The percentage of retinal ganglion cells (RGCs) showing K2P channel immunoreactivity was determined by manual counting of adult retinal sections co-stained for the RGC marker Brn3a (brain-specific homeobox/POU domain protein 3A) and relevant K2P channel antibodies. Data values shown represent pooled analysis from counting cells from randomly chosen areas of multiple sections (>10) collected from n = 3 mice at P30.