Age-related Changes In Pre-aortic Ganglion Cells Of The Rat

The age-related changes in morphology and numerical distribution of rat pre-aortic (celiac andrnsuperior mesenteric) ganglia were studied using histological techniques and stereologicalrnanalysis.rnThe pre-aortic ganglia from developing rats of embryonic days 16, 18, 20, postnatal days 1, 4, 7,rn14, 21, adult rats of 4 months and ageing rats of 24 months were dissected out, immersion fixed,rnprocessed using standard histological technique and paraffin sectioned. The sections were stainedrnwith toluidine blue and analyzed with light microscope.rnThe pre-aortic ganglia were seen as a ganglionic mass which were surrounded by a thick capsule.rnEach ganglionic mass was composed of three types of cells: neurons, glial cells or satellite cellsrnand small granular cells. The size of pre-aortic neurons, which was estimated from the meanrndiameter of neurons, was observed to increase progressively with increasing age. This incrementrnranged from 4.0 μm at embryonic day 16 to 21.2 μm at ageing with mean of 5.5 - 16.5 and SEMrn0.23 - 0.49. In addition, the change in the shape of pre-aortic neurons was estimated from thernratios of the long axis to the short axis. This coefficient of cell shape ranged from 1.0 μm atrnembryonic day 16 to 2.3 at ageing with mean of 1.3 - 1.7 and SEM of 0.04 - 0.07.rnStereological estimation of the volume of the ganglia employing the cavalieri principle showedrnthat the size of pre-aortic ganglia progressively increased with increasing age. The progressivernincrement in the volume was uniform at postnatal day 1 to 21, but the percentage incrementrnbetween 21st day and 4th month and between 4th month and 24th month was 66% and 73%,rnrespectively, for CG and 68% and 67%, respectively, for SMG. The numerical density (numberrnof neurons per unit volume) estimated by a physical dissector analysis, progressively decreasedrnwith increasing age. The progressive decrement observed was uniform at postnatal day 1 upto 21rnbut the percentage decrement was 75% for CG, 78% for SMG between 21st day and 4th monthrnand 66% for both CG and SMG between 4th month and 24th month. However, there was nornsignificant difference among the total number of neurons found in the pre-aortic ganglia at therndifferent age groups. In addition, the volume fraction of neurons which was estimated from thernratio of neurons within the ganglia, showed a progressive decrease with increasing age. Thisrndecrement was uniform at postnatal day 1 to 21, but the percentage decrement was 63% for bothrnCG & SMG between 21st day and 4th month and 76% for CG, 85% for SMG between 4th monthrnand 24th month. Furthermore, the total volume of pre-aortic neurons progressively increased fromrnpostnatal day 1 upto adult, but the mean volume increased from 0.059 to 0.066 mm3 for CG andrnfrom 0.058 to 0.064 mm3 for SMG from adult to ageing.rnIt is concluded that the rat pre-aortic ganglia reveals changes in the morphology and numericalrndistribution of neurons during development, during adulthood and ageing. These age-relatedrnchanges may be due to the increased amount of interstitial connective tissue and the accumulationrnof lipofuscin granules (age-pigments). In addition, the changes may indicate the functions of thernpre-aortic ganglia target organs, which includes stomach, intestine and accessory glands (liverrnand pancreas).rnKey Words: Pre-aortic ganglia; celiac ganglia; superior mesenteric ganglia; extracellular matrix;rndevelopment; ageing; morphology; stereology

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