The vascular responses of the isolated perfused bovine external ear to exogenous histamine and 5-HT (serotonin).

The responses of the vasculature of isolated, non-sensitized, bovine external ears to histamine and serotonin (5-HT) were evaluated while they were being perfused with Krebs-Henseleit solution. Histamine (10(-5) mol/L to 5 x 10(-3) mol/L) and 5-hydroxytryptamine (5-HT) (10(-9) mol/L to 10(-2) mol/L) caused increased vascular resistance. Mepyramine (10(-7) mol/L), cimetidine (10(-5) mol/L) and atropine (10(-6) mol/L) inhibited the responses to histamine. The responses to 5-HT were inhibited by methysergide (10(-9) mol/L) and potentiated by morphine (10(-5) mol/L). These results suggest the presence of H1 and H2 histamine, and 5-HT receptors in bovine auricular vessels, all of which cause net vasoconstriction.