To identify the chronological transcortical
change in the contralateral hemisphere
following ischemic insults, we investigated the
changes in microtubule associated protein
(MAP) and Na+-K+ ATPase expressions in the
peri-infarct zone and contralateral hemisphere,
including the hippocampus. Two days after
hypoxic ischemia, Na+-K+ ATPase immunoreactivity
was significantly enhanced in the
contralateral cortex and was maintained up to 7
days after ischemia, whereas Na+-K+ ATPase immunoreactivity in the peri- and infarct zones
was unaffected by hypoxic ischemia. In contrast,
2 to 7 days after ischemia, MAP1A and MAP2
immunoreactivity in the ipsi- and contralateral
cortex significantly decreased, whereas in layer
V, MAP1 immunoreactivity obviously accumulated
in the neurons and their processes. In the
hippocampus, 2 days after insults both MAP1A
and MAP2 immunoreactivity was significantly
reduced within the ipsi- and contralateral
hippocampus. In the contralateral hippocampus,
however, the distribution of MAP2 immunoreactivity
recovered to the sham level 7 days
after ischemia, whereas MAP1A immunoreactive
axons remained 2 months after
ischemia. The results suggest that the unilateral
elevation of Na+-K+ ATPase immunoreactivity
reflects elevated neuronal activity. In addition,
this asymmetric hyperexcitability might play an
important role in the recovery or the
reorganization of the brain, accompanied by
transcortical changes in MAPs expression.
