Mechanism of cycling of migrating myoelectric complexes: effect of morphine

Abstract

Morphine was injected intravenously at various phases of the migrating myoelectric complex (MMC) cycle to study the oscillatory characteristics of MMCs by the premature initiation of phase IIIs. All injection timings were represented as a percentage of the normal MMC period at the most proximal duodenal electrode. During the initial 20% of the MMC cycle, the mechanism of initiation of MMCs was in an absolutely refractory state in the sense that a supramaximal dose of morphine (200-300 micrograms/kg) did not initiate a premature phase III. During the remainder of the MMC cycle, the control mechanism was in a relatively refractory state. As this state progressed, premature phase III activity was initiated with diminishing doses of morphine. This was called the relatively refractory state. The initiation of a premature phase III by morphine did not affect the phase III already in progress, except that its propagation velocity was increased. Truncal vagotomy did not affect the refractory characteristics of MMCs or the action of morphine. Only large doses of naloxone (2 mg/kg) blocked the above action of morphine. The study shows that the MMC cyclic phenomenon has the characteristics of relaxation oscillators that may result from enteric neural biological clocks. The period of these oscillators can be altered by stimulants such as morphine.

Effects of Intraduodenal Bile on Interdigestive Gastrointestinal and Gallbladder Motility in Healthy Subjects

“…First, the artificial bile composition corresponded with normal human bile in its main constituents [30], and the infused amount resembled the approximate 30% of the gallbladder volume that is emptied during the MMC [2]. Second, the presence of an absolute refractory period [31]was accounted for by infusing bile at a standardised moment in the MMC cycle. Third, we accounted for an equal pH, volume and osmolarity [32]of the infusates.…”

The Role of Interdigestive Small Bowel Motility in the Regulation of Gut Microflora, Bacterial Overgrowth, and Bacterial Translocation in Rats

“…In humans and dogs, low-dose morphine can induce a premature MMC. [30][31][32] In animal studies, the gut flora seems to be an important source of endotoxins and microorganisms leading to sepsis and MOF. In general, SBBO and bacterial translocation do not inevitably lead to sepsis and MOF.…”

The involvement of opiate receptors in the effects of trimebutine on intestinal motility in the conscious dog

“…Other kinds of stimulation of the small intestine by increasing the irregular spike activity associated with an inhibition of colonic motility have already been described for other compounds such as anthraquinone derivatives (Garcia-Villar et al 1980) or for some antidopaminergic substances such as sulpiride (Bueno & Fioramonti 1983), but trimebutine has been found to be without antidopaminergic properties (Berga et al 1981). In the dog, only morphine induces a similar phase of regular spike activity on the small intestine (Sarna et al 1982) but it also induces a long lasting stimulation of colonic motility (Bueno & Fioramonti 1982). As with trimebutine, the effects of central vs peripheral administration of morphine differed.…”