Journal of Neuroscience, Vol 14, 7726-7734, Copyright © 1994 by Society for Neuroscience
Direct measurement of brain temperature during and after intraischemic hypothermia: correlation with behavioral, physiological, and histological endpoints
S Nurse and D Corbett
Division of Basic Medical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, Canada.
The aim of the present study was to evaluate critically the protection
afforded by hypothermia against ischemic injury to the hippocampus.
Hypothermic treatment was applied selectively to the brain during a 5 min
carotid artery occlusion in gerbils. Following a period of recovery, two
independent measures were used to assess hippocampal function: (1) an open
field test of spatial memory (assessment was made during the first 10 d
after ischemia) and (2) measurement of evoked potentials from area CA1 in
hippocampal slices (3 weeks after the ischemic episode). The functional
outcome portrayed by these tests was compared to a morphological evaluation
of CA1 pyramidal cells at three rostrocaudal levels. All evaluations were
carried out in the same animals. We found converging evidence that
intraischemic hypothermia provides virtually complete protection against a
5 min episode of cerebral ischemia. Animals treated with hypothermia
performed as well as sham-operated controls in a spatial memory task, had
field potentials that were indistinguishable from normal animals and CA1
cells appeared normal when assessed histologically. In contrast, ischemia
at normothermia resulted in a deficit in open field behavior (p < 0.01),
diminished field potentials in stratum radiatum (p < 0.01), and near
total loss of pyramidal cells in dorsal CA1 (p < 0.01). There was a
remarkably high correlation between these diverse measures (r ranged from
0.7 to 0.9, p < 0.01), which provides strong support for the use of
hypothermia as an effective treatment for ischemia. This study introduces a
novel approach for the evaluation of putative anti- ischemic treatments:
combining behavioral, electrophysiological, and histological
measures.(ABSTRACT TRUNCATED AT 250 WORDS)
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