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

Abstract

Clitoral and vaginal engorgement during sexual stimulation depend in part on the increase of arterial in¯ow. It has been shown that apomorphine (APO), a non-selective dopamine receptor agonist, produces penile erection by activating dopaminergic receptors in the central nervous system. Our aim was to study whether systemic administration of APO improves the hemodynamic mechanism of clitoral and vaginal engorgement in the rabbit.Female New Zealand white rabbits (3.5 ± 4 kg, n 6) were anesthetized. To examine sexual arousal function, the vaginalaclitoral branch of the pelvic nerve was stimulated electrically and maximal increases in clitoral intracavernosal and vaginal wall blood¯ows 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 mgakg) and nerve stimulation was performed after each dose. Changes in nerve-stimulated increase of clitoral intracavernosal and vaginal blood¯ows and pressures after APO was compared to those recorded before APO.Electrical stimulation of the vaginalaclitoral branch of the pelvic nerve signi®cantly increased clitoral intracavernosal and vaginal wall blood¯ows in the rabbit. Intravenous administration of APO caused concentration dependent increase in nerve stimulation-induced peak clitoral intracavernosal and vaginal wall blood¯ows reaching to statistically signi®cant at the concentration of 0.1 and 0.2 mgakg. Inravenous administration of APO greater than 0.2 mgakg (0.3 and 0.4 mgakg) were less effective or produced adverse effects on clitoral intracavernosal and vaginal wall blood¯ows. Intravenous APO also tended to increase nerve-stimulated increase of clitoral intracavernosal and vaginal wall pressures, but the effect was not statistically signi®cant.In conclusion, our studies suggest that systemic administration of APO may improve clitoral and vaginal engorgement by increasing clitoral intracavernosal and vaginal wall arterial in¯ow.

Neurologic Factors in Female Sexual Function and Dysfunction

“…Peptide histidine methionine (PHM) has effects similar to VIP but at lower potency [31]. Intravaginal prostaglandin E1 can also increase vaginal blood flow [32]. While some authors have stated that VIP is the primary neurotransmitter in the vaginal circulation [21,22], much more research in this area is required.…”

Apomorphine, systèmes dopaminergiques centraux et contrôle de l’érection

“…Chez l'animal, l'apomorphine am61iore l'arriv~e de sang dans le clitoris et le vagin [129]. Chez la rate castr6e, la quantit6 de dopamine augmente dans l'hypothalamus en r6ponse h la suppl6mentation par l'oestradiol et la progesterone, ou ~ la stimulation de la r~gion g~ni-tale [84].…”

Recent advances in female sexual dysfunction

“…Preliminary results from small pilot studies suggest vasoactive agents may be efficacious. The centrally-acting agent apomorphine causes increased clitoral and vaginal engorgement in rabbits after pelvic nerve stimulation [15] and is an effective treatment of erectile dysfunction in human males. A small pilot study found that use of a prostaglandin gel (PGE 1) that causes vasodilatation was associated with improved subjective experience of sensation and arousal in women after exposure to a visual sexual stimulus compared to placebo [16].…”