Lack of an effect of drugs acting at histamine receptors on norepinephrine-induced relaxation of porcine coronary arteries.

The effects of selective histamine receptor stimulation on relaxation to norepinephrine (NE) were determined in four sizes of spirally cut porcine coronary arteries. The four sizes of porcine coronary artery were designated very large (greater than 4.0 mm o.d.), large (1.5-2.5 mm o.d.), medium (0.8-1.2 mm o.d.), and small (less than or equal to 0.5 mm o.d.). Histamine, dimaprit, 2-pyridylethylamine, and histamine plus either mepyramine or metiamide did not alter the concentration-response curve to NE. Thus histamine receptor stimulation does not change relaxations of porcine coronary arteries to NE.