Inhibitory effects of potassium channel blockers on tetramethylpyrazine-induced relaxation of rat aortic strip in vitro.
Tetramethylpyrazine (TMP) is one of the active principles contained in Ligusticum chuanxiong Hort. (Umbelliferae), a herb that has been widely used to treat vascular disorders in China. In the present study, role of potassium channel in the vasodilatation of TMP was investigated using the effect of potassium channel blocker on TMP induced relaxation in isolated aortic rings from Wistar rats. TMP produced a concentration-dependent relaxation in the aortic rings precontracted with vasopressin or phenylephrine. Similar effect of TMP on vasoconstrictions by phenylephrine and vasopressin, induced through two different receptors, indicating the direct vasodilatation of TMP. Specific inhibitors for potassium channel were used to characterize the role of potassium channel in this action of TMP. Only the inhibitors specific to small conductance calcium-activated potassium (SK(Ca)) channel or ATP-sensitive potassium (K(ATP)) channel inhibited the action of TMP. Also, the TMP-induced relaxation was reversed by the inhibitor of soluble guanylyl cyclase in a way similar to that of K(ATP) channel blockade. The obtained results indicated that vasodilatation induced by TMP is related to the opening of SK(Ca) and K(ATP) channels.
Tsai
Chin-Chuan
CC
Department of Traditional Medicine, School of Post-Baccalaureate Chinese Medicine, China Medical College, Taichung City 40401, Taiwan.
Lai
Tung-Yuan
TY
Huang
Wei-Chan
WC
Liu
I-Min
IM
Cheng
Juei-Tang
JT
D000818:Animals; D001011:Aorta / Q000187:drug effects* / Q000378:metabolism; D001030:Apamin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004365:Drugs, Chinese Herbal; D004730:Endothelium, Vascular / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005905:Glyburide / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D010069:Oxadiazoles / Q000494:pharmacology; D020110:Pinacidil / Q000494:pharmacology; D026902:Potassium Channel Blockers / Q000494:pharmacology*; D015221:Potassium Channels / Q000378:metabolism*; D011719:Pyrazines / Q000494:pharmacology*; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D014661:Vasoconstriction / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects*; D014665:Vasodilator Agents / Q000494:pharmacology*
C095284:1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one; D004365:Drugs, Chinese Herbal; D004791:Enzyme Inhibitors; D010069:Oxadiazoles; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D011719:Pyrazines; D011810:Quinoxalines; D014665:Vasodilator Agents; D001030:Apamin; D020110:Pinacidil; D005905:Glyburide; C017953:tetramethylpyrazine