DEVELOPMENT OF DOPAMINE-BETA-HYDROXYLASE POSITIVE FIBER INNERVATION OF THE RAT HIPPOCAMPUS

Development of the noradrenergic fiber innervation of the rat hippocam pus by the locus coeruleus was examined immunohistochemically in fixed tissue from animals aged 4 days through 55 days postnatal. The presen ce of tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (DBH) im munoreactive cells and fibers was evaluated in sections of hippocampus and locus coeruleus. Large, multipolar TH- and DBH-positive cells wit h long beaded fibers were visible within locus coeruleus at all ages; no immunopositive cell bodies were found in hippocampus. In hippocampa l sections from mature animals (PN55), the highest density of DBH-stai ned fibers was found in stratum lucidum of CA3 and in the hilus and in ner molecular layer of the dentate gyrus. Whereas similar patterns of fiber positivity were found at PN21 and PN10 (although with somewhat r educed density of immunopositive fibers), the pattern was quite differ ent at PN4. Although fiber staining was relatively sparse at PN4, rela tive density of DBH fibers was highest in stratum radiatum of CA1 and subiculum. This change in staining pattern suggests that noradrenergic function in hippocampus may change as the rat matures. Double immunof luorescence techniques showed an overlap of DBH and TH positive fibers in all hippocampal regions at all ages. DBH immunostaining appeared t o be somewhat more sensitive than the TH staining. These data made it impossible to confirm the presence of significant numbers of nonnoradr energic, catecholamine-containing fibers in hippocampus. (C) 1993 Wile y-Liss, Inc.