Superoxide anion and K+ channels mediate electrical stimulation-induced relaxation in the rat basilar artery.
Electrical field stimulation (a single pulse, 0.2 ms) caused a rapid relaxation of rat basilar artery segments precontracted with different agents, but not with 30 mM KCl. This relaxation was not modified by endothelium removal, 10 microM tetrodotoxin, 1 microM propranolol, 1 microM atropine, 30 microM indomethacin, 10 microM methylene blue, 100 microM N(G)-nitro-L-arginine methyl ester or 1 microM cimetidine but it was significantly reduced by 50 and 100 U/ml superoxide dismutase. Charybdotoxin (0.1 and 0.2 microM), a blocker of large-conductance Ca2+-activated K+ channels (BK(Ca)), decreased the relaxation elicited by electrical stimulation, whereas it was unaltered by 10 microM glibenclamide or 1 microM apamin, blockers of ATP-sensitive (K(ATP)) or small-conductance K(Ca) channels, respectively. Thapsigargin (0.01 and 0.1 microM), an inhibitor of sarcoplasmic reticulum Ca2+-ATPase, increased the electrical stimulation-induced relaxation, which was nearly abolished by charybdotoxin. These results show that electrical stimulation induces endothelium-independent and non-neurogenic relaxations in the rat basilar artery. This response appears to involve generation of superoxide anion, increase of cytosolic free Ca2+ concentration and subsequent activation of BK(Ca) channels.
Departamento de Fisiología, Facultad de Medicina, Universidad, Autónoma, Madrid, Spain.
M V
MV
Conde
J
J
Marín
G
G
Balfagón
D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D001488:Basilar Artery / Q000187:drug effects / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D004558:Electric Stimulation; D009569:Nitric Oxide / Q000378:metabolism; D009638:Norepinephrine / Q000378:metabolism; D015221:Potassium Channels / Q000502:physiology*; D051381:Rats; D013481:Superoxides / Q000378:metabolism*; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology
D015221:Potassium Channels; D014665:Vasodilator Agents; D013481:Superoxides; D009569:Nitric Oxide; D000109:Acetylcholine; D002118:Calcium; D009638:Norepinephrine