Fig. 6. Effects of specific receptor antagonists on maximum contractile force developed by steroid-treated ventricle strips from both male (A) and female (B) rainbow trout at 0.5 Hz. Strips were pretreated for 10 min with flutamide (Flut; 0.1 mmol l^–1), mifepristone (Mif; 0.1 mmol l^–1) or tamoxifen (Tam; 0.25 mmol l^–1) to inhibit androgen, cortisol and estradiol receptors, respectively. Flut, Mif and Tam had no independent effects on contractile force in males or females. Steroid concentrations used were: 0.3 µmol l^–1 11-ketotestosterone (11KT), 0.3 µmol l^–1 testosterone (T), 0.1 µmol l^–1 cortisol (C) in males, 0.01 µmol l^–1 C in females, and 1 nmol l^–1 estradiol (E2) in females. In males, Flut blocked the inotropic effects of androgens (11KT and T) but not C. Mif blocked the effects of C in males and females but not 11KT and T in males and E2 in females. In females, Tam prevented the positive effects of E2 and C. All values are means + S.E.M. (N=7–10). *P<0.05 versus EtOH control strips.