Anticholinergic suppression of fetal rabbit upper gastrointestinal motility

Abstract

Objective: At birth the newborn digestive tract must assume the responsibility of assimilating nutrients for survival. Immature gastrointestinal motility in the neonate may result in impaired feedingand nutrition. Newborn gastrointestinal motility development requires the expression and functional maturation of gastrointestinal receptors. To explore the timing of fetal responses to gastrointestinalcholinergic motility agents, we assessed the effect of the anticholinergic agent atropine in the late-gestation rabbit fetus.Methods: Seven pregnant New Zealand White rabbits were studied atday 30 of their normal 31-day gestation. In each litter, two fetuses were selected as study (n = 14) and two as control (n = 14). Under ultrasound guidance, a spinal needle was percutaneouslyinserted through the maternal uterus into the fetal stomach and 0.5 ml of gastric content was aspirated. Fluorescein, labelled with colored microspheres, and either atropine (0.04 μg/g fetal body weight)or normal saline were injected in a total volume of 0.5 ml. Two hours after injection, fetuses were delivered, the small intestine harvested, and the total small intestinal length and the distance the gastrointestinalfluorescein travelled were measured by ultraviolet light optical density. The fluorescein travelled distance and the per cent motility, defined as the length of fluorescein travelled divided by the totallength of the small intestine, were calculated.Results: All fetuses survived the intragastric injection. Mean fetal body weight at delivery was 44.2 ± 6.7 and 46.8 ± 7.2 g in atropineand control fetuses, respectively. The fluorescein travelled distance (15.4 ± 4.2 vs. 19.0 ± 4.3 cm;. p < 0.01) and per cent motility (51.0 ± 8.9 vs. 63.8 ± 11.7%;p < 0.01) of atropine-treated fetuses were significantly lower than those of control fetuses.Conclusion: Fetal upper gastrointestinal motility is suppressed in response to intragastricatropine. These results indicate that fetal gastrointestinal cholinergic receptors are expressed and functional in the term (0.97 gestation) rabbit fetus. In utero administration of cholinergic agonists/antagonistsmay potentially modulate fetal gastrointestinal motility and absorption of amniotic fluid water and solutes.