Fig. 4. Transition from rest-potentiation into rest-decay after ryanodine (10 µmoll^-1) treatment in atrial and ventricular muscule of the burbot heart at 1±0.5°C. (A) Representative recordings of rest-potentiation (control) and rest-decay (ryanodine) in atrial (left) and ventricular (right) muscle. Note the prolonged twitch duration after rest in the ventricular preparation. (B) The correlation between the maximum force of contraction F_max and the duration of contraction T_DC in atrial and ventricular preparations in the absence (open symbols) and presence (filled symbols) of ryanodine. The direction of the arrows indicates a positive or negative correlation for atrial (solid lines) and ventricular (broken lines) force and duration of contraction. (C) Mean results (± S.E.M.; N=5) of F_max for the first twitch after a 10, 30 or 60 s rest period in the absence (open bars) and presence (filled bars) of ryanodine. ^**Value significantly different from control (P<0.05).