Pacemaker phase shift in the absence of neural activity in guinea‐pig stomach: a microelectrode array study

Abstract

Gastrointestinal (GI) motility is well organized. GI muscles act as a functional syncytium to achieve physiological functions under the control of neurones and pacemaker cells, which generate basal spontaneous pacemaker electrical activity. To date, it is unclear how spontaneous electrical activities are coupled, especially within a micrometre range. Here, using a microelectrode array, we show a spatio-temporal analysis of GI spontaneous electrical activity. The muscle preparations were isolated from guinea-pig stomach, and fixed in a chamber with an array of 8 × 8 planar multielectrodes (with 300 μm in interpolar distance). The electrical activities (field potentials) were simultaneously recorded through a multichannel amplifier system after high-pass filtering at 0.1 Hz. Dihydropyridine Ca 2+ channel antagonists are known to differentiate the electrical pacemaker activity of interstitial cells of Cajal (ICCs) by suppressing smooth muscle activity. In the presence of nifedipine, we observed spontaneous electrical activities that were well synchronized over the array area, but had a clear phase shift depending on the distance. The additional application of tetrodotoxin (TTX) had little effect on the properties of the electrical activity. Furthermore, by constructing field potential images, we visualized the synchronization of pacemaker electrical activities resolving phase shifts that were measurable over several hundred micrometres. The results imply a phase modulation mechanism other than neural activity, and we postulate that this mechanism enables smooth GI motility. In addition, some preparations clearly showed plasticity of the pacemaker phase shift.

Electromagnetic sensor technology for biomedical applications

“…The distance from the sample to the upper sensor head was approximately 1mm. It is known that spontaneous electrical activities in smooth muscle cell clusters have a high temperature dependence (Nakayama et al, 2006). This was confirmed with magnetic detection.…”

Network of Gut Pacemaker Cells: Spatio-Temporal Evaluation of Electrical Activity by Use of Microelectrode Array

“…In 10 antral muscle preparations with the pacemaker phase shift proceeding from the oral end in the initial observation, field potentials were continuously recorded for ~30 min. The direction of propagation was reversed in four out of 10 preparations (Nakayama et al 2006). Altogether, these results indicate that coupling of ICC pacemaker activity has plasticity and that that an ICC network can even produce reversible propagation of pacemaker potentials in the stomach.…”

“…Also, a high-pass filter (HPF) of 0.1 Hz was applied to stabilise the baseline drift of the DC potential (Brock & Cunnane, 1987). The low impedance of microelectrodes (<10 kΩ, at 1 kHz) and a HPF of 0.1 Hz enabled us to follow slow electrical oscillations of gut pacemaker activity (Nakayama et al 2006;2009).…”

“…2D) followed by a slowly decaying component (green double arrow). Nakayama et al 2006). Each trace in A shows the normalised field potential with a y-range of ±150 μV (scale bar).…”

Advances in Research on Pacemaking Function of Interstitial Cell of Cajal in Gastrointestinal Tract

“…To record electrical slow waves originating from ICC in musculature preparations, microelectrodes with low impedance (<10 kU at 1 kHz) have been recently employed. In the guinea pig stomach (Nakayama et al, 2006), such a high-performance MEA system has revealed spontaneous electrical activity synchronised with resolving phase shifts over a range of several hundred micrometers. The electrical activity frequently propagates from the oral to the anal direction, even in the presence of tetrodotoxin (TTX).…”