Effect of DA (50 µM) on pharmacologically isolated NMDA and AMPA/KA receptor-mediated EPSCs.

<p><b>A</b>: Current traces of pharmacologically isolated AMPA/KA EPSC recorded with APV (50 µM) present in the superfusing medium before (1), during (2) and after (3) superfusion with dopamine at a holding membrane potential of −100 mV. 4: the overlay of the responses before and during DA superfusion. <b>B</b>: Current traces of pharmacologically isolated NMDA receptor-mediated EPSC recorded with CNQX (20 µM) present in the superfusing medium before (1), during (2) and after (3) superfusion with dopamine at a holding membrane potential of −20 mV. 4: the overlay of the responses before and during DA superfusion. Traces in A and B represent the average of 6 sweeps. <b>C</b>: average effect of dopamine on isolated NMDA and AMPA/KA receptor-mediated EPSCs. NMDA receptor-mediated EPSC was measured at the membrane potential the response was largest, −40 mV or −20 mV and AMPA/KA receptor-mediated EPSC was measured at a holding membrane potential of −100 mV. The left and right vertical axis are for the NMDA and AMPA/KA receptor-mediated EPSCs respectively. * Statistically different from control, Student’s paired t-test, <i>P</i><0.001. <b>D</b>: Time course of the inhibitory effect (in percentage) of dopamine on AMPA/KA and on NMDA receptor-mediated EPSC shown in A and B respectively. Response was recorded every 15 s and each filled circle represent the average of 4 sweeps recorded over one minute period. The dashed rectangle represent the period during which DA (50 µM) was added to the superfusing medium, from 4 to 14 min.