title: Responsiveness of sympathetic and sensory iridial nerves to NGF treatment in young and aged rats.
abstract: Altered neuronal responses to trophic factors may play a role in neuronal maintenance in adulthood and may also be involved in neuronal atrophy in old age. We have investigated this issue in the rat iris, studying responsiveness of sympathetic and sensory iridial nerves to a range of NGF concentrations in mature and aged rats. We show here that growth responses of sensory nerves to NGF, as measured by quantitative immunohistochemistry and image analysis, were unchanged in old rats. In contrast, there was a small but significant reduction in responsiveness of aged sympathetic neurons. The shapes of the dose-response curves for sensory and sympathetic neurons were different, with a larger response over a narrower range of concentrations in sensory neurons. Lower levels of p75 immunoreactivity were observed in iridial nerves from old compared to young rats. NGF treatment had no effect on receptor staining in young rats but restored 'young' levels of p75 staining in old rats. Our results do not support the hypothesis of a primary role for NGF in maintenance or atrophy of nerves in ageing.
authors.affiliation: Department of Anatomy and Developmental Biology, Royal Free and University College Medical School, Royal Free Campus, Rowland Hill Street, NW3 2PF, London, UK.
authors.forename: I
authors.initials: I
authors.lastname: Gavazzi
authors.forename: K L
authors.initials: KL
authors.lastname: Railton
authors.forename: E
authors.initials: E
authors.lastname: Ong
authors.forename: T
authors.initials: T
authors.lastname: Cowen
mesh_terms: D000320:Adrenergic Fibers / Q000737:chemistry / Q000187:drug effects* / Q000502:physiology; D000375:Aging / Q000502:physiology*; D000818:Animals; D000906:Antibodies; D015740:Calcitonin Gene-Related Peptide / Q000032:analysis / Q000276:immunology; D007498:Iris / Q000294:innervation*; D008297:Male; D020932:Nerve Growth Factor / Q000494:pharmacology*; D009416:Nerve Regeneration / Q000187:drug effects / Q000502:physiology; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology; D009475:Neurons, Afferent / Q000737:chemistry / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D020800:Receptor, Nerve Growth Factor / Q000032:analysis / Q000276:immunology; D020917:Receptor, trkA / Q000032:analysis / Q000276:immunology; D014446:Tyrosine 3-Monooxygenase / Q000032:analysis / Q000276:immunology
chemical_list: D000906:Antibodies; D020800:Receptor, Nerve Growth Factor; D020932:Nerve Growth Factor; D014446:Tyrosine 3-Monooxygenase; D020917:Receptor, trkA; D015740:Calcitonin Gene-Related Peptide