NEURONAL COLOCALIZATION OF MESSENGER-RNAS FOR NEUROTROPHINS AND THEIRRECEPTORS IN THE DEVELOPING CENTRAL-NERVOUS-SYSTEM SUGGESTS A POTENTIAL FOR AUTOCRINE INTERACTIONS

Development and survival of neurons in the central nervous system are dependent on the activity of a variety of endogenous neurotrophic agen ts. Using combined isotopic and nonisotopic in situ hybridization hist ochemistry, we have found that subsets of neurons within the developin g forebrain coexpress the mRNAs for both neurotrophins (nerve growth f actor, brain-derived neurotrophic factor, and neurotrophic 3) and thei r receptors (p75NGFR, TrkA, and TrkB). The colocalization of mRNA for neurotrophic receptors and their ligands in presumptive neurotrophic t arget neurons suggests the potential for autocrine and paracrine mecha nisms of action during development. Such mechanisms may ensure the ons et of differentiation and survival of specific subsets of neurons prio r to and following target innervation.