Progesterone antagonism of androgen-dependent marking in gerbils

The role of progesterone (P) as an androgen antagonist in Mongolian gerbil territorial marking was assessed in the present investigation. Twenty-seven mature males were observed for two consecutive weeks in a marking apparatus. On the basis of the average of the two sessions, subjects were matched and assigned to one of three groups. All animals were orchidectomized and tested three weeks after surgery. Three days after a single postoperative session a schedule of hormonal replacement was initiated. Group 1 was administered 640 μg testosterone propionate (TP). Group 2 received 640 μg TP followed immediately by 3 mg P. A third group received 640 μg TP followed by a 1 mg injection of P. Subjects were tested for marking 24 hr after the injection for a cumulative period of 6 wk.Results indicated that (a) castration drastically reduced marking; (b) TP alone and TP + 1 mg P restored the behavior; (c) TP + 3 mg P inhibited its restoration; and (d) a significant interaction was present between hormonal therapy and the 6-wk testing interval. However, all three hormonal treatments restored sebaceous gland dimensions. Results are discussed in terms of a model of hormone-gene action.