Effects of chronic estradiol or testosterone treatment upon sexual behavior in sexually sluggish male rats.

Sexually sluggish (SS) male rats represent a small proportion of animals that take a long time to ejaculate, or sometimes they do not ejaculate, when tested on repeated occasions with sexually receptive females. The current study was done in order to evaluate whether chronic estradiol (E(2)) or testosterone (T) treatment could induce consistent ejaculatory behavior in these male rats. Those males that displayed sexual behavior but did not ejaculate in at least four of five tests were classified as SS and included in the present experiment. They were implanted subcutaneously with Silastic capsules that were empty or filled with E(2) or T. Starting one week after the implant, subjects were tested weekly with sexually receptive females for seven consecutive weeks. At the end of the experiment all subjects were weighed and sacrificed to weigh the accessory sex glands. The results showed that SS males implanted with an empty or T-filled capsule remained as such; they displayed mounts and intromissions but not a consistent pattern of ejaculation despite the twelve weeks of testing (5 screening tests and 7 with the corresponding implant). In contrast, the percentage of SS males implanted with an E(2) capsule that displayed the ejaculatory pattern was significantly reduced. Subjects treated with E(2) also displayed a higher number of mounts than the empty capsule group during several weeks of testing. At the end of the experiment the weights of the body, testicles, epididymis, seminal vesicles, and prostate of the SS male rats chronically treated with E(2) were lower than those of the empty or T capsule groups. In addition, male rats with a T implant showed lower testicular weight than the empty capsule group. These results suggest that the lack of ejaculation patter in SS male rats is not due to estrogenic or androgenic alteration.