Aquaporin‐4 (AQP4), originally known as a mercurial‐insensitive water channel, is most strongly expressed in astrocytes throughout the brain and spinal cord, as well as in ependymal cells lining the brain ventricles; it is involved in the regulation of water homeostasis in the brain.23, 24, 25 Recently, AQP4 expression has been reported to be involved in the pathology of the development of PD in a 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP)‐induced mouse model. This evidence concerns the gene AQP4 and Parkinson disease.