AGING IN THE AUTONOMIC NERVOUS-SYSTEM - A RESULT OF NERVE-TARGET INTERACTIONS - A REVIEW

There are few generalisations that can be made regarding the changes t hat occur in autonomic nerves during ageing. Old age has different eff ects, including loss of neurones, loss of axon branches and alteration s in neurotransmitters and other intracellular features. However, thes e age-related events are associated with particular and often small gr oups of neurones and are frequently species specific. Changes occur at different periods during development and maturity without any obvious age-stage at which neurodegenerative changes come to predominate. Som e of the observations regarding neuronal changes in old age can be int erpreted as the result of altered interactions between neurones and th eir peripheral target tissues. Recent studies in my laboratory support this contention. The neurotrophic theory has been used to explain suc h interactions during early development and it seems possible that, fo r example, alterations in the access of neurones to target-derived gro wth factors may underlie some of the changes that have been observed i n old age. Plasticity in the mature autonomic nervous system may also be governed by similar relationships between nerves and their target t issues.