Interstitial cells of Cajal and electrical activity of smooth muscle in porcine ileum

Aim: To identify the interstitial cells of Cajal in the porcine ileum for the first time immunohistochemically and to examine the electrical properties of intestinal smooth muscle in the same region. Methods: In vitro intracellular microelectrode recordings were made from smooth muscle cells in cross-sectional preparations from abattoir-derived healthy porcine ileum. Immunohistochemical labelling of interstitial cells of Cajal was performed using an anti-Kit antibody. Results: Slow waves were recorded in the circular muscle layer of all ileal preparations. The mean resting membrane potential of smooth muscle cells was -61.0 +/- 1.3 mV. Slow waves had a mean amplitude of 8.5 +/- 0.5 mV, a frequency of 9.9 +/- 0.1 cycles per minute and a duration of 5.6 +/- 0.1 s. A waxing and waning pattern of slow wave activity was occasionally observed. In addition, higher frequency spiking activity associated with contractions was observed in some recordings. The L-type calcium channel blocker nifedipine abolished both the spiking activity and the contractions, but had no significant effect on slow wave characteristics. Current-injection manipulation of the resting membrane potential had no effect on slow wave amplitude, frequency or duration. Kit-immunoreactive interstitial cells of Cajal were identified in the ileal samples and were present in the region of the myenteric plexus and in the circular and longitudinal muscle layers. Conclusion: This study recorded slow waves in vitro and demonstrated immunohistochemically the presence of interstitial cells of Cajal in the normal porcine ileum. This study forms a basis for future physiological and pathophysiological comparative studies of intestinal motility.