Characteristics of spontaneous and evoked motility in the isolated perfused porcine duodenum.

The aims of the study were to evaluate characteristics of spontaneous motility and of the ascending excitatory peristaltic reflex (AEPR) and intraluminal cross-sectional area in the isolated perfused porcine duodenum. The parameters were measured by an intraluminal catheter by use of the perfused side-hole technique and impedance planimetry. Respiratory parameters such as pH and oxygen consumption and the arterial perfusion pressure were monitored and did not vary significantly throughout the study time. Spontaneous motility was intense at the beginning but declined and disappeared within 45-90 min. It was abolished by atropine, epinephrine, and UK-14,304 (an alpha 2-adrenoceptor agonist). Secondary motility was evoked by intraluminal balloon distensions by raising the balloon pressure to 1.5 kPa for 1-min periods. Reproducible results regarding the AEPR, external balloon diameters to elicit the AEPR, and intraluminal cross-sectional area were obtained. The order of potency (pD2 values) for inhibition of the AEPR was the selective M3-receptor antagonist 4-DAMP greater than atropine greater than the selective M2-receptor antagonist AFDX-116 greater than the selective M1-receptor antagonist pirenzepine greater than hexamethonium. 4-DAMP was 16 and 29 times more potent than AFDX-116 (P less than 0.02) and pirenzepine (P less than 0.02). None of the drugs altered the intraluminal cross-sectional area during the balloon distensions. The model provides the opportunity for physiological and pharmacological studies of duodenal motility and duodenal cross-sectional area devoid of extrinsic neural and endocrine effects. The abolishment of the AEPR by atropine is caused by blockade of the M3-receptor in the porcine duodenum.