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连续释放，将其光反应传递穿过视网膜中的第一突触。光引起的膜电位变化调节光感受器突触传递的机制还不清楚。我们提出实验来分析从光感受器释放的生物物理机制。从光感受器的突触释放涉及快速瞬时和缓慢持续的释放成分。持续释放对于塑造突触后对光照缓慢变化的反应是重要的，而瞬时释放对突然光偏移的反应贡献更大。在目标1中，我们测试是否持续和短暂的释放组件都是由于释放从突触带或是否非带状突触释放网站也参与。在目标2中，我们确定如何释放概率的电压依赖性变化，囊泡的可释放池的大小，和囊泡补充的速率相互作用，以形成持续和短暂的突触后反应，光和暗在锥突触。在目标3中，我们测试是否由单个突触囊泡的释放引起的量子突触电流由锥体突触的胞浆谷氨酸水平的变化来调节。了解光感受器突触释放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节如何破坏视觉非常重要。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患病眼睛正常视网膜功能的疗法也很重要。公共卫生相关性：本计画研究视觉讯号传递至视网膜第一突触下游神经元的机制。除了提供对视网膜早期视觉处理的更好理解之外，理解视杆和视锥光感受器释放神经递质谷氨酸的机制对于理解突触蛋白的突变或谷氨酸释放的错误调节如何导致眼部疾病和视力丧失是必要的。通过使用视网膜干细胞、假体装置或其他手段来恢复患病眼睛的视力也需要对正常视网膜生理学的理解。

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.