SUMMARY1. Intracellular recordings were made from cells in the myenteric plexus of the human colon in freshly dissected tissue obtained from patients undergoing surgery for the removal of carcinomas or diverticular bowel.2. Twenty-seven cells from ten preparations were classified as neurones and had overshooting action potentials, an average resting potential of -54+9 mV, an average input impedance of 1-05 + 0-59 x 108 Q and a variety of synaptic inputs.3. Twenty-three (out of twenty-five neurones tested) received nicotinic fast excitatory synaptic inputs (fast e.p.s.p.s) that were blocked reversibly by hexamethonium and mimicked by acetylcholine. These nerve cells bore a close resemblance to S cells that have been characterized in the guinea-pig small-bowel myenteric plexus. 4. One cell had a long after-hyperpolarization following its impulses and was similar to AH cells in the guinea-pig small bowel.5. Three neurones received inhibitory synaptic inputs, up to 15 mV in amplitude, lasting up to 10 s, associated with a decrease in input impedance and with a reversal potential between -80 and -90 mV.6. Slow excitatory synaptic potentials were only detected in the single AH cell. The slow e.p.s.p. was associated with a depolarization of up to 12 mV, an increase in excitability and an increase in the input impedance of the neurone.7. The proportion of S and AH cells differ considerably from that reported in the guinea-pig small-bowel preparation. Possible causes of the differences are discussed.

SUMMARY Based on short recordings, the rectum has been shown to have contractions with a frequency of five to 10 cycles per minute and slow contractions at three cycles per minute. To define anorectal motility over a prolonged period of time, we have studied 12 healthy volunteers using a fine pressure sensitive anorectal probe. A total of 240 hours of recording was obtained. We observed three types of activity in the rectum: (i) runs of powerful phasic contractions with a frequency of two to three per minute, lasting for three to 10 minutes, and recurring to an interval of 92 (1.9) minutes (mean (SEM)) during the day and 56 (1.7) minutes (mean (SEM)) at night, (ii) isolated prolonged contractions lasting for 10-20 seconds and seen mainly during waking, and (iii) clusters of contractions occurring at a frequency offive to six per minute lasting for one to two minutes and seen predominantly during the postprandial period. These clusters of contractions resembled the discrete clustered contractions seen in the ileum, whereas the more powerful and prolonged runs of contractions resembled phase III activity in the small intestine. In contrast, the anal canal showed bursts of contractions which were not temporally related. Our data show that the rectum, like the upper gastrointestinal tract, exhibits periodic motor activity; it remains to be seen whether these two biorhythms are synchronous.The interdigestive migrating motor complex (MMC) and its electrical equivalent, the myelectric complex, have been shown to migrate cyclically through the small bowel of many species, including man.`X Most studies in man, aimed at investigating the cyclical nature of gastrointestinal motility, have been confined to the upper small bowel; few have studied the ileum and proximal colon.6 Anorectal studies have largely confined themselves to the measurement of resting and squeeze pressure and the study of rectoanal reflexes. The possibility that the human anorectum exhibits periodic activity has not been investigated.Water filled catheters, water or air filled balloons, sleeve catheters and force transducers have all been used to measure contractile activity in the anorectum; conflicting results have been reported.7-'0 The rectum has been described as being quiescent

The study of human colonic motility under physiological conditions has proved to be an elusive goal. We have used a two-stage pernasal technique to position sensors in the human colon for the prolonged monitoring of motility in freely ambulant subjects. Nine healthy volunteers were studied for a total recording time of 263 h, each study lasting between 13 and 48 (mean 29) h. Motor activity in all regions of the large bowel was characterized by scant and irregular contractions with infrequent bursts that did not conform to any pattern. No motor coordination was apparent between different regions of the large bowel. Contractile activity throughout the large bowel was reduced to a minimum during sleep and was enhanced on waking. Meals were an inconsistent stimulus to motor activity. The technique obviates the need for colonic preparation and allows complete freedom of the subjects throughout the study. In demonstrating the practical feasibility of this mode of studying the colon, these preliminary data highlight a requirement for the availability of appropriate equipment but raise questions about the design and use of such equipment and methods of data analysis.

Nine patients who habitually ruminated after meals underwent clinical tests and psychological questioning.

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The aim of this study was to determine whether visual analysis of graphic records of small bowel motility is a reliable method of discriminating pressure events caused by bowel wall contraction from those of extraenteric origin and to compare this method with computerized analysis. Each of six independent observers was supplied with the same pair of records of 1 h of fasting diurnal duodenojejunal motility, acquired with a 3-channel ambulant data-logging system; one record included many artifacts due to body movement while the other did not. The observers were asked to identify and classify pressure events and to measure the duration and amplitude of "true" contractions. A computer program for on-line analysis is described; the algorithm was designed to overcome the problems of a variable baseline and sudden changes in pressure due to body movements that are unavoidable in prolonged recording from the small bowel of ambulant subjects. For regular contractions (phase III of migrating motor complex) there was good agreement between observers but not for irregular contractions, particularly when movement artifacts were abundant. When the observers were asked to repeat the analysis 6 mo later, there was poor agreement with their original identification of irregular contractions and artifacts. There was, however, good agreement between the computer analysis, which was totally reproducible, and the median decisions of the observer group; this agreement supports the validity of our computer algorithm. We conclude that computer analysis is not merely a valuable ergonomic aid for analysis of large quantity of data acquired in prolonged ambulatory monitoring, but also that, even for brief recordings, it provides a standard of reproducibility unmatched by "expert" inspection. Visual analysis is unreliable and thus susceptible to subjective bias; this may, in part, account for conflicting reports of small bowel motility under similar conditions reported by different workers in our own and other laboratories.

SUMMARY Prolonged (18-24 hours) recordings of the pattern of small intestinal motor activity have been made, using radiotelemetry, in seven patients before surgery for chronic duodenal ulcer, seven after truncal vagotomy, and four with persistent post-vagotomy diarrhoea. There was no difference in the pattern of fasting cyclical activity between the three groups but the duration of feeding activity after a standard meal was reduced in asymptomatic truncal vagotomy patients compared with duodenal ulcer controls (p

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