AN ANALYSIS OF THE DEPRESSOR RESPONSES TO HISTAMINE IN THE CAT AND DOG: INVOLVEMENT OF BOTH H_1 - AND H_2-RECEPTORS

摘要

1. The depressor responses to histamine, in anaesthetized cats and dogs, have been shown to involve both histamine H_1 - and H_2- receptors. 2. In both species, histamine caused dose-dependent falls in blood pressure. The dose-response curve could be displaced to the right by administration of mepyramine 2.5 x 10~(-6) mol/kg i.v. The displacement was maximal with a dose-ratio of less than ten. 3. Metiamide alone, up to 2 x 10~(-6) mol kg~(-1) min~(-1), had no significant effect on the histamine dose-response curve. 4. When administered in the presence of mepyramine, metiamide, 4 x 10~(-7) and 2 x 10~(-6) mol kg~(-1) min~(-1), caused dose-dependent displacements to the right, of the histamine dose-response curve greater than could be achieved with mepyramine alone. 5. The results indicate the presence of both histamine H_1- and H_2-receptors in the cardiovascular system of the cat and dog. Both receptors produce a common response, i.e. a fall in blood pressure.