Effects of exogenous motilin and morphine on interdigestive gastrointestinal motor activity after total duodenectomy in dogs

Our aim was to determine the role of endogenous motilin in initiation of motor patterns of the upper gut. We studied the motor response to intravenous motilin and morphine in six dogs after total duodenectomy and in six normal dogs. Motilin (0.1 μg/kg) and morphine (200 μg/kg) induced large-amplitude gastric contractions after duodenectomy. The duration of gastric contractions after motilin (4.4 ± 0.3 minutes; mean ± SEM) was less than spontaneous or motilin-induced gastric phase III in controls (21 ± 2 minutes and 11 ± 2 minutes, respectively; p < 0.01), while the response to morphine (7.4 ± 3.7 minutes) was less than spontaneous (21 ± 2 minutes; p < 0.01) but similar to morphine-induced phase III in controls (7.7 ± 0.9 minutes). After morphine, plasma motilin increased by 51 ± 6 pg/ml, but the magnitude of increase was not correlated with the effectiveness of morphine in inducing gastric contractions. Both agents induced phase III-like activity in the jejunum. The durations of jejunal phase III activity after motilin (6.2 ± 0.3 minutes) and morphine (6.4 ± 0.3 minutes) were greater than spontaneous phase III after duodenectomy (4.8 ± 0.4 minutes; p≤ 0.05) and in controls (4.7 ± 0.2 minutes; p < 0.05). The latency of response to motilin in the stomach (0.2 ± 0.1 minute) was less than in jejunum (8.9 ± 0.6; p < 0.05), but the latency after morphine was not different in stomach and jejunum (2.9 ± 0.9 minutes and 2.8 ± 0.8 minutes, respectively). These observations suggested that the duodenum, possibly by the release of endogenous motilin, may 'recruit' and further augment the gastric response to initiation of the migrating motor complex. Also, the mechanism for initiation of the migrating motor complex in the stomach and in the jejunum may differ.