Moxonidine, an antihypertensive agent, is permissive to alpha1-adrenergic receptor pathway in the rat-tail artery.
To investigate whether alpha1-adrenergic receptors were involved in the contractile response of tail arteries to moxonidine, isolated ring segments of tail arteries from male adult Sprague-Dawley rats were studied. Moxonidine (EC50 = 1.3 microM) and the alpha1-agonist phenylephrine (EC50 = 2.5 microM) increased tension development in the rat-tail artery similarly. The response to moxonidine (1 microM) could be blocked by both alpha1-adrenoceptor blockers prazosin (IC50 = 1 nM), and urapidil (IC50 = 14 nM), and also by alpha2-adrenoceptor blockers, yohimbine (IC50 = 49 nM) and efaroxan (IC50 = 49 nM). Combination drug treatment (urapidil and yohimbine, or yohimbine and prazosin) was more effective in blocking the contractile response to moxonidine, than treatment with prazosin or urapidil alone. Comparison of pA2 values for prazosin in the presence of moxonidine (9.35) or phenylephrine (10.2) confirm that alpha1-adrenergic receptors are involved in the contractile response of rat-tail artery to moxonidine.
George
Oommen K
OK
Department of Physiology and Pharmacology, Loma Linda University, School of Medicine, Loma Linda, California 92354, USA.
Gonzalez
Ramon R
RR
Edwards
Lincoln P
LP
D058668:Adrenergic alpha-1 Receptor Antagonists; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology*; D004347:Drug Interactions; D007093:Imidazoles / Q000494:pharmacology*; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D010879:Piperazines / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014661:Vasoconstriction / Q000187:drug effects*; D015016:Yohimbine / Q000494:pharmacology
D058668:Adrenergic alpha-1 Receptor Antagonists; D000959:Antihypertensive Agents; D007093:Imidazoles; D010879:Piperazines; D015016:Yohimbine; C015568:urapidil; C043482:moxonidine; D011224:Prazosin