Long-term increase of Sp-1 transcription factors in the hippocampus after kainic acid treatment

Systemic administration of kainic acid (KA), a glutamate receptor agonist, causes robust seizures and has been used as an excellent rodent model for human temporal lobe epilepsy. Recently, we have demonstrated that a single injection of KA increases the steady-state levels of proenkephalin (PENK) mRNA in the rat hippocampus for at least one year. However, the molecular mechanisms underlying this long-term increase in PENK mRNA levels have not been clearly defined. To determine the possible involvement of the Sp-l transcription factors in this regulation, electrophoresis mobility-shift assays were used to study the expression of Sp-l factors in the hippocampus after KA treatment. The results showed that then are long-lasting increases in Sp-l DNA-binding activity. The Sp-l DNA-binding complexes were only competed by the non-radioactive Sp-l element and not by ENKCRE2, AP-I or CRE elements, indicating the specificity of Sp-l DNA-binding activity. Since the expression of Sp-l parallels the time course of long-lasting increase in the expression of PENK mRNA and mossy fiber sprouting after KA treatment, we hypothesize that the increase in Sp-l activity may be associated with the long-term changes in the plasticity of hippocampal function after KA-induced seizures. (C) 1999 Elsevier Science B.V. All rights reserved.