Rieke F, Schwartz E A
Department of Pharmacological and Physiological Sciences, University of Chicago, Illinois 60637.
Neuron. 1994 Oct;13(4):863-73. doi: 10.1016/0896-6273(94)90252-6.
The voltage-gated Ca2+ current in cone photoreceptors operates over only a small part of the physiological voltage range produced by light and, consequently, appears insufficient for controlling transmitter release. We have used a whole-cell voltage clamp to measure membrane current and the capacitance change produced by exocytosis in solitary cone and rod photoreceptors isolated from the salamander retina. In both types of photoreceptor, Ca2+ influx through voltage-gated Ca2+ channels initiated exocytosis. In addition, Ca2+ influx through a cGMP-gated channel in the inner segment and synaptic processes of cones also initiated exocytosis. The cGMP-gated current sustained exocytosis over the entire physiological voltage range.
视锥光感受器中的电压门控Ca2+电流仅在光产生的生理电压范围的一小部分内起作用，因此，似乎不足以控制递质释放。我们使用全细胞膜片钳来测量从蝾螈视网膜分离出的单个视锥和视杆光感受器中膜电流以及胞吐作用产生的电容变化。在这两种类型的光感受器中，通过电压门控Ca2+通道的Ca2+内流引发了胞吐作用。此外，通过视锥细胞内段和突触小体中的cGMP门控通道的Ca2+内流也引发了胞吐作用。cGMP门控电流在整个生理电压范围内维持胞吐作用。
