Objective - To determine the effects of cisapride on feline colonic smooth muscle function. Design - In vitro smooth muscle mechanical measurements. Animals - Intact colon was obtained from healthy 2- or 3-year-old cats. Procedure - Longitudinal smooth muscle strips from proximal and distal portions of feline colon were suspended in physiologic buffer solution (37 °C, 100% O2, pH 7.4), attached to isometric force transducers, and stretched to optimal muscle length. Control responses were obtained at each muscle site with acetylcholine (10-8 to 10-4 M), cholecystokinin (10-11 to 10-7 M), substance P (10-11 to 10-7 M), or neurotensin (10-11 to 10-7 M). Muscles were then stimulated with cumulative (10-9 to 10-6 M) or bolus (10-6 M) doses of cisapride in the absence or presence of tetrodotoxin (10-6 M) and atropine (10-6 M), nifedipine (10-6 M), or calcium-free buffer solution. Results - Cisapride stimulated contractions of longitudinal smooth muscle from proximal and distal portions of feline colon that were similar in magnitude to contractions induced by substance P and neurotensin. Cisapride contractions were only partially inhibited by tetrodotoxin (10-6 M) and atropine (10-6 M), suggesting that cisapride responses are only partially dependent on enteric cholinergic nerves. Nifedipine (10-6 M) inhibited the maximal contraction to cisapride (10-6 M) by approximately 80%. Removal of extracellular calcium did not inhibit cisapride contractions to a greater extent than did inhibition by nifedipine, indicating that calcium influx through voltage-dependent calcium channels was predominantly responsible for the dependence of the cisapride contraction on extracellular calcium. Conclusions - Cisapride-induced contractions of feline colonic smooth muscle are largely smooth muscle-mediated and dependent on calcium influx, and are only partially dependent on enteric cholinergic nerves. Clinical Relevance - Cisapride may be useful in the treatment of feline colonic motility disorders.
|Original language||English (US)|
|Number of pages||6|
|Journal||American journal of veterinary research|
|State||Published - Apr 1 1996|