α受体激动对绵羊心脏浦肯野纤维延迟后除极的影响

EFFECTS OF ALPHA- ADRENORECEPTOR EXCITATION ON THE DELAYED AFTER-DEPOLARIZATION OFSHEEP CARDIAC PURKINJE FIBERS

用乙酰毒毛旋花子成元０．２μｍｏｌ／Ｌ诱发绵羊心脏浦肯野纤维产生延迟后除极（ＤＡＤ），采用细胞内微电极记录。在用普奈洛尔１．０μｍｏｌ／Ｌ阻断β受体条件下，苯肾上腺素１．０μｍｏｌ／Ｌ使ＤＡＤ幅值由８．１±２．２ｍＶ增至９．５±２．８ｍＶ，时程由２４０±４７ｍｓ延长到２７３±４７ｍｓ（ｎ＝１３，ＰＭ＜０．０１），ＤＡＤ上升速率由０．０３９±０．０２３Ｖ／ｓ增至０．０５１±０．０２６Ｖ／ｓ（ｎ＝１３，Ｐ＜０．０５），ＤＡＤ在动作电位后出现的时间提前了３０±４７ｍｓ（ｎ＝１３，Ｐ＜０．０５）。用去甲肾上腺素１．０μｍｏｌ／Ｌ增强ＤＡＤ引起触发活动时，酚妥０拉明１．８μｍｏｌ／Ｌ不能抑制触发活动，普奈洛尔１．０μｍｏｌ／Ｌ能抑制之。上述结果表明α受体激动对ＤＡＤ有轻度增强作用，但由ＤＡＤ引起的触发活动，α受体阻滞剂的抑制作用不如β受体阻滞剂有效。

By using acetyl strophanthidin (AS)0.2μmol/L,the delayed after-deplarization(DAD)was induced in sheep cardiac Purkinje fibers and recorded with intra-cellular microelectrode.When bead-adrenoceptor was blocked by proptanolol 1.0μmol/L,phenylephrine 1.0μmol/L increased the amplitude of DAD from 8.1±2.2 mV to9.5±2.8 mV,prolonged the duration of DAD from 240±47 ms to 273±47 ms(n=13,P<0.01)and increased the up rising velocity of DAD from of 0.39±0.023V/s to 0.051±0.026 V/s(n=13, P<0.05).The DAD occured earlier for 30±47 ms to preceding action potential (n= 13,P<0.05).When triggered acting potentials were induced by norepinephrine 1.0 μmol/L on the basis of DAD,proptanolol1.0 μmol/L could suppress the triggered.beats while phentolamine 1.μmol/L showedlittle effect.The above results indicate that excitation of alpha-receptor had only slightaugmentation effect on DAD.However,for the triggered activity induced by DAD,the inhibitory effect of bead-blockers are stronger than that of alpha-blockers.