A study of the ovulation-inhibiting effects of dexamethasone in the domestic hen

Laying hens were injected with a series of graded doses of dexamethasone following the terminal oviposition of a sequence to determine the effect of this compound on the time of ovulation. It was found that injection of 10-500 micrograms of dexamethasone/kg inhibited ovulation but there was no evidence of an ovulation-inducing effect when the dose was reduced below 10 micrograms/kg. The results for dexamethasone are in contrast to the effects of corticosterone which inhibits ovulation at high doses and induces ovulation at lower doses providing the hens are injected at the stage of the ovulatory cycle used in this study. It is suggested that the ovulation-inducing action of corticosterone involves a target site remote from the hypothalamic-pituitary axis.