Postjunctional alpha 2-adrenoceptors in blood vessels: effect of age.

To investigate the impact of age on function of vascular postjunctional alpha 2-adrenoceptors in tail arteries of F-344 rats aged 6 and 20 months, vasoconstrictor responses of isolated ring segments were studied. In both 6 and 20 months old animals, norepinephrine concentration response curves were significantly shifted to the right in the presence of the alpha 2-adrenoceptor antagonists idazoxan (300 nM) or rauwolscine (50 nM). Furthermore, in both age groups alpha 2-adrenoceptor agonists UK14304 (300 nM) or BHT920 (25 nM) produced significant enhancements in the vasoconstrictor response to the selective alpha 1-adrenoceptor agonist, methoxamine. Concentration response curves for norepinephrine and methoxamine were not different with age. These data verify the existence of postjunctional alpha 2-adrenoceptors and demonstrate that the function of these receptors does not change with age. This supports the proposition that overall vascular adrenergic function in blood vessels is maintained with advancing age.