Monoamine oxidase inhibition and brain catecholamine levels in the rat following treatment with chlordimeform

Abstract Norepinephrine and dopamine levels in rat brain increase by 51.7 and 70.3%, respectively, within 14 hr of intraperitoneal injection of 24 mg chlordimeform/kg wet wt. An inhibition of monoamine oxidase (MAO) activity in mitochondrial extracts from brains and livers of chlordimeform-treated rats occurred concomitantly with the elevation of catecholamine levels. In the brain extract the oxidative deamination of tyramine was inhibited by 8.1% and that of 2-phenylethylamine by 54.5%, whereas in the liver preparation the extent of inhibition using these substrates was 23.8 and 31.1%, respectively. The results suggest specific inhibition of type B MAO, and the conclusion was substantiated by use of clorgyline, a specific inhibitor of type A MAO. The results are discussed in light of the observation that rats which are exposed to sublethal concentrations of chlordimeform display pronounced behavioral changes.