Cerebral ischemia in rats was produced by our adaptation of the 2VO method of (Smith et al., 1984) and as described previously (Preston and Webster, 2004). Ischemia was effected for 12 min by combining bilateral carotid artery occlusion with hypovolemic hypotension to minimize compensatory vertebral blood flow. Each rat was anesthetized with sodium pentobarbital (65 mg/kg i.p.), intubated using a pediatric laryngoscope, and mechanically ventilated (Harvard rodent ventilator, Ealing Scientific, St. Laurent PQ) with a 30:70 mixture of O2 and N2. delivered at 35–40 breaths/min, 3 ml volume. Tympanic and colonic temperatures were measured using YSI 511 and 402 thermistor probes (Yellow Springs Instruments, Yellow Springs, OH, USA) and were maintained close to 37.5 ±0.5 (°C) by means of a circulating water pad under the supine rat. The tail artery was cannulated and arterial blood sampled to measure blood gases and pH. Ventilation rate was adjusted if required to obtain physiologically normal blood gas parameters (Preston and Webster, 2004). The common carotid arteries were exposed and freed for placement of vascular clamps. Arterial pressure was monitored by a polygraph (Biopac Systems, Galeta, CA, USA) and Statham pressure transducer hooked by a Y-connection to the tail artery catheter. Pressure was lowered by withdrawing 7–8 ml of tail artery blood into a 10 ml heparinized syringe. Both common carotid arteries were then occluded by vascular clamps for 12 min during which time arterial pressure was maintained between 42–47 mmHg by adjusting the volume of blood in the syringe. The blood was then returned to the rat, the incisions closed with sutures, and mechanical ventilation withdrawn. Colonic temperature monitoring was continued and normothermia maintained in a lamp-warmed cage until the rat recovered from anesthesia. Sham-operated animals underwent an identical procedure, including lowering blood pressure to 42–47 mmHg for 12 min, except that the carotid arteries were not clamped. This group served as a control to rule out possible factors other than ischemia that might alter the recovery, such as stress resulting from handling, surgery, change in blood pressure, and transportation to another laboratory for immunohistochemical procedures.