Amerini S, Piazzesi G, Giotti A, Mugelli A
Arch Int Pharmacodyn Ther. 1984 Jul;270(1):97-105.
We used intracellular microelectrodes to study the effect of alpha-adrenoceptor stimulation on automaticity of sheep cardiac Purkinje fibers exposed to low (10(-5) - 4 X 10(-5) M) barium concentrations. Concentrations of norepinephrine (NE) (3 X 10(-8) - 3 X 10(-7) M), which did not induce spontaneous activity in the absence of barium, consistently induced or enhanced it (if already present) in the presence of barium. Similar results were obtained in the presence of practolol (10(-6) M), which in 13 out of 17 experiments did not counteract the effect of NE. However, phentolamine (3 X 10(-7) M) caused a slowing or blocking of the spontaneous activity induced by NE in barium-treated preparations either in the presence or in the absence of practolol. We conclude that alpha-adrenergic responsiveness is enhanced in barium-treated Purkinje fibers and that under these experimental conditions, alpha-adrenoceptor stimulation may influence automaticity. The possible mechanisms underlying such effects are discussed.
我们使用细胞内微电极来研究α-肾上腺素能受体刺激对暴露于低浓度（10⁻⁵ - 4×10⁻⁵M）钡的绵羊心脏浦肯野纤维自律性的影响。去甲肾上腺素（NE）（3×10⁻⁸ - 3×10⁻⁷M）的浓度在没有钡的情况下不会诱导自发活动，但在有钡存在时却始终诱导或增强自发活动（如果已经存在的话）。在有心得宁（10⁻⁶M）存在的情况下也得到了类似的结果，在17个实验中的13个实验中，心得宁并未抵消NE的作用。然而，酚妥拉明（3×10⁻⁷M）在有或没有心得宁存在的情况下，都会使钡处理过的制剂中由NE诱导的自发活动减慢或阻断。我们得出结论，在钡处理过的浦肯野纤维中α-肾上腺素能反应性增强，并且在这些实验条件下，α-肾上腺素能受体刺激可能影响自律性。讨论了这种效应潜在的可能机制。
