Selective Inhibition by Progesterone of Androgen-Induced Behavior in Male Ring Doves (Streptopelia risoria)1

Abstract

Male ring doves (Streptopelia risoria) were castrated and then tested 7 days later, when both the bowing-coo and the nest-call (2 items of male sexual behavior) had disappeared. They were then injected daily for 14 days with testosterone propionate (.2 mg/day/bird), after which the occurrence of these 2 behavior patterns was again assessed. Both items of behavior had been significantly reinstatedasa result of the androgen replacement therapy. The birds were then divided into 4 groups for a further period of 7 days of treatment, as follows: (N = 10) testosterone propionate treatment continued; (N = 10) testosterone propionate continued with added progesterone (.1 mg/day/bird); (N = 7) no hormone treatment; (N = 9) progesterone treatment alone (.1 mg/day/bird). Progesterone, in the presence of the circulating androgen, virtually completely inhibited the occurrence of the bowing-coo. The effect of adding progesterone to the administered androgen during these 7 days was the same as that of withdrawing androgen treatment. By contrast, progesterone had no effect upon the occurrence of the nest-call, which remained frequent under continued androgen replacement therapy, regardless of the presence or absence of additional progesterone. We conclude that progesterone is capable of selectively inhibiting the reactions of some neural mechanisms to androgen, while leaving others unaffected. The progesterone thus acts, not by inactivating the androgen or by generally antagonizing it, bat possibly by specifically insulating some neural sites against it. The results are discussed in terms of events occurring during the normal breeding cycle in these birds.