Singular and interactive effects of testosterone and estrogen on territorial marking in castrated male Mongolian gerbils ( Meriones unguiculatus)

Abstract

Territorial marking by the male Mongolian gerbil ( Meriones unguiculatus) is normally androgen dependent. In the present study it is demonstrated that estrogen will also restore marking behavior in adult castrate males although it appears to be less effective than testosterone. Estrogen will also cause obvious regrowth of the ventral sebaceous marking gland but only minor growth of the seminal vesicles. When testosterone and estrogen are administered together, the testosterone effect upon marking behavior is significantly depressed. These findings lead to the conclusion that the brain area controlling this behavior is responsive to both testosterone and estrogen, and when the two are administered together there is active competition for receptor sites in the brain. The mechanisms governing territorial marking appear to be quite similar to those described for sex behavior in the rat and other rodents and may indicate convergent evolution for behaviors involved in gene transmission.