Upregulation of the P2X7 receptor after cryogenic injury to rat brain.

The P2X7 receptor is a member of the P2X family of adenosine triphosphate-gated ion channels. It is expressed in the central nervous system and is associated with several pathological conditions. Here, we examined the expression of P2X7 with immunohistochemistry after cryogenic injury to the rat cortex. One day after cortical cryogenic injury, P2X7 immunoreactive cells were increased in regions surrounding the cold-injured site. These P2X7 positive cells were also immunoreactive for OX42, a microglial marker, and possessed the short, thick processes that are characteristic of activated microglia. These results suggest that the increased local expression of P2X7 may be associated with microglial activation, contributing to detrimental and/or protective functions around the cold-injured site.