Hypothermia suppresses nitric oxide elevation during reperfusion after focal cerebral ischemia in rats.

We aimed to investigate effect of temperature on the jugular levels of nitric oxide (NO) at reperfusion after focal cerebral ischemia. Both nitrosyl hemoglobin (HbNO) (2.5 +/- 0.4 microM) and plasma nitrite plus nitrate levels (61 +/- 5 microM) in rats under normothermia (approximately 37 degrees C) after 30 min of reperfusion following 2 h of left middle cerebral artery occlusion were significantly high, compared with sham operated rats (1.3 +/- 0.1 microM, 40 +/- 4 microM, respectively). Both HbNO (1.5 +/- 0.3 microM) and nitrite plus nitrate levels (43 +/- 7 microM) under moderate hypothermia (approximately 32 degrees C) were significantly low, compared with normothermic rats. HbNO (2.8 +/- 0.8 microM) and nitrite plus nitrate levels (65 +/- 8 microM) under mild hyperthermia (approximately 39 degrees C) were not significantly high. These results firstly demonstrated that hypothermia suppresses the elevation in intrajugular NO after cerebral ischemia-reperfusion.