Effects of PYY on the interdigestive migrating myoelectric complex in the small intestine in vivo and the neural and endocrinal mechanisms of the effects

Objective To investigate the effects of peptide YY (PYY) on the interdigestive migrating myoelectric complex (MMC) in the small intestine in vivo and explore the neural and endocrinal mechanisms of the effects. Methods Sprague-Dawley rats were supplied with a venous catheter and bipolar electrodes in the duodenum and jejunum for electromyography of stomach and small intestine in wake state. PYY,phentolamine,nitro-L-arginine (L-NNA,the inhibitor of nitric oxide synthase) and atropine were served with PYY respectively. The plasma motilin levels before and after the infusion of PYY were observed. Results At all the three recording points,PYY lengthened the circle length of MMC [from (591.90±128.98)s to (999.25±216.59)s,P<0.01] and lowered the frequency of phase Ⅲ [from (39.28±8.40) min-1 to (22.08±3.13) min-1,P<0.01],amplitude of phase Ⅲ [from (0.320±0.060)mV to (0.179±0.030)mV,P<0.01],and the portion of phase Ⅲ over the whole circle length [from (28.61±5.84)% to (15.43±5.16)% ,P<0.01]. Phentolamine had no influence on the role of PYY. Administered L-NNA combined with PYY,the percentage of phase Ⅲ increased [(42.09±8.67)%] compared with that of control (P<0.01) and compared with that of PYY administered alone (P<0.01) too. Atropine combined with PYY showed stronger depressing effects on MMC. No significant difference was found between the plasma motilin levels before and after the infusion of PYY. Conclusion PYY may inhibit the interdigestive intestine motility through the none-adrenergic none-cholinergic tract,while the α-receptor tract and circulating motilin are probably not involved in the depressing effect.

Role of the area postrema of medulla oblongata in the regulation of canine interdigestive migrating motor complex

OBJECTIVE: To determine the effect of the area postrema (AP) of the medulla oblongata on gastrointestinal interdigestive migrating motor complex (MMC) and the plasma motilin level. METHODS: Interdigestive MMC activities of the antrum and duodenum were recorded by strain gauge implanted on the serosa of 8 conscious dogs. A cannula was intubated in femoral vein for motilin injection. The plasma motilin concentration was measured by RIA. We observed: (1) normal interdigestive MMC activity and fluctuations in plasma motilin concentration; (2) the effects of electrically damaging the AP on MMC activity and plasma motilin level; (3) whether intravenous injection of motilin could induce phase III contractions after the AP was destroyed. RESULTS: (1) Typical interdigestive MMC with phase I, II, III, and IV was recorded in normal dogs. Phase III was concurrent with the peak of plasma motilin level. (2) In damaged AP dogs, antroduodenal interdigestive MMC contractions were suppressed; cyclic, phasic and migratory pattern of MMC was disrupted. Plasma motilin concentration was decreased. Intravenous injection of motilin could not induce phase III contractions. CONCLUSIONS: The area postrema might play an important role, which is mediated by motilin, on the regulation of interdigestive MMC.