title: Neurotrophin receptor and tyrosine hydroxylase gene expression in aged sympathetic neurons.
abstract: Ribonuclease protection measurements revealed decreases of 26% in p75 neurotrophin receptor mRNA and 30% in trkA mRNA in superior cervical ganglia (SCG) of aged Long-Evans rats. These declines were not related to the presence of a spatial memory impairment, whose presence is known to strongly predict increased hypothalamic-pituitary-adrenal axis activity in these aged animals. A similar decrease with age was observed in p75, but not cyclophilin mRNA levels in SCG from F-344 inbred rats. In situ hybridization with paired sections from mature and aged F-344 rats revealed a 25% decline in the mean neuronal labeling index (LI) for p75 mRNA. In other paired sections, mean trkA LI decreased 16%, tyrosine hydroxylase (TH) LI increased 74% and cyclophilin LI did not change. Neuronal hypertrophy, p75 decreases and TH increases all occurred to a greatest extent in intermediate-sized neurons, resembling those innervating the pineal and cerebral vessels. In contrast to other SCG targets, this innervation is known to decline nearly 50% with aging. Retrograde tracer/in situ hybridization studies will be required to establish whether decreased p75 represents a marker for selective axonal regression and also to determine the significance of increased TH and neuronal hypertrophy.
authors.affiliation: Department of Medicine, Montreal General Hospital and Research Institute, McGill University, Quebec, Canada.
authors.forename: G A
authors.initials: GA
authors.lastname: Kuchel
authors.forename: W
authors.initials: W
authors.lastname: Rowe
authors.forename: M J
authors.initials: MJ
authors.lastname: Meaney
authors.forename: C
authors.initials: C
authors.lastname: Richard
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000097:blood; D000375:Aging / Q000378:metabolism*; D000591:Amino Acid Isomerases / Q000096:biosynthesis; D000818:Animals; D002352:Carrier Proteins / Q000096:biosynthesis; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D007091:Image Processing, Computer-Assisted; D017403:In Situ Hybridization; D008297:Male; D018782:Maze Learning / Q000502:physiology; D009474:Neurons / Q000201:enzymology / Q000378:metabolism*; D019696:Peptidylprolyl Isomerase; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D020800:Receptor, Nerve Growth Factor; D017475:Receptors, Nerve Growth Factor / Q000378:metabolism*; D012260:Ribonucleases / Q000378:metabolism; D017783:Superior Cervical Ganglion / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D013564:Sympathetic Nervous System / Q000201:enzymology / Q000378:metabolism*; D014446:Tyrosine 3-Monooxygenase / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D002352:Carrier Proteins; D012333:RNA, Messenger; D020800:Receptor, Nerve Growth Factor; D017475:Receptors, Nerve Growth Factor; D000324:Adrenocorticotropic Hormone; D014446:Tyrosine 3-Monooxygenase; D012260:Ribonucleases; D000591:Amino Acid Isomerases; D019696:Peptidylprolyl Isomerase