On the neuromuscular paralysis produced by procaine.

1. The effects of procaine on neuromuscular transmission in the rat phrenic nerve diaphragm preparation have been examined using intracellular recording techniques.2. The paralysis produced by procaine resembled that produced by tubocurarine and it is concluded that this effect of procaine results from a change in post-junctional sensitivity to transmitter; at low rates of stimulation procaine did not depress the transmitter release.3. During high frequency stimulation of the phrenic nerve a distinct form of prejunctional failure was observed. It is suggested that this depression results from a combination of local anaesthesia and anoxia and that it would explain reports of a reduction in the amount of transmitter released when assayed in a conventional manner.