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- Title
Alteration in α- and β- adrenoceptor profile of rabbit-knee-joint blood vessels due to chronic inflammation.
- Authors
Najafipour, Hamid; Niazmand, Saeid
- Abstract
Experiments were performed to investigate the nature of α- and β-adrenoceptors in blood vessels supplying the posterior capsule of the chronically inflamed rabbit knee joint, and results were compared to the finding from previous experiments on the normal and acutely inflamed joint to assess any alteration which may occur in the adrenoceptor profile due to the chronic inflammation process. Electrical stimulation of the posterior articular nerve resulted in vasoconstriction that was completely blocked by phentolamine. This constrictor response was almost equally inhibited by prazosin and yohimbine. The dose–response curves to close intraarterial injection of α-adrenoceptor agonists showed a rank-order potency of adrenaline = clonidine = phenylephrine. The adrenaline dose–response curve was shifted to the right by administration of α-antagonists with a rank-order potency of phentolamine = prazosin = yohimbine. At this stage of experiments, there was an equal response of α1- and α2- adrenoceptors in blood vessels of the chronically inflamed rabbit knee joint. In another group of animals, the neurally mediated vasodilatation, which appeared after administration of phentolamine, was completely blocked by propranolol and was reduced significantly by ICI118551, but the effect of atenolol was not significant. The dose–response curve to close intraarterial injection of β-adrenoceptor agonists showed a rank-order potency of: isoprenaline > salbutamol > dobutamine. The isoprenaline dose–response curve was shifted to the right by administration of β-antagonists with rank-order potency of propranolol > ICI118551 > atenolol. These experiments showed a greater β2-adrenoceptor response than β1-adrenoceptor response in chronically inflamed rabbit-knee-joint blood vessels. Overall, compared to previous experiments on normal joint in which α2- and β1-adrenoceptor responses predominated, and in acutely inflamed joint in which an equal α1/α2 and β1/β2 response was shown, in chronically inflamed joint the sympathetic constriction response was returned toward normal. No more α-adrenoceptor shift had happened, and the shift of β1 to β2 response continued.
- Subjects
ADRENERGIC receptors; KNEE; BLOOD vessels; INFLAMMATION; CATECHOLAMINES; NEUROTRANSMITTERS
- Publication
Pflügers Archiv: European Journal of Physiology, 2006, Vol 453, Issue 1, p23
- ISSN
0031-6768
- Publication type
Article
- DOI
10.1007/s00424-006-0105-2