绵羊心浦肯野纤维d-受体和β-受体激动时离子流Isi和Ix的变化

当绵羊心浦肯野纤维α-和β-受体分别激动时,用双微电极法电压箝制术研究慢内向离子流Isi和延迟整流外向离子流Ix的变化。心得安阻断β-受体时,苯肾上腺素5.0×10~(-6)mol/L使Isi的峰值由17.5增加到26nA(n=6,P<0.05).并使Isi由失活到完全恢复的时间由293±51ms延长到441±109ms(n=4,P<0.05),但对Ix无明显影响。酚妥拉明阻断α-受体时,异丙肾上腺素4×10~(-7)mol/L使Isi峰值由27.7增加到40.8nA(n=7,P<0.05),对Isi的动力过程无明显影响,却使Ix尾电流的幅值由6.7增加到14,4nA(n=6,P<0.05)。表明α-和β-受体激动剂作用的差异在于对延迟整流离子流的影响不同。

CHANGES OF Isi AND Ix IN SHEEP CARDIAC PURKINJE FIBERS DURING ALPHA- AND BETA- ADRENOCEPTOR EXCITATION

When alpha- and beta- adrenoceptors were activated respectively in sheep cardiac Purkinje fibers, changes of the slow inward current (Isi) and delayed rectifier current (Ix) were studied by using two-microelectrode voltage clamp technique. When beta-receptor was blocked by propranolol, phenylephrine 5.0 x 10(-6) mol/L increased the peak value of Isi from 17.5 to 26 nA (n = 6, P less than 0.05) and prolonged the ms recovery time of Isi from inactivation from 293 +/- 51 ms to 441 +/- 190 (n = 4, P less than 0.05). Phenylephrine had no effect on the delayed rectifier current (Ix). When alpha-adrenoceptor was blocked by phentolamine, isoprenaline of 4 x 10(-7) mol/L increased the peak value of Isi from 27.7 to 40.8 nA (n = 7, P less than 0.05) and had no effect on the kinetics of Isi, but it did increase the tail current (Ix) peak value from 6.7 to 14.4 nA (n = 6, P less than 0.05). The results suggest that alpha- and beta-adrenoceptor agonists differ in their effects on delay rectifier current.