Abstract

Rat pups can be induced to ingest a liquid diet, totally independent of the rat dam, from as early as one day of age. From its onset, this "independent ingestion" is contingent on deprivation. Up to one week of age, this response is regulated exclusively by stomach fill and dehydration. But beginning around 9 days of age, deprived pups that have received gastric infusions of glucose or other carbohydrates show reduced intake. This ingestion- inhibiting stimulus may be mediated by several possible mechanisms, including chemoreceptive processes within the gastrointestinal tract, blood glucose level, or cellular glucoprivation. The latter possibility was addressed in this study. Non-deprived rat pups ranging from 12 to 20 days of age were given injections of 2-deoxyglucose (2-DG) ranging from 0.2 to 1.2 mg/g or control injections of distilled H₂0. 2-DG produces cellular glucoprivation and triggers feeding in adults by competing with blood glucose for transport into cells. After a two hour delay, feeding responsiveness was assessed by placing pups In a warm incubator and then allowing 30 minute access to Half & Half milk product. Intake was determined by weight gain and behavioral observations were made during the tests. Cellular glucoprivation was assessed by blood glucose assays in pups given the same injections. Blood samples and feeding tests cannot be done using the same pups. The 2-DG injections triggered dose-dependant lncreases in blood glucose at all ages, indicating that this treatment did compete with blood glucose for transport and thus produced cellular glucoprivation in rat pups as in adults. However, glucoprivation was not associated with increased intakes. Rather, at 15 and 20 days of age, 2-DG injections that produced significant increases in blood glucose actually decreased ingestion. Thus high doses of 2-DG may be debilitating to pups, a proposition supported by stomach-content data taken after feeding tests. These flndings do not support a cellular-glucoprlvic mechanism for deprivation-dependent ingestion in preweanling rats, and therefore open the way for further studies on other mechanisms.