Differential behavioral response to dopamine D-2 agonists by sexually naive, sexually active, and sexually inactive male rats

This study was performed with male rats categorized as sexually naive (SN), sexually active (SA), or sexually inactive (SI). In a first experiment the effects of the dopamine (DA) D-2 agonist SND 919 (0.05, 1, and 10 mg/kg) on the copulatory behavior of SN, SA, and SI rats were assessed. In a second experiment the DA D-2 agonist B-HT 920 (0.2 mg/kg) was used, and examination was limited to SN and SA rats. The effects exerted on stretching-yawning, penile erection, and sedation by the same compounds at the same doses in these three rat categories were also investigated. The main findings were that SND 919 and B-HT 920 facilitated ejaculation in SA rats, and that the rats that were different as regards level of sexual activity Exhibited different behavioral responses to the two DA agonists.