POSTJUNCTIONAL ALPHA-2-ADRENOCEPTORS IN BLOOD-VESSELS - EFFECT OF AGE

To investigate the impact of age on function of vascular postjunctiona l a2-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 month old animals, norepinephrine concentration respons e curves were significantly shifted to the right in the presence of th e alpha2-adrenoceptor antagonists idazoxan (300 nM) or rauwolscine (50 nM). Furthermore, in both age groups alpha2-adrenoceptor agonists UK1 4304 (300 nM) or BHT920 (25 nM) produced significant enhancements in t he vasoconstrictor response to the selective alpha1-adrenoceptor agoni st, methoxamine. Concentration response curves for norepinephrine and methoxamine were not different with age. These data verify the existen ce of postjunctional alpha2-adrenoceptors and demonstrate that the fun ction of these receptors does not change with age. This supports the p roposition that overall vascular adrenergic function in blood vessels is maintained with advancing age.