The regulation of energy balance and metabolism are related to signals of circadian and seasonal rhythmicity. In this respect, it is essential the actions of melatonin and glucocorticoids in the liver, the central organ of systemic regulation of energy metabolism. Our objective was to investigate, by Western blot analysis, the main changes in the glucocorticoid pathway and the expression of enzymes of energy metabolism in the liver of male Wistar rats (±200g, n=8/group) subjected to surgical removal of the pineal gland after sodium thiopental (50 mg/kg, ip) anesthesia (PIN), and replaced with nocturnal melatonin in drinking water (1mg/5ml water/100g of body weight – PM) compared to control animals (CT) measured every 3 hours around the clock, starting at ZT 3 (lights on-ZT0, lights off-ZT12). Circadian variation of the results (ANOVA/ cosinor) showed that expression of glucocorticoid receptor presented ultradian rhythm and varies over a period of 8 hours in CT and PM groups, whereas the period of variation changed to 12 hours in PIN. The transcription factor DexRas and the enzyme 11βHSD1 presented increased expression in pinealectomized animals at ZT3 (DexRas: 0.63±1 for CT vs 0.9±0.1 for PIN vs 0.95±0.1 for PM; 11βHSD1: 11±1.5 vs 24±2 vs 27±5). In addition, we observed at ZT15 and 21 the lowest expression of DexRas (0.5±0.1 vs 0,6±0.1 vs 0.3±0.1 and 0.7±0.05 vs 0.6±1.7 vs 0.5±0.06, respectively) and highest expression of 11βHSD1 (52±3 vs 37±3 vs 40±3 and 41±1.5 vs 51±3 vs 27±2 respectively), which indicates an inverse correlation between the expression of these proteins. Regarding enzymes of energy metabolism, PIN group at ZT24 showed increased expression of phosphoenolpyruvate carboxykinase (1.80±1 vs 2.40±1 vs 1.82±1), demonstrating changes on gluconeogenesis in pinealectomized animals. Glucose 6-phosphatase (G6Pase) presented an expression peak at ZT6 in PIN (1.4±0.7 vs 0.75±0.1 vs 0.7±0.1). At nocturnal ZTs, the expression of G6Pase in PIN and PM is diminished in all ZTs (mean of 0.7±0.3 for both groups vs 1.3±0.2 for CT). The expression of glucokinase follow the same patterns in all groups over the ZTs evaluated (mean of 0.6±1), however there is decreased expression in PIN (0.7±0.1 vs 0,4±0.1 vs 0.6±0.1) in the period between ZT18 and 0. Values are expressed as mean±SEM of arbitrary units of optical densitometry and were analyzed by two-way ANOVA. In all cases, β-actin expression was used for data normalization and p≤0.05 was adopted. These preliminary results indicate correlation between the signals of melatonin and glucocorticoids, suggesting that absence of melatonin alter the circadian pattern of protein expression of the glucocorticoids pathway as well as the enzymes of energetic metabolism.