THE EFFECT OF AN OPIATE RECEPTOR ANTAGONIST ON THE ILEAL BRAKE MECHANISM IN THE RAT

Studies investigated the effect of the opiate antagonist naloxone (10 mg/kg) on stomach to caecum transit (SCTT) during ileal infusion of sa line or Intralipid. SCTT of the head of the meal was measured by hydro gen analysis and meal distribution by the radiolabelled meal technique . Intralipid delayed SCTT by delaying both gastric emptying (p < 0.01) and small bowel transit. Naloxone did not affect SCTT during ileal sa line infusion, but produced a distal shift (p < 0.05) in the geometric centre of the meal and increased radioactivity in the caecum (p < 0.0 01) 100 min after gavage. Naloxone abolished the delayed SCTT of the m eal induced by ileal lipid infusion, with an associated increase in ra dioactivity in the caecum at 200 min (p < 0.01), although the geometri c centre was shifted proximally within the intestine (p < 0.01). The r esults suggest that the ileal brake is mediated in part by endogenous opiate pathways.