Dopamine induces contraction in the proximal, but relaxation in the distal rat isolated small intestine.
Neurosci Lett
; 465(1): 21-6, 2009 Nov 06.
Article
de En
| MEDLINE
| ID: mdl-19733212
ABSTRACT
In the gut, dopamine is released by enteric neurons and modulates motility of small intestine smooth muscle cells. Here, we systematically analyzed the dopamine-induced effects on the longitudinal smooth muscle of different sections of the rat isolated small intestine. We found that exogenous dopamine had biphasic effects and could lead to both an early contraction and a late relaxation, depending on the region of small intestine. Thus, dopamine-induced early contractions were commonly observed in the duodenum, but less frequently in the jejunum, and rarely in the ileum. The amplitudes of these early contractions showed a striking regional dependence (duodenum>jejunum>ileum) and were significantly blocked by SCH23390 and raclopride. Conversely, dopamine-induced late relaxations were regularly obtained in the ileum and in the jejunum, but less frequently in the duodenum. Interestingly, the amplitudes of these relaxations showed an inverse regional dependence (ileum>jejunum>duodenum), and were insensitive to dopamine receptor antagonists. Rather, they were significantly inhibited by propranolol and prazosin. We conclude that dopamine exerts differential effects on smooth muscle motility in different regions within the rat small intestine. In proximal parts, dopamine predominantly causes D(1) and D(2) dopamine receptor-dependent contraction, whereas it leads to alpha and beta adrenoceptor-dependent relaxation in more distal parts.
Texte intégral:
1
Collection:
01-internacional
Base de données:
MEDLINE
Sujet principal:
Dopamine
/
Duodénum
/
Iléum
/
Jéjunum
/
Contraction musculaire
/
Muscles lisses
Limites:
Animals
Langue:
En
Journal:
Neurosci Lett
Année:
2009
Type de document:
Article
Pays d'affiliation:
Allemagne