Torda C
Int J Neurosci. 1981;14(3-4):153-61. doi: 10.3109/00207458108985828.
Calmodulin has been isolated from the outer segment of toad (Bufo marinus) photoreceptors. Bioelectric processes have been recorded from the same preparation during various experimental conditions. The results led to the conclusion that during illumination the rotation of the chemoreceptors opens the Ca channels, and free Ca is versed into the intermembrane space of the outer segment. Changes of this free Ca concentrations depend on fast influx and slower removal (mainly dependent on Ca binding on calmodulin and back-diffusion into the disc membrane). The changes of the free Ca concentrations generate the changing hyperpolarization, a Ca-dependent process of first phases of encoding the photic stimulus. The effectiveness of Ca to generate the oscillating hyperpolarization depends on optimum state of bioelectric potentials. This potential seems to be regulated by the effective decrease of cGMP concentrations by the increased activity of the cGMP phosphodiesterase during illumination (a sudden and gross regulation). A finer regulation is exerted by Ca during its release and removal (e.g., Ca-dependent decrease of Na channels, decreased release of cGMP by Ca-dependent inhibition of guanylate cyclase activity and increased phosphodiesterase activity by both free Ca and Ca-bound calmodulin).
钙调蛋白已从蟾蜍（海蟾蜍）光感受器的外段中分离出来。在各种实验条件下，已从同一标本记录了生物电过程。结果得出结论，在光照期间，化学感受器的旋转打开了钙通道，游离钙进入外段的膜间空间。这种游离钙浓度的变化取决于快速流入和较慢的清除（主要取决于钙与钙调蛋白的结合以及向盘膜的反向扩散）。游离钙浓度的变化产生了不断变化的超极化，这是光刺激编码第一阶段的钙依赖性过程。钙产生振荡超极化的有效性取决于生物电势的最佳状态。这种电势似乎在光照期间通过cGMP磷酸二酯酶活性增加导致cGMP浓度有效降低来调节（一种突然且总体的调节）。在钙的释放和清除过程中，钙发挥更精细的调节作用（例如，钙依赖性降低钠通道，通过钙依赖性抑制鸟苷酸环化酶活性降低cGMP的释放，以及游离钙和钙结合的钙调蛋白均增加磷酸二酯酶活性）。
