Fig. 2. (A) Effects of adrenergic agonists and antagonists on haemodynamic variables in the turtle Trachemys scripta. Recordings from one individual (#11/group2) of mean arterial blood pressures and mean blood flows in the pulmonary and systemic circuits, as well as heart rate (fH). P_pul and P_sys are the arterial pressures in the pulmonary and systemic circulation, respectively. _LAo is blood flow in the left aortic arch, and _LPA is the blood flow in the left pulmonary artery. The trace depicts resting conditions and measurements following injections of norepinephrine (norepi), phenylephrine (phenyl) and phentolamine (phent). (B) Heart rate and (C) pulmonary and systemic resistances in group2 turtles (N=6) following injection of agonists and antagonists. ^a indicates a significant difference (P<0.05) compared with resting conditions, and ^b indicates significant difference (P<0.05) compared with the variables obtained following phentolamine. Prop, propranolol.