Search for a male contraceptive: the effect of gossypol on sexual motivation and epididymal sperm.

Studies of men and animal models have reported informally that gossypol reduces fertility without behavioral disruptions. In the present research, we used an animal model and quantitative psychobiologic methods to examine the capacity of gossypol to suppress sperm reserves and to maintain both libido and performance. Sexually experienced male rats were exposed for 11 weeks to either 5, 10 or 20 mg gossypol/kg body weight, values representing the moderate to threshold dosages for induction of sterility. Behavioral changes over weeks of administration and reproductive physiology at necropsy were measured. Results showed that the expected dose-response reduction in gamete quantity and quality was accompanied by reductions in reproductive organ weights and copulatory performance, but the reductions were modest and principally with the higher dosages. On the other hand, there was the suggestion of a dose-response suppression of motivation, or interest in seeking and maintaining contact with a receptive female. Indeed, the characteristic pattern of a progressive loss of sperm motility and numbers with dose and time of exposure to gossypol closely paralleled the pattern of behavioral decrements. Implications of the data are that: 1.) gossypol may induce sterility in males at the expense of loss of motivation, and 2.) sexual performance and libido can vary in dependently. Future assessments of a substance under consideration as a contraceptive agent should consider quantitative measurement of both components of sexual behavior.