Impaired function of alpha‐2 adrenoceptors in smooth muscle of mesenteric arteries from spontaneously hypertensive rats

• Published in: British journal of pharmacology Vol. 125; no. 6; pp. 1144 - 1149
• Main Authors: Feres, Teresa, Borges, Antonio Carlos R, Silva, Eneida G, Paiva, Antonio C M, Paiva, Therezinha B
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-11-1998; Nature Publishing
• Subjects: Adrenergic alpha-Agonists - pharmacology; Adrenergic alpha-Antagonists - pharmacology; Alpha‐2 adrenoceptors; Animals; Apamin - pharmacology; Arterial hypertension. Arterial hypotension; Biological and medical sciences; Biological Factors - physiology; Blood and lymphatic vessels; Brimonidine Tartrate; Cardiology. Vascular system; endothelium; Endothelium, Vascular - drug effects; Endothelium, Vascular - physiology; Enzyme Inhibitors - pharmacology; Experimental diseases; Female; Hypertension - physiopathology; In Vitro Techniques; Medical sciences; membrane potential; Membrane Potentials - drug effects; Membrane Potentials - physiology; mesenteric arteries; Mesenteric Arteries - drug effects; Mesenteric Arteries - physiopathology; Mesenteric Arteries - ultrastructure; Muscle, Smooth, Vascular - drug effects; Muscle, Smooth, Vascular - physiopathology; Muscle, Smooth, Vascular - ultrastructure; Nitric Oxide - physiology; Nitroarginine - pharmacology; potassium channels; Prazosin - pharmacology; Quinoxalines - pharmacology; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Receptors, Adrenergic, alpha-2 - drug effects; Receptors, Adrenergic, alpha-2 - physiology; spontaneously hypertensive rats; Hypertension; α2-Adrenergic receptor; Pathophysiology; Rat; Potassium ion; Rodentia; Electrophysiology; Cardiovascular disease; Smooth muscle; Ionic channel; Strain specificity; In vitro; Vertebrata; Mesenteric artery; Mammalia; Animal; Nitric oxide; Blood vessel; Genetics; Circulatory system; Endothelium derived relaxing factor; Membrane potential
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1038/sj.bjp.0702177

1
The α2‐adrenoceptor function in mesenteric arteries of spontaneously hypertensive rats (SHR) was investigated by comparing membrane potential changes in response to adrenergic agonists in preparations from female SHR, Wistar‐Kyoto (WKY) and normotensive Wistar rats (NWR).
2
Resting membrane potential was found to be less negative in mesenteric arteries from SHR than in those from NWR and WKY. Apamin induced a decrease in the membrane potential of mesenteric artery rings without endothelium from NWR and WKY, but had no effects in those from SHR. Both UK 14,304 and adrenaline, in the presence of prazosin, induced a hyperpolarization that was significantly lower in de‐endothelialized mesenteric rings from SHR than in those from NWR and WKY. In mesenteric rings with endothelium, however, similar hyperpolarization was observed in the three strains.
3
In NWR mesenteric rings with endothelium the hyperpolarization induced by activation of α2‐adrenoceptors was abolished by apamin, whereas in intact SHR mesenteric rings this hyperpolarization was slightly reduced by apamin and more efficiently reduced by Nω‐nitro‐l‐arginine.
4
It is concluded that the activity of potassium channels coupled to α2‐adrenoceptors is altered in the smooth muscle cells of SHR mesenteric arteries, contributing to their less negative membrane potential. On the other hand, the endothelial α2‐receptors are functioning in mesenteric vessels from SHR and their stimulation induces a hyperpolarization mainly through the release of nitric oxide.
British Journal of Pharmacology (1998) 125, 1144–1149; doi:10.1038/sj.bjp.0702177