Abstract

ABT-229 (8,9-anhydro-4"-deoxy-3′-N-desmethyl-3′-N-ethylerythromycin B-6,9-hemiacetal), a synthetic derivative of erythromycin (ERY) with no antibiotic activity, has been shown to bind to motilin receptors and stimulate contractile activity of the antrum and small intestine. The objective of this study was to determine the effect of ABT-229 on canine gastric emptying (GE) and contractile activity of the antrum and duodenum in response to a solid meal. Six beagles were used to determine GE of a solid meal and contractile activity in response to either vehicle, ABT-229 (0.17, 0.83, 2.5, or 5.0 μg/kg/min), ERY (33.3 μg/kg/min), or cisapride (CIS) (10 μg/kg/min). Lag (t_lag), half-emptying (t_1/2), and complete emptying (t_full) times were determined. Contractile data were analyzed for motility index and gastroduodenal coordination. Compared with vehicle, ABT-229 dose dependently accelerated GE,t_lag was decreased at the two highest doses,t_1/2 was decreased compared with vehicle at the three highest doses, and t_full was decreased at all doses compared with vehicle. ERY also decreasedt_1/2 and t_full, whereas CIS decreased all GE parameters. The slopes of the linear phase of GE curves for all drugs and doses were greater than those for vehicle. ABT-229 dose dependently increased the motility index as well as gastroduodenal coordination. ABT-229 (two highest doses) and CIS accelerated GE of a solid meal by decreasing the lag phase and increasing the rate of GE, whereas ERY only increased the rate of GE. The data suggest that ABT-229 is 7- to 40-fold more potent than ERY in accelerating GE.