The Journal of Neuroscience, October 1, 1999, 19(19):8234-8243
Persistent Increased DNA-Binding and Expression of Serum Response
Factor Occur with Epilepsy-Associated Long-Term Plasticity Changes
T. Allen
Morris1,
Neda
Jafari2,
Ann C.
Rice1,
Olavo
Vasconcelos1, and
Robert J.
DeLorenzo1, 2, 3
Departments of 1 Neurology, 2 Pharmacology
and Toxicology, and 3 Biochemistry and Molecular
Biophysics, Medical College of Virginia, Virginia Commonwealth
University, Richmond, Virginia 23298
We have previously shown that NMDA receptor activation during
status epilepticus (SE) is required to produce epilepsy in in vitro and in vivo models. As in human
symptomatic epilepsy, the epilepsy in these models is permanent,
suggesting that the pathological activation of NMDA receptors causes
permanent plasticity changes in the brain. Ca2+
influx through NMDA receptors is known to transiently activate a key
transcription factor, serum response factor (SRF). Thus, we
investigated whether this factor, in terms of its expression and
ability to bind to the consensus serum response element, was altered long term in the pilocarpine model of epilepsy. In hippocampal nuclear extracts, SRF binding to DNA was significantly increased over
saline-injected control rats at 24 hr and at 8 weeks after the onset of
SE. This increase was shown to be the result of significantly elevated
levels of SRF. DNA binding was also persistently increased in the
cortical, but not in the cerebellar, extracts. Hippocampal expression
of SRF was localized to neurons using immunohistochemistry. NMDA
receptor activation during SE was required for these changes to take
place, and the spontaneous seizures seen in epileptic rats did not
appear to be responsible for the increase in SRF. The results
demonstrate that SRF is persistently elevated after SE in the
pilocarpine model of epilepsy and support the theory that long-term
gene changes in this model occur and are associated with the
long-lasting plasticity changes that are initiated during epileptogenesis.
Key words:
epilepsy; serum response factor; neuronal plasticity; seizure; status epilepticus; hippocampus; SRF
Copyright © 1999 Society for Neuroscience 0270-6474/99/19198234-10$05.00/0