Pancuronium, vecuronium, and d-tubocurarine inhibit and succinylcholine stimulates choline acetyltransferase activity

The effects of the nondepolarizing muscle relaxants (NDMR), pancuronium, vecuronium, and d-tubocurarine and a depolarizing muscle relaxant, succinylcholine, were studied on choline acetyltransferase (ChAT) activity. A radiochemical assay was used in the determination of ChAT activity using purified placental enzyme. Pancuronium at concentrations of 10(-7) M, 10(-6) M, 10(-5) M, 10(-4) M, and 10(-3) M inhibited ChAT activity by 3, 10, 15, 40 and 85 per cent, respectively; vecuronium at concentrations of 10(-6) M, 10(-5) M, 10(-4) M, and 10(-3) M inhibited ChAT activity by 5, 10, 26 and 57 per cent, respectively; d-tubocurarine at concentrations of 10(-6) M, 10(-5) M, 10(-4) M, and 10(-3) M inhibited ChAT activity by 0, 4, 12.5 and 29 per cent, respectively; whereas succinylcholine at concentrations of 10(-7) M, 10(-6) M, 10(-5) M, and 10(-4) M activated ChAT activity by 8, 10, 1, and 2 per cent, respectively. Even though our present data demonstrated a significant dose-dependent inhibitory effect on ChAT activity by pancuronium, vecuronium and d-tubocurarine, it is unlikely that this inhibitory effect will contribute to the mechanism of action of NDMR. Our data, however, may suggest an additional mechanism for the phenomena of tetanic and train-of-four fades that are seen following the administration of nondepolarizing muscle relaxants.