The action of amantadine on the rat uterus: its interaction with oxytocin and the effects of several ionic modifications of the medium.

The influence of amantadine on the contractile responses of the rat uterus to oxytocin in the presence of several ionic modifications of the external medium was studied both in situ and in vivo. Oxytocic effects of amantadine were observed in vivo (1 and 5 mg/kg), and in vitro (9.3 times 10-7 M to 2.8 times 10-6 M); possible competitive partial potentiation of the contractile effect of oxytocin was also observed. Amantadine, 9.35 times 10-6, 1.3 times 10-5 and 1.8 times 10-5 M, significantly reduced oxytocic activity. Calcium ions antagonized the oxytocic and antioxytocic effects of amantadine. Excess K+ and the presence of Mg2+ ions (1.8 mM/l and 1.08 mM/l respectively) reversed the antioxytocic effect of amantadine. Propranolol also reversed the antioxytocic effect of amantadine. It is postulated that the oxytocic effect of amantadine may be related to antagonism of calcium; antioxytocic activity may be explained by stabilization of the resting cell membrane, inhibiting ionic flow, and also by its catecholamine-liberating activity.