P2RY2 and nervous system disorder: However, while we observed an increase in the number of microglial cells in the cortex of VPA rats mediated by purinergic receptors, the morphology of microglial cells underwent a transition that is characteristic of reactive microgliosis, which has previously been associated with the down-regulation of microglial P2Y12 receptor expression [128], as demonstrated in various neurological disorders [128,129].