Fig. 3. Effect of DA on posterior gills previously stimulated with the adenylyl cyclase activator forskolin (10 µmol l^-1); mean was calculated 40-60 min after the beginning of the experiment. Perfusion with 10 µmol l^-1 DA did not produce consistent effects; 50 µmol l^-1 partially reversed the stimulating effect of forskolin on V_te (P<0.05; N=7, mean was obtained 80-100 min after the beginning of the experiment). Dotted line represents mean control value obtained after 20 min of perfusion with 30 saline. Asterisk, significantly different from -DA values.