Ingestive behavior of rats with ibotenic acid lesions of the dorsomedial hypothalamus

Abstract

Rats with electrolytic or kainic acid (KA) lesions of the dorsomedial hypothalamic nucleus area (DMHA-L) are hypophagic, hypodipsic, and have a reduced body weight (BW) compared with controls. In the present study, male Sprague-Dawley rats received bilateral ibotenic acid (IBO) lesions of the DMHA (3 micrograms in 0.3 microliter) or sham (S) operations. During the next 32 days the IBO DMHA-L rats showed reduced (P less than 0.01) food and water intake, BW, and linear growth (P less than 0.03), although having a normal Lee obesity index. After a 24-h fast both groups became hyperphagic (P less than 0.01) with the DMHA-L group eating the most (P less than 0.01) during the 1st h; lost BW was regained at the same rate. In the absence of food, DMHA-L rats took less (P less than 0.01) water (data normalized) than S rats. During 24 h of water deprivation, both groups ate similar amounts of food (data normalized); following deprivation the groups were hyperdipsic. Both groups increased their food intake when given 300 mg/kg of 2-deoxy-D-glucose, which contrasts rats with electrolytic or KA DMHA-L rats. Both groups decreased their food intake when given cholecystokinin (3 micrograms/kg ip), which contrasts rats with electrolytic DMHA-L. The DMHA-L rats were not deficient in plasma glucose, insulin, growth hormone, or plasma Na+ and K+. Histology revealed many, but not all neurons, were destroyed in the DMN after IBO. The data indicate that IBO, electrolytic, or KA lesions of the DMHA produce similar but not identical physiological changes.