title: Age-dependent changes in noradrenergic locus coeruleus system in wild-type and APP23 transgenic mice.
abstract: Alzheimer's disease (AD), a neurodegenerative disorder, is characterized by the loss of neurons in specific regions of the CNS including the locus coeruleus (LC), the major noradrenergic locus in the CNS. Several animal models of AD have been developed that exhibit some of the pathophysiological changes in the CNS that are observed in AD patients. The purpose of this study was to determine if the integrity of the LC noradrenergic system is altered in the amyloid precursor protein 23 (APP23) mouse model of AD at the age of 3, 6 and 12 months through quantification of tyrosine hydroxylase (TH) mRNA expression. Despite a previous study suggesting alterations in the noradrenergic transmission system of APP23 mice, the current study failed to show altered TH-positive neuronal numbers or expression in LC noradrenergic neurons of APP23 mice versus wild-type (WT) littermates. However, the present study did demonstrate an age-dependent effect on TH mRNA expression. Both the number of TH-containing neurons and the amount of TH-positive grains/neuron significantly increased between the age of 3 and 6 months with no difference between 6 and 12 months. These observations indicate that any study comparing the noradrenergic system between WT (C57Bl/6) and experimental mice must strictly choose the age to be tested and limit age differences between control and experimental groups to the absolute minimum. More importantly, when long-term therapeutic interventions targeting the noradrenergic system are applied to mouse models, and related parameters are studied longitudinally, care should be taken to distinguish between potential therapeutic and strain-specific developmental or age-related alterations.
authors.affiliation: Northwest Network for Mental Illness Research, Education, and Clinical Center, Veterans Administration Puget Sound Health Care System, and Department of Psychiatry and Behavioral Science, University of Washington, Seattle 98195, USA.
authors.forename: Patricia
authors.initials: P
authors.lastname: Szot
authors.forename: Debby
authors.initials: D
authors.lastname: Van Dam
authors.forename: Sylvia S
authors.initials: SS
authors.lastname: White
authors.forename: Allyn
authors.initials: A
authors.lastname: Franklin
authors.forename: Matthias
authors.initials: M
authors.lastname: Staufenbiel
authors.forename: Peter Paul
authors.initials: PP
authors.lastname: De Deyn
mesh_terms: D000375:Aging / Q000378:metabolism*; D016564:Amyloid beta-Protein Precursor / Q000235:genetics*; D000818:Animals; D008125:Locus Coeruleus / Q000166:cytology / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009474:Neurons / Q000166:cytology / Q000201:enzymology; D009638:Norepinephrine / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis; D014446:Tyrosine 3-Monooxygenase / Q000096:biosynthesis / Q000235:genetics
chemical_list: D016564:Amyloid beta-Protein Precursor; D012333:RNA, Messenger; D014446:Tyrosine 3-Monooxygenase; D009638:Norepinephrine