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KMID : 0811720000040060463
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Korean Journal of Physiology & Pharmacology
2000 Volume.4 No. 6 p.463 ~ p.470
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Relaxant Effect of 4-Aminopyridine on the Mesenteric Artery of Rat
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Se-Hoon Kim/Se-Hoon Kim
Tae-Im Lee
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Abstract
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It has been well known that 4-aminopyridine (4-AP) has an excitatory effect on vascular smooth muscle due to causing membrane depolarization by blocking K+?channel. However, we observed that 4-AP had an inhibitory effect on the mesenteric artery of rat. Therefore, we investigated the mechanism of 4-AP-induced vasorelaxation. The mesenteric arcuate artery and its branches were isolated and cut into ring. The ring segment was immersed in HEPES-buffered solution and its isometric tension was measured. 4-AP (0.1∼10mM) induced a concentration-dependent relaxation, which was unaffected by NO synthase inhibitor, NG?nitro?L?arginine methylester (100μM) or soluble guanylate cyclase inhibitor, methylene blue (100μM). Glibenclamide (100μM), ATP-sensitive K+ channel blocker, did not exert any effect on the 4-AP-induced vasorelaxation. 4-AP relaxed the sustained contraction induced by 100 mM K+ or Ca2+ ionophore, A23187 (100μM) in a dose-dependent manner. In addition, 4-AP significantly decreased the phasic contractile response to norepinephrine in the absence of extracellular Ca2+. However, 4-AP did not block the 45Ca influx of rat aorta. From the above results, we suggest that 4-AP may not block the Ca2+ influx through Ca2+?channel, but act as a nonspecific vasorelaxant in arterial smooth muscle.
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KEYWORD
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Mesenteric artery, 4-aminopyridine, Vasorelaxation,
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