[Effects of melatonin on muscle contractility and neuromuscular blockade produced by muscle relaxants].

Effects of melatonin on muscle contractility and on the blocking properties of succinylcholine and vecuronium were investigated in vitro using phrenic nerve-hemidiaphragm preparations of rats. Melatonin (26-520 microM) alone had almost no effect on the contractility. Melatonin (260 microM) markedly potentiated the block produced by succinylcholine, but melatonin had no effect on the block produced by vecuronium. Because the property of the block produced by succinylcholine is nicotinic receptor desensitization, we consider that melatonin potentiates succinylcholine-induced block with facilitation of the desensitization. These results suggest that melatonin has calcium channel blocking effect.