Inhibitory effects of sexual steroidal hormones on the responses of the isolated guinea-pig lleum to acetylcholine and histamine.

Six sexual steroidal hormones (progesterone, pregnenolone, testosterone, ethinyl-oestradiol, oestriol and oestrone) inhibit acetylcholine- and histamine-induced contractions of the isolated guinea-pig ileum. Different degrees of inhibitory capacity were found. High concentrations of PGE1 and F2alpha reverse some of these inhibitions. This reversal seems to be non-specific and probably related to sensitization of the ileal smooth muscle by prostaglandins. The inhibitory action of sexual steroids might be non-specific as well. But a "corticoid-like" effect cannot be excluded.