Fig. 6. Effects of anoxia, hyperkalemia, acidosis, adrenaline and hypercalcemia on cardiac performance in cold-acclimated C. picta. The experiments were performed at 5°C and show isometric twitch force of ventricular strips as a percentage of untreated control force. The changes in the buffer solution were applied either (A) one by one to show the isolated effects, or (B) in sequence to investigate the combined effects. The experimental changes used were as follows: anoxia; hyperkalemia (K⁺ from 2.5 to 10 mmol l^–1); acidosis (pH from 7.9 to 6.9); adrenaline (10 µmol l^–1) and hypercalcemia (Ca²⁺ from 2 to 6 mmol l^–1). Data are from Overgaard et al. (Overgaard et al., 2005).