Circadian changes in the RNA content of rat hypothalamic nuclei in relation to food intake

The ribonucleic acid (RNA) and protein content of the ventromedial hypothalamic nuclei (VMH), the lateral hypothalamic areas (LHA) and the cortex (C) of adult male Wistar rats followed free access to food and water were determined at 6-hour intervals (at 6.00, 12.00, 18.00 and 24.00 h); the RNA and protein content of the suprachiasmatic nuclei (SCN) were determined at 12.00 and 24.00 h. The RNA content of the VMH, LHA and SCN differed at various intervals; in the cortex it did not alter significantly. The highest RNA concentration in the VMH was recorded at 18.00 h and in the LHA at 24.00 h, after which, in both areas, it fell. The lowest RNA content in the LHA and the VMH was found at 12.00 h. In the SCN, the RNA concentration at 24.00 h was significantly higher than at 12.00 h. The protein content did not alter significantly during the circadian cycle in any of the structures examined.