Measurement of cerebral reactive hyperemia at the initial post-ischemia reperfusion stage under normothermia and moderate hypothermia in rats.
Inhibition of the initial events occurring immediately after ischemia-reperfusion seems to be beneficial for reducing the extent of subsequent chronic neuronal cell injury. We investigated the effects of moderate hypothermia (32 degrees C) commencing 30 min before ischemia on reactive hyperemia by measuring cerebral blood flow (CBF) with a laser-Doppler flowmeter at the initial ischemia-reperfusion stage (60 min) following 10 min of global cerebral ischemia in rats. In normothermia, CBF was increased to approximately 240% and decreased thereafter, although it remained at approximately 150% after 60 min of ischemia-reperfusion. In contrast, hypothermia increased CBF to more than 270% after ischemia-reperfusion, then recovered to the basal level within 30 min. The period of reactive hyperemia under normothermia tended to be shortened by pre-administration of an NMDA antagonist, in a manner similar to hypothermia. Furthermore, hypothermia inhibited the presence of cells with caspase-3-like immunoreactivity in the hippocampal CA1 sector after 8 h of ischemia-reperfusion. Our findings indicate that hypothermia tends to shorten the period of reactive hyperemia during the initial ischemia-reperfusion stage. This phenomenon may be partly associated with activation of NMDA receptors and a beneficial effect of hypothermia in resisting progression of the neurotoxic cascade in the first 8 h after ischemia-reperfusion.
Kunimatsu
Teruhito
T
Division of Dental Anesthesiology, Department of Comprehensive Dentistry, Kanagawa Dental College, Yokohama Dental and Medical Clinic and Clinical Training Center, Yokohama, Kanagawa, Japan. kunimatsu@hama.kdcnet.ac.jp
Yamashita
Anzu
A
Kitahama
Homare
H
Misaki
Toru
T
Yamamoto
Toshiharu
T
D000818:Animals; D017209:Apoptosis; D056547:CA1 Region, Hippocampal / Q000166:cytology / Q000201:enzymology / Q000293:injuries*; D053148:Caspase 3 / Q000502:physiology; D002560:Cerebrovascular Circulation; D007036:Hypothermia, Induced; D017078:Laser-Doppler Flowmetry; D008297:Male; D009474:Neurons / Q000201:enzymology; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology*; D015427:Reperfusion Injury / Q000175:diagnosis / Q000517:prevention & control*
D016194:Receptors, N-Methyl-D-Aspartate; D053148:Caspase 3