Slow-wave Oscillator Research Articles

The electrical activity of the cat colon in vivo. I. The normal electrical activity and its relationship to contractile activity.

1. Spontaneous electrical and contractile activity were studied in the colon of fasted, unanesthetized cats. Needle electrodes and strain-gage transducers had been implanted on the serosal side along the colon 10 days to 5 months prior to the experiments. 2. Electrical activity consisted of spikes, oscillations, and slow waves. Slow waves were omnipresent. Spikes and oscillations occurred intermittently. 3. Mean slow-wave frequency was 5.3 cpm in the ascending, 5.4 cpm in the transverse, and 5.5 cpm in the descending colon. 4. Spike bursts exhibited 2 different rhythmic patterns: a) short bursts which were phase locked to slow waves; b) prolonged sequences occurring at frequencies of 0.7–1.4 cpm. The first type was prevalent in the proximal, the second one in the distal colon. 5. The patterns of contractions followed those of the spikes, i.e. contractions of the descending colon were very slow and sustained, in contrast to the proximal colon. 6. It is concluded that motility of the intact colon is determined largely by 2 types of electrical oscillators: A slow-wave oscillator which is more labile than in upper parts of the gut and an ultraslow oscillator.

Longitudinal axial coupling of slow waves in proximal cat colon.

CHRISTENSEN, JAMES, AND RICHARD L. HAUSER. Longitudinal axial coupling of slow waves in proximal cat colon. Am. J. Physiol. 22 l(1) : 246-250. 197 1 .-We studied spreading patterns of electric slow waves of circular muscle in longitudinal axis of cat colon. The colon, opened lengthwise, was pinned flat, serosa down, in a bath equilibrated with 957, OQ--5y0 CO2 at 36.5-37.5 C. Six volume-recording electrodes, put on circular muscle, exposed by removal of the mucosa, recorded slow waves simultaneously from six sites 5.8 mm apart. The first was just below the ileocecal junction. 1Ve determined proportion of time when slow waves were phase locked across all six electrodes, direction of spread and time delay while slow waves were phase locked, distance over which slow waves were phase locked, and oscillator frequency. During phase lock across all six points (67% of the time) slow waves spread orad 8.7y0, caudad 3.5y0, and split (orad proximally, caudad distally) 87.9y0 of the time. Apparent velocity orad, 2.6 & 1.1 (SD) mm/set, was less than caudad, 3.6 =t 2.1 (SD) mm/set, (P = 0.005). Distance over which phase lock occurred varied from 5.8 to 28.8 mm. Frequency was 3.12 =t 1.62 (SD) cycles/min. Distance of phase lock and direction of phase lag vary and may affect fecal flow through effects on integration and polarization of wall movements. Different apparent velocities in the two directions suggest rectification in coupling of slow-wave oscillators.

Electrical activity of small intestinal smooth muscle

Intestinal slow waves occur spontaneously and continuously in most mammalian species studied, including man, regardless of the presence or absence of contractions. They originate in the longitudinal muscle. Spikes may or may not occur during slow wave depolarization. Spikes initiate contractions, the maximal frequency of which is equal to the frequency of slow waves. Slow waves seem to provide a timing mechanism which allows spiking and subsequent contractions only at regular intervals. Slow waves are conducted from longitudinal to circular muscle along interconnecting strands of muscle fibers, thereby coordinating contractions in the two layers. The frequency of intestinal slow waves is amazingly constant in any one part of the gut; it averages 11.8 cycles per minute in human duodenum and declines to 9.0 cycles per minute in lower ileum. The negative aboral frequency gradient is stepwise, with variable lengths of intestine operating at successively lower frequencies. Within each constant frequency region, slow waves seem to be conducted aborally from a pacemaker, and apparent conduction times can be measured as the lag between corresponding points on waves recorded from two sites along the gut. However, conduction may be more apparent than real. Slow waves may originate from all cells or groups of cells in the longitudinal muscle, which would then act as a long series of oscillators. Coupling of these oscillators so that the faster ones drive the slower ones would result in many of the features of slow wave activity in the intestine. Apparent conduction times may simply represent the phase lag between a driving and a driven oscillator. The well known coordination between contractions in the gastric antrum and those in the duodenal bulb can be explained by the presence of attenuated gastric slow waves a short distance into the duodenal bulb. In this region, the duodenal slow waves are superimposed on gastric waves resulting in augmentation of those duodenal waves directly after antral activity. These augmented waves are more likely to result in spikes and, therefore, contractions of the duodenal bulb than are the ordinary duodenal slow waves. Transection (with healed end to end anastomosis) or merely damage to the myenteric plexus abolishes coupling along the chain of slow wave oscillators so that aboral regions are no longer driven by higher frequency regions oral to the injury. The maximal frequency of contraction is, therefore, decreased below such an injury. Frequency of slow waves within a segment of gut with damaged myenteric plexus is even lower than it is aboral to such a segment. The myenteric plexus is apparently involved somehow in coupling of slow wave activity along the gut and in establishing the uncoupled spontaneous frequency of slow waves. Feeding has no effect on frequency of slow waves but does lead to an increased percentage of slow waves having spikes, and, therefore, a decrease in the amount of time the gut is mechanically quiescent. Analysis of electrical spiking provides a convenient means of following the effects of feeding on intestinal contractions. A number of studies on patients with a variety of disorders have been reported but no diagnostic value of electroenterography has been established, although its use at surgery to determine the extent of irreversible bowel damage may prove to be useful.