Sauviat M P
Br J Pharmacol. 1980;71(1):41-9. doi: 10.1111/j.1476-5381.1980.tb10907.x.
1 The effects of a new alkaloid, ervatamine, on transmembrane currents of frog atrial fibres were studied by the double sucrose gap voltage clamp technique. 2 Ervatamine (2.8 x 10(-4) M) blocked the action potential without altering the resting membrane potential. 3 The alkaloid depressed the peak INa. The dissociation constant for the blocking effect of ervatamine on gNa fast was 2.35 X 10(-5) M with a one to one relationship between the drug molecule and the Na channel. Ervatamine did not alter the apparent equilibrium potential for Na, as well as the activation and inactivation parameters of gNa fast. This suggests that the alkaloid inhibitory effect on gNa can be attributed to a reduction in gNa. 4 Ervatamine prolonged the rate of reactivation of the Na system. It inhibited gNa in a frequency-dependent manner; this indicates that the alkaloid acts on open Na channels i.e. that the drug has to enter the channel or cross the membrane to produce the block. 5 Ervatamine inhibited Ina slow which occurs in Ca-free, tetrodotoxin-containing solutions and moderately decreased ICa which occurs in Na-free solutions. The drug increased the background K current (IK1) and did not alter the time-dependent K current (Ix1). 6 The present study shows that ervatamine is a good inhibitor of both fast and slow gNa. This drug also shares some common electrophysiological properties with antiarrhythmic drugs namely: the frequency-dependent inhibition of the fast gNa and the ability to slow the reactivation of the Na carrying system.
采用双蔗糖间隙电压钳技术研究了一种新生物碱——刺桐胺对蛙心房纤维跨膜电流的影响。
刺桐胺（2.8×10⁻⁴ M）可阻断动作电位，而不改变静息膜电位。
该生物碱可降低INa峰值。刺桐胺对gNa快速阻断作用的解离常数为2.35×10⁻⁵ M，药物分子与钠通道之间呈一对一关系。刺桐胺不改变钠的表观平衡电位，以及gNa快速的激活和失活参数。这表明该生物碱对gNa的抑制作用可归因于gNa的降低。
刺桐胺延长了钠系统的再激活速率。它以频率依赖性方式抑制gNa；这表明该生物碱作用于开放的钠通道，即药物必须进入通道或穿过膜才能产生阻断作用。
刺桐胺抑制了在无钙、含河豚毒素的溶液中出现的Ina慢电流，并适度降低了在无钠溶液中出现的ICa电流。该药物增加了背景钾电流（IK1），且不改变时间依赖性钾电流（Ix1）。
本研究表明，刺桐胺是快速和慢速gNa的良好抑制剂。该药物还与抗心律失常药物具有一些共同的电生理特性，即：对快速gNa的频率依赖性抑制以及减缓钠转运系统再激活的能力。
