Synaptic Transmission: Modulation, Plasticity And Effect

综合神经科学实验室(LIN)的研究重点是确定神经调节和可塑性的潜在机制，以及酒精和其他滥用药物对这些神经功能的影响。正在进行的研究正在研究酒精对NMDA和非NMDA谷氨酸受体功能的影响。我们使用基因靶向的NR2A-/-小鼠来检测酒精对含有或不含有NR2A亚单位的NMDA受体的抑制作用。NR2a-/-小鼠的神经元中乙醇对NMDARs的抑制作用增强，这种作用在小脑颗粒细胞中比在皮质神经元中更明显。我们还在进行研究，以检测酒精对自体神经元培养中突触和非突触NMDA受体的影响。在这项准备工作中，我们还将研究酒精对突触和非突触池之间NMDAR运输的影响。最近的研究结果还表明，乙醇与环噻嗪相互作用，作用于AMPA型谷氨酸受体。 我们正在继续研究背侧纹状体的突触可塑性，也在研究海马区和杏仁核类似的可塑性变化。我们已经证明，内源性大麻素作为激活突触前CB1受体的逆行信号，在纹状体长期突触抑制(LTD)的启动中起着关键作用。我们已经积累的证据表明，内源性大麻素是通过涉及ANANDAME膜转运体系统的反向运输从突触后神经元释放出来的。我们还研究了另一种依赖内源性大麻素的突触可塑性形式-去极化诱导的抑制(DSI)在海马CA1神经元中的出生后发育。DSI在~P14-P16开始表达，我们有证据表明DSI的出现可能是由于CA1锥体神经元内源性大麻素产生机制的发展。有趣的是，DSI所涉及的内源性大麻素的释放似乎并不涉及LTD诱导所涉及的运输系统。 我们还利用新实现的分离带有GABA能突触连接的神经元的技术，开始探索导致杏仁核和纹状体神经元DSI和LTD的内源性大麻素产生的分子机制。结合高效液相色谱和质谱学的研究表明，D2多巴胺受体与去极化和谷氨酸受体的激活一起，促进了纹状体内源性大麻素的产生。我们还使用这些技术来表征纹状体花生胺水平的发育增加，这似乎与视觉感觉输入的开始有关。目前的实验正在探索增强的内源性大麻素水平与皮质纹状体突触突触可塑性的发育变化之间的联系。 生化研究的目的是了解将受体激活与可塑性诱导联系起来的细胞内信号，并确定长期抑郁和DSI的机制。我们观察到ERK型MAPK的CB1受体激活主要是通过抑制腺苷环化酶来实现的。我们希望确定这一通路在突触前终末是否活跃。我们还在研究CB1激活对突触前小泡相关蛋白的磷酸化和功能的影响，以开始了解该受体如何在神经递质分泌中产生持久的变化。 我们正在研究的受体是药物滥用的目标，在与成瘾有关的神经通路中发挥着突出的作用。从长远来看，我们有兴趣更好地了解这些受体在药物耐受和依赖以及成瘾发展过程中对药物寻找和突触可塑性的作用。 安德鲁·霍姆斯博士已经接受了行为科学和遗传学(SBSG)代理科长的职位。他将启动使用基因靶标小鼠的研究，以检查酒精和药物滥用的分子基础，以及压力与酒精的相互作用。结构生物学(SB)科，将在未来两年内设立，以便研究膜蛋白结构和酒精与膜蛋白的相互作用。

The focus of research in the Laboratory of Integrative Neuroscience (LIN) is the determination of mechanisms underlying neuromodulation and plasticity and the effects of alcohol and other drugs of abuse on these neuronal functions. Ongoing studies are examining alcohol effects on NMDA and non-NMDA glutamate receptor function. We have used gene-targeted NR2A-/- mice to examine ethanol inhibition of NMDA receptors that contain or lack the NR2A subunit. Ethanol inhibition of NMDARs is enhanced in neurons from NR2A-/- mice, and this effect is more pronounced in cerebellar granule cells than in cortical neurons. We are also undertaking studies to examine alcohol effects on synaptic versus non-synaptic NMDA receptors in autaptic neuronal cultures. We will also examine alcohol effects on NMDAR trafficking between synaptic and non-synaptic pools in this preparation. Recent findings also indicate that ethanol interacts with cyclothiazide actions on AMPA-type glutamate receptors. We have continued studies of synaptic plasticity in dorsal striatum, and are also investigating similar plastic changes in hippocampus and amygdala. We have shown that endocannabinoids, acting as retrograde signals that activate presynaptic CB1 cannabinoid receptors, play a key role in initiation of striatal long-term synaptic depression (LTD). We have accumulated evidence that the endocannabinoids are released from postsynaptic neurons via "backward-transport" involving an anandamide membrane transporter system. We have also examined postnatal development of another endocannabinoid-dependent form of synaptic plasticity, depolarization-induced suppression of inhibition (DSI) in hippocampal CA1 neurons. DSI begins to be expressed at ~P14-P16, and we have evidence that the appearance of DSI is probably due to development of endocannabinoid production mechanisms in CA1 pyramidal neurons. Interestingly, release of endocannabinoids involved in DSI does not appear to involve the transport system implicated in LTD induction. We have also begun to explore the molecular mechanisms involved in endocannabinoid production leading to DSI and LTD in amygdala and striatal neurons using newly-implemented techniques for isolating neurons with attached GABAergic synaptic boutons. Studies using combined HPLC and mass spectrometry have indicated that D2 dopamine receptors, in conjunction with depolarization and glutamate receptor activation, enhance production of the endocannabinoid anandamide in striatum. We have also used these techniques to characterize developmental increases in striatal anandamide levels that appear to be tied to the onset of visual sensory input. Current experiments are exploring the link between enhanced endocannabinoid levels and developmental changes in synaptic plasticity at corticostriatal synapses. Biochemical studies are aimed at understanding the intracellular signals that link receptor activation to induction of plasticity, and determining the mechanisms involved in long-lasting depression and DSI. We have observed that CB1 receptor activation of the ERK-type MAP kinase is mediated predominantly through inhibition of adenylyl cyclase. We hope to determine if this pathway is active in presynaptic terminals. We are also examining effects of CB1 activation on phosphorylation and function of presynaptic vesicle-associated proteins to begin to understand how this receptor may produce lasting alterations in neurotransmitter secretion. The receptors we are examining are targets for drugs of abuse and play prominent roles in neuronal pathways implicated in addiction. In the long-term we are interested in gaining a better understanding of the role of these receptors in drug-seeking and synaptic plasticity during the development of drug tolerance and dependence, as well as addiction. Dr. Andrew Holmes has accepted the position of Acting Chief of the Section on Behavioral Science and Genetics (SBSG). He will initiate studies using gene-targeted mice to examine the molecular basis of alcohol and drug abuse, as well as stress-alcohol interactions. The Section on Structural Biology (SB) that will be set up within the next two years to allow studies of membrane protein structure and alcohol interactions with membrane proteins.