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.
|Number of pages||9|
|Publication status||Published - 1 Feb 1998|
- Nerve regeneration