Studies were performed in male Golden Syrian hamsters (Charles River Laboratories, Boston, MA) weighing 80–90 g. Animal handling and care followed the NIH Guide for Care and Use of Laboratory Animals. The experimental protocol was approved by the UCSD Institutional Animal Care and Use Committee. Briefly, animals were anesthetized using sodium pentobarbital (40mg/kg IP). Animal preparation included: (i) left jugular vein and left femoral artery catheterization, (ii) tracheotomy (polyethylene-90 tube), and (iii) left ventricle (LV) conductance catheter introduction through the right carotid artery. Animals were placed in the supine position on a heating pad to maintain core body temperature at 37 °C. Animals were mechanically ventilated (TOPO ventilator, Kent Scientific, Torrington, CT) using room air (respiration rate of 90 breaths/min; peak inspiratory pressure of 20 cmH2O). After instrumentation, volatile anesthesia (0.6%/vol Isoflurane, Drägerwerk AG, Lübeck, Germany) was administered using a vaporizer connected to the ventilator. Depth of anesthesia was continually verified via toe pinch, if needed, isoflurane was increased by 0.1%/vol to prevent animal discomfort. Experimental setup is presented in Figure 1 (Chatpun and Cabrales 2010 (link)).