Influence of substance P on myoelectric activity of the small bowel.

The effects of substance P (SP) on intestinal myoelectric activity were examined in conscious dogs with implanted silver electrodes on the small doses (0.25-1.0 nmol . kg-1 . h-1) raised the frequency of interdigestive myoelectric complexes and also increased preburst activity, mostly in the upper small bowel. The ileum was relatively less sensitive to the stimulatory action of sp. At higher doses (2.04.0 nmol . kg-1 . h-1) SP caused a fedlike motility pattern. In the doses used SP did not change the foodinduced motility pattern. The effects of SP on myoelectric activity were blocked by atropine or pirenzepine. We conclude that SP was participate in neurally mediated changes in intestinal motility.