Caffeine as a psychomotor stimulant: mechanism of action

The popularity of caffeine as a psychoactive drug is due to its stimulant properties, which depend on its ability to reduce adenosine transmission in the brain. Adenosine A₁ and A_2A receptors are expressed in the basal ganglia, a group of structures involved in various aspects of motor control. Caffeine acts as an antagonist to both types of receptors. Increasing evidence indicates that the psychomotor stimulant effect of caffeine is generated by affecting a particular group of projection neurons located in the striatum, the main receiving area of the basal ganglia. These cells express high levels of adenosine A_2A receptors, which are involved in various intracellular processes, including the expression of immediate early genes and regulation of the dopamine- and cyclic AMP-regulated 32-kDa phosphoprotein DARPP-32. The present review focuses on the effects of caffeine on striatal signal transduction and on their involvement in caffeine-mediated motor stimulation.Received 8 July 2003; received after revision 7 September 2003; accepted 6 October 2003     

Substance P-like immunoreactivity in the frog dorsal root ganglia

Summary The distribution of substance P-like immunoreactivity was studied in the thoracic dorsal root ganglia of the frogRana esculenta by immunohistochemistry. Substance P-like immunoreactivity was contained in approximately 50% of primary sensory neurons. The immunoreactive fibers arising from the cell bodies are collected in small bundles within the ganglia neuropil before entering the central and peripheral roots.     

基本放大器图解法中直线方程的推导及应用

本文运用解析几何的数学知识,将基本放大器图解法中所涉及的几条直线方程的方程式推导出来,它们既是对教材的丰富和补充,又容易让学生从数学的角度去接受和掌握,能极大地提高学生综合运用图解法分析问题、解决问题的能力。     

基底神经节与运动控制的研究进展

基底神经节对于随意运动的发起和执行设计具有重要的作用,本文通过查阅分析相关的文献资料,综述了目前关于基底神经节各通路核团在运动控制中的功能作用,并展望进一步研究基底神经节．丘脑．皮层通路的环路工作机制,为今后运动神经控制的研究工作提供一些参考．     

柞蚕幼虫在体胸神经节自发放电活动的观察

本文以柞蚕五龄幼虫为材料,运用微电极电生理技术,以胞外记录的方法,记录了柞蚕虫在体胸神经节的自发放电活动．结果,柞蚕幼虫胸神经节胞外自发放电有三种形式慢节律单个放电、簇状放电及连续放电．     

Which neurological abnormalities and neuropsychological impairments share the same substrate in psychosis?

Approximately 60% of subjects with schizophrenia present minor neurological signs (neurological soft signs, NSS), which include abnormalities in sensory and motor performance indicative of a non-specific cerebral dysfunction. These are also present in healthy individuals and relatives of patients with psychosis, at significantly lower rates. The excess of NSS in psychosis may be a potential endophenotype for this disorder, and reflect the same neurodevelopmental brain dysfunction that also underlies the cog...     

小流域治理20年后千烟洲生物量的变化

小流域治理前,千烟洲植被以草丛为主,间有小部份灌丛,生物量极低。自1982年实行小流域治理至今,千烟洲生物量有了极大提高,植被覆盖率也显著增加,林地面积从1982年底的0.4%提高到1999年底的93.3%。乔木层每公顷胸高断面积为27.63m2,其中马尾松、湿地松、杉木、板栗及枫香这5种人工树种共占84.3%,这表明全站植物生物量主要由人工林决定。天然次生林中,格药柃单位面积胸高断面积最大。用相关生物量模型计算全试验区4个优势种地上部分生物量之和为32035t。其中湿地松生物量最大为25990t,占81.1%,枫香最小为874t。     

Sensing life: regulation of sensory neuron survival by neurotrophins

Neurotrophins are a family of structurally and functionally related neurotrophic factors which, in mammals, include: nerve growth factor, brain-derived neurotrophic factor, neurotrophin-3 (NT-3), and NT-4/5. In addition to their canonical role in promoting neuronal survival, these molecules appear to regulate multiple aspects of the development of the nervous system in vertebrates, including neuronal differentiation, axon elongation and target innervation, among others. Actions of neurotrophins and of their receptors in vivo are being analyzed by loss-of-function or gain-of-function experiments in mice. Here, we review the phenotypes of the primary sensory system in these mutant mouse strains and the different strategies specifically involved in the regulation of neuronal survival by neurotrophins in this portion of the nervous system. Received 10 December 2001; received after revision 11 May 2002; accepted 13 May 2002 RID="*" ID="*"Corresponding author.     

First episode psychosis with extrapyramidal signs prior to antipsychotic drug treatment

Extrapyramidal movement disorders are common in chronic schizophrenia, and may be an intrinsic feature of the illness as well as related to antipsychotic drug treatment. Similar dysfunctions at illness onset may have implications for outcome, and for under- standing the mechanisms of illness. The objectives were to examine the clinical correlates of pre-treatment movement disorders at first episode of psychosis, and determine associations with neuropsychological function and striatal structure. Never medicated subjects were recruited from consecutive admissions to Early Psychosis Programs with defined catchment areas in Hong Kong, China, and Halifax, Canada. Standardized clinical, neuropsychological and brain imaging assessments were carried out at baseline and following acute and long term treatment with typical or atypical antipsychotic drugs. At the Hong Kong site, we studied 84 subjects with first episode psychosis (n = 10 with EPS). At the Halifax site, we studied 40 subjects with first episode psychosis (n = 17 with EPS), and 23 healthy comparison subjects. Subjects with movement disorders prior to treatment (EPS+) had higher total PANSS scores at baseline (mean elevation 19.9% Hong Kong, P = 0.016; 14.7% Halifax, P = 0.049). In subjects treated with atypical antipsychotics (all Halifax), EPS+ status at baseline predicted more movement disorders at long term follow up (P = 0.0005). In both cohorts, EPS+ subjects had poorer acute symptomatic treatment response assessed with the PANSS (Hong Kong P = 0.005; Halifax P = 0.017). Neuropsychological impairment related to executive dysfunction appeared greater in a small sam- ple of EPS+ subjects (Hong Kong, effect size 0.26-0.27, P < 0.05). Caudate volumes were 4.5% larger in EPS+ compared with EPS-subjects (Halifax P = 0.042), and correlations between striatal volumes and age were different in the EPS+ group. In conclu- sion, pre-treatment EPS is present in a substantial minority of subjects with first episode psychosis, appears to persist at long term follow up, and is associated with poorer response of symptoms to treatment. Selective impairment of executive function and stria- tal enlargement provides evidence of abnormalities of brain function and structure associated with this aspect of early psychosis.     

帕金森病的机器人模型

帕金森病是一种典型的由于基底神经节病变引起的运动紊乱性疾病.首先分析了基底神经节在脊椎动物行为选择过程中所起的作用并建立了相应的数学模型,然后研究了帕金森病对基底神经节行为选择性能的影响,在此基础之上,设计了基于行为的机器人控制体系结构,将正常和帕金森病的基底神经节的行为选择模型嵌入到其中用于机器人行为选择.研究结果表明,"患有"帕金森病的机器人能表现出一定的帕金森病症状.