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

Abstract

Lammers WJ, Stephen B, Karam SM. Functional reentry and circus movement arrhythmias in the small intestine of normal and diabetic rats. Am J Physiol Gastrointest Liver Physiol 302: G684 -G689, 2012. First published December 29, 2011; doi:10.1152/ajpgi.00332.2011.-In a few recent studies, the presence of arrhythmias based on reentry and circus movement of the slow wave have been shown to occur in normal and diseased stomachs. To date, however, reentry has not been demonstrated before in any other part of the gastrointestinal system. No animals had to be killed for this study. Use was made of materials obtained during the course of another study in which 11 rats were treated with streptozotocin and housed with age-matched controls. After 3 and 7 mo, segments of duodenum, jejunum, and ileum were isolated and positioned in a tissue bath. Slow wave propagation was recorded with 121 extracellular electrodes. After the experiment, the propagation of the slow waves was reconstructed. In 10 of a total of 66 intestinal segments (15%), a circus movement of the slow wave was detected. These reentries were seen in control (n ϭ 2) as well as in 3-mo (n ϭ 2) and 7-mo (n ϭ 6) diabetic rats. Local conduction velocities and beat-to-beat intervals during the reentries were measured (0.42 Ϯ 0.15 and 3.03 Ϯ 0.67 cm/s, respectively) leading to a wavelength of 1.3 Ϯ 0.5 cm and a circuit diameter of 4.1 Ϯ 1.5 mm. This is the first demonstration of a reentrant arrhythmia in the small intestine of control and diabetic rats. Calculations of the size of the circuits indicate that they are small enough to fit inside the intestinal wall. Extrapolation based on measured velocities and rates indicate that reentrant arrhythmias are also possible in the distal small intestine of larger animals including humans. slow wave; diabetes; wavelength THE SMOOTH MUSCLE LAYER OF the gastrointestinal (GI) tract generates spontaneous electrical activities that are referred to as "slow waves." These slow waves are dependent on the interstitial cells of Cajal in the myenteric plexus (ICC-MY) and are important for maintaining normal GI motility (8, 9).In a recent study, we investigated the propagation of slow waves in a streptozotocin (STZ) model of diabetes in rats. The purpose of that study was to correlate the expected decrease in slow wave propagation with the reported decrease in the census of ICC-MY in the small intestine (8,10,20,30). To our initial surprise, we did not measure a significant decrease in slow wave propagation although there was a reduction in the number of ICC-MY by ϳ50% (10). We concluded from that study that the reduction of ICC-MY was not enough to block slow wave propagation.Further analysis of the propagation in both control and in 3-and 7-mo diabetic rats, however, revealed another unexpected result. 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 ...

Effect of Ethanol Exposure on Slow Wave Activity and Smooth Muscle Contraction in the Rat Small Intestine

“…A similar event also occurred in another experiment at 3 % ethanol superfusion. In both cases, the circuits were quite small and smaller than seen in a previous study [15]. In fact, since the circuit involved 5, respectively 6 neighboring electrodes, the total distance travelled could be estimated at 5.3 and 6 mm.…”

“…In these cases, the length of the pathway was estimated at approximately 5-6 mm. The size of these reentrant loops is much smaller than those found in reentries that occurred during control and in diabetic rats [15]. As described elsewhere, the size of the circuit is determined by the velocity of the propagating wave front in the circuit and the time it takes for the tissue to recover from the previous excitation [31][32][33].…”

“…With a revolution time of 2620 ms respectively 2275, the velocity in the circuit could be estimated at 0.21 and 0.26 cm/s. With these values, we can estimate the wavelength of the two circuits at 0.59 and 0.55 mm, respectively, which is much smaller than what was seen in diabetic tissues in the same species (1.3 ± 0.5 mm) [15].…”

“…The two displayed reentries (Fig. 4) are quite small as evidenced by the limited number of electrodes located along the path of the rotating circuit, possibly indicating a short wavelength [15]. In these cases, the length of the pathway was estimated at approximately 5-6 mm.…”

“…The electrical recordings were analyzed using a custom-made program (SmoothMap, written in Delphi) as shown in previous reports [14,15]. The movies were transferred to Mac Pro (Apple) using a commercial software package (iMovie, Apple).…”