To further investigate the possible role of α‐syn in the more severe neuronal pathology in MPTP‐treated AQP4−/− PD mice, we assessed the expression levels of α‐syn mRNA and protein in the midbrains of AQP4+/+ and AQP4−/− mice after acute or chronic MPTP intoxication. The gene discussed is AQP4; the disease is Parkinson disease.