[Monoamine oxidase activity of the brain of Locusta migratoria in normal conditions and after intoxication by two insecticides: chlordimeform and dieldrin].

Our investigations have shown up an MAO activity in locust brain, by the use of a radio-isotopic method, as much at larval as at adult stage. This MAO activity is in a sample of 34,3 dpm/mg of brain tissue (wet weight). Investigations have also been undertaken on effects of dieldrin and chlordimeform poisoning on this MAO activity. Even at sublethal dosages, chlordimeform causes a significant inhibition of MAO activity in vivo. This finding is in accordance with Beeman and Matsumura's work in vitro. Moreover, acute poisoning by dieldrin produces more than 60% of inhibition of MAO, 3 hours after administration of 115 microng of this insecticide by injection in the hoemocelian cavity.