Submitted on July 8, 2002
Accepted on June 9, 2003
SOURCES AND IMPLICATIONS OF BASAL NITRIC OXIDE IN SPONTANEOUS CONTRACTIONS OF GUINEA-PIG TAENIA CAECI
Catalina Caballero-Alomar1*, Carmen Santos1, Diego Lopez2, Maria Teresa Mitjavila2, and Pere Puig-Parellada1
1 Unitat de Farmacologia, Facultat de Medicina, Universitat de Barcelona, Barcelona, Barcelona, Spain
2 Departament de Fisiologia, Facultat de Biologia, Universitat de Barcelona, Barcelona, Barcelona, Spain
* To whom correspondence should be addressed. E-mail: catalina{at}medicina.ub.es.
We examined in vitro the source and role of basal nitric oxide (NO) in proximal segments of guinea-pig taenia caeci in non-adrenergic - non-cholinergic (NANC) conditions. We measured the effect of the NO synthase inhibitor, NG-nitro-L-arginine methylester (L-NAME, 10-4 M) and a neuronal blocker, tetrodotoxin (TTX, 10-6 M) or both, on spontaneous contractions and on the production of basal NO by electron paramagnetic resonance (e.p.r.). Both L-NAME and TTX, when tested alone, increased the amplitude and frequency of contractions. NO production was abolished by L-NAME, and 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, the NO production was inhibited in both cases. These findings suggest that basal NO consists of a 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.
