Effects of Histamine and Serotonin on the Contractility of Isolated Pregnant and Nonpregnant Human Myometrium

Abstract

The effects of histamine and serotonin and their antagonists on contractile activity of pregnant and nonpregnant human uterine strips were studied. Both histamine and serotonin (5-HT) increased contractions, pregnant preparations were more responsive than nonpregnant ones. The effects of histamine and 5-HT were blocked by pyrilamine and methysergide, respectively. Pyrilamine (10^––7–10^––6M) acted as a competitive antagonist of the effect of histamine, whereas methysergide (10^––7–10^––6M) inhibited the response to 5-HT in a noncompetitive manner. Cimetidine and ketanserine were completely ineffective at the doses tested. It is suggested that the increase of contractile activity observed at the end of pregnancy could be partly mediated by the effect of histamine and 5-HT on smooth muscle of the human myometrium.