Xiaoyaosan Decoction Regulates Changes in Neuropeptide Y and Leptin Receptor in the Rat Arcuate Nucleus after Chronic Immobilization Stress

The arcuate nucleus (ARC) in the basal of hypothalamus plays an important role in appetite regulation and energy balance. We sought to investigate the central neuroendocrine mechanism of appetite decrease and weight loss under chronic stress by observing the regulatory effects of Xiaoyaosan decoction in the expression of leptin receptor (ob-R) and neuropeptide Y (NPY) in the ARC. Our results showed that bodyweight and food intake of rats in the 21-day stress group increased slower than those of the normal group. Higher contents of Leptin and ob-R were noted in the 21-day stress group compared with control rats, while NPY expression was not statistically different. Xiaoyaosan powder can significantly downregulate the contents of leptin and ob-R in the hypothalamus of stressed rats. These findings suggest that increase of ob-R expression in the ARC is possibly one key central neuroendocrine change for the somatic discomfort. Weight loss and decreased food intake in rats caused by the binding of leptin to ob-R in hypothalamus do not appear to utilize the NPY pathway. This study also suggests that ob-R in the ARC may act as the target of Xiaoyaosan in regulating the symptoms such as appetite decrease and bodyweight loss under chronic stress.