Heyward P M, Chen C, Clarke I J
Prince Henry's Institute of Medical Research, Clayton, Australia.
Neuroendocrinology. 1993 Dec;58(6):646-54. doi: 10.1159/000126605.
Cell-intact patch-clamp recording was used to determine the electrophysiological responses of sheep anterior pituitary gonadotropes to stimulation with gonadotropin-releasing hormone (GnRH). Cells were identified prior to recording by reverse haemolytic plaque assay (RHPA), or using morphological criteria in preparations enriched in gonadotropes by Percoll density gradient centrifugation. Most cells identified by RHPA did not generate action potentials, and responses to GnRH were inconsistent. The majority of gonadotropes in enriched preparations however spontaneously generated action potentials requiring the entry of both extracellular Na+ and Ca2+, and involving tetraethylammonium-sensitive K+ channels. Two-minute GnRH application (10(-7) M) evoked a characteristic sequence of changes in action potential generation. The immediate response was an inhibition of action potentials, followed by a recovery of these events, with a progressive decline in amplitude over about 10 min. The cells then remained quiescent for up to 1 h. The results indicate that GnRH may evoke an initial hyperpolarization involving Ca(2+)-dependent K+ channels, followed by a sustained depolarizing response, with consequent inactivation of action potential generation.
采用全细胞膜片钳记录技术来测定绵羊垂体前叶促性腺细胞对促性腺激素释放激素（GnRH）刺激的电生理反应。在记录之前，通过反向溶血空斑试验（RHPA）或在经Percoll密度梯度离心法富集促性腺细胞的制剂中使用形态学标准来识别细胞。通过RHPA识别的大多数细胞不产生动作电位，并且对GnRH的反应不一致。然而，富集制剂中的大多数促性腺细胞自发产生动作电位，这需要细胞外Na+和Ca2+的进入，并涉及对四乙铵敏感的K+通道。施加两分钟的GnRH（10^(-7) M）会引起动作电位产生的一系列特征性变化。即时反应是动作电位受到抑制，随后这些事件恢复，在大约10分钟内幅度逐渐下降。然后细胞保持静止长达1小时。结果表明，GnRH可能引发涉及Ca(2+)依赖性K+通道的初始超极化，随后是持续的去极化反应，从而导致动作电位产生失活。
