Motilin and Myoelectric Complexes in the Pig

Amongst the humoral factors suspected to control myoelectric migrating complexes (M.M.C.), motilin has been postulated to be an important one. Exogenous motilin infusion was shown to induce M.M.C. like those naturally occurring in fasted dogs while it was without effect during the postprandial pattern (1). The hypothesis of a regulation of M.M.C. by circulating motilin was supported by low motilin levels during the postprandial pattern and synchronous variations of plasma motilin levels with M.M.C.: peak plasma motilin occurred with regular spiking activity (R.S.A.) phase and the lowest concentrations were found during quiescence in fasted dogs (2,3). Moreover, a dose of synthetic porcine motilin inducing a plasma motilin concentration similar to the peak values recorded in fasted dogs, could induce a R.S.A. like activity in the duodenum (2). As compared to that, controversial results were reported in the pig: motilin was found to be either released phasically with the M.M.C. in fasting pigs (4), or unrelated in any identifiable causal manner in association with M.M.C. according to others (5). In addition, infusions of natural or synthetic 13-Nlemotilin are unable to induce a premature M.M.C. (5). Such discrepancies, in the pig, might be related to inter-individual variations. It was indeed observed that motilin peaks may occur in dogs without M.M.C. being present, and as well M.M.C. may occur when motilin is undetectable (6). In the man too, though a statistical close relationship was evidenced between M.M.C. and plasma motilin levels (7), wide inter and intra individual fluctuations and also unrelated M.M.C. and motilin peaks were recorded (8).