Yves Ruckebusch

Rate of flow of digesta and electrical activity of the small intestine in dogs and sheep.

1. Spiking activity of the small intestine in the conscious dog and sheep was recorded continuously from electrodes chronically implanted on the jejunum and summed at intervals of 20 sec. The activity was related to the transit time and flow rate of intestinal contents as estimated by phenol red and by dilution of continuous marker infusions respectively. Also in some sheep the flow of digesta was measured directly from a cannula in the proximal part of the jejunum, and also by use of an electromagnetic flow meter. 2. In the fasted dog and in sheep on a normal diet the intestinal activity was characterized by a migrating myo‐electric complex comprising an irregular phase followed by a regular phase. These migrating myo‐electric complexes occurred regularly after a period of inactivity at a frequency of 15–20/24 hr. In dogs after feeding, a continuous spiking activity appeared and persisted for periods of 7–8 hr. This was associated with much higher rates of flow and shorter transit times than were observed during fasting. In sheep, continuous spiking activity could be induced by intravenous injection of 5‐hydroxytryptophan and this, similarly, was accompanied by a more rapid flow and a shorter transit time than recorded during the control period. 3. In both species the longest transit time occurred when a phenol red bolus was injected during the period of electrical inactivity. Relatively short transit times were observed when the bolus was administered just before the period of regular spiking activity. 4. When relaxation of the bowel was induced by intraperitoneal injection of hypertonic saline there was no spiking activity and the transit time for the infused solution was greatly lengthened, especially in the sheep. A noticeable flow of digestive contents persisted in the dog. 5. In the sheep the intestinal contents flowed intermittently during periods of 10–15 min and at the same frequency as the migrating myo‐electric complex. Two thirds of this flow took place in the 4–6 min immediately preceding the periods of irregular spiking activity. 6. It is concluded that in the fasted dog and in the sheep the migrating myo‐electric complex controls the pressure gradients on which the flow of intestinal contents depends. This is accomplished in the main by the prolonged phase of irregular spiking activity, and it is suggested that the regular spiking activity which follows it, though not in itself propulsive, serves as a barrier to prevent backflow of digesta into the quiescent part of the intestine. When continuous spiking activity is induced, by feeding in the dog and by injection of 5‐hydroxytryptophan in the sheep, no part of the intestine is quiescent and the transit time is shortened by the incessant irregular spiking activity.

The propagation of segmental contractions along the small intestine

1. The electrical activity of the small intestine of conscious dogs, rabbits and sheep was recorded by means of chronically implanted electrodes and was related to mechanical changes in the bowel.

Effects of anesthesia and surgical procedures on intestinal myoelectric activity in rats

Electrical spiking activity of the duodenum and jejunum was recorded from chronically implanted electrodes in rats during volatile or barbiturate anesthesia and following laparotomy. The normal pattern of electrical spiking activity in the fasted rat, with myoelectric complexes at 15-min intervals, was transiently replaced by quiescence during ethyl ether anesthesia. A slight increase in irregular spiking activity occurred after induction with pentobarbital, and the only effect of thiopental anesthesia was a reduction in the velocity of propagation of the complexes by 20%. Under barbiturate anesthesia, incision of the skin did not inhibit myoelectric activity, but incision of each abdominal muscle layer had an immediate and transient inhibitory effect; the deeper the layer, the longer was the inhibition. Peritoneal incision consistently produced inhibition of spiking activity which was prolonged by exposure of the bowel to air and intestine handling. The inhibitory effects produced by surgery persisted after vagotomy or transection of the spinal cord at the thoracic level but disappeared after splanchnicectomy. The above results suggest that a somatovegetative reflex with efferent pathways in the splanchnic nerves is involved in the first stage of operative inhibition of intestinal myoelectric complexes.Electrical spiking activity of the duodenum and jejunum was recorded from chronically implanted electrodes in rats during volatile or barbiturate anesthesia and following laparotomy. The normal pattern of electrical spiking activity in the fasted rat, with myoelectric complexes at 15-min intervals, was transiently replaced by quiescence during ethyl ether anesthesia. A slight increase in irregular spiking activity occurred after induction with pentobarbital, and the only effect of thiopental anesthesia was a reduction in the velocity of propagation of the complexes by 20%. Under barbiturate anesthesia, incision of the skin did not inhibit myoelectric activity, but incision of each abdominal muscle layer had an immediate and transient inhibitory effect; the deeper the layer, the longer was the inhibition. Peritoneal incision consistently produced inhibition of spiking activity which was prolonged by exposure of the bowel to air and intestine handling. The inhibitory effects produced by surgery persisted after vagotomy or transection of the spinal cord at the thoracic level but disappeared after splanchnicectomy. The above results suggest that a somatovegetative reflex with efferent pathways in the splanchnic nerves is involved in the first stage of operative inhibition of intestinal myoelectric complexes.

Circadian variation in the propagation velocity of the migrating motor complex

Using twin intraluminal pressure-sensitive radiotelemetric capsules for prolonged monitoring of proximal small bowel motility in healthy volunteers, we observed a significant (p less than 0.001) variation between daytime (6.44 +/- 0.74 cm/min, mean +/- SD) and nocturnal (2.90 +/- 0.35 cm/min) propagation velocities of the migrating motor complex. An identical variation in propagation velocity was observed in patients suffering from the irritable bowel syndrome. These data suggested a circadian variation, but did not exclude alternative hypotheses. Data were therefore compiled from healthy sheep and pigs supplied with ad libitum rations each morning and adapted to a 12 h light, 12 h dark schedule. Recording from implanted electrodes showed a significant (p less than 0.01) reduction in migrating motor complex velocity from 27.8 +/- 5.1 cm/min by day to 16.7 +/- 3.1 cm/min at night in sheep, and from 20.6 +/- 2.4 to 13.4 +/- 1.9 cm/min in pigs. The nocturnal reduction remained when the animals were fed in the evening. These observations suggest a circadian variation in mammalian migrating motor complex propagation velocity that is not merely a function of variation in intraluminal content.

Sleep cycles and kinesis in the foetal lamb

Abstract Continuous recording of foetal ECoG, eye and body movements and heart rate were carried our in the same animal during late pregnancy and perinatal period. Alternation of NREM sleep and REM sleep was recorded in 5 foetal lambs as an ultradian rhythm occupying 90% of the time during the 3 weeks prior to birth. The period of the rhythm was 30–40 min with a ratio of NREM/REM of 1/1 from 4 months post-conceptional age until 6–8 h before birth. Foetal kinetic behaviour was differentiated into simple or complex movements and gross activity. Kinesis, particularly the periods of gross activity which accompanied foetal alert wakefulness, was both more frequent and more intense during the night-time. After birth, the total sleep time was reduced to 40% of the recording time, at one week post-partum the ratio of NREM/ REM was 5/1. In the neonate the NREM-REM sleep cycles persisted but the period was reduced by half. Three to five sleep cycles were grouped in episodes of 90–120 min, separated by wakefulness and alimentary behaviour. Throughout the experiment, the main criterion for distinguishing alert wakefulness from NREM sleep was oculomotor activity. Wakefulness occupied about 10% of each 24 h period pre-partum and 60% post-partum.

Electrical activity of the ovine jejunum and changes due to disturbances

Spike potential activity of the jejunum was recorded from chronically implanted electrodes in conscious sheep. The activity was summed at 20-sec intervals before, during, and after induction of diarrhea, small-bowel obstruction, and after nerve section. Sheep on a normal diet regimen exhibited migrating myoelectric complexes at a frequency of 18/24 hr. These complexes displayed irregular and regular activities which occupied 67% of the recording time. A common pattern observed during the manipulations was disorganization of the motor profile. The normal pattern was replaced by continuous spiking activity followed in many cases by total quiescence. After vagotomy the complexes still occurred but the duration of irregular spiking activity was decreased. These experiments suggest that the migrating myoelectric complex acts as a regulating factor and suggests that the ratio of irregular to regular activity is dependent on the influence of extrinsic nerves.Spike potential activity of the jejunum was recorded from chronically implanted electrodes in conscious sheep. The activity was summed at 20-sec intervals before, during, and after induction of diarrhea, small-bowel obstruction, and after nerve section. Sheep on a normal diet regimen exhibited migrating myoelectric complexes at a frequency of 18/24 hr. These complexes displayed irregular and regular activities which occupied 67% of the recording time. A common pattern observed during the manipulations was disorganization of the motor profile. The normal pattern was replaced by continuous spiking activity followed in many cases by total quiescence. After vagotomy the complexes still occurred but the duration of irregular spiking activity was decreased. These experiments suggest that the migrating myoelectric complex acts as a regulating factor and suggests that the ratio of irregular to regular activity is dependent on the influence of extrinsic nerves.

Postoperative Intestinal Motility in Dogs and Sheep

Electrical activity of the small intestine was recorded from chronically implanted electrodes in dogs and sheep. The effects of laparotomy and surgical procedures were identified under general anesthesia. Laparotomy induced in both species a complete inhibition of electrical spiking activity during the stage of muscular and peritoneal incision. The inhibitory period due to laparotomy was shorter in dogs than in sheep and in both species less marked at the duodenal level. A secondary period of inhibition (ileus) lasting from 6 hr for a resection of the colon to 24 hr for a transection of the small bowel was observed in dogs after a transient phase of normal activity during 3–6 hr. The period of inhibition due to abdominal surgery lasted from 48 to 72 hr and occurred at the time of surgery in sheep. In both species, inhibition due to laparotomy and surgical procedures was prevented by splanchnicectomy. The results showed that myoelectric activity of the different parts of the small intestine is specifically inhibited and/or disorganized through peripheral reflex pathways. They are activated at different degrees by laparotomy and abdominal surgery.Electrical activity of the small intestine was recorded from chronically implanted electrodes in dogs and sheep. The effects of laparotomy and surgical procedures were identified under general anesthesia. Laparotomy induced in both species a complete inhibition of electrical spiking activity during the stage of muscular and peritoneal incision. The inhibitory period due to laparotomy was shorter in dogs than in sheep and in both species less marked at the duodenal level. A secondary period of inhibition (ileus) lasting from 6 hr for a resection of the colon to 24 hr for a transection of the small bowel was observed in dogs after a transient phase of normal activity during 3–6 hr. The period of inhibition due to abdominal surgery lasted from 48 to 72 hr and occurred at the time of surgery in sheep. In both species, inhibition due to laparotomy and surgical procedures was prevented by splanchnicectomy. The results showed that myoelectric activity of the different parts of the small intestine is specifically inhibited and/or disorganized through peripheral reflex pathways. They are activated at different degrees by laparotomy and abdominal surgery.

Colonic myoelectrical activity and propulsion in the dog

Electrical spike activity was recorded on the colon of the dog. The duration of the bursts of the spike was used to divide the spike activity into two different types: long and short spike bursts (LSB and SSB). LSBs lasted from 7 (ascending) to 37 sec (descending) and SSBs lasted about 1 sec, independent of the site. These measurements were applied to colons of colostomized dogs for which the colonic transit time was negatively correlated to the LSBs expressed as percent of the time. The effects of high- and low-residue diets were tested. Intake of large amounts of dry food was associated with an increase of the LSB activity. A meat diet was accompanied with an increase of the SSB activity. These results suggest a propulsive effect for the LSBs stimulated by large amounts of colonic contents while the SSB activity may reflect some degree of emptiness.Electrical spike activity was recorded on the colon of the dog. The duration of the bursts of the spike was used to divide the spike activity into two different types: long and short spike bursts (LSB and SSB). LSBs lasted from 7 (ascending) to 37 sec (descending) and SSBs lasted about 1 sec, independent of the site. These measurements were applied to colons of colostomized dogs for which the colonic transit time was negatively correlated to the LSBs expressed as percent of the time. The effects of high- and low-residue diets were tested. Intake of large amounts of dry food was associated with an increase of the LSB activity. A meat diet was accompanied with an increase of the SSB activity. These results suggest a propulsive effect for the LSBs stimulated by large amounts of colonic contents while the SSB activity may reflect some degree of emptiness.

On the Relevance of Non‐steroidal Anti‐inflammatory Drugs in the Prevention of Paralytic Ileus in Rodents

Abstract— In the mouse, the gastrointestinal transit of a charcoal marker, halved following the intraperitoneal administration of acetic acid, was no longer inhibited after pretreatment with the nonsteroidal anti‐inflammatory drugs (NSAIDs), indomethacin, ketoprofen, piroxicam or ximoprofen (0·25–2·5 mg kg−1 orally). In the fasted rat, the migrating myoelectric complex pattern of the small intestine which was disrupted for about one hour by acetic acid was unaltered by pretreatment with indomethacin or ximoprofen (0·5 mg kg−1 i.p.). In the anaesthetized rat, the inhibition by about 50% of the gastrointestinal transit due to laparotomy, did not occur following treatment with NSAIDs. It is concluded that NSAIDs prevent the occurrence of chemically‐induced and postoperative ileus in rodents, an effect probably related to the analgesic properties of NSAIDs.

Comparative effects of opiate agonists on proximal and distal colonic motility in dogs.

The colonic motility index was measured in dogs, by using strain-gauge transducers, before and after administration of opiate agonists. Fentanyl, a mu-compound, ethylketazocine (EKC), a kappa-compound, and [D-Ala2,Leu5]enkephalin (DADLE), a delta-agonist, were administered by intravenous (i.v.) or intrathecal (i.t.) routes. Fentanyl (2-10 nmol X kg-1 i.v.) induced a dose-related period of hyperactivity characterized by an increase in both tone and frequency of contractions in the distal portion of the colon, whereas a period of hypomotility following a short-lived period of increased activity was elicited on the proximal colon. Fentanyl (0.1, 0.2 nmol X kg-1 i.t.) had inhibitory effects on both proximal and distal colon. Small doses of EKC (2-4 nmol X kg-1) administered i.t. or larger doses (20-40 nmol X kg-1 i.v.) inhibited colonic motility for a dose-related duration, the effects of EKC being more marked on the distal colon than on the proximal colon. The administration of DADLE, 1-2 nmol X kg-1 i.t., and 40-20 nmol X kg-1 i.v., inhibited and stimulated the colonic contractions, respectively, in both proximal and distal colon. The results demonstrated that the colonic opiate-mediated responses may vary according to the route of administration, the portion of the colon studied and the opioid agonist used. Opiate agonists when administered centrally show a tendency to modulate colonic activity in a similar way whatever the type of agonist.