Finally, while the down-regulation of KCC2 in adults after nerve injury, ischemia, inflammation, or deafferentation can be adaptive in most cases, it may sometimes come at a price, i.e., it can be accompanied by abnormal neural activity resulting in various diseases, namely autism, neuropathic pain, spasticity, and epilepsy (Coull et al., 2003; Boulenguez et al., 2010; Jaenisch et al., 2010; Toda et al., 2014; Sivakumaran et al., 2015). Here, SLC12A5 is linked to autism.