title: Differences in the synaptic complement of thoracic motoneurons of adult and ageing cats after permanent or reversible axotomy.
abstract: We have compared the effects of intercostal nerve crush (reversible axotomy) or nerve transection with proximal ligation (permanent axotomy) on the somatic synaptic terminals of thoracic motoneurons of adult (1-2 years) and ageing (10-15 years) cats. Retrograde axonal transport of horseradish peroxidase (HRP) was used to identify axotomised motoneurons; control motoneurons were labelled by the intramuscular injection of HRP. Synaptic frequency and cover of control motoneurons in adult and ageing cats was similar. In adults, 8-16 days following both types of axotomy, synaptic cover was halved without any significant change in synaptic frequency. By 32-64 days following reversible axotomy, synaptic frequency and cover were not significantly different from controls. By contrast, 32-64 days following permanent axotomy synaptic frequency and cover were reduced to 30-50% of adult control values. In ageing cats 2 months following reversible axotomy, synaptic frequency and cover were reduced to 40% and 33% of ageing control values, respectively, while no significant change from controls was found 2 months following permanent axotomy. The long-term synaptic response of axotomised motoneurons in ageing cats is therefore opposite to that of adults.
authors.affiliation: Department of Anatomy and Developmental Biology, The Royal Free Hospital School of Medicine, London, UK.
authors.forename: I P
authors.initials: IP
authors.lastname: Johnson
authors.forename: C K
authors.initials: CK
authors.lastname: Gowda
authors.forename: T A
authors.initials: TA
authors.lastname: Sears
authors.forename: A S
authors.initials: AS
authors.lastname: Hunter
mesh_terms: D000367:Age Factors; D000375:Aging / Q000502:physiology*; D000818:Animals; D019771:Axotomy; D002415:Cats; D008854:Microscopy, Electron; D009046:Motor Neurons / Q000473:pathology* / Q000648:ultrastructure; D013569:Synapses / Q000502:physiology* / Q000648:ultrastructure