Active regulation to be lean by rats with ventromedial hypothalamic lesions

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52 adult female Long-Evans rats with electrolytic or radio-frequency thermocoagulatory lesions of the ventromedial hypothalamus (VMH) lived on pellet fragments or powdered chow containing as much as 1.2% quinine sulfate or lived in Skinner boxes with 45-mg pellets delivered contingent on FRs of leverpressing up to FR 128. Body weights maintained by VMH Ss were determined by the percentage of quinine in or the contingency of reinforcement of the food on which they lived. Even when Ss lived on highly adulterated or response-contingent food and were lean, they ate more of that food when the ambient temperature was reduced and less of that food during several weeks of forced feeding of eggnog. Weight maintenance in the cold and caloric compensation during forced feeding were as precise for VMH Ss eating highly adulterated chow or Noyes pellets contingent on high FRs as for VMH Ss eating laboratory chow ad lib, even though the former Ss at the time maintained weights no greater than intact Ss and the latter Ss were grossly obese. Regulation in the cold or during forced feeding was only a little less precise for Ss with lesions than for intact Ss. It may be as characteristic of VMH Ss that they eat to become lean and remain lean as that they eat to be obese. (36 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved)

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