Cerebral Cortex, Vol 8, 481-491, Copyright © 1998 by Oxford University Press
F Liang, LD Le and EG Jones
Chronic focal epilepsy is associated with synaptic plasticity and growth of
new connections. Brain-derived neurotrophic factor (BDNF) is associated
with each of these processes in normal brain and shows acute up-regulation
in models of generalized epilepsy. Here, using an experimental model of
focal epilepsy, we show persistent up-regulation of BDNF mRNA, independent
of that of other growth factors, in association with the development and
persistence of chronic seizures. In situ hybridization histochemistry
revealed that rats perfused within 2-3 days after seizure onset had
widespread increases in BDNF mRNA levels in the neocortex. Rats perfused at
later times, however, showed focal up-regulation of BDNF mRNA at the
injection site and down- regulation in a surrounding cortical zone. Nerve
growth factor and neurotrophin-3 mRNAs were not significantly altered.
These reciprocal changes in BDNF gene expression in the epileptic focus and
the cortical surround may contribute to plastic changes in epileptic
neuronal circuits that accompany the transition from acute to chronic
epilepsy. BDNF down-regulation in the surround is likely to be associated
with the inhibitory surround that hampers seizure spread, but facilitates
the persistence of a chronic epileptic focus.
Reciprocal up- and down-regulation of BDNF mRNA in tetanus toxin- induced epileptic focus and inhibitory surround in cerebral cortex
Department of Anatomy and Neurobiology, University of California, Irvine 92697-1280, USA.
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