Propagated motor activity in the small intestine of urethane-anaesthetized rats: inhibitory action of sympathetic and capsaicin-sensitive nerves.

1. In the duodenum/small intestine of urethane-anesthetized rats, a series of atropine- and hexamethonium-sensitive phasic contractions activity were recorded by using a balloon. With two balloons, one in the proximal duodenum (B1) and the other at a distal site (B2) a co-ordinated motor activity was observed which migrated from B1 to B2. 2. Spontaneous activity of the duodenum was greater in either adrenalectomized, guanethidine- or capsaicin-pretreated than in control rats. In guanethidine-pretreated animals a series of atropine-resistant but hexamethonium-resistant rhythmic contractions could be demonstrated. 3. In control rats, distension of the balloon produced an inhibitory effect on rhythmic contractions which were ultimately suppressed. Distension had little inhibitory effect on duodenal motor activity of adrenalectomized, guanethidine- or capsaicin-pretreated rats. 4. These findings indicate that the propagated motor activity in the duodenum/small intestine of urethane anesthetized rats can be modulated by the adrenals as well as sympathetic and capsaicin-sensitive nerves.