Effects of progesterone and dihydrotestosterone on stimulation of androgen-dependent sex behavior, accessory sex structures, and in vitro binding characteristics of cytosolic androgen receptors in male whiptail lizards (Cnemidophorus inornatus).

Progestins often act as potent antiandrogens in male birds and mammals. Experiments with lizards find that progestins can both inhibit (when given in high dosages) or stimulate (when given in low dosages) male-typical sex behavior in gonadectomized individuals. This study shows that in the little striped whiptail lizard exogenous progesterone (P) facilitates androgen-dependent sex behaviors in males yet fails to stimulate seasonal activation of androgen-dependent accessory sex structures. Analysis of androgen receptors (AR) in brain and kidney cytosol of the little striped whiptail lizard reveals similarities with the AR of the mouse. The data indicate that despite the ability of P to mimic the actions of androgens in activating sex behaviors in males of this species, the characteristics of the AR are conserved with respect to other vertebrate species.