IBOTENIC ACID IN THE MEDIAL SEPTUM INCREASED BRAIN-DERIVED NEUROTROPHIC FACTOR MESSENGER-RNA LEVELS IN THE DORSAL RAT HIPPOCAMPAL-FORMATION

Excitotoxic lesion of the medial septum with ibotenic acid leading to partial disappearance of the septal cholinergic nerve cells was used t o investigate the role of cholinergic mechanisms in the control of tro phic factors for hippocampal plasticity, namely brain-derived neurotro phic factor (BDNF) and glucocorticoid receptor (GR). Their mRNA levels were tested by in situ hybridization 13 days after the lesion. A pers istent and widespread increase of BDNF mRNA was found in all parts of the dorsal hippocampal formation that was not accompanied by a signifi cant modification in GR expression. The present data suggest that subc ortical excitotoxic lesions at the septal level have long-term consequ ences for the adaptive trophic responses occurring in the dorsal hippo campus.