C-fos protein expression in the nucleus of the solitary tract correlates with cholecystokinin dose injected and food intake in rats

C-fos protein expression was investigated in the nucleus of the solitary tr act (NTS) in response to increasing cholecystokinin (CCK) doses and food in take in rats by counting the number of c-fos protein positive cells in the NTS. C-fos protein expression in the NTS dose-dependently increased in resp onse to CCK, the lowest effective dose being 0.1 mu g/kg. The ED50 for c-fo s protein expression in the NTS in response to CCK was calculated to be 0.5 to 1.8 mu g/kg, depending on the anatomical level of the NTS investigated. Food intake increased c-fos protein expression in the NTS, the maximum num ber of c-Sos protein positive cells being reached at 90 min after the start of food intake. Regression analysis identified a positive correlation betw een c-Sos protein expression and the amount of food intake. Our data indica te that subpopulations of the NTS that are activated by CCK or food intake are involved into the short-term regulation of food intake and the neural c ontrol of feeding by the caudal brainstem. (C) 1999 Elsevier Science B.V. A ll rights reserved.