Nervous release of vasoactive intestinal polypeptide from the feline uterus: pharmacological characteristics.

1. The release of the neuropeptide, vasoactive intestinal polypeptide (VIP), from the uterus in response to electrical stimulation of the hypogastric and pelvic nerves was examined in non-pregnant anaesthetized cats. 2. Efferent stimulation of the pelvic nerve caused an increase in the release of VIP, which was unaffected by atropine and adrenoceptor antagonists, but completely abolished by hexamethonium. 3. Efferent stimulation of the hypogastric nerves induced a marked increase in the release of VIP, which was blocked by hexamethonium. After atropine and adrenoceptor blockade the nervously induced VIP response was undiminished and accompanied by an increase in uterine venous blood flow. 4. The results suggest that the VIP-containing neurones in the uterus are intrinsic under preganglionic influence of pelvic and hypogastric nervous activity. It is proposed that VIP is a neurotransmitter in the feline uterus involved in non-cholinergic, non-adrenergic mechanisms such as the uterine vasodilation observed after hypogastric nerve stimulation.