CLOSING THE PYLORUS DECREASES THE SIZE OF LARGE MEALS IN THE RAT

We previously reported (Davis, J. D.; Smith G: P.; Sayler, J. L. Reduc tion of intake in the rat due to gastric filling. Am. J. Physiol. 272: R1599-R1605, 1997.) that confining ingested fluid to the stomach by cl osing the pylorus decreased the intake of solutions that stimulated pa rticularly large intakes. Those solutions differed in the type of of o rosensory and postoral stimulation so the nature of the control over i ngestion was unclear. We report here a study of the role of orosensory stimulation alone in controlling intake in rats with a closed pylorus . Rats were given 30-min intake tests with the pylorus open and closed with 0.2 M glucose, and with 0.2 M glucose + 1.25 mM sodium saccharin , 2.5 mM sodium saccharin and 5.0 mM sodium saccharin. Intake was redu ced on the cuff-closed test relative to the cuff-open test with the tw o highest concentrations of saccharin, bur not with the two lowest. Wh en ingesting the glucose solutions with the two highest concentrations of saccharin the initial rate of ingestion was greater and the declin e in the rate of ingestion was slower than when the rats ingested the glucose solutions with 1.25 mM saccharin or no saccharin. We showed by means of a meta-analysis of previously published and unpublished data that a high rate of licking at the beginning of a test combined with a relatively slow rate of decline in the rate of licking during it are the characteristics of ingestive behavior on cuff-open tests that wil l lead to a reduction of intake when ingested fluid is confined to the stomach. (C) 1998 Elsevier Science Inc.