T. Cowen et al., TRANSPLANTED SWEAT GLANDS FROM MATURE AND AGED DONORS DETERMINE CHOLINERGIC PHENOTYPE AND ALTERED DENSITY OF HOST SYMPATHETIC-NERVES, Journal of the autonomic nervous system, 58(3), 1996, pp. 153-162
Contact with sweat gland acini causes sympathetic neurons to switch fr
om a catecholaminergic to a cholinergic phenotype during development a
nd following experimental manipulations. Substantial reductions of cho
linergic innervation have been shown in the sweat glands of ageing rat
s and humans. Using in oculo transplantation, we have now studied whet
her sweat gland target tissues retain the capacity to regulate changes
in the phenotype of sympathetic neurons observed in maturity and old
age, including a switch from catecholaminergic to cholinergic characte
rs. Markers have been used which indicate changes in nerve fibre morph
ology (the pan-neuronal marker, PGP9.5) as well as neurotransmitter ex
pression (acetylcholinesterase (AChE), vasocative intestinal polypepti
de (VIP) and tyrosine hydroxylase (TH)). Sweat glands from young and o
ld donor rats became reinnervated by an organotypic pattern of choline
rgic host nerves. Surgical sympathectomy demonstrated that these choli
nergic nerve fibres originate from sympathetic neurons of the host sup
erior cervical ganglion (SCG), Retrograde tracing combined with staini
ng for VIP (a marker associated with cholinergic phenotype in neurons
supplying sweat glands) showed that SCG neurons projecting to irises w
ith sweat gland implants may be induced to express VIP. We hypothesise
that these neurons have been switched from their normal catecholamine
rgic phenotype to a cholinergic one by contact with the sweat gland im
plants. Transplants from old donors attracted a density of reinnervati
on by young host nerves which was appropriate to the age of the donor,
thus old sweat glands received a significantly reduced density of inn
ervation compared to young glands. Despite the reduced density of inne
rvation, there was no obvious difference in the ability of young and o
ld implants to induce the switch to a cholinergic phenotype, suggestin
g that different mechanisms regulate nerve growth and neurotransmitter
phenotype.