GASTRIC CONTRACTIONS PRODUCE PHASIC CHANGES IN PERFUSION-PRESSURE

This study examined the relationship between motility and perfusion pressure of an ex vivo segment of the canine stomach perfused at constant flow. Changes in luminal pressure were used to quantitate contractile force. Under control conditions, spontaneous contractions increased luminal pressure by 18.8 +/- 1.1 mmHg and gastric perfusion pressure by 14.2 +/- 0.8 mmHg. Changes in luminal and perfusion pressures during contractions were highly correlated (r2 = 0.963, P < 0.0001, 109 observations in 5 dogs). In separate studies, we assessed the effects of atropine, neostigmine (an acetylcholinesterase inhibitor), and bethanechol (a muscarinic cholinergic agonist). Atropine attenuated the peristaltic-induced changes in perfusion pressure in a concentration-dependent manner (10(-9) to 10(-6) M) with nearly total inhibition at the highest dose. Neostigmine (10(-9) to 10(-6) M) and bethanechol (10(-8) to 10(-5) M) stimulated contractions, resulting in dose-related increases in luminal and perfusion pressures. Our results demonstrate that cholinergic-dependent contractions produce marked, phasic changes in gastric perfusion pressure.