Antagonism by pindolol, but not betaxolol, of 8-OH-DPAT-induced facilitation of male rat sexual behavior.

8-OH-DPAT (0.25 mg/kg s.c.) produced a facilitation of the male rat sexual behavior, characterized by a decrease in the number of intromissions preceding ejaculation and in the time to ejaculation. This facilitation of the sexual behavior was antagonized by administration of the 5-HT and beta-adrenoceptor antagonist pindolol (4 mg/kg i.p.), but not by the selective beta-adrenoceptor antagonist betaxolol (4 mg/kg i.p.). Neither pindolol (2-8 mg/kg), nor betaxolol (2-8 mg/kg), produced any statistically significant effects per se on the male rat sexual behavior, as observed here (mounts, intromissions, ejaculation latency or the post-ejaculatory interval). A higher dose (16 mg/kg) of betaxolol produced a statistically significant reduction in the number of intromissions preceding ejaculation and in the ejaculation latency. The antagonism by pindolol of 8-OH-DPAT-induced effects on male rat sexual behavior suggests an involvement of 5-HT1A receptors in the facilitation of this behavior produced by 8-OH-DPAT.