The effects of erythromycin on motor and electrical behavior of the antrum, pylorus, and duodenum were determined in chronically instrumented, awake dogs. Erythromycin infusion resulted in an abrupt, powerful increase in motility. The motility index increased 18-fold in the antrum, 15-fold in the pylorus, and 8-fold in the duodenum. Bradyarrhythmia with a 30% decrease in slow-wave frequency occurred in all animals. Retrograde giant contractions in association with retching and vomiting occurred in 88% of the dogs. Neostigmine was less potent than erythromycin in increasing motility. Hexamethonium given intra-arterially during erythromycin infusion abolished motility for 7.2 +/- 2.9 min and intra-arterial atropine did so for 51 +/- 25 min. Hexamethonium or atropine restored the electrical slow-wave frequency. The results provide evidence that erythromycin action involves cholinergic pathways including ganglionic transmission.

This study examined changes in gastric motility after interruption of the intramural nervous circuitry from the proximal portion of the stomach to the antrum by a circumferential gastric myotomy. Seven extraluminal strain gauge force transducers and five platinum electrodes were implanted along the antropyloroduodenal region, and gastric emptying was studied by X-ray after a 280-g solid meat meal mixed with barium. The motility index increased aboral to the myotomy by 106 and 69% in the distal antrum and pylorus, respectively, in the first postprandial 30-60 min because of the loss of an inhibitory neural influence from the proximal part of the stomach. Destabilization of the basic electrical rhythm occurred in 50% of the dogs. This was apparent as tachyarrhythmia or bradyarrhythmia and an early postprandial 2-11% decrease in slow-wave frequency and a 100% increase in slow-wave amplitude. Coordination of corporoantropyloric contractions was disorganized. Frequent segmenting and antidromic contractions were associated with reduced periods of optimal emptying and disturbed intragastric chyme transport into the constricted antrum. A 10-30% gastric emptying delay of approximately 50 min was a consequence of myotomy despite an increased antroduodenal motor gradient after myotomy. The overall results suggest that intact intramural innervation and muscular continuity are essential for coordination of corporoantropyloric motility and normal gastric emptying.

Mechanical and electrical activity in the antrum, pylorus, and duodenum was evaluated in the conscious dog, instrumented with seven strain gauges and five platinum electrodes. 17-Norleucine-vasoactive intestinal peptide (17-N-Leu-VIP) or 17-N-Leu-VIP plus NG-nitro-L-arginine methyl ester (L-NAME) was injected intra-arterially close to the pylorus to identify influences of nitric oxide (NO) on effects of VIP. VIP concentration was measured by radioimmunoassay in serum samples collected from the cubital and portal veins before and up to 2 h after VIP injection. VIP (0.004-0.006 mg.kg-1.10 min-1) abolished phasic contractions in the interdigestive state for 16.8 min and in the digestive state for 14.4 min, whereas whole serum VIP concentration rose above 42.4 +/- 13 pmol/l. Administration of L-NAME did not significantly influence the effects of VIP. Aftereffects of VIP, consisting of a reduced motility index, lasted 33 +/- 10.6 min in the interdigestive state and 44.5 +/- 42 min in the digestive state. This VIP aftereffect in the interdigestive state was shortened in time by the addition of L-NAME. The results overall suggest that NO release is a factor only in the aftereffects of VIP.

To evaluate the role of endogenous opioids in regulation of upper gastrointestinal motility in unanesthetized dogs and to differentiate the actions on mu- and delta-opioid receptors, seven strain gauges and five platinum electrodes were chronically implanted at the serosa along the antrum and duodenum and connected to a plug in the neck of the dog. Signals were processed by a Hellige AC amplifier, a rectilinear recorder, and a data aquisition system. A motility index (MI) was calculated and together with the electrical data a contractile activity percentage (CAP) was determined for consecutive 30 min periods. The delta-opioid antagonist ICI 741 864 and the mu-receptor blocker naloxone were injected intraarterially through a chronic Groshong catheter placed in the pyloric region and connected to a subcutaneous port. After a meal of solid food, ICI 174 864 increased motility relative to controls in the antrum averaged over 5 hr by 144.4%+/-26 for the MI and 73%+/-26 for CAP; after naloxone MI increased by 222%+/-60 and CAP 121%+/-76. In the duodenum, ICI 174 864 decreased MI over a range of 57% to 22% (P < 0.05). Naloxone increased MI and CAP significantly after 2.5 hr. We interpreted the results of ICI 174 864 in the duodenum to reflect suppression of a tonic opioid influence at the delta-receptor mainly at the prevertebral ganglion. In the interdigestive state in 56% of the dogs, naloxone delayed the occurrence of phase III of the migrating myoelectric complex (MMC) for up to 370 min, while under ICI 174 864, normal interdigestive cycles were present. Disturbance of the timing of the interdigestive cycles at central mu-opioid receptors may by involved in the effect.

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