Sympathetic vasodilation in the rat anterior choroid mediated by beta(1)-adrenoceptors.
Electrical stimulation of the preganglionic superior cervical nerve produced a frequency-dependent vasoconstrictor response in the anterior choroidal blood vessels of the eye of anesthetized rats. Systemic administration of phentolamine (5 mg kg(-1)) reversed the vasoconstriction to a vasodilator response. This sympathetic-evoked vasodilation was not antagonized by inhibition of nitric oxide synthase with N(G)-nitro-L-arginine methyl ester (L-NAME) (20 mg kg(-1)) or by inhibition of cyclo-oxygenase with indomethacin (20 mg kg(-1)). Intravenous administration of propranolol (1 mg kg(-1)), as well as selective beta(1)-adrenoceptor antagonists atenolol (3 mg kg(-1)), timolol (0.3 mg kg(-1)), and betaxolol (0.1 mg kg(-1)), totally abolished the sympathetic nerve evoked ocular vasodilation. In contrast, the selective beta(2)-adrenoceptor antagonist, ICI-118, 551 ((+/-)-1-[2, 3-(Dihydro-7-methyl-1H-inden-4-yl)oxy]-3-[(1-methylethyl)amino]-2- butanol) (0.3 mg kg(-1), i.v.), was without effect. These results support the conclusion that the residual sympathetic ocular vasodilation observed in the rat anterior choroid after alpha-adrenoceptor blockade is mediated exclusively by neurogenic release of norepinephrine acting on vascular beta(1)-adrenoceptors.
Kawarai
M
M
Department of Biosciences, Teikyo University of Science and Technology, Yamanashi, Japan.
Koss
M C
MC
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D058671:Adrenergic beta-1 Receptor Antagonists; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D002829:Choroid / Q000098:blood supply / Q000294:innervation / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D010646:Phentolamine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018342:Receptors, Adrenergic, beta-1 / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000502:physiology*; D014661:Vasoconstriction; D014664:Vasodilation / Q000187:drug effects
D000317:Adrenergic alpha-Antagonists; D058671:Adrenergic beta-1 Receptor Antagonists; D000319:Adrenergic beta-Antagonists; D004791:Enzyme Inhibitors; D018342:Receptors, Adrenergic, beta-1; D011433:Propranolol; D019331:NG-Nitroarginine Methyl Ester; D007213:Indomethacin; D010646:Phentolamine