Effect of serotonin on uterine blood flow in pregnant and nonpregnant sheep

Abstract

A chronically catheterized preparation was used to determine the effects of serotonin (5 hydroxytryptamine) on uterine blood flow in unanesthetized pregnant and nonpregnant sheep. An intra-arterial catheter was placed in a branch of the main uterine artery to allow administration of serotonin directly into the uterine vasculature and blood flow was monitored via electromagnetic flow transducers on the main uterine arteries. Serotonin produced dose related decreases in uterine blood flow in both pregnant and nonpregnant ewes. These vasoconstrictor responses to serotonin were significantly attenuated by the serotonin antagonist, methylsergide. In contrast, responses to norepinephrine were modified, suggesting specificaty of blockade. Methylsergide produced increases in systemic arterial pressure in nonpregnant ewes and reduced uterine blood flow by 50% in both pregnant and nonpregnant animals. These data demonstrate that the ovine uterine vasculature contains serotonin receptors and that their stimulation results in vasoconstriction. Elevated circulating levels of the vasoactive compound could significantly alter uterine henodynamics and lead to compromised uterine blood flow during pregnancy.