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Dopamine induces contraction in the proximal, but relaxation in the distal rat isolated small intestine.
- Source :
-
Neuroscience letters [Neurosci Lett] 2009 Nov 06; Vol. 465 (1), pp. 21-6. Date of Electronic Publication: 2009 Sep 03. - Publication Year :
- 2009
-
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.
- Subjects :
- Adrenergic alpha-Antagonists pharmacology
Adrenergic beta-Antagonists pharmacology
Animals
Benzazepines pharmacology
Dopamine Antagonists pharmacology
Duodenum drug effects
Ileum drug effects
In Vitro Techniques
Jejunum drug effects
Male
Muscle Contraction drug effects
Muscle Relaxation drug effects
Muscle Relaxation physiology
Muscle, Smooth drug effects
Prazosin pharmacology
Propranolol pharmacology
Raclopride pharmacology
Rats
Rats, Wistar
Time Factors
Dopamine metabolism
Duodenum physiology
Ileum physiology
Jejunum physiology
Muscle Contraction physiology
Muscle, Smooth physiology
Subjects
Details
- Language :
- English
- ISSN :
- 1872-7972
- Volume :
- 465
- Issue :
- 1
- Database :
- MEDLINE
- Journal :
- Neuroscience letters
- Publication Type :
- Academic Journal
- Accession number :
- 19733212
- Full Text :
- https://doi.org/10.1016/j.neulet.2009.08.080