Mice are anesthetized with pentobarbirtal (60 mg/kg, i.p.), intubated, and ventilated using a rodent ventilator. The chest cavity was entered through the 2nd intercostal space, and the aorta isolated. A 7-0 prolene suture is placed around the aorta between the innominate artery and left carotid artery. A 26G or 27G needle is tied onto the aorta and later removed. The chest is then closed in layers. The animal is kept warm and the rectal temperature is maintained at 37oC. The animal is then weaned from the ventilator, kept in an incubator with humidified oxygen, and returned to cage after recovering from anesthesia.