Axotomized medial septal-diagonal band neurons express Jun-like immunoreactivity

The expression of the transcription factors Fos and Jun was studied in rat brain after transection of the fornix-fimbria (FF) using polyclonal antibodies to these proteins and immunocytochemical detection methods. FF-transection lead to a massive induction of Jun-like immunoreactivity (JLI) in neurons in the medial septal nucleus and in the vertical limb of the diagonal band of Broca, within 48 hours and lasting up to 14 days after lesion. Fos was not induced in these neurons after FF-transection. These results indicate that axotomized medial septal and diagonal band of Broca neurons selectively and rapidly express JLI. The role of Jun expression in axonal regeneration or neuronal death is discussed.