Delayed P2X4R expression after hypoxia–ischemia is associated with microglia in the immature rat brain

In a preterm hypoxia–ischemia model in the post-natal day 3 rat, we characterized how the expression of purine ionotropic P2X4 receptors change in the brain post-insult. After hypoxia–ischemia, P2X4 receptor expression increased significantly and was associated with a late increase in ionised calcium binding adapter molecule-1 protein expression indicative of microglia cell activation. Minocycline, a potent inhibitor of microglia, attenuated the hypoxia–ischemia-induced increase in P2X4 receptor expression. We postulate that P2X4 receptor-positive microglia may represent a population of secondary injury-induced activated microglia. Future studies will determine whether this population contributes to the progression of injury in the immature brain.