Antioxotremorine action of propranolol.

1. The influence of propranolol on the neuromuscular, tremor-producing and muscarinic effects of oxotremorine was examined. 2. In the isolated rat phrenic nerve-diaphragm preparation the neuromuscular blocking effect of oxotremorine was inhibited by propranolol in a dose-dependent manner. 3. Propranolol intensified the paralytic effect of tubocurarine in the rat diaphragm and prevented antagonism of tubocurarine paralysis by tetraethylammonium. 4. Propranolol was devoid of any curare-like effect in the isolated rectus abdominis muscle of the frog. 5. Vasodepressor responses to oxotremorine in rats and spasmogenic responses to oxotremorine in guinea-pig ileum were not antagonized by propranolol. 6. A dose-dependent antagonism of oxotremorine-induced tremor in mice was observed after pretreatment with propranolol and it is suggested that this effect is due to an antagonism of a presynaptic effect of oxotremorine at skeletal neuromuscular junctions.