Effect of α2-adrenergic, cholinergic, and nonsteroidal anti-inflammatory drugs on myoelectric activity of ileum, cecum, and right ventral colon and on cecal emptying of radiolabeled markers in clinically normal ponies

Abstract

Abstract Objective To determine effect of xylazine hydrochloride (XYL), yohimbine hydrochloride (YOH), bethanechol chloride (BET), neostigmine methyl sulfate (NEO), or flunixin meglumine (FLU) on ileocecocolic myoelectric activity and passage of radiolabeled markers from the cecum. Animals 6 healthy adult ponies. Procedure A cecal cannula was surgically implanted, and 12 were sutured to the ileum, cecum, and right ventral colon. After a 12-hour nonfeeding period, 370 MBq of technetium 99m-labeled sulfur colloid in egg albumen and 37 MBq of indium 111-labeled diethyltriaminepentaacetic acid in 60 ml of water were injected into the cecal apex. All drugs were administered IV as a bolus, with the exception of NEO, which was given SC: XYL, 0.5 mg/kg of body weight; YOH, 0.075 mg/kg; BET, 0.025 mg/kg; NEO, 0.025 mg/kg; FLU, 1.1 mg/kg; and saline solution (SAL), 10 ml. Drugs were administered in a randomized complete block design, each treatment was administered twice to each pony, and dual-phase scintigraphic images were obtained. The time to 50% emptying (t 50 ) and the slope of the emptying curve (β) were derived from the calculated power exponential equation. Results The t 50 after BET (184.8 ± 16.5 minutes) and NEO (124.7 ± 16.5 minutes) administration were significantly shorter than values after saline (230.2 ± 17.1 minutes) administration. The t 50 after XYL administration (250.5 ± 18.6 minutes) was longer, and that after YOH administration (190.1 ± 16.2 minutes) was shorter, than the t 50 after saline administration, but neither difference was significant. The t 50 and β after FLU administration differed from those after saline administration. Myoelectric data appeared to be well correlated with drug-induced alterations in isotope clearance. Conclusions and Clinical Relevance Cholinergic agonists, BET and NEO, have significant effects on the myoelectric activity of ileum, cecum, and right ventral colon, with the net effect of hastening cecal emptying. ( Am J Vet Res 1998;59:320–327)