Fig. 1. Haemodynamic parameters in an anaesthetised South American rattlesnake Crotalus durissus (525 g), before and after injection of adrenaline (10 µg kg^-1), phenylephrine (10 µg kg^-1) and isoproterenol (10 µg kg^-1). Arrows indicate injection of the various drugs. Grey bars indicate occlusion of blood flow from the heart to measure mean circulatory filling pressure (MCFP). P_sys, systemic blood pressure; P_CV, central venous pressure; _pul, pulmonary cardiac output; _LAo, left aortic cardiac output; fH, heart rate. (1 cm H₂O=0.098 kPa.)