PREVENTION BY ANTAGONISTS OF THE TOXIC ACTION OF 5‐HYDROXYTRYPTAMINE ON PREGNANCY

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Abstract
As 5‐hydroxytryptamine can interrupt pregnancy in all its stages in mice and as pregnancy can be protected from the action of 5‐hydroxytryptamine by either progesterone or by prolactin only in early (days 1 to 6) but not in late pregnancy (day 14), the present experiments with two antagonists of 5‐hydroxytryptamine, namely methysergide and cyproheptadine, were carried out. Each compound antagonized the action of 5‐hydroxytryptamine in late pregnancy. The toxic effects produced by 5‐hydroxytryptamine are probably due to a direct action on the placental circulation which is prevented by the antagonists. In early pregnancy, methysergide prevented the effect of 5‐hydroxytryptamine, which is believed then to act on the central nervous system, interfering with luteal activity. Cyproheptadine alone interrupted early pregnancy, an action which was prevented by progesterone.