Propranolol and morphine.

The morphine blocking and anticonvulsant effects of propranolol were investigated in mice. Three different convulsant procedures (electroshock, pentylenetetrazol and thebaine) were used. In addition, LD50's of morphine after different doses of propranolol were done. Sotalol was used as a control drug to check which of the effects of propranolol could be regarded as due to beta blockade. Morphine LD50 in mice is not altered by pre-treatment with propranolol. The anticonvulsant characteristics of propranolol are different from those of sotalol, the former acting mainly on the tonic phase of the seizures. This study does not support the hypothesis that propranolol is a morphine antagonist but reinforces the idea that propranolol has definite central nervous system effects.