Age-associated changes in distribution of the P2X2 receptor in the major pelvic ganglion of the male rat.

Abstract

P2X purinoceptors constitute a group of ligand-gated ion channels one of which, the P2X2 receptor has previously been described in neurons within autonomic ganglia, including the major pelvic ganglion (MPG). Earlier work strongly suggests that age-associated attrition of sympathetic but not parasympathetic MPG neurons occurs but there have been no investigations of age-related changes in P2X2 receptor expression in autonomic ganglia or to determine whether the receptor is localised in one or both of the two MPG neuronal subpopulations. In the current study, immunocytochemistry was employed to label cells expressing the P2X2 receptor in the MPG from young and aged male Wistar rats. By combining P2X2 receptor immunocytochemistry with the immunolocalisation of tyrosine hydroxylase (TH), the numbers of sympathetic (TH+) and parasympathetic (TH-) neurons expressing the P2X2 receptor were determined. In young rats P2X2 receptor expression was found in 93.08+/-3.2% of TH- (parasympathetic) neurons. In aged rats a similar analysis revealed no significant difference in the number of TH- neurons expressing the P2X2 receptor. In contrast a significant increase in the number of TH+ sympathetic neurons expressing P2X2 was observed in the MPG of aged rats (10.70+/-2.26%) in comparison to the young group (2.38+/-0.78%). Age-related changes in the numbers of small intensely fluorescent (SIF) cells which were highly P2X2 positive were also quantified, revealing a small reduction in number with age. This study has demonstrated the preferential localisation of P2X2 receptors to parasympathetic MPG neurons and suggests that purinergic transmission in the pelvic organs maybe largely unaffected by ageing.