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Abstract

Fat has been described to both accelerate and slow intestinal transit. We hypothesized that the fat-induced jejunal brake depends on the combined accelerating effect of CCK and the slowing effect of an opioid pathway. Using a multifistulated model, intestinal transit was measured in four dogs, while 60 mM oleate was delivered into the proximal gut with either 0 or 6 mg naloxone, and 0.1 mg/kg devazepide (a peripheral CCK-A-receptor antagonist) administered intraluminally and intravenously, respectively. In a second study, intestinal transit was measured in seven dogs, while naloxone was delivered intraluminally at 0-, 3-, 6-, or 12-mg doses. Compared to the jejunal brake (marker recovery of 50.1 +/- 2.6%), intestinal transit was slowed by the CCK-A antagonist (36.4 +/- 8.3%; P < 0.05) and accelerated by naloxone (82.0 +/- 6.8%; P < 0.05). The accelerating effect of CCK occurred early in the transit response, while the dose-dependent effect (P < 0.05) of naloxone occurred later. We conclude that fat-induced jejunal brake depends on the early accelerating effect of CCK and the later slowing effect of a naloxone-sensitive opioid pathway.