Title: Network of Gut Pacemaker Cells: Spatio-Temporal Evaluation of Electrical Activity by Use of Microelectrode Array
Abstract: IntroductionThe word 'pacemaker' prompts us to imagine 'heart beats' and also an 'electric cardiogram'.However, spontaneous electrical activity occurs in numerous tissues and organs in the autonomic nervous system, such as in the gastrointestinal and urinary tracts, trachea, uterus, lymph ducts, etc. (Takaki et al, 2010).Recent studies have revealed that special interstitial cells in these tissues and organs act as pacemaker cells.In particular, in the gastrointestinal tract, pacemaker cells surround the myenteric plexus between the circular and longitudinal muscle layers.Since these cells express abundant tyrosine kinase, Kit receptors, on the surface, Kit-immunoreactivity and kit cDNA are used as markers for special pacemaker cells.Moreover, these cells are now referred to as interstitial cells of Cajal (ICC) due to their histological features of the network (Maeda et al. 1992;Faussone-Pellegrini and Thuneberg, 1999;Sanders et al. 1999;Rumessen and Vandervinden, 2003;Takaki, 2003).It is widely accepted that peristaltic movement of the gastrointestinal tract is organized by a network of enteric neurons in the myenteric plexus: Ascending contraction and descending relaxation simultaneously occur to forward luminal contents.It is hypothesized that ICC may also make an essential contribution to the co-ordinated actions of gastrointestinal motility through their network (Nakayama et al. 2006;2009, see also Fig. 7).There are an increasing number of papers that report the impairment of ICC in GI motility disorders, for example, in inflammatory bowel diseases (IBD) (Suzuki et al.