Capsaicin-induced nitric-oxide-dependent relaxation in isolated dog urethra.
Capsaicin (5 x 10[-8] to 5 x 10[-5] M) produced a non-adrenergic and non-cholinergic phasic relaxation in a concentration-dependent manner in isolated dog urethral preparations precontracted by noradrenaline. The mode of action of capsaicin was investigated with special reference to the possible involvement of endogenous nitric oxide (NO). A marked tachyphylaxis was observed in the responses to capsaicin. Pretreatment with NG-nitro-L-arginine-methyl-ester (L-NAME) prevented or markedly reduced the inhibitory effect of L-NAME. Methylene blue inhibited the capsaicin-induced relaxation. In preparations stored at 4 degrees C for 72 h, the reduction in the capsaicin-induced relaxation was significantly greater than that in the relaxation induced by either electrical field stimulation or by sodium nitroprusside. We conclude that capsaicin produces an endogenous-NO-dependent relaxation in the isolated dog urethra via mechanisms that deteriorate during cold storage of the preparations.
Nishizawa
S
S
The First Department of Physiology, Shinshu University School of Medicine, Asahi, Matsumoto, Japan.
Igawa
Y
Y
Okada
N
N
Ohhashi
T
T
D000818:Animals; D002211:Capsaicin / Q000494:pharmacology*; D003080:Cold Temperature; D004285:Dogs; D004558:Electric Stimulation; D005260:Female; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009126:Muscle Relaxation / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000294:innervation / Q000502:physiology*; D009479:Neuropeptides / Q000494:pharmacology / Q000502:physiology; D009569:Nitric Oxide / Q000502:physiology*; D009599:Nitroprusside / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology / Q000502:physiology; D014521:Urethra / Q000294:innervation / Q000502:physiology*; D019459:Urothelium / Q000502:physiology; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology / Q000502:physiology; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology
D009479:Neuropeptides; D010446:Peptide Fragments; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D009599:Nitroprusside; D009569:Nitric Oxide; D014660:Vasoactive Intestinal Peptide; C047945:vasoactive intestinal peptide (10-28); D002211:Capsaicin; D009638:Norepinephrine