Yen M H, Lee S H, Ho S T
Eur J Pharmacol. 1985 Jul 11;113(1):61-7. doi: 10.1016/0014-2999(85)90343-7.
The pressor effect of 4-aminopyridine (4-AP) was studied in anesthetized cats and in isolated cat aortic ring preparations. A significant increase in blood pressure (38.9 +/- 11.4 mmHg) was observed following intravenous administration of 4-AP (0.3 mg/kg). The elevated blood pressure lasted for 1.3 h and returned to the control level after 1.5 h. The pressor effect of 4-AP was not blocked by prior administration of phentolamine (2 mg/kg i.v.) or by pretreatment with reserpine (2 mg/kg i.m., once a day for two consecutive days). In vitro, a dose-dependent tonic contraction of aortic ring was noted after addition of 4-AP into the bathing fluid. The ED50 of 4-AP was significantly greater than that of norepinephrine (NE) (8 X 10(-4) M vs. 10(-7) M). Phentolamine (10(-6) M) antagonized the contractile response to NE but not that to 4-AP, whereas verapamil (10(-5) M) attenuated the 4-AP induced contractile response. A diminished contractile effect was also obtained when aortic ring preparations were bathed in calcium-free solution. These data suggest that the sympathetic nervous system plays a minor role in the pressor effect of 4-AP and that the increased calcium influx may account, at least partially, for the vasoconstricting effect of 4-AP.
在麻醉猫和离体猫主动脉环标本中研究了4-氨基吡啶（4-AP）的升压作用。静脉注射4-AP（0.3mg/kg）后观察到血压显著升高（38.9±11.4mmHg）。血压升高持续1.3小时，1.5小时后恢复到对照水平。预先给予酚妥拉明（2mg/kg静脉注射）或利血平预处理（2mg/kg肌肉注射，连续两天每天一次）均不能阻断4-AP的升压作用。在体外，向浴液中加入4-AP后，主动脉环出现剂量依赖性的张力性收缩。4-AP的半数有效剂量（ED50）显著大于去甲肾上腺素（NE）（8×10(-4)M对10(-7)M）。酚妥拉明（10(-6)M）拮抗对NE的收缩反应，但不拮抗对4-AP的收缩反应，而维拉帕米（10(-5)M）减弱4-AP诱导的收缩反应。当主动脉环标本置于无钙溶液中时，收缩效应也减弱。这些数据表明，交感神经系统在4-AP的升压作用中起次要作用，钙内流增加可能至少部分解释了4-AP的血管收缩作用。
