Measurement of gastric emptying during and between meal intake in free-feeding Lewis rats.

A new scintigraphic measurement technique is described that allows accurate assessment of gastric emptying in between as well as during a number of successive meals. Measurements were made every minute of food intake, gastric nutrient filling, and gastric emptying over a 6 h, 40 min period in conscious, free-feeding, loosely restrained rats. Before receiving access to the food, the animals had been deprived for a period of 31 h. Over the full duration of the experiment, an average rate of gastric emptying of 2.46 +/- 0.18 (SE) kcal/h was established. During most meals, however, the gastric emptying rate was increased so that an average of 26.9 +/- 2.7% of the ingested calories was emptied while the animals were feeding, with an average emptying rate of 0.15 +/- 0.014 kcal/min or 8.88 +/- 0.84 kcal/h. This transient increase in the rate of gastric emptying was followed by a subsequent slowing of gastric emptying after meal termination; in the 10-min postmeal interval, an average emptying rate of 0.96 +/- 0.12 kcal/h was found. Despite these fluctuations during and immediately after meals, a relatively constant rate of caloric emptying is maintained over longer periods. There were no differences between the emptying rate during the first meal when the gastrointestinal tract was still empty, compared with later meals when the gastrointestinal tract had been filled with food. The emptying rate during the 10-min postmeal interval, however, was significantly reduced during later meals. The results suggest that gastric emptying is controlled by different mechanisms during and after the ingestion of food and that these mechanisms remain in effect at various degrees of gastrointestinal filling.