Fig. 4.

Dopamine D₁ receptor activation enhances postsynaptic NMDA receptor-mediated inward currents independently of synaptic transmission. A, Data pooled from five cells showing that bath application of NMDA (20 μm) induced an inward current. When NMDA was reapplied in the same five cells 5–10 min after application of the D₁receptor agonist SKF 38393 (10 μm), NMDA-induced currents were enhanced. Cells were voltage-clamped at −80 to −90 mV with tetrodotoxin (200 nm) present throughout. B,Continuous record of membrane current from an individual neuron (1 of the 5 in A; voltage-clamped at −90 mV) showing the reversible enhancement of the NMDA-mediated current by SKF 38393 (10 μm).