AP-1 activity rises by stimulation-dependent c-Fos expression in auditory neurons.

Acoustical or intracochlear stimulation may induce expression of the immediate early gene product c-Fos in neurons throughout the auditory brainstem. Attempting to estimate its consequences, we sought to determine if c-Fos expression occurs in neurons that also contain c-Jun p39 with which it could form the heterodimeric transcription factor AP-1 to activate a large number of genes, among them several involved in neuroplastic remodeling. Following intracochlear stimulation, c-Fos and c-Jun were found to be colocalized in nuclei of many neurons at all levels of the subcortical auditory system. We conclude that stimulation triggers Fos-Jun dimerization, causing cascades of gene expression that potentially culminate in structural changes of neurons affected by the specific pattern of activity imposed on the neuronal system.