Jacobs R S, McNiece D M
J Pharmacol Exp Ther. 1977 Aug;202(2):404-10.
Facilitatory effects of SQ 20009 [1-ethyl-4-(isopropylidenehydrazine)-1H-pyrazolo-(3,4-b)-pyridine-5-carboxylic acid, ethyl ester, HCl] were investigated at the frog sartorious neuromuscular junction. A dose-dependent increase in miniature end-plate potential frequency occurred without changes in miniature end-plate potential amplitude. Significant increases in the amplitude and the rate of rise of the end-plate potential and reduction in the incidence of end-plate potential failures were observed in magnesium blocked muscle. The increase in end-plate potential amplitude and rate of rise appeared calcium dependent. No significant changes in passive membrane resistance or muscle membrane sensitivity to acetylcholine were observed. Twitch studies employing direct and indirect stimulation of the rat diaphragm preparation demonstrated a preferential facilitation of the indirect response rather than a direct action on the muscle fiber. The facilitatory effect of SQ 20009 on evoked and spontaneous release were of approximately equal orders of magnitude, suggesting that the drug may affect a common mechanism in the two release processes.
在青蛙缝匠肌神经肌肉接头处研究了SQ 20009[1-乙基-4-(亚异丙基肼)-1H-吡唑并-(3,4-b)-吡啶-5-羧酸乙酯，盐酸盐]的易化作用。微小终板电位频率呈剂量依赖性增加，而微小终板电位幅度无变化。在镁阻断的肌肉中，观察到终板电位幅度和上升速率显著增加，终板电位失败发生率降低。终板电位幅度和上升速率的增加似乎依赖于钙。未观察到被动膜电阻或肌肉膜对乙酰胆碱的敏感性有显著变化。采用直接和间接刺激大鼠膈肌标本的抽搐研究表明，优先易化间接反应而非对肌纤维有直接作用。SQ 20009对诱发释放和自发释放的易化作用大致处于相同数量级，表明该药物可能影响这两个释放过程中的共同机制。
