Fig. 1. Effects of the injection of saline, isoproterenol (5 mg kg^-1) and phentolamine (2 mg kg^-1) on heart rate (A) and systolic and diastolic blood pressure (B) in the toad Bufo woodhousei. Values for each toad from hour 1, 3 and 5 following injection were averaged into a single data point for each condition, which were then averaged and plotted as means ± 1 S.D. (N=5 toads).