Characterization of nerve-induced relaxation of gastrointestinal sphincteric smooth muscle in a South American opossum (Didelphis albiventris)
Rev. bras. pesqui. méd. biol
; Braz. j. med. biol. res;30(6): 793-9, jun. 1997. ilus, graf
Article
em En
| LILACS
| ID: lil-194182
Biblioteca responsável:
BR1.1
RESUMO
The presence of inhibitory nonadrenergic noncholinergic (NANC) intrinsic innervation of the circular muscle of the gastrointestinal sphincters of the South American (SA) opossum was investigated in vitro. Isolated circular muscle strips from the esophagogastric and ileocolonic junctions but not from the gastroduodenal (pylorus) region developed spontaneous tension. Tetrodotoxin (TTX, 1 muM) augmented the spontaneous tension only in the ileocolonic junction strips. Electrical field stimulation of esophagogastric and ileocolonic junction strips caused frequency-dependent responses consisting of a relaxation at lower frequencies (<1 Hz) and a biphasic response or contraction at higher frequencies. In the strips from the pyloric region electrical field stimulation abolished the spontaneous activity at lower frequencies and induced contractions at higher frequencies. The responses elicited by electrical field stimulation in the three sphincters were abolished by TTX (1 muM). Electrical field-induced contractions were reduced while relaxations were enhanced by atropine (1 muM). In the presence of atropine (1 muM) and guanethidine (3 muM), electrical field stimulation, nicotine and ATP induced frequency-or concentration-dependent relaxations of the three sphincters that were abolished by TTX (1 muM). Isoproterenol and sodium nitroprusside caused concentration-dependent relaxations which were TTX-resistant. These findings indicate that the sphincteric circular muscle of the SA opossum gastrointestinal tract is relaxed by the activation of intrinsic NANC nerves and therefore can be used as a model for the study of the mechanisms involved in these responses.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
LILACS
Assunto principal:
Gambás
/
Piloro
/
Atropina
/
Tetrodotoxina
/
Técnicas In Vitro
/
Estimulação Elétrica
/
Junção Esofagogástrica
/
Guanetidina
/
Isoproterenol
/
Relaxamento Muscular
Tipo de estudo:
Prognostic_studies
Limite:
Animals
País/Região como assunto:
America do sul
Idioma:
En
Revista:
Braz. j. med. biol. res
/
Rev. bras. pesqui. méd. biol
Assunto da revista:
BIOLOGIA
/
MEDICINA
Ano de publicação:
1997
Tipo de documento:
Article
/
Project document
País de publicação:
Brasil