Blockade of ATP-sensitive potassium channels prevents the attenuation of the exercise pressor reflex by tempol in rats with ligated femoral arteries.
We reported previously that tempol attenuated the exercise pressor and muscle mechanoreceptor reflexes in rats whose femoral arteries were ligated, whereas tempol did not attenuate these reflexes in rats whose femoral arteries were freely perfused. Although the mechanism whereby tempol attenuated these reflexes in rats whose femoral artery was ligated was independent of its ability to scavenge reactive oxygen species, its nature remains unclear. An alternative explanation for the tempol-induced attenuation of these reflexes involves ATP-sensitive potassium channels (K(ATP)) and calcium-activated potassium channels (BK(Ca)), both of which are opened by tempol. We tested the likelihood of this explanation by measuring the effects of either glibenclamide (0.1 mg/kg), which blocks K(ATP) channels, or iberiotoxin (20 or 40 μg/kg), which blocks BK(Ca) channels, on the tempol-induced attenuation of the exercise pressor and muscle mechanoreceptor reflexes in decerebrated rats whose femoral arteries were ligated. We found that glibenclamide prevented the tempol-induced attenuation of both reflexes, whereas iberiotoxin did not. We also found that the amount of protein comprising the pore of the K(ATP) channel in the dorsal root ganglia innervating hindlimbs whose femoral artery was ligated was significantly greater than that in the dorsal root ganglia innervating hindlimbs whose femoral arteries were freely perfused. In contrast, the amounts of protein comprising the BK(Ca) channel in the dorsal root ganglia innervating the ligated and freely perfused hindlimbs were not different. We conclude that tempol attenuated both reflexes by opening K(ATP) channels, an effect that hyperpolarized muscle afferents stimulated by static contraction or tendon stretch.
Pennsylvania State Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, USA.
Katsuya
K
Yamauchi
Audrey J
AJ
Stone
Sean D
SD
Stocker
Marc P
MP
Kaufman
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D015153:Blotting, Western; D003497:Cyclic N-Oxides / Q000008:administration & dosage / Q000494:pharmacology*; D003655:Decerebrate State; D005263:Femoral Artery / Q000601:surgery*; D005727:Ganglia, Spinal / Q000187:drug effects* / Q000378:metabolism; D005905:Glyburide / Q000494:pharmacology*; D006339:Heart Rate / Q000187:drug effects; D007269:Injections, Intra-Arterial; D054086:KATP Channels / Q000187:drug effects* / Q000378:metabolism; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / Q000187:drug effects / Q000378:metabolism; D008026:Ligation; D008297:Male; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000294:innervation*; D010455:Peptides / Q000494:pharmacology; D026902:Potassium Channel Blockers / Q000494:pharmacology*; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012018:Reflex / Q000187:drug effects*; D013113:Spin Labels; D013997:Time Factors; D000099161:Kcnj11 Channel
D003497:Cyclic N-Oxides; D005905:Glyburide; D054086:KATP Channels; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D010455:Peptides; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D013113:Spin Labels; D000099161:Kcnj11 Channel; C494842:Kcnma1 protein, rat; C092520:uK-ATP-1 potassium channel; C064719:iberiotoxin; C001803:tempol