The effect of various monoamine oxidase (MAO) inhibitors on the response of blood pressure of rats and cats to tyramine.

The "cheese effect" is the clinically most important side effect of structurally different MAO inhibitors. It occurs mainly as a result of the interaction of MAO inhibitor with tyramine in foodstuffs. Anaesthetised rats and cats were used in order to investigate and compare the influence of the effect of tyramine by selective MAO type-B inhibitors with that produced by non-selective and A-selective MAO inhibitors on the one hand, and on the other hand, different MAO-B inhibitors with (-)deprenyl. (-)Deprenyl was the only one which inhibited the effect of tyramine in the experimental animals used, while other MAO inhibitors potentiated the tyramine effect. Therefore this study indicates that not only non-selective and A-selective inhibitors potentiate the effect of tyramine but selective inhibitors of B-type MAO as well. The inhibition of tyramine uptake by (-)deprenyl is a remarkable exception from the rule.