Brain derived neurotrophic factor and trk B mRNA expression in the brain of a brain stem-spinal cord regenerating model, the European eel, after spinal cord injury.

Evidence from mammalian studies suggests that brain derived neurotrophic factor (BDNF) and its receptor, trk B, are upregulated in neuronal cell bodies after injury. Although fish possess neurotrophins and display rapid functional and morphological recovery after central nervous system (CNS) injury, to date few studies have examined neurotrophin expression during CNS regeneration. In this study, RT-PCR was used to investigate the effect of complete spinal cord transection on the mRNA expression of BDNF and its receptor, trk B, in the eel brain at a range of timepoints after injury. The spatial expression pattern of BDNF mRNA in the brain was also assessed before and after injury using in situ hybridization. Marked changes in BDNF and trk B mRNA levels in the eel brain were not detected during the recovery period after cord transection. In addition, the spatial expression pattern of BDNF mRNA in the eel brain appeared unchanged after injury. Our results are in contrast with the increase reported in mammals but are in line with studies examining neurotrophin expression during CNS regeneration in other anamniotic vertebrates.