Cyclic AMP-mediated release of peptide YY (PYY) from the isolated perfused rabbit distal colon

We have investigated the role of the colonic nervous system in regulating the release of peptide YY (PYY) from the isolated perfused rabbit distal colon. In addition, we have studied the role of cAMP- and Ca(2+)-dependent mechanisms in mediating the release of PYY. We investigated three agents which stimulate increases in intracellular cAMP (vasoactive intestinal polypeptide (VIP), cholera toxin, and forskolin) and three agents which raise intracellular Ca2+ concentrations (substance P, carbachol, and the calcium ionophore A23187). The three cAMP-dependent agents, VIP (10(-7) M and 3 x 10(-7) M), cholera toxin (100 micrograms), and forskolin (10(-6) M and 10(-5) M) significantly stimulated release of PYY (P < 0.05). Tetrodotoxin (3 x 10(-6) M) did not alter forskolin (10(-5) M) stimulated release of PYY. Substance P (10(-9) M and 10(-8) M), carbachol (10(-5) M), and A23187 (10(-6) M) failed to stimulate the release of PYY. These results suggest that the colonic neurotransmitter VIP participates in the modulation of PYY release from rabbit distal colons. Further, these studies suggest that release of PYY is mediated by cAMP-dependent pathways.