Fig. 2. Effects of bolus injections (2 and 10 µg kg^-1) of adrenaline, phenylephrine and isoproterenol on haemodynamic variables in anaesthetised South American rattlesnakes Crotalus durissus: (A) P_sys, mean systemic blood pressure; (B) P_CV, central venous blood pressure; (C) fH, heart rate; (D) MCFP, mean circulatory filling pressure; (E) _pul, pulmonary cardiac output; (F) _sys, systemic cardiac output. Black bars represent control values. Grey bars represent values after injection of the various adrenergic agonists. Values are means ± S.E.M. (N=6). Asterisks indicate a significant difference relative to control values. (1 cm H₂O=0.098 kPa.)