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In vitro effects of bethanechol on equine gastrointestinal contractility and functional characterization of involved muscarinic receptor subtypes

2005; Wiley; Volume: 28; Issue: 6 Linguagem: Inglês

10.1111/j.1365-2885.2005.00693.x

1365-2885

Mariana Marti, Meike Mevissen, Hans H. Althaus, Adrian Steiner,

Asthma and respiratory diseases

The goal of this study was to investigate the effect of bethanechol (BeCh) on contractility patterns of smooth muscle preparations of equine duodenum descendens, jejunum, caecum and pelvic flexure in vitro . Concentration–response relationships were developed for BeCh using in vitro assays with and without preincubation of muscarinic (M) receptor antagonists for M 2 and M 3 receptors. BeCh induced a significant, concentration‐dependent increase in contractile response in equine intestine in specimens with circular orientation. The maximal effect was largest for jejunal specimens with no difference in EC 50 within the different locations investigated. The M 2 antagonist, AF‐DX 116, caused a rightward shift of the concentration–response curve and the M 3 antagonist, 4‐DAMP (1,1‐dimethyl‐4‐diphenylacetoxypiperidinium iodide), almost completely inhibited the effect of BeCh over the entire concentration–response curve. These data provide evidence that, although the effect of BeCh is predominantly mediated by M 3 receptors, M 2 muscarinic receptors also play a role in BeCh‐induced contraction in specimens of equine intestine. The involvement of other muscarinic receptor subtypes cannot be excluded. Further studies are necessary to understand the effect of BeCh in vivo including diseased animals.