DMI-induced sexual effects in male rats: Analysis of DMI's acute and chronic actions on copulatory behavior and on the genital motor pattern of ejaculation

Desipramine (DMI) is a tricyclic antidepressant that alters male sexual function. This work was designed to study the effects of acute and chronic DMI treatments on male rat copulatory behavior, discriminating between spinal and behavioral DMI actions on the ejaculatory response. To this aim, sexually experienced male Wistar rats received DMI (7.5 or 15 mg/kg, i.p.) for 14 days and were tested for sexual behavior on Days 1, 7 and 14 of treatment. Besides, the genital motor pattern of ejaculation (GMPE) was recorded in anaesthetized, spinal male rats after acute (1–10 µg, i.v.) or 14-day chronic DMI (15 mg/kg, i.p.) treatment. Results showed that acute and chronic DMI treatments reduced the ejaculatory threshold by decreasing intromission number and ejaculation latency of male rats, in successive copulatory series. The intensity of the effects depended on the dose and treatment duration. DMI acute treatment activated GMPE expression only at the lower doses and these responses exhibited modified parameters. Chronic DMI reduced the number of discharges and increased the frequency of discharge of spontaneous GMPE responses, affected mechanically evoked ones and increased the number of GMPEs expressed after repeated genital stimulation as compared to control rats. DMI treatments affected copulatory behavior both at brain and spinal levels and its effects on ejaculation, assumed to be similar in behavioral and spinal models, differed.