Effect of some central nervous system acting drugs on rat brain and liver monoamine oxidase activity

A number of central nervous system acting drugs were administered to male rats. At certain time intervals after the administration of these drugs, the rats were sacrificed. Liver and brain monoamine oxidase (MAO) activities were determined. The drugs employed were: ethyl alcohol, cognac, hexobarbital, diazepam, imipramine and chloralose. Results obtained indicated that the liver MAO activity was not altered by any of these drugs. Brain MAO activity, contrary to in vitro studies, was increased by alcohol and cognac. The increase was not due to a direct effect of alcohol on the enzyme activity, since the in vitro addition of equivalent concentrations of alcohol, as those calculated to be present in vivo, to brain homogenates resulted in a decrease rather than an increase in activity.