Absence of a persistently elevated 37 kDa fos-related antigen and AP-1-like DNA-binding activity in the brains of kainic acid-treated fosB null mice.

Chronic stimulation of the nervous system or acute administration of kainic acid results in a persistent increase in AP-1-like DNA-binding activity in the brain. However, the composition and function of these AP-1 complexes remain controversial. By comparing wild-type and fosB-null mice treated with kainic acid, we establish that the complexes comprise JunD in association with an approximately 37 kDa Delta-FosB species. Delta-FosB was expressed persistently in neurons in many areas of the CNS, even though fosB mRNA only increased transiently. This implies that the 37 kDa protein is very stable. fosB-/- mice are predisposed to seizures. Therefore, the chronic expression of Delta-FosB elicited by kainic acid seizures may be indicative of a compensatory/protective role in the pathophysiology of epilepsy.