Gastric distension alters frequency and regularity but not amplitude of the gastric slow wave

The aim of this study was to assess effects of gastric distension on gastric slow waves using internal and cutaneous electrodes and the correlation between these two measurements. The study was performed in five dogs implanted with one pair of serosal electrodes and a gastric cannula. Gastric slow waves were recorded using both cutaneous and internal electrodes in several sessions with different volumes (150-600 mL) of gastric distension with a barostat balloon. Bethanechol was injected in one of sessions. The results revealed that (i) Gastric distension reduced slow wave frequency in a volume-dependent manner and induced bradyarrhythmia at a volume of 600 mL, but had no effects on the amplitude of gastric slow waves. (ii) The cutaneous electrogastrogram (EGG) was significantly correlated with the internal recording in slow wave frequency (r = 0.88, P < 0.001) and regularity (r = 0.44, P = 0.035. (iii) The EGG amplitude was not increased when the stomach was distended but increased after bethanechol. Gastric distension volume dependently reduces slow wave frequency and induces gastric dysrhythmia at a large volume. The frequency and rhythmicity of the slow wave measured from the EGG are significantly correlated with those recorded from the internal electrodes. Relative increase in EGG amplitude reflects contractility rather than the distension of the stomach.