Netwrok-forming interstitial cells with c-Kit-immunoreactivity are present in the myenteric plexus of the gut. From the histological resemblance these cells are referred to as interstitial cells of Cajal (ICC), and are now believed to act as pacemaker cells (1,2). Pacemaker potentials generated from ICC are synchronized with phase shifts over several hundred micrometers (3). Ca2+-dependent plasmalemmal ion channels periodically activated in ICC are responsible for pacemaker potentials (4,5). It is therefore deduced that intracellular Ca2+ oscillations in these cells are the primary mechanism. Suzuki et al. (6) have demonstrated that InsP3 receptors play an essential role in ICC pacemaking. Furthermore, ICC pacemaker Ca2+ activity appears to also require ryanodine receptors and plasmalemmal Ca2+ permeable channels, such as TRP homologues (7,8). ICC-like interstitial cells are distributed throughout the body, e.g. urinary tract, uterus, vasculature and ES-gut. It is likely that these cells act as pacemaker cells and/or modulate smooth muscle spontaneous rhythmicity (8-10). (1) Huizinga JD et al. (1995) Nature 373, 347-349. (2) Dickens EJ et al. (1999) J Physiol 514, 515-531. (3) Nakayama S et al. (2006) J Physiol 576, 727-738. (4) Huizinga JD et al. (2002) Gastroenterology 123, 1627-1636 (5) Goto et al. (2005) J Physiol 559, 411-422. (6) Suzuki H et al. (2000) J Physiol 525, 105-111. (7) Aoyama M et al. (2004). J Cell Sci 117, 2813-2825. (8) Hashitani H (2006) J Physiol 576, 707-714. (9) Burdyga T & Wray S (2005) Nature 436, 559-562. (10) Takaki M et al. (2006) Stem Cells 24, 1414-1422. [J Physiol Sci. 2007;57 Suppl:S15]
