Inhibition of crop sac growth by dexamethasone in ring doves (Streptopelia risoria).

Abstract

When either dexamethasone (100 μg) or progesterone (100 μg), but not corticosterone (1.0 mg) or testosterone propionate (100 μg), was administered daily to male ring doves (Streptopelia risoria) during a reproductive cycle, normally occurring crop—sac growth was completely suppressed. A second experiment was done to determine whether this steroid suppression of the crop—sac response to prolactin occurred at the target organ or the hypothalamo—pituitary level. The crop—sac growth response was therefore measured in male ring doves maintained in isolation after administration of exogenous prolactin in combination with either dexamethasone or progesterone. The mean ratio of crop weight (g)/body weight (g) X 100 was 1.62 ± 0.27 for prolactin—treated doves, 1.73 ± 0.54 for prolactin plus dexamethasone treated doves, and 1.72 ± 0.17 for prolactin plus progesterone—treated doves. These experiments indicate that progesterone and dexamethasone exert their suppressive effects on the hypothalamus, the pituitary or bo...