摘要:

To clarify whether a hypo or hyperfunctioning mesocorticolimbic system is the neural substrate of Attention-Deficit Hyperactivity Disorder (ADHD), we carried out a morphometric analysis on an animal model, the Naples high excitability rat (NHE). Male adult NHE and control rats were used for tyrosine hydroxylase (TH) immunocytochemistry in the ventral tegmental area and substantia nigra in coronal cryostat sections. PC-assisted image analysis showed larger DA neurones in the ventral tegmental area but not in the substantia nigra of NHE rats than in controls, associated with a higher expression of TH in the neuropil. Thus, the increased activity and impaired attention of NHE rats are associated with a hyperfunctioning mesocorticolimbic system in this ADHD model.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Regional cerebral blood flow (rCBF) in healthy controls and non-demented, non-depressed Parkinsonian patients was measured using H215O PET while subjects performed a prelearned pattern recognition task with delayed response. To investigate differences between the two groups in response to reward, the experimental design consisted of three reinforcement conditions: no reinforcement consisting of nonsense feedback, positive symbolic reinforcement and monetary reward. In the controls, monetary reward activated bilaterally the striatum and anterior cingulate gyrus, as well as unilaterally the left cerebellum, midbrain and medial frontal gyrus. Symbolic reinforcement revealed a similar pattern of activation, except that the striatum and left midbrain showed no activation. The Parkinsonian patients responded to monetary reward with increased activation bilaterally in the cerebellum, medial frontal gyrus, and anterior cingulate gyrus as well as unilaterally in the right fusiform gyrus and midbrain and left caudate nucleus and precentral gyrus. Symbolic reinforcement induced significantly increased rCBF in the right cerebellum only. Compared with symbolic reinforcement, monetary reward produced extended activation of temporoparietal association cortex. The pattern observed in the controls demonstrates the role in reward processing of dopaminergic mesolimbic pathways in the healthy human brain, whereas the pattern in the Parkinsonian patients suggests the involvement of compensatory cortical loops in the diseased brain.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Nociceptin/orphanin FQ (NC), the endogenous ligand for the G-protein coupled nociceptin receptor (NCR), has a modulatory role in various physiological processes including neuro-transmitter release. We have examined the effects of NC, the analogues NC(1–13)NH2and [F/G]NC(1–13)NH2and the competitive antagonist [Nphe1]NC(1–13)NH2(Nphe1) on glutamate efflux during an acute simulated ischaemic challenge in rat cerebrocortical slices. The increase in glutamate efflux seen with ischaemia was inhibited by NC (EC50250 nM). At micromolar concentrations, the analogues were found to have a similar effect on glutamate efflux compared to NC. In all cases, inhibition of glutamate efflux was abolished by Nphe1(30 μM). These results suggest a neuroprotective action for NC.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Recent evidence suggests that aberrant nicotinic receptor (nAChR) expression plays an important role in schizophrenia. The present study sought to examine the distribution of nAChRs within the thalamus and associated cholinergic structures by examining nAChR subunit mRNA expression usingin situhybridization histochemistry. Transcripts for α4 and β2 subunits were found in high levels in all thalamic nuclei and at lower levels in cholinergic nuclei (PPTg and MS/VDB). Distribution of mRNA encoding for additional subunits was restricted; lower β3 subunit transcript levels were detected in the anterior thalamic nuclei and portions of the lateral and posterior thalamic nuclei, with α7 transcripts being detected in cholinergic nuclei, the IMD and very low levels in the RTN. Low levels of α6 and β3 transcript were found only within the RTN.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

L-Arginine (L-Arg), a substrate for nitric oxide synthase (NOS) at a dose of 250–500 mg/kg, i.p., significantly reduced the duration of immobility both in the forced swimming test (FST) and in the tail suspension test (TST), two models of depression in mice, without changing locomotion in an open field. Paradoxically, a similar effect was observed with the administration of NG-nitro-L-arginine (L-NNA) (0.3–10 mg/kg, i.p.), an inhibitor of NOS. However, higher doses of L-Arg (750–1000 mg/kg) and L-NNA (30 mg/kg) did not produce any antiimmobility effect in FST and TST. The inactive isomers D-Arg (100–1000 mg/kg, i.p.) and D-NNA (0.3–30 mg/kg, i.p.) did not affect immobility duration in either the FST and TST. Preadministration of L-NNA (30 mg/kg, i.p.), but not of D-NNA completely blocked the anti-immobility effect of L-Arg (500 mg/kg, i.p.) in the FST. Similarly, L-Arg (750 mg/kg, i.p.), but not D-Arg blocked the anti-immobility effect of L-NNA (3 mg/kg, i.p.) in the FST. The results indicate that either the synthesis of NO or the inhibition of its synthesis may produce antidepressantlike effects when assessed in the FST and TST. The physiological meaning of this finding is still obscure, but it could indicate that NO has a dual role in the modulation of depression.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The present study addresses the separate activities of frontal and temporal MMN generators which might be differentially affected by a change in the probability of standard stimuli. As the probability of standard stimuli was increased, the frontal MMN component significantly increased in amplitude, while the temporal one was not affected. Correspondingly, the scalp current density (SCD) maps showed that the temporal MMN generator was activated even at low probability of standard stimuli, suggesting that even the weak memory trace could start the automatic mismatch process, whereas the frontal MMN generator was activated only with increased probabilities of standard stimuli, suggesting that the stronger the memory trace is, the easier it might trigger the involuntary switching of attention to stimulus change.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The number of presynaptic vesicles that are immediately available for release, the readily releasable pool (RRP), is a strong determinant of synaptic strength and plasticity. The properties of the RRP in individual GABAergic synapses were examined in superior colliculus cultures. The RRP was depleted by high frequency trains and cumulative evoked IPSC amplitudes (CA) were calculated. The amplitude of monoquantal responses (q) was determined on the basis of mlPSC histograms. On average, the RRP, defined as CA/q, comprised about 10 vesicles. About 60% of the RRP could be released by a single stimulus. After depletion, the RRP was replenished with a time constant of about 14 s. These data provide information for further studies on the capacity of individual inhibitory synapses to modulate sensory information transfer.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Deviant anatomical asymmetry of perisylvian cortex is argued to be linked to specific language impairment (SLI). However, no studies have examined whether deviant functional asymmetry underlies the processing of spoken language. In the current study, brain-electrical activity was recorded from 31 scalp sites to the function word ‘the’ embedded in auditorally presented stories and nonsense contexts. The SLI children showed reversed asymmetry at electrode sites over temporal cortex compared to control children in processing this word in all contexts. They also appear to lack some contribution from a deep neural generator in processing ‘the’ in the story. This investigation is the first to demonstrate a direct link between deviant neurophysiological asymmetry and the processing of spoken language in children with SLI.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

PEP-19 is a calmodulin-regulatory protein found specifically within neurons, though cellular functions of this protein have not been determined. In an effort to define potential effects of PEP-19, PC12 cell lines expressing this protein were generated and subjected to apoptotic stimuli. As measured by LDH release, cell death in PEP-19 expressing cells was 2-to 5-fold less following u.v. irradiation, and 2- to 4-fold less following staurosporine treatment than controls. Additionally, PEP-19-expressing cells displayed decreased DNA ladder formation, chromatin condensation, and caspase activation following staurosporine treatment. Overall, these results demonstrate that PEP-19 can inhibit apoptotic processes in PC12 cells, suggesting a potential regulatory mechanism for pathways leading to cell death.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Deficiencies of Ca2+homeostasis are proposed to play an important role in neuronal ageing and/or neurodegeneration. The aim of this study was to investigate, in a defined neuronal population, primary cerebellar granule neuron culture, the time-dependent changes in Ca2+homeostasis and compare them with data obtained in cerebellar brain slices from aged rats. In neurons aged in culture (DIV 23), a small decrease in the resting [Ca2+]iwas associated with a decrease in the maximal rate of [Ca2+]iincrease upon KCl-induced depolarization and in the amplitude of the [Ca2+]iresponse, when compared with mature neurons (DIV 9). The most significant change of [Ca2+]isignal parameters was a 50% decrease in the rate of [Ca2+]irecovery after the stimulation. These results were similar to those obtained in aged brain slices, and indicate that primary neuronal cultures could serve as a model for studying the age-related changes in Ca2+homeostasis.

ISSN:0959-4965    

出版商:OVID    

年代:2000

数据来源: OVID