迷走神经与心室肌细胞钙内流关系的探讨

Relation between Vagal Nerve and Calcium Influx in Rabbit Ventricular Fibers

用浮置微电极技术观察了高血钙时兔心室肌细胞跨膜电位(TMP)的变化,以及刺激迷走神经对这些变化的影响。结果表明,高血钙可使心室肌细胞动作电位时程(APD)缩短,O相上升速率([dv/dt]_(max))减慢,刺激迷走神经可消除高血钙引起的[dv/dt]_(mac)的改变,在用氯化四乙基胺(TEA)阻断K通道后,这些作用仍部分出现,并且APD_(30)及APD_(50)缩短。上述结果提示,迷走神经对心室肌细胞跨膜电位的影响,不仅能提高膜对K^+的通透性,而且还可能抑制钙内流。

The effect of vagal nerve on the calcium influx was studied in rabbit ventricular fibers. The transmembrane potentials (TMP) of the ventricular myocardial cells were recorded by floating microelectrode technique, The result showed that hypercalcemia shortened the action potential duration (APD) and slowed the maximum upstroke velocity of phase 0 ([dv/dt]mas), Vagal stimulation could abolish the decre ase in [dv/dt]max caused by hypercalcemia. The vagal nerve did not change the heart rate when K channels were blocked with tetraethylammonium (TEA) chloride, but APD30 and APD50 were shortened from 73.97±9.01 and 90.09±12.94 ms (mean±S) to 69.57±9.62 and 84.59±11.44ms respectively (P<0.05). These results suggested that the effects of vagal nerve on the myocardial transmembrane potentials not only incre ase K conductance, but also suppress Ca influx.