Regulation of Photoreceptor Neurotransmission

描述（由申请人提供）：光感受器通过调节含谷氨酸囊泡的持续释放，将其光反应传递到视网膜的第一突触。光诱发膜电位变化调节光感受器突触传递的机制尚不清楚。我们提出实验来分析光感受器释放的生物物理机制。光感受器的突触释放包括快速的瞬时释放和缓慢的持续释放。持续释放对于形成对缓慢光照变化的突触后反应很重要，而瞬时释放对突变光偏移的反应更有贡献。在Aim 1中，我们测试了持续的和短暂的释放成分是否都是由于从突触带释放，或者是否也涉及非带状突触释放位点。在目的2中，我们确定了释放概率、可释放囊泡池的大小和囊泡补充速率的电压依赖性变化如何相互作用，以形成锥体突触对光和暗的持续和短暂的突触后反应。在Aim 3中，我们测试了由单个突触囊泡释放引起的量子突触电流是否受到锥体突触胞质谷氨酸水平变化的调节。了解光感受器释放突触的机制对于理解视觉的基本机制以及突触蛋白突变或谷氨酸释放的错误调控如何破坏视觉是很重要的。了解正常的视网膜生理学对于设计使用视网膜干细胞或假体装置恢复病变眼睛正常视网膜功能的治疗方法也很重要。

DESCRIPTION (provided by applicant): Photoreceptors transmit their light responses across the first synapse in the retina by regulating the continuous release of glutamate-containing vesicles. The mechanisms by which light-evoked changes in membrane potential regulate synaptic transmission from photoreceptors are not well understood. We propose experiments to analyze the biophysical mechanisms of release from photoreceptors. Synaptic release from photoreceptors involves both fast transient and slow sustained components of release. Sustained release is important for shaping post-synaptic responses to slow changes in illumination and transient release contributes more to responses at abrupt light offset. In Aim 1, we test whether sustained and transient components of release are both due to release from the synaptic ribbon or whether non-ribbon synaptic release sites are also involved. In Aim 2, we determine how voltage-dependent changes in release probability, the size of the releasable pool of vesicles, and the rate of vesicle replenishment interact to shape sustained and transient post-synaptic responses to light and dark at the cone synapse. In Aim 3, we test whether quantal synaptic currents evoked by release of individual synaptic vesicles are regulated by changes in cytosolic glutamate levels at the cone synapse. Understanding the mechanisms of synaptic release from photoreceptors is important for understanding basic mechanisms of vision and how vision is disrupted by mutations in synaptic proteins or mis-regulation of glutamate release. Understanding normal retinal physiology is also important for designing therapies to restore normal retinal function to diseased eyes using retinal stem cells or prosthetic devices.