马钱子碱对豚鼠心脏乳头肌慢反应动作电位的影响

用细胞内微电极技术观察了马钱子碱（ｂｒｕｃｉｎｅ）对离体豚鼠乳头肌高Ｋ＋除极异丙肾上腺素（Ｉｓｏ）和组织胺（Ｈｉｓ）诱发的慢反应动作电位（ＳＡＰ）的影响。结果表明，低浓度的ｂｒｕｃｉｎｅ延长慢反应动作电位５０％、９０％动作电位时程（ＡＰＤ５０、ＡＰＤ９０），较高浓度的ｂｒｕｃｉｎｅ则抑制ＳＡＰ的幅度（ＡＰＡ）、Ｏ期最大上升速率（Ｖｍａｘ）以及收缩力（Ｆｃ）。将台氏液中Ｃａ２＋浓度由２．０ｍｍｏｌ／Ｌ提高至４．０ｍｍｏｌ／Ｌ时，ｂｒｕｃｉｎｅ对组织胺诱发ＳＡＰ的ＡＰＡ、Ｖｍａｘ以及Ｆｃ的抑制作用反转，提示ｂｒｕｃｉｎｅ可能阻滞心肌Ｃａ２＋通道。

Effects of Brucine on Slow Action Potentials in Guinea Pig Papillary Muscle

The effects of Brucine were studied on the slow action potentials induced by isoprenaline and histamine in high K depolarized guinea pig papillary muscles by means of conventional glass microelectrodes. It was demonstrated that Brucine prolonged the slow action potential duration at 50% and 90% repolarization (APD 50 ,APD 90 ).At high concetration, Brucine suppressed the maximal upstroke velocity (Vmax),action potential amplitude (APA) and contractile force(Fc). The inhibitory effects of Brucine on the APA, Vmax and Fc were antagonised partially by the elevation of the extracellular concentration of calcium from 2.0 to 4.0mmol/L. These results indicated that Brucine could block the Ca 2 channels.