Regional vascular resistance and heart rate responses mediated through H1- and H2-histamine receptors in the unanaesthetised rabbit

Abstract

The effects of histamine infusions (10-100 μg/kg/min) on heart rate and hindlimb, carotid, mesenteric and renal vascular resistance were investigated in unanaesthetised rabbits after "total" autonomic effector block to abolish reflex effects. Histamine caused a rise in heart rate that was predominately due to stimulation of H2-receptors (blocked by metiamide). Hindlimb and carotid vascular resistance did not change significantly during histamine infusion. However, after blocking H2-receptors with metiamide histamine infusions produced dose-related vasoconstriction in these beds while after H1-receptor block with mepyramine histamine caused dose-related vasodilatation indicating that H1- and ..