Facultad de Veterinaria y Zootecnia, Universidad de Colima, Avenida 25 de Julio 965, Colima, Mexico.
Pflugers Arch. 2011 Aug;462(2):235-43. doi: 10.1007/s00424-011-0962-1. Epub 2011 Apr 13.
Pilocarpine is a nonspecific agonist of muscarinic receptors which was recently found to activate the M(2) receptor subtype in a voltage-dependent manner. The purpose of our study was to investigate the role of the acetylcholine (muscarinic)-activated K(+) current (I (KACh)) on the negative chronotropic effect of pilocarpine in rabbit sinoatrial node. In multicellular preparations, we studied the effect of pilocarpine on spontaneous action potentials. In isolated myocytes, using the patch clamp technique, we studied the effects of pilocarpine on I (KACh). Pilocarpine produced a decrease in spontaneous frequency, hyperpolarization of the maximum diastolic potential, and a decrease in the diastolic depolarization rate. These effects were partially antagonized by tertiapin Q. Cesium and calyculin A in the presence of tertiapin Q partially prevented the effects of pilocarpine. In isolated myocytes, pilocarpine activated the muscarinic potassium current, I (KACh) in a voltage-dependent manner. In conclusion, the negative chronotropic effects of pilocarpine on the sinatrial node could be mainly explained by activation of I (KACh).
毛果芸香碱是一种非特异性毒蕈碱受体激动剂，最近发现它以电压依赖性方式激活 M(2)受体亚型。我们的研究目的是探讨乙酰胆碱（毒蕈碱）激活的 K(+)电流 (I (KACh)) 在毛果芸香碱对兔窦房结负性变时作用中的作用。在多细胞标本中，我们研究了毛果芸香碱对自发性动作电位的作用。在分离的心肌细胞中，应用膜片钳技术，我们研究了毛果芸香碱对 I (KACh) 的作用。毛果芸香碱使自发性频率降低，最大舒张电位超极化，舒张去极化速率降低。这些作用部分被 tertiapin Q 拮抗。Cs 和 calyculin A 在 tertiapin Q 存在下部分阻止了毛果芸香碱的作用。在分离的心肌细胞中，毛果芸香碱以电压依赖性方式激活毒蕈碱钾电流 I (KACh)。结论：毛果芸香碱对窦房结的负性变时作用主要可以通过激活 I (KACh)来解释。
