Effect of dexmedetomidine on ejaculatory behavior and sexual motivation in intact male rats

Premature ejaculation is the most common sexual disorder in young men. Consequently, there is an intense search for efficient and safe pharmacological treatments. Insofar, almost no effective treatment with acute effects is available. In this study, we evaluated the effects of the noradrenergic alpha(2) receptor agonist dexmedetomidine on sexual incentive motivation and copulatory behavior in male rats. Sexual incentive motivation was tested in a large rectangular arena connected to two small incentive stimulus cages containing either a male or sexually receptive female rat. There was no sexual interaction possible between the experimental subjects and the incentives during this test. Approach to the incentives constituted the measure of sexual incentive motivation. After the sexual incentive motivation test, the subjects were tested for copulatory behavior in a regular copulation test for 30 min. Doses of 0.1 and 1 mu g/kg of dexmedetomidine (i.p.) had no effect on any of the indices of locomotor activity or on parameters of sexual incentive motivation. With regard to copulatory behavior, it was found that the dose of 1 mu g/kg prolonged the latency to the first ejaculation, while the latency to second ejaculation showed a tendency to increase. The absence of an effect on indices of sexual incentive motivation or general activity showed that the actions of dexmedetomidine in this study were limited to ejaculatory mechanisms. Insofar as the ejaculation latency in the male rat is predictive of prolonged ejaculation latency in men, it can be proposed that dexmedetomidine is of potential utility for the treatment of premature ejaculation. (C) 2012 Elsevier Inc. All rights reserved.