Effect of Stress on Fasting-Induced Ghrelin, Orexin and Galanin Secretion in Male Rats Fed Different Levels of Their Energy Requirement

Ghrelin, orexin, and galanin are orexigenic factors in rodents and humans which participate in adaptive response to weight loss. On the other hand, weight loss and fasting is accompanied by increased levels of epinephrine (Ep) and cortisol (Cor). In this study, we investigated the effects of Ep and Cor on fasting-induced ghrelin, orexin, and galanin secretion in rats fed different levels of their energy requirements. Forty five male Wistar rats (300-350 g, 15 per group) were fed a diet containing 100, 50, and 25% of their energy requirement for 10 days followed by 2 days of fasting. Animals were then anesthetized for carotid artery cannulation for injections and blood samplings. Rats received either 3 µg Ep/kg body weight (BW), 3 µg Cor/kg BW, or a combination of those two (0.1 mg in 1 ml of phosphate-buffered saline). Blood samples were collected before, 30, 60, and 120 min after injection. In normal and 50% food restricted groups, fasting ghrelin levels fell after Ep and combination of Ep and Cor injection (P < 0.05), whereas, orexin were decreased by combination of Ep and Cor injection in rats fed 100% of their needs and Ep alone in rats fed 50%. Galanin just fell after combination of Ep and Cor injection in both starved (50%) and normal rats. In contrast, all groups whit 25% fed ad libitum did not response to any injections (P > 0.05). These results indicate that Ep suppresses starvation-induced secretion of ghrelin, orexin, and galanin in normal (100%) and starved (50%) rats and their response to Ep might be affected by weight loss.