Parkinson's disease (PD) is a chronic neurodegenerative disease that is up to 90% idiopathic and occurs randomly in the population, possibly due to environmental factors. It is characterized by the progressive loss of dopaminergic neurons in the brain region called substantia nigra pars compacta (SNpc). This results in a range of motor and non-motor symptoms that severely impact the life quality of the affected individual. Studies have shown that gut dysbiosis in Parkinson's disease precedes neuronal degeneration, and our laboratory found that one of the environmental factors, dim light at night (dLAN), can alter gut microbiota composition in mice by activating the sympathetic nerve. However, it would cause degeneration of dopaminergic neurons in the brain. Therefore, it remains unclear why dLAN can truly rescue gut microbiota dysbiosis, thereby theoretically making the brain better through the Gut-Brain axis, but ultimately brain neuronal degeneration still occurs. To investigate how dLAN affects progression in the gut and specific brain regions of PD patients, we use the intraperitoneal injection of epinephrine to simulate sympathetic nerve to investigate behavioral change and the concentration of short-chain fatty acids produced by gut microbiota in SNCA pA53T mice under normal light condition. On the other hand, to investigate how dLAN affects PD progression in the long-term period, we implant the Gradient Index (GRIN) Rod lenses into SNpc in SNCA mice to see how neurons in SN respond to acute light in vivo.