The Journal of Neuroscience, 1999, 19:RC42:1-6
RAPID COMMUNICATION
Progressive Unilateral Damage of the Entorhinal Cortex Enhances
Synaptic Efficacy of the Crossed Entorhinal Afferent to Dentate Granule
Cells
Julio J.
Ramirez,
Ketan R.
Bulsara,
Sandra C.
Moore,
Karl
Ruch, and
William
Abrams
Laboratory of Behavioral Neuroscience, Department of Psychology,
Davidson College, Davidson, North Carolina 28036
Progressive injury to the mammalian CNS often reduces the
severity of lesion-induced deficits or spares the behavior from deficits altogether. The mechanism(s) underlying this behavioral sparing is not clearly understood, but axonal sprouting is a likely candidate. To test this possibility, unilateral, two-stage
(progressive) lesions of the entorhinal cortex, which are known to
accelerate sprouting by the crossed temporodentate pathway and spare
spatial memory function, were made in rats. We examined the changes in synaptic efficacy (as measured by the amplitude and slope of evoked population EPSPs) of the crossed temporodentate projection after either one-stage or progressive unilateral lesions of the entorhinal area. Whereas the synaptic efficacy of the one-stage group did not
differ significantly from the control group at 4, 6, or 8 d after
the lesion, the synaptic efficacy of the crossed temporodentate pathway
in the progressive lesion group significantly increased above the
control values as early as 4 d after the lesion and remained
stable thereafter. Axonal sprouting thus may provide a mechanism by
which to account for behavioral sparing after progressive brain damage.
Key words:
crossed temporodentate pathway; entorhinal cortex; functional reorganization; hippocampus; neuroplasticity; sprouting
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