温度对青蛙离体感觉神经元中γ-氨基丁酸诱导的氯离子电流的影响。

The effect of temperature on the GABA-induced chloride current in isolated sensory neurones of the frog.

作者信息

ffrench-Mullen J M, Tokutomi N, Akaike N

机构信息

Department of Physiology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.

出版信息

Br J Pharmacol. 1988 Nov;95(3):753-62. doi: 10.1111/j.1476-5381.1988.tb11701.x.

DOI:10.1111/j.1476-5381.1988.tb11701.x

PMID:2463028

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC1854228/

Abstract

The effect of temperature on the kinetics of the activation and inactivation phases of gamma-aminobutyric acid (GABA)-induced Cl- current (ICl) was examined in frog isolated sensory neurones. 2. The peak ICl was reversibly reduced on changing the temperature and temperature-dependent coefficients were shown to exist, with the highest Q10 (1.58) occurring between 5-15 degrees C. 3. At both room temperature (20 degrees C) and 10 degrees C, the GABA dose-response curve was sigmoidal with a Hill coefficient of 2 and half-maximal responses to GABA, Kd, of 1.3 x 10(-5)M and 1.1 x 10(-5)M, respectively. Thus, indicating no change in the binding affinity of GABA when the temperature was decreased. 4. At GABA concentrations greater than 10(-5)M, both the activation and inactivation phases of the GABA-induced ICl consisted of double exponentials, fast and slow components respectively, in the temperature range of 10 to 30 degrees C. 5. The fast (tau af) and slow (tau as) activation time constants decreased with an increase in temperature and increased with a reduction in temperature. With an increased temperature, the reduction in peak ICl was due to a reduction in the slow time constant with no significant change in the fast time constant. 6. Both the fast (tau if) and slow (tau is) inactivation time constants were also increased by cooling to 10 degrees C; heating to 30 degrees C had little effect. 7. The concentration-dependence (10(-5) to 10(-3)M) of the slow activation (tau as) and inactivation (tau is) time constants was unaltered by the change in temperature. Similarly, the lack of concentration-dependence shown by the fast activation (tau af) and inactivation (tau if) time constants was unaltered by the temperature change. 8. From recordings made with 'inside-out' patches, the probability of opening of the GABA-induced Cl- channels showed a marked increase with cooling to 10 degrees C compared to room temperature (20 degrees C), with no change in channel conductance. 9. The change in the GABA-induced ICl at different temperatures is, therefore, not due to changes in binding but to subsequent channel activation. Possible mechanisms whereby this occurs are discussed.

摘要

在青蛙离体感觉神经元中研究了温度对γ-氨基丁酸（GABA）诱导的氯离子电流（ICl）激活和失活阶段动力学的影响。2. 改变温度时，ICl峰值可逆性降低，且存在温度依赖性系数，在5 - 15摄氏度之间Q10最高（1.58）。3. 在室温（20摄氏度）和10摄氏度时，GABA剂量反应曲线均为S形，希尔系数为2，对GABA的半最大反应Kd分别为1.3×10⁻⁵M和1.1×10⁻⁵M。因此，表明温度降低时GABA的结合亲和力无变化。4. 在GABA浓度大于10⁻⁵M时，在10至30摄氏度温度范围内，GABA诱导的ICl的激活和失活阶段分别由双指数组成，即快速和慢速成分。5. 快速（τaf）和慢速（τas）激活时间常数随温度升高而降低，随温度降低而增加。随着温度升高，ICl峰值降低是由于慢速时间常数降低，快速时间常数无显著变化。6. 冷却至10摄氏度时，快速（τif）和慢速（τis）失活时间常数也增加；加热至30摄氏度影响不大。7. 慢速激活（τas）和失活（τis）时间常数的浓度依赖性（10⁻⁵至10⁻³M）不受温度变化影响。同样，快速激活（τaf）和失活（τif）时间常数缺乏浓度依赖性也不受温度变化影响。8. 从“内向外”膜片钳记录可知，与室温（20摄氏度）相比，冷却至10摄氏度时，GABA诱导的氯离子通道开放概率显著增加，通道电导无变化。9. 因此，不同温度下GABA诱导的ICl变化不是由于结合改变，而是由于随后的通道激活。讨论了发生这种情况的可能机制。