Inhibition of monoamine oxidase activity after combined action of chlordimeform with the antidepressant nialamide.

The 40-day oral administration of 5, 10, and 50 mg/kg chlordimeform to male rats moderately decreased monoamine oxidase activity (MAO) in the brain, liver, and serum, determined with the substrates kynuramine, tyramine, tryptamine, serotonin, dopamine, and benzylamine. The enzyme was inhibited predominantly in the liver. The study of MAO inhibition after 10 days application of 2, 6, 10, 15, and 20 mg/kg nialamide revealed that 2 mg/kg had a threshold effect. A dose of 6 mg/kg resulted in a pronounced decrease in the enzyme activity. Experiments with a 30-day application of 5, 10 and 50 mg/kg chlordimeform were made, followed by treatment with 6 mg/kg nialamide in combination for another 10 days. The statistical evaluation by the Student's t-test demonstrated increased MAO inhibitory action. Dose-effect relationship was established with kynuramine in liver, brain, and serum, and with benzylamine in liver.