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275 DEVELOPMENT OF SMALL BOWEL MOTILITY IN BEAGLE PUPPIES

To investigate the neonatal development of upper small bowel (SB) peristalsis and the effect of pentagastrin (PG) on motility, we monitored duodenal intraluminal pressure manometrically in 11 beagle puppies from birth until weaning at 5 wk. The response rate of the system employed was 150 mm Hg/sec. Electrodes were implanted on the SB serosal surface for subsequent monitoring of myoelectric activity during the first 2 mo. in 3 add'l puppies. During the first 3 wk there was an increase in duodenal contraction rate immediately after a liquid meal from 11±0.4/min to 16±1/min (p <0.001) followed by a slight decrease during weaning. Peak duodenal pressure increased from 17 to 38 mm Hg (p < 0.002), and subsequently decreased to 25 mm Hg with weaning. The duration of each contraction shortened during the first 3 wk from 3.4 to 2.4 sec (p <0.001). Myoelectric monitoring revealed a gradual increase in slow wave activity from 14 to 20 cycles/min in both fasting and fed states, corresponding with the increased contractions observed in the manometric studies. These developmental changes are similar to those which occur in the beagle lower esophageal sphincter (LES) and stomach during suckling and weaning. However, in contrast to the lack of sensitivity to PG by the beagle LES and stomach during the first week, SB contractions were inhibited on day 1 with 0.03-8 ug/kg PG s.c. We speculate that the differential PG sensitivity of LES, stomach, and SB during the first week of life in the beagle is due to differential gastrin receptor number and/or affinity.