Histamine H2-receptors modulate systemic anaphylaxis: a dual cardiovascular action of histamine in calves

Depressor changes in carotid blood pressure caused by histamine or anaphylaxis in calves, were incompletely blocked by the H(1)-receptor antagonist mepyramine. Burimamide, the selective histamine H(2)-receptor antagonist, potentiated the depressor actions of histamine and anaphylaxis. Potentiated depressor responses were inhibited by mepyramine. Observations are consistent with histamine stimulating both H(1)- and H(2)-receptors to cause respectively vasodilatation and vasoconstriction.