Atypical beta-adrenoceptors in the rat isolated common carotid artery.
1. The possible existence of atypical beta-adrenoceptors in vascular smooth muscle of the rat common carotid artery was examined in this study. 2. Isoprenaline produced concentration-dependent relaxation of noradrenaline (10(-7) M) precontracted ring segments of the carotid artery. The relaxation was not affected by endothelial denudation. 3. Propranolol (10(-8) M-3 x 10(-7) M) shifted the isoprenaline curve to the right without suppressing the maximum response. However, the slope (0.74) of the Schild plot was significantly (P < 0.05) less than 1. 4. Salbutamol (beta 2), CGP 12177 and BRL 37344 (beta 3) also concentration-dependently relaxed noradrenaline precontracted artery segments. These relaxations were not affected by propranolol (10(-7) M). Pretreatment of the artery segments with BRL 37344 did not desensitize the tissue to the relaxant effect of isoprenaline, CGP 12177 and salbutamol. 5. It is concluded that atypical beta-adrenoceptors exist in vascular smooth muscle of the common carotid artery.
Department of Pharmacology & Toxicology, Faculty of Medicine, Kuwait University, Safat.
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Oriowo
D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000420:Albuterol / Q000494:pharmacology; D000818:Animals; D017536:Carotid Artery, Common / Q000187:drug effects* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004983:Ethanolamines / Q000494:pharmacology; D005260:Female; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D011412:Propanolamines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011943:Receptors, Adrenergic, beta / Q000032:analysis / Q000187:drug effects / Q000502:physiology*
D000318:Adrenergic beta-Agonists; D004983:Ethanolamines; D011412:Propanolamines; D011943:Receptors, Adrenergic, beta; C057368:BRL 37344; D007545:Isoproterenol; D000420:Albuterol; C033394:CGP 12177