Fig. 7. Effects of D2-like dopamine (DA) antagonists, spiperone (A) (10 µmol l^-1; N=6) and domperidone (B) (50 µmol l^-1; N=6) on transepithelial potential differences (V_te) of posterior gills of Chasmagnathus granulatus. Mean control values (antagonist alone), were obtained 40-50 min after the beginning of the experiment. Both antagonists completely blocked the DA (10 µmol l^-1) stimulating effect; means were calculated 60-80 min after the beginning of the experiment. Only when domperidone was used was the blockade reversible.