Figure 5.

Blockade of D₂-like but not D₁-like DA receptors reduces the rotenone-induced effect via a GABA-mediated mechanism. A, Both the dopamine transporter blocker GBR12909 (1 μm) and the D₁ receptor antagonist SCH23390 (10 μm), bath applied before and during the application of 1 μm rotenone, did not prevent the reduction of the mean field potential amplitude produced by the application of 1 μm rotenone. B, Conversely, the preincubation with the D₂ receptor antagonist l-sulpiride (sulp; 10 μm) significantly reduced the rotenone-mediated reduction of the field potential amplitude. Note, however, that the concomitant application of SCH23390 reversed the effect exerted by l-sulpiride. C, The histogram summarizes cumulative data of membrane potential changes recorded 20 min after the onset of 1 μm rotenone showing that the action of l-sulpiride was not affected by the glutamate receptors antagonists APV and CNQX. D, Time courses of the rotenone-induced mean inward current in control conditions and in the presence of 10 μm l-sulpiride. E, The l-sulpiride-mediated effect against the rotenone-induced dysfunction was blocked by both the GABA_A receptor antagonist bicuculline (bic; 3 μm) and the chloride channel blocker picrotoxin (PTX; 30 μm) in field potential experiments.