Quantification of the Effects of the Volume and Viscosity of Gastric Contents on Antral and Fundic Activity in the Rat Stomach Maintained Ex Vivo

The aim of this study was to examine the effect of varying the rheological properties of perfusate on the volume and muscular activity of the various compartments of the rat stomach. Image analysis was used to quantify the activity of the ex vivo stomach preparations when perfused according to a ramp profile. The area of the fundus increased to a greater extent than that of the body when watery or viscous material was perfused. However, initial distension of the corpus was greater and occurred more rapidly when viscous material was perfused. Only the fundus expanded when perfusion followed the administration of verapamil. The frequency of antrocorporal contractions decreased significantly and the amplitude of antrocorporal contractions increased significantly with increase in gastric volume. The velocity of antrocorporal contractions did not vary with gastric volume but varied regionally in some preparations being faster distally than proximally. Neither the frequency, amplitude or velocity of antrocorporal contractions differed when pseudoplastic rather than watery fluid was perfused. However, the characteristics of antrocorporal contractions changed significantly when the stomach was perfused with material with rheological characteristics that induce different patterns of wall tension to those normally encountered. Hence, the mean frequency and speed of propagation of antrocorporal contractions increased and their direction of propagation became inconstant.