P2Y12R was originally found to be expressed only by platelets (Hollopeter et al., 2001), however further studies reported that it is functionally present in microglial cells, the resident immune cells of the brain, where it can play a role in their activation (Haynes et al., 2006). In vivo experiments confirm a role for P2Y12 in microglia. P2Y12-deficient mice showed a diminished early response to focal injury and microglia from these animals was much less responsive to purine nucleotides in terms of cell migration (Haynes et al., 2006). Recently, it was shown that ADP stimulation of microglia P2Y12R induced ERK1/2 and paxillin Ser83 phosphorylation, which play a role in the regulation of focal adhesions and actin cytoskeleton rearrangement (Lee et al., 2012). Moreover, in hippocampal slices, the receptor has been shown to stimulate process extension through the activation of integrin- extracellular matrix interaction (Ohsawa et al., 2010; Swiatkowski et al., 2016).