CDP-choline-induced contractions in the mouse gastric fundus through purinoceptors and Rho/Rho-kinase signalling

Aims: This study aimed to investigate the effects of cytidine-5'-diphosphocholine (CDP-choline), an endogenous lipid precursor, on the reactivity of the mouse gastric fundus and to determine the mechanism(s) mediating its effects. Main methods: Possible contractile effect of CDP-choline (10(-5)-10(-2) M) was investigated in the absence and presence of a muscarinic receptor antagonist, atropine (3 x 10(-6) M), an acetylcholine esterase inhibitor, physostigmine (10(-6) M), a Na+ channel blocker, tetrodotoxin (TTX, 3 x 10(-6) M), a Rho-kinase inhibitor, Y-27632 (10(-5) M), a purinoceptor antagonist, suramin (2 x 10(-4) M), a nitric oxide synthase inhibitor, N-G-nitro-L-arginine (L-NA, 3 x 10(-4) M), a Ca2+ channel blocker, nifedipine (10(-6) M), an alpha(7) nicotinic receptor antagonist, methyllycaconitine citrate (MLA, 10(-6) M) and a G protein (G(i/o)) inhibitor, pertussis toxin (PTX, 2 mu g/ml). The metabolites of CDP-choline, namely choline (10(-4)-10(-2) M), cytidine 5'-triphosphate (CTP, 10(-5)-10(-2) M), cytidine (10(-5)-10(-2) M) and cytidine monophosphate (CMP, 10(-3)-10(-2) M) were also tested. Besides, phosphorylation of MYPT1, which indicates Rho-kinase activity, was also detected. Key findings: COP-choline produced contractions in a concentration-dependent manner. The contractions were not affected by atropine, physostigmine, TTX, PTX, MLA or L-NA. However, Y-27632, suramin or nifedipine partly reduced these contractions. COP-choline increased phosphorylation of MYPT1. Among COP-choline metabolites, cytidine had no contractile effects. However, choline induced considerable contractions, which were sensitive to atropine. CMP and CTP had also contractile activity, comparable to that of COP-choline. Significance: These results suggest that CDP-choline produced contraction through, at least in part, purinoceptors and Rho/Rho-kinase signalling in the mouse gastric fundus