THE BIOLOGICAL RESPONSES OF AXOTOMIZED ADULT MOTONEURONS TO BRAIN-DERIVED NEUROTROPHIC FACTOR

Recent studies showed that brain-derived neurotrophic factor (BDNF) pr events developing motoneurons from naturally occurring and axotomy-ind uced cell death. Here we examined whether adult motoneurons retain res ponsiveness to BDNF. Consistent with previous studies, we found that a dult spinal and brainstem motoneurons expressed the mRNA of BDNF recep tor, trkB. in addition, the trkB immunoreactivities were readily detec ted in the adult spinal and brainstem motoneurons. We then demonstrate d that axotomized adult motoneurons responded to exogenous BDNF. BDNF administered locally markedly attenuated the lesion-induced decrease o f ChAT immunoreactivity and activity and enhanced the lesion-induced r eexpression of low-affinity NGF receptor immunoreactivity in adult fac ial motoneurons. Furthermore, we found BDNF administered subcutaneousl y, intravenously, and into the cerebral ventricle attenuated the lesio n-induced decrease of ChAT immunoreactivity in adult facial motoneuron s in a dose-dependent fashion. Our data indicate that adult motoneuron s retain their responsiveness to BDNF, suggesting that BDNF may be use ful as a therapeutic agent for adult motoneuron disease.