Relaxation of rat tail artery to electrical stimulation.

Rat tail artery strips relax in response to electrical stimulation (0.1-8Hz, 9V, 1.0msec) following contraction induced by norepinephrine (5.9 X 10(-7)M). The relaxation is not altered by treatment of the strips with atropine, propranolol, tetrodotoxin or indomethacin nor by chemical denervation with 6-hydroxydopamine. Incubation of strips in calcium-free solution reduced the contractile response to norepinephrine and blocked relaxation in response to 4Hz electrical stimulation. Histamine antagonists (H2 receptor subclass: cimetidine, metiamide) inhibited the relaxation to electrical stimulation in a dose-dependent manner. These results suggest that relaxation to electrical stimulation in rat tail artery is modulated by calcium and by the H2 subclass of histamine receptors.