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Objective: To investigate the mechanism behind the inhibitive effect of somatostatin (SST) on the intestinal migrating contraction in vivo by observing the effect of SST on spontaneous contractions of the circular muscle of the isolated small intestine and visualizing SST and SST receptor 2 (SSTR2) in the intestinal muscle., Methods: Transverse segments of macaque intestine from laparotomy, were mounted in a perfusion system. The effects of SST on their phasic contractions were recorded. SST and SSTR2 in the intestinal muscles of macaque were visualized by immunohistochemical staining and hybridization in situ., Results: SST (1 x 10(-7) mol/L to 1 x 10(-4) mol/L) significantly increased the frequency of phasic contractions, in a dose-dependent manner, r = 0.984, P < 0.05; (8.33 +/- 1.53) times/min (SST 1 x 10(-7) mol/L) vs (2.67 +/- 0.58) times/min (blank control), P < 0.05. The contractive amplitudes of the isolated circular muscle were also enhanced with the increasing concentration of SST range from 1 x 10(-7) mol/L to 1 x 10(-5) mol/L, r = 0.991, P < 0.05. Both SST and SSTR2 were localized in myenteric nerve plexus between the longitudinal and the circular muscle of the macaque intestine., Conclusions: SST directly promoted spontaneous contractions of the circular muscle of macaque intestine via mediation of SSTR2 in myenteric nerve plexus between the longitudinal and the circular muscle. It is contributed to the inhibitive effect of SST on the intestinal migrating contractions.