Morphometric analyses of the neurons and microvessels of
perfusion-fixed hypogastric (HG) and 13th thoracic (T13) ganglia have
been performed in male Wistar rats aged 4, 24 and 30 mo. Estimations of
HG volume employing the Cavalieri principle have also been performed
and showed that the size of the aged HG is increased by 42%. Routine
histological staining of the ganglia with Masson's trichrome
indicated that this may be due to the increased amount of interstitial
connective tissue which was apparent in the aged animals. The number of
neurons per unit area progressively decreased by 38% between ages 4 and
24 mo and by 16% between ages 24 and 30 mo in the HG and by 25% (4 and
24 mo) and 2% (24 and 30 mo) in the T13 ganglion. The total number of
neurons in the HG however, estimated by a physical disector analysis,
was constant with age. The number of microvessels per unit area,
microvessel diameter, neuronal and nuclear areas did not differ
significantly between the 3 age groups studied. This observed increase
in ganglionic volume and decrease in neuronal packing density may be
associated with changes in the extracellular matrix, in particular in
glycosaminoglycans whose presence was indicated by metachromasia of the
ganglia with toluidine blue. The extracellular matrix was therefore
characterised using a panel of monoclonal antibodies against
glycosaminoglycans and laminin. Chondroitin-6 sulphate and
chondroitin-4 sulphate were present in the interstitial connective
tissue, and there was an increase in the expression of both these
epitopes at 24 mo, noteably surrounding neuron cell bodies. The
expression of chondroitin-4 sulphate/dermatan sulphate was
unchanged, thus implying a decreased expression of dermatan sulphate
with age. Keratan sulphate and the native chondroitin sulphate epitopes
were absent from the ganglia at both ages. Laminin expression was
increased in the aged ganglia. It is therefore clear that the
constituents of the extracellular matrix are not constant throughout
the adult lifespan and that the extracellular matrix may influence
neuronal survival in old age. This is the first report characterising
age-related changes in the extracellular matrix of autonomic
ganglia.