Figure 8.

Schematic of working hypothesis for astrocytic Cx43-mediated late-phase neuropathic pain. CCI induces a persistent upregulation of Cx43 in spinal cord astrocytes. Cx43 expression and activity is also upregulated by TNF-α, secreted from microglia. Upregulation of Cx43 hemichannel activities results in CXCL1 release. Astrocytic CXCL1 secretion activates CXCR2 on neurons (central terminals of primary sensory neurons and spinal cord neurons), leading to enhanced excitatory synaptic transmission in nociceptive neurons (e.g. lamina IIo excitatory interneurons) and sustained neuropathic pain in the late-phase. Additionally, CXCL1 can also be secreted from intact or injured primary afferents in the spinal cord especially in the early phase of CCI.