Effect of meptazinol on neuromuscular transmission in the isolated rat phrenic nerve-diaphragm preparation.

Meptazinol has been shown to have significant effects on neuromuscular transmission in the isolated rat phrenic nerve-diaphragm preparation. The response of the preparation to indirect electrical stimulation was increased in a concentration-dependent manner by meptazinol hydrochloride 2-32 micrograms ml-1. Meptazinol 0.5-2 micrograms ml-1 antagonized the effects the tubocurarine on this preparation, and in concentrations of 1 microgram ml-1 and greater, potentiated suxamethonium. These effects were similar to those obtained with neostigmine and it was demonstrated that meptazinol had significant anti-cholinesterase activity in the concentrations used. Inhibition of cholinesterase with ecothiopate revealed a neuromuscular blocking activity of meptazinol in concentrations as low as 0.25 micrograms ml-1.