The effect of age on the sensitivity of pre- and postsynaptic alpha-adrenoceptors to agonists and antagonists in the rat |
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Authors: | R. P. McAdams J. F. Waterfall |
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Affiliation: | (1) Department of Pharmacology, Wyeth Research (UK), Huntercombe Lane South, Taplow, SL6 0PH Maidenhead, Berkshire, UK;(2) Department of Biology, Roche Products Ltd, AL7 3AY Welwyn Garden City, Herts, UK |
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Abstract: | Summary Age-related changes in presynaptic alpha-2 and postsynaptic alpha-1 adrenoceptors have been determined using the rat isolated vas deferens and the thoracic aorta, respectively. The IC50 values of clonidine, B-HT 933 and UK 14,304 for inhibition of the electrically evoked contractions of the vas deferens were significantly higher in 50 week old rats when compared with rats of 5 weeks. Similarly, EC50 values for the contraction of the thoracic aorta by noradenaline, methoxamine and phenylephrine were significantly increased in 50 week old rats compared with 5 week old rats. No age-related changes in the potency of the selective alpha-2 adrenoceptor antagonists yohimbine and Wy 26392 were detected in the vas deferens. Similarly, there were no age-related changes in the alpha-1 adrenoceptor antagonist potency of indoramin or prazosin on the aorta.The results of the present study suggest that the potency of both alpha-1 and alpha-2 adrenoceptor agonists, as measured by their respective EC and IC50 values decreases with increasing age. |
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Keywords: | Age Presynaptic alpha-adrenoceptors Post-synaptic alpha-adrenoceptors Rat vas deferens Rat thoracic aorta |
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