Effect of AWD 52-39 on vasoconstriction induced by noradrenaline and 5-hydroxytryptamine in vitro and in vivo in rats.

The vascular effect of the potential nootropic AWD 52-39 (1; N,N-diacetoxyethyl-9,10-dihydrolysergic acid amide) as well as its influence on noradrenaline- or 5-HT-induced vasoconstriction were studied in the isolated rat aorta and in anesthetized normotensive and pithed rats. Vasoconstriction was determined by measuring the increase in mean arterial pressure (MAP). Both in vitro and in pithed rats, 1 caused a slight vasoconstriction, whereas a dose-dependent short-lasting decrease in mean arterial pressure was found in normotensive rats. In vitro and in pithed rats, 1 exerted no influence on the noradrenaline-induced vasoconstriction, while the 5-HT-induced contractile response was significantly inhibited. These findings characterize 1 as a competitive antagonist at vascular 5-HT2 receptors without any alpha-adrenolytic effect.