Miller J L, Picones A, Korenbrot J I
Department of Physiology, School of Medicine, University of California at San Francisco 94143.
Curr Opin Neurobiol. 1994 Aug;4(4):488-95. doi: 10.1016/0959-4388(94)90048-5.
Rod and cone photoreceptors respond to light with distinct sensitivity and kinetics. Recent biochemical and electrophysiological studies demonstrate that the enzymes of the phototransduction cascade are similar, but not identical, in these two photoreceptor types. In contrast, light or voltage stimulation generates changes in the cytoplasmic concentration of Ca2+ in the outer segment that are far larger and faster in cones than in rods. This distinction reflects rod-cone differences in each of the elements that control Ca2+ homeostasis: cell volume, the rate of Ca2+ clearance from the outer segment, the cytoplasmic Ca2+ buffering, and the Ca2+ influx through cGMP-gated ion channels.
视杆和视锥光感受器对光的反应具有不同的敏感度和动力学特性。最近的生物化学和电生理学研究表明，在这两种光感受器类型中，光转导级联反应的酶相似但并不相同。相比之下，光或电压刺激在外段细胞质中产生的Ca2+浓度变化，视锥细胞比视杆细胞大得多且快得多。这种差异反映了在控制Ca2+稳态的各个要素中视杆细胞和视锥细胞的差异：细胞体积、外段Ca2+清除率、细胞质Ca2+缓冲以及通过cGMP门控离子通道的Ca2+内流。
