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Hypertension and enhanced β‐adrenoceptor‐mediated facilitation of noradrenaline release produced by chronic blockade of adenosine receptors
Author(s) -
Guimarães S.,
AlbinoTeixeira A.,
Paiva M.Q.
Publication year - 1995
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1995.tb14944.x
Subject(s) - isoprenaline , endocrinology , medicine , phenoxybenzamine , stimulation , adenosine , facilitation , chemistry , propranolol , adenosine receptor , adrenergic receptor , receptor , norepinephrine , biology , agonist , neuroscience , dopamine
1 The study was undertaken to compare the β‐adrenoceptor‐mediated facilitation of noradrenaline release in the tail artery of vehicle‐treated rats and of rats rendered hypertensive by chronic administration of 1,3‐dipropyl‐8‐sulphophenylxanthine (DPSPX). Artery rings were loaded with [ 3 H]‐noradrenaline, and five periods of electrical stimulation (1 Hz for 2 min) were applied. To eliminate the influence of prejunctional α 2 ‐adrenoceptors, the tissues were pre‐exposed to 1 μm phenoxybenzamine. 2 Isoprenaline caused a concentration‐dependent increase of tritium overflow elicited by electrical stimulation. It was more effective in arteries from DPSPX‐treated than in those from vehicle‐treated rats; isoprenaline (27.8 nM) increased by 30% tritium overflow in vessels from vehicle‐treated rats whereas isoprenaline (7.0 nM) produced a 30% increase in vessels from DPSPX‐treated animals. Furthermore, the maximal effect of isoprenaline was a 32.6% increase in control rats but a 48.6% increase in DPSPX‐treated rats. 3 These results show that the sympathetic nerve endings of the rat tail artery are endowed with prejunctional β‐adrenoceptors which mediate facilitation of noradrenaline release elicited by electrical stimulation. They also suggest that adenosine receptors and β‐adrenoceptors interact at the prejunctional level and that impairment of this ‘talk’ may lead to the development of a hypertensive state.