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.