Abstract
Changes in tensions wre monitored isometrically on spiral strips of freshly obtained human varicose and dog saphenous and femoral veins. Cumulative dose-reserpine curves for noradrenaline (NA) were shifted to the right in the presence of dihydroergotamine (DHE). pA 10 values, calculated from the shifts at the 50% effect levels were 5.6 on human varicose, 7.2 on dog saphenous and 8.4 on femoral veins. DHE stimulted the three preparations in about the same concentration ranges (pD 2 7.5, 8.3 and 8.0) but compared with NA it had different intrinsic activities (0.3, 0.1 and 0.16 on human varicose, dog saphenous and femoral veins respectively). On dog saphenous veins about 30% of DHE-induced contractions could be blocked by phentolamine and about 60% by indomethacin. DHE provoked a significant increase in the level of prostaglandin E-like substances(s) in the bathing fluid. The results suggest that the venoconstrictor response to DHE is mediated partially through α-adrenoceptors and the enhanced synthesis of prostaglandins may also contribute.
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