Payne R, Flores T M
Department of Zoology, University of Maryland, College Park 20742.
J Comp Physiol A. 1992 Mar;170(3):311-6. doi: 10.1007/BF00191419.
The latent period before depolarization of Limulus ventral photoreceptors by light flashes was compared with that following brief, intracellular, pressure-injection of d-myo-inositol 1,4,5 trisphosphate. At temperatures between 18 degrees C and 22 degrees C and with an extracellular calcium concentration of 10 mM, the responses of 4 cells to light and to injections of 100 microM inositol trisphosphate displayed average latencies of 71 and 56 ms, respectively. The latencies of responses to InsP3 included an estimated 20 ms dead-time inherent in the injection method. Reducing the temperature lengthened the latency of the response to light (Q10 approximately 3.2 between 7 and 22 degrees C) more than that to inositol trisphosphate (Q10 approximately 2.3). Bathing the photoreceptors in seawater containing no added calcium and 1 mM of the calcium chelator EGTA greatly increased the latency of the light response at all temperatures, but did not increase the latency of the response to inositol trisphosphate. We conclude that the response to inositol trisphosphate lacks the calcium- and temperature-sensitive latent period which characterizes the response to light. If inositol trisphosphate acts, via the release of stored calcium, to stimulate an intermediate in the visual cascade, then that intermediate would appear to be downstream from the latency-generating mechanism.
将鲎腹侧光感受器被闪光激发去极化前的潜伏期，与在细胞内短暂进行压力注射d - 肌醇1,4,5 - 三磷酸（inositol 1,4,5 trisphosphate）后的潜伏期进行了比较。在18摄氏度至22摄氏度之间的温度以及细胞外钙浓度为10 mM的条件下，4个细胞对光和100 microM肌醇三磷酸注射的反应，平均潜伏期分别为71毫秒和56毫秒。对肌醇三磷酸（InsP3）反应的潜伏期包括注射方法固有的约20毫秒的停滞时间。降低温度使对光反应的潜伏期延长（在7摄氏度至22摄氏度之间Q10约为3.2），比对肌醇三磷酸反应潜伏期的延长（Q10约为2.3）更明显。将光感受器置于不添加钙但含有1 mM钙螯合剂乙二醇双四乙酸（EGTA）的海水中浸泡，在所有温度下都极大地增加了光反应的潜伏期，但并未增加对肌醇三磷酸反应的潜伏期。我们得出结论，对肌醇三磷酸的反应缺乏对光反应所特有的钙敏感和温度敏感的潜伏期。如果肌醇三磷酸通过释放储存的钙来刺激视觉信号传导级联反应中的一个中间环节，那么该中间环节似乎位于产生潜伏期的机制的下游。
