title: An investigation of age-related changes in pre- and postjunctional alpha-adrenoceptors in human saphenous vein.
abstract: The responsiveness of prejunctional alpha 2-, postjunctional alpha 1- and postjunctional alpha 2-adrenoceptors was examined in human isolated saphenous veins from male patients in the age range 37-70. There was no age-related alteration in the prejunctional potency of the alpha 2-adrenoceptor agonist xylazine for inhibiting the stimulation-evoked overflow of tritium in tissues preincubated with [3H]noradrenaline. The alpha 2-adrenoceptor antagonist yohimbine (0.01-1 microM) and the alpha 1-adrenoceptor antagonist prazosin (0.1-1 microM) significantly reduced stimulation-evoked contractions in a concentration-dependent manner. There was no significant age-related correlation for the potency of prazosin but there was a significant negative correlation between the potency of yohimbine and age (r = 0.70, n = 11, P less than 0.05), i.e. the potency of yohimbine decreased with increasing age. The decreased postjunctional potency of yohimbine may reflect a loss of alpha 2-adrenoceptors with increasing age.
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D004558:Electric Stimulation; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D011224:Prazosin / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology*; D012501:Saphenous Vein / Q000187:drug effects / Q000502:physiology*; D014316:Tritium / Q000378:metabolism; D014661:Vasoconstriction / Q000187:drug effects; D014991:Xylazine / Q000494:pharmacology; D015016:Yohimbine / Q000494:pharmacology
chemical_list: D011942:Receptors, Adrenergic, alpha; D014316:Tritium; D014991:Xylazine; D015016:Yohimbine; D011224:Prazosin