Dreijer A M, Kits K S
Graduate School of Neurosciences of Amsterdam, Neuroscience Research Institute, Vrije Universiteit, Faculty of Biology, The Netherlands.
Neuroscience. 1995 Feb;64(3):787-800. doi: 10.1016/0306-4522(94)00446-c.
Two types of high-voltage-activated calcium currents were identified in whole-cell voltage-clamp recordings of the neuroendocrine caudodorsal cells, which control egg-laying in the freshwater snail Lymnaea stagnalis. The currents were: (i) a rapidly inactivating high-voltage-activated current, with an activation threshold of -40 mV and maximal amplitude at +10 mV; and (ii) a slowly inactivating high-voltage-activated current, with a threshold of -10 mV and a peak at +30 mV. Both currents were reduced by nifedipine and verapamil, but not by omega-conotoxin GVIA, suggesting that they belong to the L-type family of calcium currents. The voltage-dependence of inactivation of the rapidly inactivating high-voltage-activated current was bell-shaped. Time-constants of inactivation ranged from 10 to 25 ms. Steady-state inactivation was characterized by a potential of half maximal inactivation of -21.7 +/- 3.4 mV and a slope factor of 8.1 +/- 1.7 mV. The voltage-dependence of inactivation of the slowly inactivating high-voltage-activated current was S-shaped. Time-constants of inactivation increased with depolarization up to a maximum of 300 ms. The steady-state inactivation parameters were a potential of half maximal inactivation of +6.8 +/- 2.2 mV and a slope factor of 6.0 +/- 1.1 mV. The membrane-permeable analog of cAMP, 8-chlorophenylthio-cyclic AMP, predominantly increased the slowly inactivating high-voltage-activated current, and shifted its voltage-dependence of activation and inactivation 10 mV to the left. The rapidly inactivating high-voltage-activated current was slightly increased by 8-chlorophenylthio-cyclic AMP. 8-Bromo-cyclic GMP and the phorbol ester, 12-O-tetradecanoyl-13-phorbol acetate, had qualitatively similar effects. Both agents enhanced the rapidly inactivating current and, to a lesser degree, the slowly inactivating current, without affecting their voltage-dependence. The cyclic AMP-dependent protein kinase inhibitor, Walsh inhibitor peptide, antagonized the stimulating effect of 8-chlorophenylthio-cyclic AMP. The broad-spectrum protein kinase inhibitor 1-(5-isoquino-linylsulfonyl)-2-methyl-piperazine (H-7) strongly attenuated the effects of 8-chlorophenylthio-cyclic AMP, 8-bromo-cyclic GMP and 12-O-tetradecanoyl-13-phorbol acetate, suggesting that all treatments increase both types of high-voltage-activated calcium currents through phosphorylation of the channel-complex.
在控制淡水蜗牛椎实螺产卵的神经内分泌尾背细胞的全细胞膜片钳记录中，鉴定出了两种类型的高电压激活钙电流。这两种电流分别是：（i）一种快速失活的高电压激活电流，激活阈值为-40 mV，在+10 mV时达到最大幅度；（ii）一种缓慢失活的高电压激活电流，阈值为-10 mV，在+30 mV时达到峰值。两种电流都被硝苯地平和维拉帕米降低，但不受ω-芋螺毒素GVIA影响，这表明它们属于L型钙电流家族。快速失活的高电压激活电流的失活电压依赖性呈钟形。失活时间常数范围为10至25毫秒。稳态失活的特征是半最大失活电位为-21.7±3.4 mV，斜率因子为8.1±1.7 mV。缓慢失活的高电压激活电流的失活电压依赖性呈S形。失活时间常数随着去极化增加，最大可达300毫秒。稳态失活参数为半最大失活电位为+6.8±2.2 mV，斜率因子为6.0±1.1 mV。cAMP的膜通透性类似物8-氯苯基硫代环磷酸腺苷主要增加缓慢失活的高电压激活电流，并将其激活和失活的电压依赖性向左移动10 mV。快速失活的高电压激活电流略有增加。8-溴环鸟苷酸和佛波酯1,2-十四酰佛波醇-13-乙酸酯具有定性相似的作用。两种药物都增强了快速失活电流，并在较小程度上增强了缓慢失活电流，而不影响它们的电压依赖性。环磷酸腺苷依赖性蛋白激酶抑制剂沃尔什抑制肽拮抗8-氯苯基硫代环磷酸腺苷的刺激作用。广谱蛋白激酶抑制剂1-（5-异喹啉磺酰基）-2-甲基哌嗪（H-7）强烈减弱8-氯苯基硫代环磷酸腺苷、8-溴环鸟苷酸和1,2-十四酰佛波醇-13-乙酸酯的作用，这表明所有处理都是通过通道复合物的磷酸化来增加两种类型的高电压激活钙电流。
