Effect of diet hydration on food and water intake, efficiency of food utilization and response to fast and realimentation in rats with dorsomedial hypothalamic hypophagia and growth retardation.
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Mature male Sprague-Dawley rats that had received bilateral electrolytic lesions in the dorsomedial hypothalamic nucleus (DMNL rats) at weaning and sham-operated controls, were divided into four groups. One DMNL and one control group were given a diet consisting of equal parts (w/w) of Purina Laboratory Chow and tap water (Mash). A second DMNL and control group received powdered lab chow (Powder). During an 11-day baseline period both DMNL groups were profoundly hypophagic, however, both Mash-fed DMNL rats and controls ate more than their Powder-fed counterparts. This pattern obtained whether or not the Mash water was considered in the calculations. Despite their lesion-induced hypodipsia, Mash-fed DMNL rats and controls compensate almost perfectly for the hydration water in the Mash by reducing water intake from drinking bottles. In contrast to previous experiments using pelleted lab chow, DMNL rats showed reduced water/food intake ratios compared with their controls. However, these ratios were above unity, as were those of the controls. The Delta Lee Index was greater in the Mash-fed DMNL rats than in the controls but similar to the Powder-fed DMNL rats. Efficiency of food utilization (EFU) was greatest in the Mash-fed DMNL rats, even when Mash water was not included in its computation. During a three-day fast DMNL rats drank less water than their controls, irrespective of previous dietary hydration. Body weight loss and loss in Lee Index in percent of pre-fast values were less severe in the DMNL rats, again irrespective of previous dietary hydration. During a five-day realimentation period similar food and water intake patterns were observed as during the baseline period. Regaining of lost body weight and Lee Index in per cent were similar in all rats, but Mash-fed DMNL rats utilized food more efficiently than their controls. Plasma glucose, free fatty acids and total protein were similar among the groups at sacrifice but plasma glycerol levels were higher in the Mash-fed DMNL rats than in their controls and Powderfed DMNL rats. The data are interpreted to mean that although DMNL rats are grossly hypophagic and hypodipsic and grow poorly they will respondas do controlsto the weight gain- and food intake-promoting properties of a hydrated diet. 1982, Academic Press Inc. (London) Limited. All rights reserved.
