The arctic ground squirrel brain is resistant to injury from cardiac arrest during euthermia.
OBJECTIVE
Hetereothermic mammals tolerate hypoxia during euthermy and torpor, and evidence suggests this tolerance may extend beyond hypoxia to cerebral ischemia. During hibernation, CA1 hippocampal neurons endure extreme fluctuations in cerebral blood flow during transitions into and out of torpor as well as reductions in cerebral blood flow during torpor. In vitro studies likewise show evidence of ischemia tolerance in hippocampal slices harvested from euthermic ground squirrels; however, no studies have investigated tolerance in a clinically relevant model of in vivo global cerebral ischemia. The purpose of the present study was to test the hypothesis that the euthermic Arctic ground squirrel (AGS; Spermophillus parryii) is resistant to injury from asphyxial cardiac arrest (CA).


METHODS
Estrous-matched female rats were used as a positive control. Female euthermic AGS and rats were subjected to 8-minute CA. At the end of 7 days of reperfusion, AGS and rats were fixed for histopathological assessment.


RESULTS
In rats subjected to CA, the number of ischemic neurons was significantly higher (P<0.001) compared with control rats in hippocampus and striatum. Cortex was mildly injured. Surprisingly, neuronal counts in AGS were not significantly different in CA and control groups in these brain regions.


CONCLUSIONS
These data demonstrate that AGS are remarkably tolerant to global cerebral ischemia during euthermia. A better understanding of the mechanisms by which AGS tolerate severe reductions in blood flow during euthermia may provide novel neuroprotective strategies that may translate into significant improvements in human patient outcomes after CA.
Cerebral Vascular Disease Research Center, Department of Neurology and Neuroscience, Leonard M. Miller School of Medicine, University of Miami, Miami, FL 33101, USA.
Kunjan R
KR
Dave
Ricardo
R
Prado
Ami P
AP
Raval
Kelly L
KL
Drew
Miguel A
MA
Perez-Pinzon
D000222:Adaptation, Physiological; D000818:Animals; D001110:Arctic Regions; D002545:Brain Ischemia / Q000209:etiology / Q000473:pathology / Q000503:physiopathology*; D002560:Cerebrovascular Circulation; D006323:Heart Arrest / Q000503:physiopathology*; D006605:Hibernation; D009474:Neurons / Q000473:pathology; D051381:Rats; D012589:Sciuridae