Gastric emptying of enterally administered liquid meal in conscious rats and during sustained anaesthesia

Background Gastric motility studies are frequently conducted with anaesthetized animal models. Some studies on the same animal species have reported differences in vagal control of the stomach that could not be explained solely by slightly different experimental conditions. A possible limitation in the comparison between similar studies relates to the use of different anaesthetic agents. Furthermore, anaesthetic effects may also limit generalizations between mechanistic studies of gastric function and the gastric function of conscious animals. In the present study, we used the [ ¹³C]-breath test following a liquid mixed-nutrient test meal (Ensure^®, 1 ml) with the aim to investigate the rate of gastric emptying in animals that were either conscious or anaesthetized with either Inactin^® or urethane. Methods One week after determining the maximum ¹³CO₂ concentration, time to peak [¹³C] recovery and gastric half emptying time in control, conscious rats, we repeated the experiment in the same rats anaesthetized with Inactin^® or urethane. Key Results Our data show that Inactin^® anaesthesia prolonged the time to peak [¹³C] recovery but did not significantly reduce the maximum ¹³CO₂ concentration nor delay gastric half emptying time. Conversely, urethane anaesthesia resulted in a significant slowing of all parameters of gastric emptying as measured by the maximum ¹³CO₂ concentration, time to peak [¹³C] recovery and half emptying time. Conclusions & Inferences Our data indicate that Inactin® anaesthesia does not significantly affect gastric emptying while urethane anaesthesia profoundly impairs gastric emptying. We suggest that Inactin®, not urethane, is the more suitable anaesthetic for gastrointestinal research.