Development of dopamine‐beta hydroxylase—positive fiber innervation of the rat hippocampus

Abstract

Development of the noradrenergic fiber innervation of the rat hippocampus by the locus coeruleus was examined immunohistochemically in fixed tissue from animals aged 4 days through 55 days postnatal. The presence of tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (DBH) immunoreactive cells and fibers was evaluated in sections of hippocampus and locus coeruleus. Large, multipolar TH- and DBH-positive cells with long beaded fibers were visible within locus coeruleus at all ages; no immunopositive cell bodies were found in hippocampus. In hippocampal sections from mature animals (PN55), the highest density of DBH-stained fibers was found in stratum lucidum of CA3 and in the hilus and inner molecular layer of the dentate gyrus. Whereas similar patterns of fiber positivity were found at PN21 and PN10 (although with somewhat reduced density of immunopositive fibers), the pattern was quite different at PN4. Although fiber staining was relatively sparse at PN4, relative 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 immunofluorescence techniques showed an overlap of DBH and TH positive fibers in all hippocampal regions at all ages. DBH immunostaining appeared to be somewhat more sensitive than the TH staining. These data made it impossible to confirm the presence of significant numbers of nonnoradrenergic, catecholamine-containing fibers in hippocampus.

Redox Dysregulation Affects the Ventral But Not Dorsal Hippocampus: Impairment of Parvalbumin Neurons, Gamma Oscillations, and Related Behaviors

“…Furthermore, noradrenaline induces secretion of IL-6 by astrocytes (Maimone et al, 1993), as IL-6 is responsible (via a NOX-dependent superoxide overproduction) of PV impairment in ketamine-treated and aged rodents Dugan et al, 2009). Interestingly, noradrenergic innervations in VH are especially dense in CA3 and hilus of the DG (Oleskevich et al, 1989) and reach maximum density after weaning age (Moudy et al, 1993), coinciding in time and location with the oxidative stress observed in GCLM Ϫ/Ϫ mice. Thus, a compromised GSH system might not cope with high levels of noradrenaline release in the ventral CA3 and DG, causing a regional oxidative stress.…”

Interneurons of the hippocampus

“…In the hippocampal formation, noradrenergic innervation is particularly dense in areas receiving mossy fiber input, i.e., in the hilus of the dentate gyrus and in stratum lucidum of the CA3 subfield. Stratum lacunosum-moleculare of the CA1 region is also heavily innervated, but other regions and layers receive relatively sparse input (Loy et Moudy et al, 1993).…”

Dopamine D1/D5 Receptors Mediate Informational Saliency that Promotes Persistent Hippocampal Long-Term Plasticity

“…However, DA levels in the hippocampus do not just depend on dopaminergic innervations, as lesions in, for example, hippocampal noradrenergic neurons significantly reduce DA levels (Bischoff et al 1979). Moreover, locus coeruleus (LC) fibers densely innervate the hippocampal formation including the stratum radiatum (Moudy et al 1993) and enable a direct release of DA from noradrenergic LC fibers in the CA1 region (Smith and Greene 2012). It is thus possible that DA might be released from noradrenergic fiber terminals to “compensate” for the limited, or absent, VTA-mediated release of DA to the stratum radiatum and other dorsal hippocampal subregions, thus enabling DA to regulate synaptic plasticity and learning processes that are mediated by dorsal hippocampal structures.…”