THE MECHANISM OF THE VASODEPRESSOR RESPONSE TO TYRAMINE IN DOGS

¹ Department of Pharmacology, Northwestern University Medical School, Chicago, Illinois

The depressor response to intravenous injections of tyramine was studied in normal and reserpine-treated dogs. Cutaneous flushing and respiratory inhibition were seen during the depressor response. When injected intracutaneously, tyramine elicited a triple response, or cutaneous bluing in Evans Blue-treated dogs. Pretreatment with the antihistamines tripelennamine or chlorpheniramine reduced the depressor response. Crossover tachyphylaxis was observed between the depressor response to tyramine and that to compound 48/80. The fall in blood pressure from tyranmine, like that from 48/80, was associated with an elevation of blood histamine levels. We therefore conclude that the depressor response to tyramine is mediated through time release of histamine.