Neuropathic pain is characterized by spontaneous pain, pain sensations, and tactile allodynia. The pain sensory system normally functions under a fine balance between excitation and inhibition. Neuropathic pain arises when this balance is lost for some reason. In past reports, various mechanisms of neuropathic pain development have been reported, one of which is the downregulation of K+-Cl−-cotransporter-2 (KCC2) expression. In fact, various neuropathic pain models indicate a decrease in KCC2

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... pression. This decrease in KCC2 expression is often due to a brain-derived neurotrophic factor that is released from microglia. However, a similar reaction has been reported in astrocytes, and it is unclear whether astrocytes or microglia are more important. This review discusses the hypothesis that astrocytes have a crucial influence on the alteration of KCC2 expression.