Regulation of Photoreceptor Neurotransmission

描述(申请人提供)：光感受器通过调节含有谷氨酸的囊泡的持续释放，通过视网膜的第一突触传递它们的光反应。光诱发的膜电位变化调节光感受器突触传递的机制还不是很清楚。我们建议用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既包括快速的瞬时释放，也包括缓慢的持续释放。持续释放对形成对光照缓慢变化的突触后反应很重要，而瞬时释放对突然光偏移的反应有更大的贡献。在目标1中，我们测试了持续性和暂时性释放成分是否都是由于突触带的释放，或者是否也涉及非突触释放部位。在目标2中，我们确定了释放概率、可释放小泡池的大小和小泡补充速度的电压依赖变化如何相互作用，以形成锥体突触对光明和黑暗的持续和瞬时突触后反应。在目标3中，我们测试由单个突触小泡释放所诱发的量子突触电流是否受到锥体突触胞浆谷氨酸水平变化的调节。了解光感受器突触释放的机制对于了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节如何扰乱视觉具有重要意义。了解正常的视网膜生理对于设计使用视网膜干细胞或假体设备恢复患病眼睛的正常视网膜功能的治疗方法也很重要。与公共健康相关：该项目研究视觉信号在视网膜第一突触处传递到下游神经元的机制。除了提供对视网膜早期视觉处理的更好理解外，了解视杆和视锥感受器释放神经递质谷氨酸的机制对于了解突触蛋白的突变或谷氨酸释放的错误调节如何导致眼病和视力丧失是必要的。为了通过使用视网膜干细胞、假体或其他手段恢复患病眼睛的视力，还需要了解正常的视网膜生理学。

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. PUBLIC HEALTH RELEVANCE: This project studies the mechanisms by which visual signals are transmitted to downstream neurons at the first synapse in the retina. In addition to providing a better understanding of early visual processing by the retina, understanding the mechanisms by which rod and cone photoreceptors release the neurotransmitter glutamate is necessary to understand how mutations in synaptic proteins or mis-regulation of glutamate release lead to eye disease and vision loss. An understanding of normal retinal physiology is also needed for restoring vision to diseased eyes by the use of retinal stem cells, prosthetic devices, or other means.