Previous studies on ageing animal and human subjects have demonstrated
a significant overall decline in
neuronal numbers in the myenteric plexus of the enteric nervous system
(ENS). Our study aimed to confirm
this observation by counting myenteric neurons stained with the
panneuronal markers PGP 9.5 and NADH-diaphorase. We also wished to examine
the possibility that
particular subpopulations of neurons are
vulnerable. Therefore, we have immunostained and counted a
number of nerve cell groups within the
myenteric plexus of old and young Sprague Dawley rats using
markers which reflect some of the neuronal
phenotypes present, including ChAT and VIP. The number of neurons
demonstrating NADH-diaphorase
activity was significantly reduced (P<0.05) by
approximately 15% in old rats. However, the number of
neurons stained for PGP 9.5 immunohistochemistry was not reduced
and demonstrated larger numbers of
neurons than the NADH-diaphorase method. None of the other
neuronal markers studied showed any
significant reductions with age. In contrast to previous work,
this study has gathered little evidence for
extensive cell loss in the myenteric plexus of the aged rat, either in
overall populations, or in any of the
principal functional groups of neurons.