Sources and implications of basal nitric oxide in spontaneous contractions of guinea pig taenia caeci.
We examined in vitro the source and role of basal nitric oxide (NO) in proximal segments of guinea pig taenia caeci in nonadrenergic, noncholinergic (NANC) conditions. Using electron paramagnetic resonance (EPR), we measured the effect of the NO synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME, 10(-4) M), the neuronal blocker tetrodotoxin (TTX, 10(-6) M), or both on spontaneous contractions and on the production of basal NO. Both L-NAME and TTX, when tested alone, increased the amplitude and frequency of contractions. NO production was abolished by L-NAME and was inhibited by 38% by TTX. When tested together, L-NAME in the presence of TTX or TTX in the presence of L-NAME had no further effect on the amplitude or frequency of spontaneous contractions, and the NO production was inhibited. These findings suggest that basal NO consists of TTX-sensitive and TTX-resistant components. The TTX-sensitive NO has an inhibitory effect on spontaneous contractions; the role of TTX-resistant NO is unknown.
Caballero-Alomar
Catalina
C
Unitat de Farmacologia, Facultat de Medicina, Universitat de Barcelona, Spain. catalina@medicina.ub.es
Santos
Carmen
C
Lopez
Diego
D
Mitjavila
M Teresa
MT
Puig-Parellada
Pere
P
D000818:Animals; D003106:Colon / Q000502:physiology*; D004578:Electron Spin Resonance Spectroscopy; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006168:Guinea Pigs; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000502:physiology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000502:physiology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D009599:Nitroprusside / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology
D004791:Enzyme Inhibitors; D020030:Nitric Oxide Donors; D009599:Nitroprusside; D009569:Nitric Oxide; D013779:Tetrodotoxin; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester