Reduction of intake in the rat due to gastric filling.

With two exceptions, the literature shows that confining ingested fluid to the stomach of a rat during an intake test had no effect on the volume ingested. In the two exceptions (J. D. Davis and J. L. Sayler, Physiol. Behav. In press. J. A. Deutsch, Handbook of Behavioral Neurobiology. Neurobiology of Food and Fluid Intake, edited by E. M. Stricker. New York: Plenum, 1990, vol. 10), intake with the cuff open was very large, suggesting that, when intake on cuff-open tests exceeds some critical volume, confining all of it to the stomach during the test will reduce intake. To test this, we measured intake of three different solutions known to stimulate large intake with the pylorus open and closed. In cuff-closed tests, intake was less than in cuff-open tests. In cuff-closed tests, rate of licking began to decline within 5-6 min when only about one-quarter of the ultimate contents of the stomach had accumulated, indicating that some signal from the stomach slowed the rate of ingestion before the full capacity of the stomach was reached. This shows that the stomach is sensitive to its contents when it contains only a small proportion of its capacity.