Diurnal patterns in water and food intake and body weight changes in rats with hypothalamic lesions.

KAKOLEWSKI, JAN W., EDWARD DEAUX, JANICE CHKISTENSEN, AND BAWAI~A CASE. LXurnal patterns in water and food intake and body ~c&ht changes in rats xith hypothalamic leszbns. Am. J. Physiol. 22 l(3) : 7 1 l-7 18. 1971 .-The diurnal patterns of water and food intake, water-to-food ratio, and body weight changes were examined in rats with bilateral hypothalamic lesions and intact control rats of the same age and sex. Rats with ventromedial hypothalamic (VMH) lesions, after the dynamic phase, displayed a permanent loss of the diurnal rhythm in food intake, a 180* reversal of the diurnal rhythm in the pattern of body weight changes, and hypophagia, whereas the water intake and water-to-food ratio remained similar to preoperative levels, Rats with lateral hypothalamic (LH) lesions, after recovery, displayed a decrease in water and food intake and an augmentation of body weight loss exclusively during the light phase of the diurnal cycle. Also, a more pronounced diurnal rhythm in food intake and a loss of the diurnal rhythm in the regulation of water-to-food ratio was found in rats with LH lesions. Since, after VMH or LH lesions, the animals continued to regulate the ingestive behavior and controlled their body weight, the concepts regarding the function of these two hypothalamic structures, presumed to be primary regulatory centers, appear to be oversimplified. An alternative view, regarding the hypothalamic structures as a necessary but secondary link in the modulation of ingestive behavior, is presented.