Fig. 4
Dopamine (DA)-induced inhibitory action correlated with sensitivity to the D2-like receptor (D2R) agonist. A: In the presence of the D2R antagonist sulpiride, the effect of QPR was completely blocked (a), whereas the inhibitory action induced by the α2-AdR agonist clonidine (Clon) remained unaffected (b). A schematic drawing of the action sites of the two types of catecholaminergic receptors is shown on the right. B: Despite the blocking of D2Rs by sulpiride, DA-induced suppression was partially sustained (a). Blocking D2Rs also affected NA-induced suppression of eEPSC amplitude. The dotted lines represent the extent of eEPSC amplitude suppression observed in the absence of receptor antagonists. These results suggest that DA and NA may activate α2-AdRs and D2Rs, respectively. A schematic drawing of the action sites of DA and NA is shown on the right.
