DEVELOPMENT OF DOPAMINE-BETA-HYDROXYLASE POSITIVE FIBER INNERVATION IN COCULTURED HIPPOCAMPUS-LOCUS-COERULEUS ORGANOTYPIC SLICES

Development of the noradrenergic innervation of the rat hippocampus by the nucleus locus coeruleus was examined immunohistochemically in the roller tube organotypic cultured slice preparation. Slices of rat hip pocampus and locus coeruleus were co-cultured on glass coverslips for 2-6 weeks and evaluated for the presence of dopamine-beta-hydroxylase (DBH) and tyrosine hydroxylase (TH) immunoreactive cells and fibers. L arge, multipolar DBH- and TH-positive cells were visible within the lo cus coeruleus; an occasional cell appeared near or just within co-cult ured hippocampal tissue and in connecting fiber tracts. DBH-positive c ells tended to concentrate near the edges of locus coeruleus tissue. L ocus coeruleus slices cultured alone showed little indication of fiber outgrowth in any direction. In co-cultures, however, beaded DBH- and TH-positive fibers were directed toward the hippocampus. The majority of these fibers entered the hippocampus in the hilar/CA3 region and fo rmed extensive collateral branches. Light microscopy suggests that DBH -positive fiber growth was densest at or near the pyramidal cell layer in CA3b and CA3c and in the infragranular region of the dentate hilus . This pattern of noradrenergic innervation of hippocampus by co-cultu red locus coeruleus in vitro appears very similar to the pattern estab lished in vivo (see Moudy et al., companion article, this issue). (C) 1993 Wiley-Liss, Inc.