Evidence against VIP as the inhibitory transmitter in non-adrenergic, non-cholinergic nerves supplying the longitudinal muscle of the mouse colon.

Vasoactive intestinal peptide (VIP) had two types of effects on the longitudinal muscle of the mouse distal colon. At low concentrations (10(-8) M) VIP induced a contraction which seemed to be related to the production of prostaglandins as it was abolished after preincubation with indomethacin (10(-6) M). At higher concentrations (3 X 10(-8) and 10(-7) M) VIP induced relaxations which developed slowly and were related to stimulation of the adenylate cyclase activity of the smooth muscle cells. There is no evidence that VIP is the non-adrenergic, non-cholinergic transmitter released by electrical stimulation in this preparation and responsible for rapid relaxation of the smooth muscle.