REGIONALLY SPECIFIC INDUCTION OF BDNF AND TRUNCATED TRKB.T1 RECEPTORSIN THE HIPPOCAMPAL-FORMATION AFTER INTRASEPTAL INJECTION OF KAINIC ACID

The septo-hippocampal cholinergic and GABAergic systems were lesioned with single unilateral injections of kainic acid (KA) into the septum to further characterize the role of these afferents in the regulation of hippocampal brain-derived neurotrophic factor (BDNF) expression. Ne arly all cells expressing choline acetyltransferase, trkA or glutamic acid decarboxylase mRNA disappeared in the medial septum 7 days after the neurotoxin administration. The lesion resulted in a complete loss of CA3 pyramidal cells, and robust increases in BDNF mRNA levels in hi ppocampal granular dentate cells and in the amygdala. There were rapid transient increases of BDNF mRNA levels in the hippocampal formation and cortex. In addition, we found a strong induction of truncated trkB .T1 mRNA receptors in the stratum radiatum and stratum oriens of the C A3 subfield. The prolonged induction of BDNF mRNA levels suggests an i mportant role of this neurotrophin, possibly mediated by truncated trk B receptors, in the regulation of hippocampal plasticity following inj ury. (C) 1998 Elsevier Science B.V.