Effects of a novel dopamine-receptor agonist RDS-127 (2-N,N-di-n-propylamino-4,7-dimethoxyindane), on hormone levels and sexual behavior in the male rat.

Selective changes in the mating pattern occurred 30 minutes following administration of RDS-127 (3.0 mg/kg, IP) to sexually experienced adult male rats. Marked decreases in intromission frequency and ejaculation latency were observed. These data indicate a potent effect upon conummatory mechanisms underlying copulatory behavior. The lack of effect upon arousal state was further demonstrated utilizing a "mounting test" (in which the penis is anesthetized by topical application of tetracaine hydrochloride). No difference in mounting behavior was seen. Seminal plugs were noted in a large percentage of treated animals at the time of anesthetic application. Additionally, a six-fold decrease in plasma prolactin and a lesser decrement in plasma luteinizing hormone were evident. Finally, in sexually experienced castrate animals, RDS-127 induced mounting in two thirds and intromissive and ejaculatory patterns in one third of the treated animals, 35 days postcastration. These effects were greatly attenuated by 56 days postcastration. The selective alteration of consummatory mechanisms, with little or no effect upon arousal status, suggests a neurochemical separation of these two components in the intact male rat.