Contractile response to electrical stimulation of the small intestine in anesthetized and awake dogs

To test whether small bowel contraction can be induced by electrostimulation similar to in vitro results in anesthetized and awake animals, five dogs had stainless steel electrodes implanted on the serosal surface of the jejunum and ileum. Fifty milliamperes of 500-microseconds 910-Hz currents induced a 50-80-mm Hg pressure increase in the jejunum with a threshold of 25 mA. Transverse stimulation was studied long-term in two dogs. The mean pressure change for 500-microseconds 910-Hz 25-mA stimulation in 10 studies was 26 mm Hg (0-75). The thresholds ranged between 15 mA and currents not tolerated by the animal. For 200-microseconds 1.67-kHz 30-mA stimulation, the mean pressure change was 28 mm Hg (0-75 mm Hg, n = 16). On 10 occasions, the pressure increased further after termination of the stimulus (off response), with a mean of 48 mm Hg (10-85). Electrical currents elicit a mechanical response in the small intestine of the intact animal, which resembles the in vitro observations. Currents necessary to evoke contractions in the physiologic range are tolerated by the trained animal.