BDNF IS A NEUROTROPHIC FACTOR FOR DOPAMINERGIC-NEURONS OF THE SUBSTANTIA-NIGRA

Brain-derived neurotrophic factor (BDNF), present in minute amounts in the adult central nervous system 1, is a member of the nerve growth factor (NGF) (ref. 2) family, which includes neurotrophin-3 (NT-3) (refs 3-5). NGF, BDNF and NT-3 all support survival of subpopulations of neural crest-derived sensory neurons 3-5; most sympathetic neurons are responsive to NGF (ref. 2), but not to BDNF 1,6,7; NT-3 and BDNF, but not NGF (ref. 6), promote survival of sensory neurons of the nodose ganglion 3-8. BDNF, but not NGF, supports the survival of cultured retinal ganglion cells 9 but both NGF and BDNF promote the survival of septal cholinergic neurons in vitro 10,11. However, knowledge of their precise physiological role in development and maintenance of the nervous system neurons is still limited. The BDNF gene is expressed in many regions of the adult CNS 12-14, including the striatum 12. A protein partially purified from bovine striatum, a target of nigral dopaminergic neurons, with characteristics apparently similar to those of BDNF, can enhance the survival of dopaminergic neurons in mesencephalic cultures 15. BDNF seems to be a trophic factor for mesencephalic dopaminergic neurons, increasing their survival, including that of neuronal cells which degenerate in Parkinson's disease. Here we report the effects of BDNF on the survival of dopaminergic neurons of the developing substantia nigra.