Systemic administration of apomorphine improves the hemodynamic mechanism of clitoral and vaginal engorgement in the rabbit

Clitoral and vaginal engorgement during sexual stimulation depend in part o n the increase of arterial inflow. It has been shown that apomorphine (APO) , a non-selective dopamine receptor agonist, produces penile erection by ac tivating dopaminergic receptors in the central nervous system. Our aim was to study whether systemic administration of APO improves the hemodynamic me chanism of clitoral and vaginal engorgement in the rabbit. Female New Zealand white rabbits (3.5-4 kg, n = 6) were anesthetized. To ex amine sexual arousal function, the vaginal/clitoral branch of the pelvic ne rve was stimulated electrically and maximal increases in clitoral intracave rnosal and vaginal wall blood flows and pressures were recorded. After this APO was injected intravenously in a dose-response manner (0.05, 0.1, 0.2, 0.3 and 0.4 mg/kg) and nerve stimulation was performed after each dose. Cha nges In nerve-stimulated increase of clitoral intracavernosal and vaginal b lood flows and pressures after APO was compared to those recorded before AP O. Electrical stimulation of the vaginal/clitoral branch of the pelvic nerve s ignificantly increased clitoral intracavernosal and vaginal wall blood flow s in the rabbit. Intravenous administration of APO caused concentration dep endent increase in nerve stimulation-induced peak clitoral intracavernosal and vaginal wall blood flows reaching to statistically significant at the c oncentration of 0.1 and 0.2 mg/kg. Intravenous administration of APO greate r than 0.2 mg/kg (0.3 and 0.4 mg/kg) were less effective or produced advers e effects on clitoral intracavernosal and vaginal wall blood flows. Intrave nous APO also tended to increase nerve-stimulated increase of clitoral intr acavernosal and vaginal wall pressures, but the effect was not statisticall y significant. In conclusion, our studies suggest that systemic administration of APO may improve clitoral and vaginal engorgement by increasing clitoral intracavern osal and vaginal wall arterial inflow.