The expression of mRNA coding for brain-derived neurotrophic factor (BDNF) and for its functional receptor, the full-length tyrosine kinase receptor trkB (trkB mRNA), was examined in early postnatal and adult rat retina by in situ hybridization using digoxygenin and radioactively-labeled oligonucleotide probes. BDNF and trkB mRNAs are expressed in the ganglion cell layer at postnatal-days (PN) 1, 4, 7, 14, 60, in proximal neuroblastic layer (PN 1, 4, 7), and proximal inner nuclear layer (PN 14, 60). Subpopulations of developing and mature retinal cells are thus capable of synthesizing BDNF.