Abstract

Context and objective: Sexual arousal is centrally modulated by hypothalamic neuropeptides. The part neuropeptides play in peripheral arousal, however, has not received much attention. Female sexual arousal is mostly dependent on the relaxation of the vagina’s vascular and non-vascular smooth muscles. There have been no in vitro studies on vaginal arteries to date; instead, all research has been on vaginal strips. This study compared the effects of neuropeptides from the sexual hypothalamus on the arteries and vaginal wall strips of rabbits.

Experimental strategy: Isometric tension from strips and arteries was measured using tissue bath and wire myography procedures, respectively.

Important outcomes: Vasoactive Intestinal Peptide (VIP) and Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) relaxed both preparations; these effects were only countered by the PAC1 antagonist PACAP 6-38 (1 nM) and the VIP/PACAP antagonist VIP6-28 (10 nM). mg). Both preparations were relaxed by the melanocortin agonist a-melanocortin-stimulating hormone (1 mM), but not by bremelanotide (1 mM). Vaginal preparations were contracted by oxytocin and vasopressin, which the V1A might exacerbate. Only arteries were constricted by neuropeptide Y (NPY) and the NPY Y1 agonist Leu31, Pro34; NPY was inhibited by the NPY Y1 receptor antagonist BIBP 3226. Arteries were constricted by melanin-concentrating hormone (MCH; 1 mM).

Final thoughts and ramifications: Hypothalamic neuropeptides have the ability to relax and contract the arteries and vaginal strips. Both central and peripheral female sexual arousal may benefit from the use of NPY Y1, V1A, MCH1, and VIP/PAC1 agonists. Which preparation is crucial for female sexual arousal is a question that is raised by variations in the neuropeptide effects of the preparations.