We evaluated the effect of morphine on motility, flow and transit in the distal ileum and ICJ in 8 healthy volunteers who swallowed a multilumen tube (O.D. 8 mm) of 11 side holes. Six closely spaced side holes (intervals 1.5 cm) spanned the ICJ, one distal hole was located in cecum, 4 proximal ports recorded ileal activity. Tubes were located fluoroscopically; maintenance of position was ... [Show full abstract] monitored by frequency of rhythmic contractions. Ileal flows were assessed by marker dilution over a 20 cm segment, ileal to cecal transit by injecting lactulose and measuring breath H2. Recordings lasted 5–6 hr fasting, 7–8 hr after drugs and 5–6 hr postprandially (plus drugs); mouth to ileal transit was marked by PEG in meals. A factorial design permitted assessment, double-blinded and randomized, of the actions of morphine sulfate (100 μg/kg i.v.), naloxone (40 pg/kg i.v. plus infusion of 10 μg/kg hrly) and atropine sulfate (7 μg/kg i.v. plus 4 μg/kg hrly).