The neurotrophin receptors trkA, trkB and trkC are differentially regulated after excitotoxic lesion in rat striatum.

In the present work, we examined the time-dependent changes in trkA, trkB and trkC mRNA levels induced by the injection of glutamate receptor agonists into the striatum. Changes in trk mRNAs induced by quinolinate, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA), kainate or 1S,3R-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD) were analyzed by a ribonuclease protection assay. All high-affinity neurotrophin receptors showed differential regulation after intrastriatal injury. Up-regulation of trkA expression was observed in kainate- or ACPD-injected striata at 10 and 24 h, respectively, whereas quinolinate injection induced down-regulation between 4 and 6 h after injury. Interestingly, all the excitatory amino acid receptor agonists induced up-regulation of trkB-kinase mRNA levels. This increase was maximal between 2 and 4 h after injection except in kainate injected striata, which showed the peak of expression at 10 h. In contrast, no changes in trkC mRNA expression were observed after striatal excitotoxic injury. In conclusion, our results show that trk receptor mRNA levels are differentially regulated by excitatory amino acid receptor agonists in the striatum, suggesting that changes in the levels of neurotrophin receptors might be involved either in synaptic plasticity processes or in neuronal protection in the striatal excitotoxic paradigm.