Activation of some P2YRs has shown to inhibit the excitatory transmission mediated by postsynaptic NMDA receptors and increase the inhibitory action of the GABAA receptors prompting LTP.226,234 In the CA1 region of hippocampus, released ATP from astrocytes has shown to result in LTD of synapses from neighboring neurons via activation of the presynaptic P2Y receptors, indicating participation of ATP from activated astrocytes in this form of plasticity.140 In a specific region of the brain, the medial habenular nucleus that is involved in depression, stress, and nicotine withdrawal234,235 an application of UTP or UDP resulted in LTP of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor-mediated currents, apparently through activation of presynaptic P2Y4R.226
