Effects of surface gastric pacing on gastric myoelectrical activity and plasma motilin in a canine model of gastric motility disorders.

OBJECTIVE: To investigate the effects of surface gastric pacing on gastric myoelectrical activity and plasma motilin concentration in a canine model of gastric motility disorders. METHODS: Ten healthy mongrel dogs were divided into two groups: an experimental group of six dogs and control group of four dogs. The model of gastric motility disorders was established in the experimental group with truncal vagotomy combined with injection of glucagon. Gastric serosal myoelectrical activity was recorded with a four-channel computer analysis device. Plasma motilin concentration was measured with a radioimmunoassay (RIA) kit. Surface gastric pacing at 1.1-1.2-fold the intrinsic slow-wave frequency superimposed with a series of high frequency pulses (10-30 Hz) was performed for 45 min daily for 1 month in the conscious dogs. RESULTS: The basic electrical rhythm (BER) amplitude (2.32 +/- 0.35 mV) and propagation velocity (4.06 +/- 0.40 cm/s) of the dogs with bilateral truncal vagotomy in the fed state decreased more significantly than those of the controls (4.25 +/- 0.12 mV, 6.92 +/- 0.24 cm/s) (P < 0.03). After long-term surface gastric pacing, the BER amplitude (3.97 +/- 0.19 mV) and propagation velocity (5.57 +/- 0.48 cm/s) was increased significantly compared with before pacing (P < 0.05). Postprandial gastric dysrhythmias were provoked by large doses of glucagon; the percentage of regular slow waves of the dogs with vagotomy was markedly reduced from 67.4 +/- 6.2% at baseline to 10.0 +/- 6.7% (P < 0.001), and that of the control was also decreased from 87.1 +/- 6.9% to 35.0 +/- 11.0% (P < 0.01), but the entrainment of gastric slow waves was 100% by means of gastric pacing at optimal parameters. There was a significant increase in the plasma concentration of motilin at the phase III of the interdigestive myoelectrical complex (IMC III) in the dogs with bilateral truncal vagotomy (baseline vs vagotomy, 184.29 +/- 9.81 pg/mL vs 242.09 +/- 17.22 pg/mL; P< 0.01). However, the plasma motilin concentration (212.55 +/- 11.20 pg/mL; P < 0.02) was decreased significantly after long-term gastric pacing. Before gastric pacing the plasma motilin concentration showed an equally negative correlation with the BER amplitude, and propagation velocity in the dogs with vagotomy in the fed state (r = -0.473, r = -0.807, P < 0.04), but after long-term gastric pacing, the plasma motilin concentration showed an equally positive correlation with the BER amplitude and propagation velocity (r = 0.523, r = 0.896, P < 0.02). CONCLUSIONS: Surface gastric pacing with optimal pacing parameters is able to entrain completely propagated slow waves, improve the parameters of gastric myoelectrical activity and normalize gastric dysrhythmias induced by a pharmacological agent. Surface gastric pacing might be useful in the treatment of gastric dysrhythmia. The gastric myoelectrical activity correlated well with the plasma motilin concentration before and after pacing, which suggests that motilin could modulate the effect of gastric pacing through alteration of the gastric myoelectrical parameters.

Effects of gastric pacing on gastric emptying and plasma motilin.

AIM: To investigate the effects of gastric pacing on gastric emptying and plasma motilin level in a canine model of gastric motility disorders and the correlation between gastric emptying and plasma motilin level. METHODS: Ten healthy Mongrel dogs were divided into: experimental group of six dogs and control group of four dogs. A model of gastric motility disorders was established in the experimental group undergone truncal vagotomy combined with injection of glucagon. Gastric half-emptying time (GEt(1/2)) was monitored with single photon emission computerized tomography (SPECT), and the half-solid test meal was labeled with an isotope-(99m)Tc sulfur colloid. Plasma motilin concentration was measured with radioimmunoassay (RIA) kit. Surface gastric pacing at 1.1-1.2 times the intrinsic slow-wave frequency and a superimposed series of high frequency pulses (10-30 Hz) was performed for 45 min daily for a month in conscious dogs. RESULTS: After surgery, GEt(1/2) in dogs undergone truncal vagotomy was increased significantly from 56.35+/-2.99 min to 79.42+/-1.91 min (P<0.001), but surface gastric pacing markedly accelerated gastric emptying and significantly decreased GEt(1/2) to 64.94+/-1.75 min (P<0.001) in animals undergone vagotomy. There was a significant increase of plasma level of motilin at the phase of IMCIII (interdigestive myoelectrical complex, IMCIII) in the dogs undergone bilateral truncal vagotomy (baseline vs vagotomy, 184.29+/-9.81 pg/ml vs 242.09+/-17.22 pg/ml; P<0.01). But plasma motilin concentration (212.55+/-11.20 pg/ml; P<0.02) was decreased significantly after a long-term treatment with gastric pacing. Before gastric pacing, GEt(1/2) and plasma motilin concentration of the dogs undergone vagotomy showed a positive correlation (r=0.867, P<0.01), but after a long-term gastric pacing, GEt(1/2) and motilin level showed a negative correlation (r=-0.733, P<0.04). CONCLUSION: Surface gastric pacing with optimal pacing parameters can improve gastric emptying parameters and significantly accelerate gastric emptying and can resume or alter motor function in a canine model of motility disorders. Gastric emptying is correlated well with plasma motilin level before and after pacing, which suggests that motilin can modulate the mechanism of gastric pacing by altering gastric motility.