Ruth J A, Eiden L E
Neuropeptides. 1984 Mar;4(2):101-8. doi: 10.1016/0143-4179(84)90120-3.
Leucine-enkephalin (LE) at 10(-8) M reduces the maximum chronotropic response of isolated spontaneously beating rat atria to exogenously added (-)-norepinephrine (NE) by approximately 27%, with no effect on the NE ED50 (1.5 X 10(-7) M) for positive chronotropy. This modulatory effect of LE is completely blocked by addition of 10(-7) M naloxone, and seems to be catecholamine-receptor specific, since the positive chronotropic response to forskolin is unaltered in the presence of LE. Isoproterenol (ISO)-induced positive chronotropy is also attenuated by LE. This effect is markedly dependent on the extracellular calcium concentration: LE actually causes a greater than two-fold enhancement of the positive chronotropic effect of ISO at low (0.5 mM) extracellular calcium concentration. A possible role for enkephalins to modulate catecholamine action on the heart via an alteration of catecholamine-induced inward calcium flux is discussed.
10⁻⁸M的亮氨酸脑啡肽（LE）可使离体自发搏动的大鼠心房对外源性添加的（-）-去甲肾上腺素（NE）的最大变时反应降低约27%，而对NE引起正性变时作用的半数有效浓度（ED50，1.5×10⁻⁷M）无影响。LE的这种调节作用可被添加10⁻⁷M纳洛酮完全阻断，且似乎具有儿茶酚胺受体特异性，因为在LE存在的情况下，对福斯高林的正性变时反应未改变。异丙肾上腺素（ISO）诱导的正性变时作用也会被LE减弱。这种作用明显依赖于细胞外钙浓度：在低细胞外钙浓度（0.5mM）时，LE实际上会使ISO的正性变时作用增强两倍以上。本文讨论了脑啡肽通过改变儿茶酚胺诱导的内向钙内流来调节儿茶酚胺对心脏作用的可能机制。
