-derived cells undergoing mitosis showed over twice the levels of p75NTRimmunoreactivity (pixel intensity measured on a confocal microscope) on their surface to that shown by non-mitotic neural crest cells. However, there was no significant difference between the levels of Ret on mitotic and non-mitotic neural crest cells.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Motor imagery is known to involve brain regions vital to the performance of motor skills including primary motor cortex. The present results show that, following cerebral vascular accidents (CVAs) affecting a variety of these regions, many adults with left or right upper-limb paralysis (i.e. hemiparesis/hemiplegia) retain the ability to accurately represent prehensile movements involving the impaired limb. This suggests that during the acute phase of recovery many CVA patients can use motor imagery to activate partially damaged motor networks;a process that may facilitate functional reorganization. This ability was, however, compromised in cases with right posterior parietal or left frontal lesions. This pattern is consistent with the hypothesis that imagined prehension, like actual reaching and grasping, involves a network of highly interconnected areas distributed throughout parietal and frontal cortices.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Microinjection of neuropeptide Y (NPY) into the paraventricular nucleus (PVN) of the hypothalamus stimulates eating and increases respiratory quotient. In contrast, administration of opioid receptor antagonists reduces food intake and suppresses NPY-induced feeding. The present study examined whether naloxone methiodide, an opioid antagonist, would suppress the potentiation of NPY on energy substrate utilization, when injected into the PVN. Naloxone methiodide was injected at doses of 0.1 and 1.0 μg, 10 min prior to NPY treatment. NPY was administered immediately prior to the start of the nocturnal period and RQ was determined using an open-circuit calorimeter. Doses of 50 and 100 pmol NPY alone evoked reliable increases in RQ within 30 min of treatment. Following naloxone methiodide pretreatment, the stimulatory action of NPY was significantly attenuated. These data indicate that opioid receptors in the PVN influence the action of NPY on energy substrate utilization.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

It is now well established that nerve growth factor (NGF) plays a key role in inflammation-induced hyperalgesia. It was also reported that brain derived neurotrophic factor (BDNF), another member of neurotrophins, contributed to the pain pathway as a neurotransmitter in the CNS. The present work demonstrated a down-regulation of glial cell line-derived neurotrophic factor (GDNF) mRNA expression in dorsal spinal cord in complete Freund's adjuvant-induced unilateral arthritic rats serving as a chronic pain model. The fast occurring and long lasting down-regulations suggest that GDNF might contribute to pain pathway in a way different from neurotrophins and might play a role in the maintenance of chronic pain status.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

PET was used to providein vivoimaging of the over-expression of dopamine D2receptor (D2R) induced by adenovirus vector-mediated gene transfer in rat striatum. The uptake of three kinds of D2R-specific ligands, [11C]raclopride, [11C]nemonapride and [11C]N-methylspiperone, measured by PET was higher in the striatum injected with the vectors for D2R than the contralateral striatum injected with a control vector 2–3 days after injection. However, the uptake of [11C]SCH 23390, a dopamine D1receptor specific ligand, or [11C]β-CIT-FP, a dopamine transporter specific tracer, was not different between bilateral striata. Co-injection of excess unlabeled raclo-pride inhibited the uptake of [11C]raclopride. At day 16 the increased uptake of [11C]raclopride declined to basal level, consistent with pastin vitroassessment of this vector. In vivo imaging of D2R will permit longitudinal assessment of the eficiency of this and similar vectors in rat brain that can be related to functional changes being observed.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

It is uncertain whether frequent marijuana use adversely affects human brain function. Using PET, regional cerebral blood flow was compared in frequent marijuana users and comparable, non-using controls after at least 26 h of monitored abstention by all subjects. Marijuana users showed substantially lower brain blood flow than controls in a large region of posterior cerebellum, indicating altered brain function in frequent marijuana users. A cerebellar locus of some chronic and acute effects of marijuana is plausible, e.g. the cerebellum has been linked to an internal timing system, and alterations of time sense are common following marijuana smoking.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

We cloned the full length guinea pig H3receptor cDNA using RT-PCR amplification with primers from the human receptor and templates from brain areas. Evidence was obtained for two isoforms, designated H3L and H3S, differing by a 30 amino acid stretch within the third cytosolic loop, presumably generated by alternative splicing.In situhybridization using a selective cRNA probe showed the gene transcripts to be highly expressed in discrete neuronal populations, e.g. pyramidal cells in the cerebral cortex or cerebellar Purkinje cells, in some instances already known to express other histamine receptor subtypes.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID