An examination of age-related changes in pre- and postsynaptic alpha-adrenoceptors in the rat isolated vas deferens

Age-related changes in pre- and postsynaptic alpha-adrenoceptors were investigated in prostatic and epididymal portions of vasa deferentia from young adult (2-3 month) and 24 month old Sprague-Dawley rats, using the selective alpha 1-agonist amidephrine and the selective alpha 2-agonist xylazine. Effects of agonists were assessed against the isometric contraction to single pulse field stimulation. There was no change in the pre- or postsynaptic potency of amidephrine, but the presynaptic inhibitory potency of xylazine was significantly reduced in old rats. Therefore, in old rats there is a reduced sensitivity of presynaptic alpha 2- but no change in pre- or postsynaptic alpha 1-adrenoceptors and this may result in increased peripheral sympathetic neurotransmission.