Role of nitric oxide in mediating non-adrenergic non-cholinergic relaxation of the cat ileocecal sphincter.
The participation of nitric oxide (NO) in field stimulation- or nicotine-evoked non-adrenergic non-cholinergic (NANC) relaxation of cat ileocecal sphincter was studied in vitro. During a 30 microM noradrenaline-induced contraction, both the application of electrical field stimulation (2-20 Hz, 0.2 ms, supramaximal current intensity, 10 s duration) and (-)-nicotine (10-500 microM) produced a tetrodotoxin-sensitive relaxation. The maximal relaxation was observed at 10 Hz or 100 microM (-)-nicotine. In 12 out of 19 strips the pretreatment with N omega-nitro-L-arginine (100 microM) decreased the amplitude of the field stimulation-evoked relaxation, while in the remaining strips the relaxation was transformed into a contraction. By increasing the concentration of N omega-nitro-L-arginine up to 1 mM all strips responded to field stimulation with a frequency-dependent tetrodotoxin-resistant contraction. N omega-Nitro-L-arginine (100 microM) completely inhibited the nicotine-induced relaxation. L-Arginine (1 mM) restored the amplitude of both field stimulation- and nicotine-evoked relaxations. These data indicate that NO appears to be involved in both field stimulation- and nicotine-evoked NANC relaxations. Evidence has been obtained for the existence of tetrodotoxin-resistant NANC contraction in cat ileocecal sphincter.
Mizhorkova
Z
Z
Department of Vegetative Regulations, Bulgarian Academy of Sciences, Sofia.
Kortezova
N
N
Bredy-Dobreva
G
G
Papasova
M
M
D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives* / Q000494:pharmacology; D002415:Cats; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D007080:Ileocecal Valve / Q000187:drug effects* / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009126:Muscle Relaxation / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects* / Q000502:physiology; D009538:Nicotine / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism / Q000502:physiology*; D019335:Nitroarginine; D009638:Norepinephrine / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology
D019335:Nitroarginine; D009569:Nitric Oxide; D013779:Tetrodotoxin; D009538:Nicotine; D001120:Arginine; D009638:Norepinephrine