Destabilization of cortical dendrites and spines by BDNF

Particle-mediated gene transfer and two-photon microscopy were used to moni tor the behavior of dendrites of individual cortical pyramidal neurons coex pressing green fluorescent protein (GFP) and brain-derived neurotrophic fac tor (BDNF). While the dendrites and spines of neurons expressing GFP alone grew modestly over 24-48 hr, coexpressing BDNF elicited dramatic sprouting of basal dendrites, accompanied by a regression of dendritic spines. Compar ed to GFP-transfected controls, the newly formed dendrites and spines were highly unstable. Experiments utilizing Trk receptor bodies, K252a, and over expression of nerve growth factor (NGF) demonstrated that these effects wer e mediated by secreted BDNF interacting with extracellular TrkB receptors. Thus, BDNF induces structural instability in dendrites and spines, which, w hen restricted to particular portions of a dendritic arbor, may help transl ate activity patterns into specific morphological changes.