Fluoxetine Chronic Treatment Inhibits Male Rat Sexual Behavior by Affecting Both Copulatory Behavior and the Genital Motor Pattern of Ejaculation

Abstract

Selective serotonin reuptake inhibitors (SSRIs) are antidepressants that cause sexual dysfunction. The SSRI fluoxetine (FLX) appears to particularly affect the ejaculatory response. Ejaculation is regulated both at brain and spinal levels. To study the acute and chronic effects of FLX on male rat copulatory behavior, trying to distinguish between brain and spinal cord FLX-induced changes on the ejaculatory response. Sexually experienced male rats were intraperitoneally injected with 5 or 10 mg/kg FLX and tested for sexual behavior during 60 minutes on days 1, 7, and 14 of treatment. After a 2-day drug holiday, the males chronically treated with the high FLX dose were spinalized to record spontaneous and mechanically evoked genital motor patterns of ejaculation (GMPEs). In addition, independent groups were used to evaluate the acute effects of 1, 3, or 10 µg/rat FLX (intravenously) on the GMPE. Number of ejaculatory series and their parameters; electromyographic recordings of the GMPE in the bulbospongiosus muscles and their parameters. Acute FLX injection slightly affected sexual behavior display and dose-dependently inhibited the expression of the GMPE. Chronic FLX treatment did not inhibit copulation but produced deficits in the parameters related to ejaculation after the high dose. In these animals, the response capacity of the spinal generator of ejaculation (SGE) as well as the number of discharges in the GMPE was decreased as a result of chronic FLX treatment. Chronic FLX treatment produces inhibitory effects on male rat copulation, particularly on ejaculation, some of which are exerted directly at the SGE.