Multielectrode mapping of slow-wave activity in the isolated rabbit duodenum

Abstract

The technique of multiple simultaneous recordings from a large number of extracellular electrodes (> 100) is currently used in the study of normal and abnormal electrical conduction in the heart and the genesis of cardiac arrhythmias. To investigate whether such a system could also be applied in gastrointestinal electrophysiology, several studies were performed with this technique on segments of isolated rabbit duodenum. A multiple-electrode assembly consisting of 240 silver wires was positioned on the serosal surface of the duodenum, and the recorded signals were, after suitable processing, stored. Thereafter, analysis of all simultaneously recorded slow waves during a selected period of time was performed to reconstruct the pattern of conduction in the duodenum. The first results show that there is a considerable variation in conduction pattern, which is determined by the site of the natural pacemaker. Several experiments were performed to rule out possible deleterious effects of positioning the multiple-electrode assembly on the duodenum. Furthermore, prolonged periods of recording did not influence propagation speed and pattern provided that the positioning of the multiple electrode assembly was performed with care. Entrainment of the natural pacemaker was possible by applying electrical stimuli through 2 of the 240 extracellular electrodes during simultaneous recordings. In conclusion, multisite extracellular mapping of gastrointestinal smooth muscle is possible and can be used to study origin and spread of slow-wave activity.

Functional reentry and circus movement arrhythmias in the small intestine of normal and diabetic rats

“…The interelectrode distance was 1 mm. All electrodes were connected through shielded wires to 121 alternating current amplifiers where the signals were amplified (4,000ϫ), filtered (bandwidth 2-400 Hz), digitized (8 bits, 1-kHz sampling rate per channel) and stored on a PC hard disk (10,11). Electrical recordings from all 121 electrodes were made unipolarly with a large silver plate in the tissue bath acting as the indifferent pole.…”

“…1D). The local activation time of a slow wave was identified by the moment of maximum negative slope and marked with a cursor (10,11), whereby the reference time was determined by the timing of the first detected slow wave (time t ϭ 0.0 s at electrode 1). After all recorded slow waves had been analyzed, their activation times were displayed in the format of a grid of the original recording array of electrodes (Fig.…”

“…In ϳ15% of the segments, slow wave propagation did not originate from one or a few foci (10,11). Instead, the slow wave was seen to propagate in a circular fashion for relatively long periods of time, whereby the impulse could rotate in either a clockwise or an anticlockwise direction.…”

Patterns of electrical propagation in the intact pregnant guinea pig uterus

“…All 240 signals (amplification, ϫ4,000; band filter, 2-400 Hz; sampling, 1,000 Hz) were recorded simultaneously during burst activity (19,20). In four separate experiments, five rows of 32 electrodes each (interelectrode distance, 4 mm) were positioned around the circumference of the horn (Fig.…”

“…The digital filtering effectively removes ambient 50-Hz noise and reduces the frequency range to 2-40 Hz. The local activation time of a spike was identified by the moment of maximum negative slope (19,20) and marked with a cursor. All local activation times are related to a common reference time, determined by the timing of the first detected spike in the mapped area (Fig.…”