PPN, STN, and DR afferents have distinct postsynaptic receptor compositions in drug-naive mice. A, Example of a matched optogenetically evoked EPSC in STN with an electrically evoked EPSC in the same dopamine neuron. B, Optogenetically evoked EPSCs (black traces; stimulation for all traces at arrows) from PPN (oPPN), STN (oSTN), DR (oDR), and electrically evoked EPSCs (Elec.; stimulus artifact removed) contain both NMDA (blue traces) and AMPA (red traces) receptor-mediated currents. C, AMPA-to-NMDA receptor-mediated current ratios. oPPN-evoked EPSCs had similar amount of AMPA receptor-mediated and NMDA receptor-mediated currents with a ratio near 1. oSTN-evoked, oDR-evoked, and electrically evoked EPSCs have AMPA-to-NMDA receptor-mediated current ratios of <0.5. *p < 0.05, **p < 0.01.