POSTNATAL CHANGE IN INHIBITORY REGULATION OF INTESTINAL MOTOR-ACTIVITY IN HUMAN AND CANINE NEONATES

Motor activity was recorded in 19 preterm infants three times during the first postnatal month. There was a paucity of small intestinal motor quiescence during fasting in the first postnatal week; however, its duration significantly increased with postnatal age (p < 0.03). Although fasting motor patterns changed with postnatal age, motor responses to feeding were present within the first few days of life. Motor activity was also recorded weekly in 11 newborn dogs for 6 wk. Intestinal motor quiescence was also absent during fasting for the first postnatal week but it significantly increased with postnatal age (p < 0.002). As in the human preterm infant, a motor response to feeding was present within the first few days of life. Plasma concentrations of gastrin and peptide YY during fasting were low in the preterm human and canine neonate during the first postnatal week but plasma concentrations of both peptides increased with postnatal age. Although plasma concentrations of gastrin were low during fasting for the first postnatal week, plasma concentrations of gastrin increased significantly postprandially compared with fasting (p < 0.05). We conclude that motor quiescence during fasting becomes a more prominent feature of newborn intestinal motor function postnatally. In addition the release of two peptides that regulate motor patterns also change postnatally. Thus, postnatal changes in motor patterns and peptide release change in a parallel fashion in human preterm neonates and canine neonates. We speculate that the postnatal change in intestinal motor quiescence reflects changes in inhibitory regulation by the enteric nervous system and that the neonatal dog will provide an excellent animal model to explore the mechanisms that regulate maturation of small intestinal motor function in the preterm infant.