GROUPS of eight rats received unilateral, intrastriatal injections of 22.5 mu g brain-derived neurotrophic factor (BDNF)or cytochrome c on 3 consecutive days. Following the injection of BDNF or cytochrome c on the second day, each animal received an intrastriatal injection of 25 mu g of C-hydroxydopamine (6-OHDA). During the second week following treatment and thereafter, the animals that received BDNF had significantly fewer apomorphine-induced, contraversive rotations than did the animals that received cytochrome c. The animals that received BDNF but not those that received cytochrome c had a halo of dopaminergic axons around the injection site. Our data indicate that BDNF can attenuate the loss of dopaminergic axons and rotational asymmetry that result from an intrastriatal injection of 6-OHDA.