Blood pressure effects of monoamine oxidase inhibitors in response to orally administered tyramine in the rat

Abstract

The reversible monoamine oxidase‐A inhibitors BW 1370U87, BW 616U76, brofaromine, and moclobemide, and the irreversible nonselective monoamine oxidase inhibitor phenelzine were compared for potentiation of the pressor response to oral tyramine. Conscious rats were pretreated with doses of the monoamine oxidase inhibitors sufficient to produce 80% inhibition of brain monoamine oxidase, and then were challenged with orally administered tyramine. Blood pressure was monitored prior to and after tyramine, and peak pressor responses were compared. At a dose of 15 mg/kg tyramine, the pressor response of BW 1370U87 was statistically similar to the vehicle control response. BW 616U76, brofaromine, and moclobemide elicited mild tyramine pressor effects, whereas phenelzine resulted in a marked elevation of blood pressure. Higher doses of tyramine elicited blood pressure elevations from all of the monoamine oxidase inhibitors.