Effect of diet consistency, taste and calories on food intake of weanling rats with dorsomedial hypothalamic lesions

Abstract

Male weanling Sprague-Dawley rats with dorsomedial hypothalamic lesions (DMNL rats) primarily destroying the dorsomedial hypothalamic nuclei (DMN) showed significant hypophagia on lab chow chunks compared to sham-operated controls. When given a choice between lab chow in the form of chunks or powder, both controls and DMNL rats ate similar amounts of lab chow powder while DMNL rats ate less lab chow chunks. Total caloric consumption was the same as on chunks alone. When returned to lab chow chunks as the only source of calories, the pattern and magnitude of intake was again depressed for the DMNL rats. When offered a choice between Ginger Snaps cookies in chunk form versus powder, DMNL rats remained hypophagic in terms of chunk consumption while the intake from powder was similar in both controls and DMNL rats. When offered a choice between chunks of lab chow and Ginger Snaps, DMNL rats were again hypophagic on lab chow chunks, ate the same as the controls of the cookies, and the total caloric intake was of the same magnitude and pattern as observed in previous tests. The data suggest, but do not conclusively show, that DMNL rats are not hypophagic because they have an aversion to chewing hard food and that, when offered a diet similar in hardness to lab chow chunks, i.e., hard cookies, will prefer the less tasty but nutritionally complete lab chow. They are apparently capable of choosing a diet for complete nutrition and, as previously reported, can meter calories competently.