Suppression of pulmonary and systemic vascular histamine Hz-receptors in allergic sheep

monary and systemic vascular histamine Hz-receptors in allergic sheep. J. Appl. Physiol. 60(3): 791-797, 1986.-We have previ-ously demonstrated a depression of airway HZ-receptor function in sheep allergic to Ascaris suum antigen. To investigate whether this is a generalized defect, we studied the H1- and HZ-histamine receptor functions in the pulmonary and systemic circulations of allergic and nonallergic sheep. Pulmonary arte-rial pressure, pulmonary arterial wedge pressure, systemic ar-terial pressure, and cardiac output were measured for calcula-tion of pulmonary vascular resistance (PVR) and systemic vascular resistance (SVR) before and immediately after a rapid intrapulmonary infusion of histamine (10 pg/kg), with and without pretreatment with H1- (chlorpheniramine) and HP-(metiamide) antagonists. Histamine alone increased mean PVR to 435 and 401 % of base line and decreased mean SVR by 5