Pharmacological characterization of the postsynaptic serotonergic receptor in the human uterine artery

Serotonergic receptors are involved in many vascular functions, but only a few studies have been made in human vessels. Thus, this study aimed to characterize these receptors in the human uterine artery without endothelium. The pD2 value of serotonin (5-HT) was 5.96, but the intrinsic activity was 59% of that of noradrenaline. Spiperone and ketanserin shifted the concentration-response curves of 5-HT to the right (pA2 = 8.56 and 9.76; slopes = 0.98 and 0.83, respectively). Propranolol, yohimbine, prazosin and atropine did not significantly shift the concentration-response curves to 5-HT. Phentolamine inhibited the 5-HT response (pA2 = 6.69), and previous treatment of the vascular strips with 6-hydroxydopamine only partially reduced such an effect. The results demonstrate the existence, in the human uterine artery, of 5-HT2 receptors which are blocked by high concentrations of phentolamine. In this tissue, 5-HT does not release noradrenaline from perivascular nerves.