Robinson C P, Sastry B V
J Pharmacol Exp Ther. 1976 Apr;197(1):57-65.
The exposure of helically cut strips of rabbit aorta to mecamylamine (1 mM) for 5 minutes blocked the histamine (3.25 muM)-induced contractions completely and reduced those induced by potassium (25mM, 68%) without affecting contractions induced by norepinephrine (3.0 muM, NE) or acetylcholine (10 muM). Mecamylamine, by itself, did not exhibit agonist activity, but it increased the contractile tension of the muscle which was contracted by NE. The responses to NE were either enhanced or not affected by small doses of mecamylamine (1 mM), but were partially blocked by large doses of mecamylamine (10 mM). The antagonism exhibited by mecamylamine in low doses (1 mM) against the above agonists was reversible. The shape of the response to NE on the muscle, which was treated with a high dose of mecamylamine (20 mM) and washed, was significantly different from that of the control. Our results are consistent with the following conclusions: 1) Mecamylamine in low doses (1 mM) blocks the histamine receptor and therefore the histamine-induced contractions. Two molecules of mecamylamine are competitive with 1 molecule of histamine. 2) Mecamylamine blocks the potassium-induced contractions, but does not block completely the calcium influx in the potassium-depolarized muscles. Therefore, it may interfere partially with the utilization of extracellular or loosely bound calcium during potassium-induced contractions. 3) Mecamylamine in high doses (10 mM) partially blocks norepinephrine-induced contractions by affecting firmly bound calcium stores. 4) Procaine antagonizes the effects of NE, histamine and acetylcholine by affecting, at least partially, the firmly bound calcium stores.
将兔主动脉螺旋切割条暴露于美加明（1 mM）5分钟，可完全阻断组胺（3.25 μM）诱导的收缩，并减少钾（25 mM）诱导的收缩（减少68%），而不影响去甲肾上腺素（3.0 μM，NE）或乙酰胆碱（10 μM）诱导的收缩。美加明本身不表现出激动剂活性，但它增加了由NE收缩的肌肉的收缩张力。小剂量美加明（1 mM）对NE的反应要么增强，要么不受影响，但大剂量美加明（10 mM）可部分阻断该反应。低剂量（1 mM）美加明对上述激动剂的拮抗作用是可逆的。用高剂量美加明（20 mM）处理并冲洗后的肌肉对NE反应的形状与对照组有显著差异。我们的结果与以下结论一致：1）低剂量（1 mM）美加明阻断组胺受体，从而阻断组胺诱导的收缩。两分子美加明与一分子组胺竞争。2）美加明阻断钾诱导的收缩，但不完全阻断钾去极化肌肉中的钙内流。因此，它可能在钾诱导的收缩过程中部分干扰细胞外或松散结合钙的利用。3）高剂量（10 mM）美加明通过影响紧密结合的钙储存部分阻断去甲肾上腺素诱导的收缩。4）普鲁卡因通过至少部分影响紧密结合的钙储存来拮抗NE、组胺和乙酰胆碱的作用。
