Spatial analysis of slowly oscillating electric activity in the gut of mice using low impedance arrayed microelectrodes.

Smooth and elaborate gut motility is based on cellular cooperation, including smooth muscle, enteric neurons and special interstitial cells acting as pacemaker cells. Therefore, spatial characterization of electric activity in tissues containing these electric excitable cells is required for a precise understanding of gut motility. Furthermore, tools to evaluate spatial electric activity in a small area would be useful for the investigation of model animals. We thus employed a microelectrode array (MEA) system to simultaneously measure a set of 8×8 field potentials in a square area of ∼1 mm(2). The size of each recording electrode was 50×50 µm(2), however the surface area was increased by fixing platinum black particles. The impedance of microelectrode was sufficiently low to apply a high-pass filter of 0.1 Hz. Mapping of spectral power, and auto-correlation and cross-correlation parameters characterized the spatial properties of spontaneous electric activity in the ileum of wild-type (WT) and W/W(v) mice, the latter serving as a model of impaired network of pacemaking interstitial cells. Namely, electric activities measured varied in both size and cooperativity in W/W(v) mice, despite the small area. In the ileum of WT mice, procedures suppressing the excitability of smooth muscle and neurons altered the propagation of spontaneous electric activity, but had little change in the period of oscillations. In conclusion, MEA with low impedance electrodes enables to measure slowly oscillating electric activity, and is useful to evaluate both histological and functional changes in the spatio-temporal property of gut electric activity.

Acceleration of ileal pacemaker activity in mice lacking interleukin 10.

BACKGROUND: Epidemiological studies indicate the genetic association between irritable bowel syndrome and inflammatory bowel disease, including genetic mutations related with interleukin 10 (IL-10), serotonin, and so on. On the other hand, it becomes clearer that interstitial cells of Cajal (ICC) play a major role in gut motility by coordinating the electric activity of cellular members and generating pacemaker potentials. METHODS: Ileal musculatures containing the myenteric plexus and ICC were isolated from wild-type (WT) and IL-10-deficient mice. A microelectrode array system was used to simultaneously measure 8 × 8 field potentials over a ∼1 mm area. Nifedipine and tetrodotoxin were applied to predominantly evaluate ICC electric activity. Histological changes were also assessed by immunohistochemistry. RESULTS: Potential mapping revealed that spontaneous electric activity was synchronized throughout the recording area in ileal musculature preparations of both WT and IL-10-deficient mice, but rapid propagation was observed in the latter. The spectral power in the frequency range of 9.4 to 30.0 cpm (Pw9.4-30.0) did not differ between these preparations, but the oscillation frequency estimated using autocorrelation analysis was significantly higher in IL-10-deficient mice than in WT mice (22.16 ± 4.10 versus 15.72 ± 1.61 cpm). In immunohistochemistry, no significant changes were observed in ICC, macrophages, and enteric neurons in the ileum of WT and IL-10-deficient mice. CONCLUSIONS: This study provides evidence for accelerated pacemaker activity in the ileum of IL-10-deficient mice, not accompanied by any significant histological changes. This could be accounted, as an example, by a genetic cross-link between inflammatory bowel disease and irritable bowel syndrome.