In vitro effects of bethanechol on specimens of intestinal smooth muscle obtained from the duodenum and jejunum of healthy dairy cows

Spasmolytic effect of 1,8 cineole is mediated through calcium channel blockade in the bovine ileum

Gastrointestinal motility disorders include increased or decreased movements. Other studies have shown that herbal components, for example, essential oils can modify the increase and decrease of gastrointestinal movements of ruminants. The 1,8-cineole being obtained from the essential oil of many plants has several effects. The present study has investigated the effect of 1,8-cineole on the contractility of bovine ileum smooth muscle. The experiment was performed on the circular smooth muscle of ileum samples taken from slaughtered cows in the organ bath. Seven cumulative concentrations of 1,8-cineole from 1.00 to 1,000 µg mL^-1 were added to tissue samples. The used solution was Tyrode's solution aerated with a mixture of 95.00% oxygen and 5.00% carbon dioxide, and the temperature was set at 37.00 ˚C. The effects of 1,8-cineole on baseline contractions and three induced contractions with barium chloride, potassium chloride, and carbachol were investigated. The effects of 1,8-cineole, and verapamil (standard calcium channel blocker) on calcium channels were assessed. The results revealed that 1,8-cineole significantly inhibited spontaneous contractions as well as all spasmogen-induced contractions. The 1,8-cineole exerts its myorelaxant properties by inhibiting calcium channels in smooth muscle. It seems that 1,8-cineole has a good potential for producing antispasmodics or gastrointestinal motility modulators in veterinary medicine.

In vitro effects of bethanechol on abomasal and duodenal smooth muscle preparations from dairy cows with left displacement of the abomasum and from healthy dairy cows

This study investigated the effects of bethanechol (BeCh) on abomasal and duodenal smooth muscle preparations from dairy cows with left displacement of the abomasum (LDA) and from healthy dairy cows, and determined the role of muscarinic acetylcholine receptor subtypes 2 and 3 (M(2) and M(3)) in mediating contraction. Concentration-response curves for BeCh, with or without prior incubation with an M(2) antagonist (AF-DX 116) or an M(3) antagonist (4-DAMP), were established and evaluated. BeCh induced a significant, concentration-dependant increase in the contractility variables for all locations in both groups of cows. The inhibiting effect of 4-DAMP was stronger than that of AF-DX 116, which suggested that contractions were mediated by M(3) and to a lesser extent by M(2). The basal tone of abomasal smooth muscle was reduced in cows with LDA, which indicated hypotonia. The use of BeCh as a prokinetic drug in cows with gastrointestinal motility disorder warrants further investigation.

Messenger RNA Levels and Binding Sites of Muscarinic Acetylcholine Receptors in Gastrointestinal Muscle Layers from Healthy Dairy Cows

Acetylcholine interacts with muscarinic receptors (M) to mediate gastrointestinal (GI) smooth muscle contractions. We have compared mRNA levels and binding sites of M(1)to M(5) in muscle tissues from fundus abomasi, pylorus, ileum, cecum, proximal loop of the ascending colon (PLAC), and external loop of the spiral colon (ELSC) of healthy dairy cows. The mRNA levels were measured by quantitative RT-PCR. The inhibition of [(3)H]-QNB (1-quinuclidinyl-[phenyl-4-(3)H]-benzilate) binding by M antagonists [atropine (M(1 - 5)), pirenzepine (M(1)), methoctramine (M(2)), 4-DAMP (M(3)), and tropicamide (M(4))] was used to identify receptors at the functional level. Maximal binding (B(max)) was determined through saturation binding with atropine as a competitor. The mRNA levels of M(1), M(2), M(3), and M(5) represented 0.2, 48, 50, and 1.8%, respectively, of the total M population, whereas mRNA of M(4) was undetectable. The mRNA levels of M(2) and of M(3) in the ileum were lower (P < 0.05) than in other GI locations, which were similar among each other. Atropine, pirenzepine, methoctramine, and 4-DAMP inhibited [(3)H]-QNB binding according to an either low- or high-affinity receptor pattern, whereas tropicamide had no effect on [(3)H]-QNB binding. The [(3)H]-QNB binding was dose-dependent and saturable. B(max) in fundus, pylorus, and PLAC was lower (P < 0.05) than in the ELSC, and in the pylorus lower (P < 0.05) than in the ileum. B(max) and mRNA levels were negatively correlated (r = -0.3; P < 0.05). In conclusion, densities of M are different among GI locations, suggesting variable importance of M for digestive functions along the GI tract.

Quantitative mRNA analysis of muscarinic acetylcholine receptors in the intestine of dairy cows with spontaneous caecal dilatation-dislocation

Muscarinic receptors mediate acetylcholine-induced muscular contractions. In this study, mRNA levels of muscarinic receptor subtypes 2 and 3 (M(2) and M(3)) in the ileum, caecum, proximal loop of the ascending colon (PLAC) and external loop of the spiral colon (ELSC) were determined by quantitative polymerase chain reaction in seven cows with caecal dilatation-dislocation (CDD) and seven healthy control cows. Levels of M(2) were significantly lower in the caecum, PLAC and ELSC and levels of M(3) were significantly lower in the ileum, caecum, PLAC and ELSC of cows with CDD compared to healthy cows (P<0.05). Down-regulation of M(3) may play a role in the pathogenesis of CDD.