Although HIF-1α is protective in terms of acute heat and cold pain in the early phase, the ongoing activation of injured neurons may promote the development of chronic neuropathic pain via the upregulation of HIF-1 target genes, including GCH1 encoding GTP cyclohydrolase 1 (GTPCH) and its product tetrahydrobiopterin (BH4), which further drives NO production. Here, GCH1 is linked to Pain.