EFFECTS OF GASTRIC PACING ON CANINE GASTRIC-MOTILITY AND EMPTYING

Gastric pacing has been achieved in dogs and humans, but its effects o n gastric motility and emptying have not been thoroughly explored. Sev en dogs had bipolar electrodes placed 1 and 10 cm proximal to the pylo rus for reverse and forward pacing and monopolar recording electrodes and strain gauges placed 3, 5, and 7 cm proximal to the pylorus. After recovery, myoelectrical and contractile activity and gastric emptying of a mixed meal (50 g1 Tc-99m-labeled liver and 250 ml In-111-labeled 5% dextrose broth solution) were measured in each of three conditions : no pacing, reverse pacing, and forward pacing (frequency 0.5 cycles/ min above intrinsic pacesetter potential frequency). Reverse pacing re versed the direction of >90% of antral pacesetter potentials and peris taltic waves in six of seven dogs, prolonged the lag phase of solid em ptying, prolonged the half emptying time of solids and liquids, and in creased the antral motility index. Forward pacing entrained pacesetter potentials but had no consistent effect on emptying or antral contrac tions. In conclusion, reverse gastric pacing slows gastric emptying of digestible solids and liquids by reversing the direction of antral pe ristalsis and increasing the antral motility index, whereas forward pa cing has no such effects.