Effects of several 'membrane stabilizing' agents on frog neuromuscular junction

The effect of several "membrane stabilizing" agents was examined on spontaneously occurring frog miniature end-plate potentials (MEPPs). No consistent parallel was observed between the ability of agents to act as "membrane stabilizers" and their ability to alter MEPP frequency, Vinblastine, chlorpromazine and haloperidol increased MEPP frequency; the concentration of haloperidol which increased MEPP frequency consistently reduced the magnitude of the muscle resting membrane potential. Strychnine, methoxyflurane and practolol decreased MEPP frequency. Similarly, there was no consistent pattern of drug effects on the mean quantal content m of the end-plate potential. Chlorpromazine did not change m, and it is known that vinblastine does not influence m. Strychnine, methoxyflurane, haloperidol and practolol brought about a decline in m.