EXPANDED DISTRIBUTION OF MESSENGER-RNA FOR NERVE GROWTH-FACTOR, BRAIN-DERIVED NEUROTROPHIC FACTOR, AND NEUROTROPHIN-3 IN THE RAT-BRAIN AFTER COLCHICINE TREATMENT

The effect of intracerebroventricular injection of the mitosis inhibitor colchicine on expression of mRNA for nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin 3 was studied in the rat brain with in situ hybridization. Colchicine up-regulates mRNA for NGF and BDNF in many of the neuronal systems normally expressing these factors. In addition, after colchicine treatment NGF and BDNF mRNAs were localized in several brain areas where they normally cannot be detected. Thus, NGF MRNA was present, for example, in many motor nuclei and in the basal forebrain, and BDNF mRNA was seen in many nuclei in the brain stem and in catecholamine neurons, including dopamine neurons in the substantia nigra. The latter neurons have recently been shown to be sensitive to BDNF, and the present results show that these neurons can produce this factor themselves. A decrease in mRNA for BDNF and neurotrophin 3 was seen only in the granular-cell layer of the hippocampal formation. A strong hybridization signal for BDNF and neurotrophin 3 mRNA was also observed over several myelinated tracts in treated rats, supporting the hypothesis that glial cells as well as neurons can produce these trophic factors.