Sociosexual behaviour and paternity in procarbazine-exposed rats with or without regional testicular circulatory isolation

Male Sprague-Dawley rats were used in two experiments in which a procarbazine bolus (400 mg kg -1 body mass) was administered with or without testicular circulatory isolation in the form of brief clamping of the spermatic cord and gubernaculum during drug administration. Separate tests of aggressiveness, sexual motivation, copulatory performance and paternity over the subsequent 6 weeks were used to assess functional changes resulting from testicular circulatory isolation. Experiment I compared intermale aggression and sexual motivation of animals in groups receiving procarbazine plus testicular circulatory isolation lasting 0, 15 or 45 min with that of animals in control groups with no clamp and no drug. Experiment 2 used a 2 x 2 factorial design to evaluate sexual performance and resulting paternity in animals 2 months after testicular circulatory isolation and drug exposure compared with that in control animals. Procarbazine treatment induced minimal disruption of normal interest in a receptive female, copulatory measures (intromissions or ejaculations) and structural integrity of seminal vesicles, bulbospongiosus muscles and ventral prostate glands. Animals exposed to the drug without testicular circulatory isolation were significantly less aggressive than animals in other groups. The most profound influence of procarbazine was on paternity. Males exposed to procarbazine with or without testicular circulatory isolation impregnated notably fewer females than did control males that were not exposed to the drug. There was no evidence of recovery of normal fertility up to 10 weeks after exposure to the drug. In conclusion, the deleterious influence of procarbazine on androgen-sensitive processes appears to be specific to intermale aggression and to fertility. The testicular circulatory isolation technique, for 45 min in particular, softened the impact of the drug on social behaviour, although procarbazine suppressed fecundity even with testicular circulatory isolation.