Mechanical activity of muscular "patch pouches" from cat and rabbit stomachs

With a newly developed preparation (the gastric patch pouch), we compared the mechanical response of the proximal with that of the distal stomach to volume loads, drugs, and stimulation by an electrical field. Squares, 2 X 2 cm, were cut from the anterior and posterior walls of stomachs from cats and rabbits; the corresponding edges of opposing squares were sewn together. A luminal balloon served to change pouch volume and to monitor pouch pressure. Filling increased the width more than the length of most pouches; this difference was particularly marked in pouches from the rabbit fundus. Filling led to an initial pressure peak, after which pressure declined to a new baseline pressure plateau; emptying led to an initial pressure nadir, pressure recovery, and baseline pressure plateau. The difference between initial pressure and plateau pressure was larger in proximal than in distal pouches: hence, baseline pressures rose more sharply on filling and declined more steeply on emptying of antral than of proximal pouches. Pressure waves occurred in all antral pouches of cats and in some antral pouches of rabbits. Carbachol enhanced the pressure waves and isoproterenol inhibited them. In the fundic pouches, these drugs altered primarily the baseline pressure. Electrical field stimulation caused a relaxation in fundic pouches and a suppression of rhythmic contractions in antral pouches. The onset and the duration of nervous inhibition was comparable in fundic and in antral pouches. The baseline pressure of pouches was not affected by the presence or by the absence of the mucosa. This novel preparation is suitable to demonstrate differences in the volume-pressure relationships of the muscle coat of the proximal and the distal stomach.