title: Age-related decline in the tyrosine hydroxylase-immunoreactive innervation of the amygdala and dentate gyrus in mice.
abstract: Numbers of catecholaminergic neurons are known to decline with aging. Whether projections of these neurons to the forebrain are similarly affected is not known. High densities of tyrosine hydroxylase-immunoreactive (TH-ir) fibers are found in the hippocampal formation (CA1-3, dentate gyrus) and in the amygdala of normal adult mice. We report here that densities of TH-ir fibers in the amygdala and hippocampus in aged mice (21-26 months) decrease dramatically and in a subregion-specific fashion. There is a reduction of 35% in the dentate gyrus, while hippocampal regions CA1 through CA3 are almost entirely spared. In the amygdala the lateral, basolateral, basomedial, and central nucleus were affected, with fiber reduction ranging from 19% to 34%. These results indicate that the age-related decline of TH-ir catecholaminergic cell bodies in the substantia nigra and the ventral tegmental area induces substantial losses of TH-ir fibers in the amygdala and dentate gyrus, but not in other areas of the hippocampal formation. This suggests that region-specific factors may be implicated in the regulation of maintenance vs. degeneration of TH-ir fibers during aging.
authors.affiliation: Interdisciplinary Center for Neuroscience (IZN), Department of Neuroanatomy, University of Heidelberg, Im Neuenheimer Feld 307, 69120 Heidelberg, Germany. o.von_bohlen@web.de
authors.forename: Oliver
authors.initials: O
authors.lastname: von Bohlen und Halbach
authors.forename: Klaus
authors.initials: K
authors.lastname: Unsicker
mesh_terms: D000375:Aging / Q000502:physiology*; D000679:Amygdala / Q000201:enzymology* / Q000254:growth & development; D000818:Animals; D018891:Dentate Gyrus / Q000201:enzymology* / Q000254:growth & development; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009928:Organ Specificity; D017966:Pyramidal Cells / Q000201:enzymology / Q000502:physiology; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism*; D017557:Ventral Tegmental Area / Q000201:enzymology / Q000254:growth & development
chemical_list: D014446:Tyrosine 3-Monooxygenase