Magnesium sulfate enhances non-depolarizing muscle relaxant vecuronium action at adult muscle-type nicotinic acetylcholine receptor in vitro.

To investigate the effect of magnesium sulfate and its interaction with the non-depolarizing muscle relaxant vecuronium at adult muscle-type acetylcholine receptors in vitro. Adult muscle-type acetylcholine receptors were expressed in HEK293 cells. Drug-containing solution was applied via a gravity-driven perfusion system. The inward currents were activated by brief application of acetylcholine (ACh), and recorded using whole-cell voltage-clamp technique. Magnesium sulfate (1-100 mmol/L) inhibited the inward currents induced ACh (10 μmol/L) in a concentration-dependent manner (IC(50)=29.2 mmol/L). The inhibition of magnesium sulfate was non-competitive. In contrast, vecuronium produced a potent inhibition on the adult muscle-type acetylcholine receptor (IC(50)=8.7 nmol/L) by competitive antagonism. Magnesium sulfate at the concentrations of 1, 3, and 6 mmol/L markedly enhanced the inhibition of vecuronium (10 nmol/L) on adult muscle-type acetylcholine receptors. Clinical enhancement of vecuronium-induced muscle relaxation by magnesium sulfate can be attributed partly to synergism between magnesium sulfate and non-depolarizing muscle relaxants at adult muscle-type acetylcholine receptors.