Motor activity of vascularly perfused rat duodenum. 1. Characteristics of spontaneous movement

We developed an ex vivo model of arterially perfused rat duodenum to examine the motor activity of intestine. In this preparation, spontaneously occurring pressure waves with regular rhythm were observed. The oxygen consumption and motor activity of the intestine were compared at different arterial perfusion rates to determine the degree of oxygenation required to elicit spontaneous motility. Pressure waves with regular rhythm occurred at a frequency of 1 min-1 when the arterial perfusion was 3-5 mL min-1, and stopped when the perfusion rate fell below 2 mL min-1. Atropine and hexamethonium reduced the percentage motor index/10 min of pressure waves in a dose-dependent manner, and tetrodotoxin completely blocked motor activity. Acetylcholine stimulated motor activity, and this effect was not antagonized by TTX. These findings suggest that spontaneous contraction in the ex vivo perfused rat duodenum might be mediated by a cholinergic mechanism via muscarinic receptors on smooth muscle, but that noncholinergic mechanisms may also participate in this response.