Dexamethasone suppression of ovulation in PMS-treated immature rats

A single injection of 2.0 mg/kg dexamethasone (DXM) administered at 51 h after pregnant mare serum gonadatropin (PMS) treatment inhibited both ovulation and luteinization. S.c. injection of human chorionic gonadotropin (HGG) caused ovulation and luteinization in DXM-PMS-treated rats, whereas treatment with ACTH failed to overcome the DXM inhibitory effect. These findings are interpreted to indicate that DXM inhibits ovulation through a mechanism which might involve the central nervous system.