Abstract
The present study was designed to investigate the influence of aging on noradrenaline content and the density and pattern of prejunctional dopamine D 2 receptors in the tail (ventral caudal) artery of male Sprague-Dawley rats. Tail artery is frequently used as a model for investigating mechanisms of sympathetic vascular control and contains prejunctional dopamine receptor belonging to the D 2 subtype. Noradrenaline levels were reduced in rats of 12 months of age in comparison with 3-month-old animals. A further reduction in catecholamine concentration was found in 24-month-old rats. The density of prejunctional D 2 receptors, which was measured in frozen sections of the tail artery by using both radioligand binding and autoradiographic techniques, was reduced by about 35% in 12-month rats in comparison with 3-month rats. A decrease by about 55% versus 3-month rats and by about 20% versus 12-month rats was observed in 24-month-old rats. Neither the pharmacological profile nor the anatomical localization of prejunctional D 2 receptors was changed in the rat tail artery as a function of age. The parallel decrease in noradrenaline content and in the density of prejunctional dopamine D 2 receptor sites in the tail artery of Sprague-Dawley rats of different ages probably accounts for the lack of an age-related change of prejunctional dopamine D 2 receptor-linked responses reported in functional studies.
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