Sexual interactions between estrous female rats and castrated male rats treated with testosterone propionate or estradiol benzoate

Abstract

Estrous female rats display ‘precopulatory behaviors’ such as ear wiggling and hopping/darting when castrated males treated with testosterone propionate (TP) are placed in their vicinity and before copulatory interactions have taken place. Castrated males treated with estradiol benzoate (EB) do not elicit these precopulatory behaviors in advance of copulatory interactions. It therefore seemed of interest to study females' sexual behavior with castrated males treated with TP or EB when males or females had primary control over the temporal patterning of the behavior. Unrestrained sexual behavior (=male control) with EB-treated males was characterized by large numbers of intromissions and long periods of time preceding ejaculation, as compared with interactions with TP-treated males. The temporal pattern of sexual behavior did not change importantly when the males were tethered (=sexual behavior controlled by females). When given a choice between two sexually active castrated and tethered males, one treated with TP and the other with EB, estrous females ‘preferred’ EB-treated animals in various respects. Fewer interactions occurred with, and less time was spent in the vicinity of, TP-treated males over prolonged observation periods (115–135 min). The preference for EB-treated males disappeared, and TP- and EB-treated animals became equally attractive, when the vaginal opening of the female animals was covered with adhesive tape to prevent the occurrence of penile intromissions during mounting. It is concluded that female control over copulatory behavior does not necessarily change the females' sexual behavior. ‘Preference’ of EB-treated males to TP-treated males seems due to aversive sensory actions, during intromissions, associated with insertion of the androgen-stimulated penis and the ejaculate. Genital stimulation during mating plays an important role in the maintenance of ‘sexual motivation’ in female rats.