Dopamine (DA) can precisely modify neural circuits, and affect behaviors. Songbirds provide an excellent model for studying the role of DA in modifying circuits that underlie behavior. We examined the effects of DA on synaptic inputs to the robust nucleus of the arcopallium (RA) in adult male zebra finches using the whole cell voltage-clamp recording in vitro. DA was found to significantly decrease the frequency of spontaneous excitatory postsynaptic currents (sEPSCs) and miniature excitatory postsynaptic currents (mEPSCs), but the amplitude and the kinetic properties (rise and decay time) of the sEPSCs/mEPSCs were not altered by DA. The effects of DA were attenuated by the Dl receptor (D1R) antagonist SCH23390 but not D2 receptor (D2R) antagonist sulpiride, and mimicked by the D1R agonist SKF38393 but not D2R agonist quinpirole, which implies that DA significantly inhibited excitatory synaptic transmission via activating D1R. We also found the degree of inhibition did not increase even in a high extracellular concentration of potassium, which would activate presynaptic voltage-dependent Ca2+ channels, implying the inhibition effect of DA was independent of cadium-sensitive calcium channels.
This work was supported by the National Natural Science Foundation of China (31172092).