Ganglionic blockade by procaine in the presence of pentobarbital and diethyl ether

The interactions of procaine with pentobarbital and diethyl ether were observed on the isolated stellate ganglion of the hamster. Each drug reduced the amplitude of the compound postganglionic action potential induced by stimulation of the preganglionic nerve at 0.2 Hz. The slopes of the concentration response curves were not significantly different for the three drugs. When solutions of procaine and pentobarbital were mixed, the effect of the mixture was not significantly different from the effects of procaine and pentobarbital solutions, separately. Also, procaine shifted the concentration-response curve for pentobarbital in a manner expected for an additive interaction. When solutions of procaine and diethyl ether were mixed, the blockade by the mixture was significantly greater than the blockade by procaine and diethyl ether solutions, separately. Procaine shifted the concentration-response curve for diethyl ether in a manner that is greater than would be expected for an additive interaction. These results indicate that procaine and pentobarbital interact, additively, and that procaine potentiates the actions of diethyl ether. The potentiating interaction of procaine and diethyl ether suggests that the drugs have different mechanisms of action on the ganglion.