Neurotransmitters involved in the fast inhibitory junction potentials in mouse distal colon

We investigated, in murine colon circular muscle, the role of adenosine 5′-triphosphate (ATP) and pituitary adenylate cyclase activating peptide (PACAP) as inhibitory neurotransmitters of the fast component of nerve-evoked inhibitory junction potential (fast IJP). Fast IJP was antagonised by apamin or suramin, abolished by desensitisation with the P2Y receptor agonist, adenosine 5′-O-2-thiodiphosphate (ADPβS), unaffected by desensitisation with P2X receptor agonist, α,β-methylene ATP (α,β-meATP), and reduced by PACAP-(6-38), a PACAP receptor antagonist. ATP induced membrane hyperpolarization resistant to tetrodotoxin, Nω-nitro-L-arginine methyl ester (L-NAME) or PACAP-(6-38), but antagonise…