IS NITRIC-OXIDE THE FINAL MEDIATOR REGULATING THE MIGRATING MYOELECTRIC COMPLEX CYCLE

The main objective was to study the role of nitric oxide (NO) in the c onversion of migrating myoelectric complexes (MMC) to the irregular el ectrical activity characteristic of the postprandial state. Both rats and chickens were implanted with electrodes for electromyography in th e small intestine. Intravenous infusion of N-G-nitro-L-arginine (L-NNA ), a NO synthase inhibitor, induced an organized MMC-like pattern in f ed rats. Infusion of sodium nitroprusside, a NO donor, disrupted the M MC, inducing a postprandial-like motor pattern in fasting rats. Simila rly, in chickens L-NNA mimicked the fasting pattern, consisting of a s hortening of phase II, enlargement of phase III, orad displacement of the origin of the MMC, and an increase in the speed of phase III propa gation. An inhibition of NO synthesis seems to be involved in the indu ction of the fasting motor pattern, whereas an increase of NO mediates the occurrence of the fed pattern. It is suggested that NO might be t he final mediator in the control of small intestine motor patterns.