Blood pressure measurement
Blood pressure was recorded intraarterially with a computerized data acquisition system (ADInstruments, Bella Vista, Australia). To place the intraarterial catheter, mice were anesthetized with avertin. The standard dose was 0.014 mL/g avertin, which was made by diluting stock solution (for stock solution, 10 g 2,2,2, tribromoethanol dissolved in 10 mL tertiary amyl alcohol) 40-fold in 0.9% NaCl. The intraarterial catheter, a polyethylene tube (0.2 mm I.D., 0.5 mm O.D.) (Natsume, Tokyo, Japan) that was filled with 0.9% NaCl containing 100 U/mL heparin, was inserted into the right carotid artery and tied in place.
The blood pressure in the vessel was transmitted along the catheter to the transducer's diaphragm (MLT0699 Disposable BP Transducer; ADInstruments). The diaphragm signal was amplified through a Bridge Amplifier and recorded on a PowerLab system (LabChart 7.2; ADInstruments). Blood pressure was monitored for 2 h after the injection of the anesthetic and calculated as the average blood pressure between 45 min and 75 min after the injection (1 point per min). Statistical analysis was performed using PASW Statistics version 18.0 (SPSS Inc., Chicago, IL, USA), and differences in blood pressure between case and control groups were analyzed by independent sample t-test.