Neurodegeneration in sweat glands and skin of aged rats.

In order to compare age-associated neurodegenerative changes in peripheral nerves of laboratory mammals and humans, we have investigated the density and pattern of different nerve populations innervating sweat glands of ageing rats and compared our results with a previous study of the innervation of human sweat glands. We have also studied age-changes in subepidermal afferent nerves that may be involved in reflex activation of sweat glands. Total nerve density, measured by immunohistochemical staining for the general neuronal marker, protein gene product (PGP9.5) and image analysis, showed a significant decline around secretory coils of sweat glands of old compared to young rats. Marked reductions of acetylcholinesterase (AChE) histochemical staining and of vasoactive intestinal polypeptide (VIP)- and calcitonin gene-related peptide (CGRP)-like immunoreactivity were observed in nerves around sweat glands. In the sub-epidermis, PGP- and CGRP-like immunoreactive nerves were significantly reduced in old rats. The age-related changes in sweat gland innervation of old rats were comparable to those reported in elderly human subjects suggesting that these tissues may provide a suitable model for experimental studies of neuronal ageing.