Expression of leptin receptor in the cerebral amygdala of starved rats

Background: Starvation is a crucial process of fat metabolism, which can trigger adaptive responses. During starvation, leptin concentration falls down, but it is not clear whether the expression of leptin receptor in the brain changes. Objective: To investigate the possible changes of leptin receptor expression during starvation and the effects on the basolateral nucleus of amygdala (BLA) and the central nucleus of amygdala(CeA). Design: A randomized controlled trial. Setting and materials: The experiment was conducted at the First Hospital of Xi' an Jiaotong University. A total of 20 adult health male Sprague-Dawley(SD) rats were randomly divided into groups of 24-hour fasting, 48-hour fasting, 72-hour fasting and control group with five rats in each group. Interventions: Mass, body length and tail length of all the rats in each group were measured before and after fasting. Leptin concentration was measured by radioimmunoassay(RIA), and the expression of leptin receptor and glial fibrillary acidic protein(GFAP) were measured by ABC immunohistochemical method. Main outcome measures: 1 mass loss, Lee index and the level of serum leptin and blood sugar in rats; 2 the expression of leptin receptor; 3 the expression of GFAP. Results: After 24-hour fasting, serum leptin was decreased from (2.49 ± 0.60) μg/L to(1.26 ± 0.97) μg/L, and the mass was decreased by 4.22%. After fasting for 48 hours and 72 hours, the mass was decreased by 12.15% and 19.70% respectively, and the level of serum leptin fell to (0.78 ± 0.19) μg/L and(O.62 ± 0.16) μ g/L respectively. Compared with the normal rats, 24 hours after fasting, the expression of leptin receptor in BLA was increased[LR-IR(131 ± 8.9)/ mm², (68 ± 10.4)/ mm²], and 48 hours after fasting, leptin receptor expression[(82 ± 12.6 /mm²] was close to that of the normal rats; and 72 hours after fasting, the number of positive cells of leptin receptor was markedly decreased (49.0 ± 7.4) /mm². The expression of leptin receptor in CeA showed no significant difference before and after fasting, and 24 hours and 48 hours after fasting, staining showed that there was no difference found in the number of positive cells in BLA with GFAP compared with the control group. Conclusion: During starvation, when the level of serum leptin decreased, the expression of leptin receptor in BLA is up-regulated, so starvation may regulate the sensitivity of BLA to leptin.