The role of spontaneous neurotransmission in synaptic plasticity and behavior

描述（申请人提供）：神经传递需要突触囊泡与质膜融合，将神经递质释放到突触间隙中。一种叫做可溶性n -乙基马来酰亚胺敏感因子附着蛋白受体（SNAREs）的蛋白质通过将两种膜结合在一起并催化融合来调节这一融合过程。通常，在突触前终末的动作电位刺激过程中，钙的进入会引起多个突触产生的许多突触囊泡的同步融合。然而，在没有动作电位的情况下，一些囊泡自发融合，以稀疏和时间随机的模式释放神经递质。目前尚不清楚这种自发的神经传递是否会影响神经元功能并改变突触可塑性和行为，但先前的研究表明，它在抗抑郁药物的快速作用中具有抑制作用

DESCRIPTION (provided by applicant): Neurotransmission requires the fusion of synaptic vesicles with the plasma membrane, which releases neurotransmitter into the synaptic cleft. Proteins called soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) mediate this fusion process by bringing the two membranes together and catalyzing fusion. Canonically, calcium entry during action potential stimulation of presynaptic terminals causes synchronous fusion of many synaptic vesicles arising from multiple synapses. In the absence of action potentials, however, some vesicles fuse spontaneously, releasing neurotransmitter in a sparse and temporally random pattern. It is unclear whether this spontaneous neurotransmission shapes neuronal function and alters synaptic plasticity and behavior, but prior work has implicated its inhibition in the fast-acting antidepressant effects of low-dose ketamine administration in treatment-resistant depression. Recently, two noncanonical vesicular SNAREs, vps10p tail interactor 1a (vti1a) and vesicle-associated membrane protein 7 (VAMP7/TI- VAMP), were identified as specific modulators of spontaneous neurotransmission. Reductions in these proteins in vitro reduce the frequency of spontaneous fusion events. The overall goal of the proposed project is to identify the roles spontaneous neurotransmission plays in vivo, especially in the fast-acting antidepressant response to ketamine. To achieve this goal, vti1a and VAMP7 will be knocked down in vivo via stereotaxic injection of virus encoding shRNA into the hippocampus, an area thought to be important for ketamine's effects. The first aim of the proposed project is to determine whether vti1a and VAMP7 knockdown alters spontaneous neurotransmission and synaptic plasticity by using a combination of electrophysiological and optical recording methods. The second aim of the proposed project is to determine whether knockdown of vti1a and VAMP7 modifies ketamine's ability to produce antidepressant responses. This will be tested by measuring behavior after ketamine treatment in mice that were previously injected with the virus knocking down vti1a and VAMP7. Together, these aims will determine whether a reduction in levels of vesicular SNAREs vti1a and VAMP7 alters synaptic function and in vivo behavior. Additionally, this project will clarify upstream mechanisms responsible for the fast-acting antidepressant effects of ketamine, potentially leading to identification of additional signaling cascades that can be modified to treat depression while avoiding the abuse potential inherent in ketamine administration. This proposed project also provides valuable training to the applicant in developing techniques and professional skills important for a career in biomedical research.