Effect of vasoactive intestinal polypeptide (VIP) upon myometrial blood flow in non-pregnant rabbit

Vasoactive intestinal polypeptide (VIP) containing nerve fibres have previously been demonstrated in the female genital tract of several mammalian species including the rabbit. These nerve fibres seemingly innervate vascular and non-vascular smooth muscle. For that reason we investigated the dose-relationship between VIP (5, 50, 500 pmol . min-1 . kg-1) and myometrial blood flow (MBF) using Xenon-133 washout technique. VIP increased MBF dose-dependently. VIP was on molar base 100 times more potent than acetylcholine. The action of VIP seems to be direct on vascular smooth muscle rather than mediated by other neurotransmitters, because the MBF increase was not antagonized by atropine, adrenergic blocking agents or naloxone. These findings make it likely that VIP plays a role in the local nervous control of myometrial blood flow.