The rabbit colon consists of four distinct regions. The motility of each region is controlled by myogenic and neurogenic mechanisms. Associating these mechanisms with specific motor patterns throughout all regions of the colon has not previously been achieved. Three sections of the colon (the proximal, mid, and distal colon) were removed from euthanized rabbits. The proximal colon consists of a triply teniated region and a single tenia region. Spatio-temporal maps were constructed from video recordings of colonic wall diameter, with associated intraluminal pressure recorded from the aboral end. Hexamethonium (100 μM) and tetrodotoxin (TTX; 0.6 μM) were used to inhibit neural activity. Four distinct patterns of motility were detected: 1 myogenic and 3 neurogenic. The myogenic activity consisted of circular muscle (CM) contractions (ripples) that occurred throughout the colon and propagated in both antegrade (anal) and retrograde (oral) directions. The neural activity of the proximal colon consisted of slowly (0.1 mm/s) propagating colonic migrating motor complexes, which were abolished by hexamethonium. These complexes were observed in the region of the proximal colon with a single band of tenia. In the distal colon, tetrodotoxin-sensitive, thus neurally mediated, but hexamethonium-resistant, peristaltic (anal) and antiperistaltic (oral) contractions were identified. The distinct patterns of neurogenic and myogenic motor activity recorded from isolated rabbit colon are specific to each anatomically distinct region. The regional specificity motor pattern is likely to facilitate orderly transit of colonic content from semi-liquid to solid composition of feces.
- non-nicotinic transmission
controlled propulsion and mixing of content along the digestive tract is essential for normal life. This is achieved by a repertoire of motor patterns that ensure net flow rates appropriate for the breakdown of food, absorption of nutrients, and excretion of waste. These movements are due to coordinated contractions and relaxations of the internal circular smooth muscle layer and the external longitudinal smooth muscle. These smooth muscle layers are controlled by both myogenic mechanisms [initiated by interstitial cells of Cajal (ICCs)] and neurogenic mechanisms (via the enteric nervous system), which interact to generate diverse motor patterns (21, 31).
In the rabbit colon, four distinct colonic regions have been described (2, 16, 17, 35, 39). The first three regions form the proximal colon, and the fourth region comprises the distal colon. The first region is ∼10 cm in length and is characterized by three bands of longitudinal muscle (tenia), which form the characteristic haustral pouches. The second region is ∼20 cm in length and possesses a single tenia, and haustral pouches are present on one side of the colon only. The third region is the fusus coli; this is ∼4 cm in length, and the longitudinal muscle is present around the whole circumference. It joins the distal colon at the colonic flexure. The distal colon measures 80–100 cm. The majority of mixing and absorption of water and electrolytes occurs in the proximal colon; propulsive forces for the excretion of feces predominate in the distal colon (39).
Previous studies have investigated the motility in the rabbit proximal colon, both in vitro and in vivo (16, 17, 28, 35). Other studies of isolated segments of rabbit distal colon described neural mechanisms involved in excretion of the fecal pellets (3, 6, 10, 26). Detailed analyses of neurogenic and myogenic motility patterns throughout all regions of the colon have not been performed.
Determining patterns of motility is a necessary step to understand the motor functions of the digestive tract. Weisbrodt and Weems (43) suggested that four aspects are critical: wall motion, propulsion, fluid movement, and factors that control the contractile state of the muscle. We have used video recording to construct spatio-temporal maps of wall motion of segments of rabbit colon (15, 20, 21), recorded the intraluminal pressure, and used pharmacological tools to distinguish neurogenic from myogenic processes underlying the patterns of motor activity. We show here that each region displays distinct motility patterns corresponding to the physiological function of that region with functional transition corresponding to recognizable anatomical transitions.
Six New Zealand albino rabbits of both sexes weighing 2–4 kg were euthanized humanely by intravenous injection of pentobarbitone sodium (0.5 ml/kg) in accordance with approval by the Animal Welfare Committee of Flinders University. A ventral midline incision was made to expose the peritoneal cavity. Segments of the colon containing each of the transitional zones (Fig. 1) were removed and placed immediately into beakers containing oxygenated Krebs solution (in mM: 118 NaCl, 4.7 KCl, 1.0 NaH2PO4, 25 NaHCO3, 1.2 MgCl2, 11 d-glucose, 2.5 CaCl2) bubbled with 95% O2/5% CO2. Fecal material was gently flushed out of the proximal segments with oxygenated Krebs. The distal colonic segment was allowed to empty the fecal pellets spontaneously.
Preparations from proximal colon, colonic flexure and distal colon were studied separately (Fig. 1).
Proximal colon preparations included the three tenia section of the proximal colon and 6–10 cm of the single tenia region. These two regions are separated anatomically by the “tenia transitional zone.” Similar to Lentle et al. (28), the ventral-most tenia was set up to face the video camera, enabling two prominent haustral pouches bulging to either side.
Colonic flexure preparations comprised 6–15 cm of the proximal colon (single tenia), the fusus coli, and 6–12 cm of the distal colon. The segment was orientated so that the single tenia and the haustrated section of proximal colon were both visible.
Distal colon preparations were 10–15 cm and were taken from the region immediately proximal to the rectum (terminal distal colon). These sections were set up with no specific circumferential orientation since the longitudinal muscle covers the full circumference of the colon.
Recording commenced within 20 min of attaching the gut to the L-shaped connectors. Motor activity was recorded under resting conditions and then during slow distension (8 ml/min) by Krebs solution via the oral cannula. The maximal diameter observed in situ corresponded to its normal diameter when full of feces. We distended the isolated segments to match the maximal diameter observed in situ. After 10 min of distension were recorded, hexamethionum (100 μM) or mecamylamine (100 μM) were added to the bath to establish the dependence of patterns of motor activity on nicotinic synaptic transmission in the enteric circuits. After an additional 10 min of recording, tetrodotoxin (0.6 μM) was added to block all neural activity, revealing in full the myogenic motor patterns. In two separate preparations of distal colon after neural activity was blocked, we added carbachol (1–30 μM) to determine whether neural propagating events could be resorted (24).
Video Recording and Construction of Spatio-Temporal Maps
A digital video camera (Sony, DCR-TRV80E) was positioned above the preparation (Fig. 2), and movies of colonic wall motion were recorded (iMovie, Apple, Cupertino, CA) with a Macintosh G4 computer in clips of 10-min duration. These video recordings were then resampled to 4 frames/s and imported into custom-written software (Volumetry G7mv, Grant Hennig, University of Nevada, Reno, NV). The diameter at each point along the preparation was calculated for each frame and converted into grayscale to create a spatio-temporal map (DMap) of diameter changes (20) in periods of 10 min.
Motor patterns produced by changes in the diameters of the isolated segments were readily recognized in the DMaps. Localized reductions in the external diameter (whitening) of the gut wall were interpreted as circular muscle contractions, whereas increases in diameters (darkening) were regarded as either passive or active dilatations of the gut wall (20).
The motor patterns were readily recognized as propagating or non-propagating. Those patterns that were abolished by either hexamethonium or tetrodotoxin (TTX) were regarded as neurogenic. These include colonic migrating motor complexes (CMMCs) and peristaltic and antiperistaltic contractions. Shallow rhythmic circular muscle contractions propagating in both antegrade (anal) and retrograde (oral) directions that were not affected by either drug were called ripples and regarded as myogenic and attributed to the generation of contractions driven by networks of ICC (22). The frequency, intervals, duration, speed of propagation, and amplitude of these motor patterns were measured from the digitized maps constructed from the three colonic preparations. Since the apparent speed of propagation of these ripples depended on the delay between peaks of contractions, if the delay was very short, the contractions appear to occur in synchrony and therefore appear to propagate close to infinite speed. To provide a more meaningful value, we have reported the minimal speed of the ripples.
Hexamethonium bromide (100 μM; Sigma Aldrich), tetrodotoxin (0.6 μM; with citrate, Alomone Labs), mecamylamine (100 μM; Sigma Aldrich), and carbachol (1–30 μM; Sigma Aldrich) were used from concentrated solutions made up in distilled water.
Comparisons of frequency, amplitude, speed of propagation, and intervals between events were analyzed with one-way ANOVA with repeated measures or two-tailed, unpaired t-test using Prism software (GraphPad Software, La Jolla, CA). Data are presented as means ± SE or SD. Results were considered statistically different when P < 0.05.
In control preparations without drugs, complex patterns of motility were detected in the spatio-temporal maps. These patterns consisted of interactions between the myogenic and neurogenic contractions. To identify the patterns generated by the different mechanisms, we have described the myogenic patterns first and then the different neurogenic patterns observed. The myogenic and neurogenic motor patterns observed in each of the regions have been summarized in Table 1.
Motor Patterns in the Proximal Colon
After hexamethonium (100 μM) and TTX (0.6 μM), the motor pattern of the proximal colon with three tenia and a single tenia consisted of antegrade and retrograde propagating ripples. These ripples were shallow contractions reducing the diameter of the colon by 16 ± 7%. The direction and speed of propagation of ripples varied considerably (minimal speed 2.2 ± 0.2 mm/s aborally and 1.7 ± 0.3 mm/s orally). Ripples, whether aboral or oral, occurred at a frequency of 9.5 ± 0.6 cycles/min (cpm) (n = 5). They were associated with very small phasic pressure changes recorded by the pressure transducer at the anal end of the preparation (Fig. 2).
Ripples were also readily visible in Dmaps without either TTX or hexamethonium. In the absence of these drugs, they occurred at 9.4 ± 0.9 cpm (n = 5). Their frequency did not change when hexamethonium was added (9.3 ± 0.8 cpm, n = 5; Fig. 3).
In the proximal colon with three tenia, large haustral pouches were evident (Fig. 1). Some of the haustral indentations that separated them did not move during the experiment and probably represent fixed structures, perhaps connective tissue formations (black arrows in Fig. 2). The average distance between these fixed haustral indentations was 3.9 ± 0.2 mm (n = 5). Ripples invaded the haustral bulges and changed the diameter of the colon in this region. Similar fixed regions were also evident in the single tenia proximal colon.
The frequency of ripples in both triple and single tenia regions of the proximal colon were unaffected by TTX, even when increased distension was applied (9.5 ± 0.6 cpm; n = 5). However, in the single tenia region, a second additional myogenic activity was revealed during distension after TTX (Figs. 3 and 4). These ripples occurred at a higher frequency (31.2 ± 0.6 cpm; n = 4) and propagated more rapidly in both directions (minimal propagation velocity of 27.1 ± 3.2 mm/s orally; 10.7 ± 2.0 mm/s aborally). When the high-frequency ripples occurred at the same time as the lower-frequency ripples, they were associated with clusters of phasic pressure changes at the anal end of the preparation (Fig. 3).
Neurogenic patterns in the proximal colon.
In the region of the proximal colon with a single band of tenia, we observed spontaneous motor activity of neurogenic origin that was blocked by hexamethonium (see Figs. 2 and 6). These CMMCs consisted of antegrade propagating multiple circular muscle (CM) contractions that typically started at the tenia transitional zone. These CMMCs propagated very slowly, at just 0.1 mm/s (n = 5), and were associated with phasic increases in intraluminal pressure recorded at the anal end of the preparation (Fig. 2). They occurred at a spacing of 14.2 mm ± 1.3 (n = 5) and reduced the colonic diameter by 27 ± 8% (n = 5) of maximum diameter. They occurred at intervals of 150 ± 13.3 s (n = 5). The CMMC propagated all the way to the fusus coli (Fig. 5) at similar distances between peaks of contractions (14.9 ± 2.1 mm; P > 0.05), speeding up slightly as they approached the fusus coli (to 0.2 mm/s; P < 0.05).
Interaction Between Neurogenic and Myogenic Motor Patterns in the Proximal Colon
CMMCs interacted with the ripples as follows. On the side of the single tenia, the CMMCs appeared as smooth reductions in diameter (short light blue arrows in Fig. 2). However, on the side of the haustral pouches, these slow moving contractions summated with the ripples (short green arrows in Fig. 2), whereas the fixed haustral indentations remained visible (black arrows in Fig. 2). Ripples were associated with small longitudinal muscle contractions revealed in the Dmap by the back-and-forth motions (white arrow in Fig. 2, inset).
When the peaks of ripples coincided with the CMMC, the amplitude of CM shortening was augmented, producing rhythmic rings of CM contractions, which shifted slightly aborally with each successive beating contraction (see asterisks in Fig. 2, inset).
Motor Activity at the Fusus Coli Transition and Colonic Flexure
CMMC usually reached the fusus coli, stopping before the distal colon (Fig. 5). The background pattern of motor activity in the flexure transition and adjacent fusus coli appeared similar to the ripples that occurred through three tenia and single tenia regions of the proximal colon. They were not noticeably affected by hexamethonium or TTX, indicating their myogenic nature.
Motor Patterns in the Distal Colon
Distal to the colonic flexure, the motor patterns differed markedly from those observed in the proximal colon (Fig. 5).
Myogenic patterns in the distal colon.
Ripples were recorded in the distal colon in the absence of any pharmacological agents. However, they were more readily detected after TTX (0.6 μM). Under TTX, ripples occurred in both the section just below the colonic flexure (frequency 11.4 ± 0.8 cpm; n = 5) (Fig. 4) and in the terminal distal colon (Fig. 7) at significantly higher frequency (18.3 ± 1.3 cpm; n = 5; P < 0.05). In the section just below the flexure, ripples propagated aborally at 6.5 ± 1.0 mm/s and orally at 8.6 ± 1.6 mm/s (not significant) and in the terminal distal colon propagated aborally at 6.3 ± 2.3 mm/s and orally at 6.3 ± 1.9 mm/s (not significant).
Neurogenic patterns in the distal colon.
In the absence of drugs, distension of the distal colon below the colonic flexure elicited multiple TTX-sensitive peristaltic (antegrade) contractions. These travelled at 6.6 ± 0.8 mm/s at intervals of 22.1 ± 1.0 s (Fig. 5). These events were lumen occlusive and were preceded by longitudinal shortening. This activity was blocked by TTX (0.6 μM) (Fig. 7). Mechanically, these peristaltic contractions produced marked distension at the distal end of the preparation with corresponding pressure peaks recorded at the anal transducer (Fig. 5). Hexamethonium (100 μM) applied before TTX had little effect on their propagation velocity (7.3 ± 0.9 mm/s; not significant), although it increased the interval between antegrade contraction (35.1 ± 8.1 s; P < 0.05) (Fig. 6).
In the terminal distal colon, distension evoked similar peristaltic contractions, which propagated at 5.2 ± 0.7 mm/s (n = 5) and occurred at intervals of 23.9 ± 4.6 s (n = 5; Fig. 8). As in the proximal part of the distal colon, these were associated with longitudinal muscle shortening. Hexamethonium affected neither their speed (5.2 ± 0.9 mm/s n = 5) nor their interval (39.8 ± 11.9 s; n = 5) (Fig. 8).
In addition, interspersed with the peristaltic contractions, antiperistaltic (retrograde) contractions were also present in four of five preparations. These contractions propagated at 1.2 mm/s, a significantly slower speed than peristaltic contractions (P < 0.01) (Fig. 8) and were associated with a decrease in longitudinal muscle activity (Fig. 8). The antiperistaltic contractions continued in the presence of hexamethonium (100 μM), with an unchanged propagation velocity of 1.2 ± 0.2 mm/s (not significant; Fig. 8). TTX (0.6 μM) blocked antiperistaltic contractions (n = 5). In two experiments, mecamylamine (100 μM) failed to affect either antegrade or retrograde peristaltic contractions. In two experiments, adding carbachol (1–30 μM) after TTX failed to restore peristaltic contractions.
This is the first systematic study of the motor activity throughout the major regions of the rabbit colon. The study reveals four distinct motor patterns, one of myogenic origin and three of neurogenic origin (Table 1): 1) myogenic ripples in both proximal and distal colon; 2) CMMCs, consisting of neural slowly propagating antegrade multiple circular muscle contractions in the proximal colon; 3) antegrade neurally dependent peristaltic contractions consisting in the distal colon; and 4) retrograde neurally dependent antiperistaltic contractions consisting in the distal colon.
These regionally dependent patterns of motility underlie the slow aboral progression of content, allowing for mixing of content, absorption of water, electrolytes, and salts, during which fecal pellets are formed before excretion by defecation.
Myogenic Motor Activity in All Regions of Rabbit Colon
The ubiquitous pattern of motor activity recorded in this study was due to the ripple contractions. These are similar to those we described in the guinea pig proximal colon (14) and those described by Lentle (28). Ripples are myogenic in origin since they were not blocked by tetrodotoxin. Although during development “ripples” may be generated by smooth muscle (33), in the adult animals they are most likely generated by intrinsic networks of interstitial cells of Cajal (ICCs) that act as pacemakers (22), driving smooth muscle slow waves, which generate muscle contractions. Electromyographic recording from proximal and distal colon showed slow waves with very similar frequencies to the myogenic ripples recorded in the present study (1, 34) and which occur with a similar, relatively low frequency along the entire colon.
The speed of propagation of these myogenic contractions is likely to reflect intercellular connectivity in the networks of ICCs. In the Dmaps of this study, myogenic ripples propagated in both directions. There is a sharp transition of speed of propagation at the colonic flexure with ripples propagating at much higher speeds in the distal colon (Fig. 4). Similar myogenic ripples have been described in rat intestine (8).
Ehrlein described in vivo myogenic contractions with mainly retrograde propagation, which he called “haustral activity with rolling movements” (16). As Ehrlein suggested (16), it seems likely that myogenic ripples are primarily involved in mixing rather than propulsion of content.
Are Haustra Fixed?
In the three tenia region of the proximal colon, deep haustrations were readily visible. Contractile activity in empty or modestly distended segments was mostly myogenic since neither hexamethonium or TTX affected its amplitude in either CM or LM. The deep indentations that delineated the haustra did not change in location during experiments, indicating that these are probably fixed points, probably due to connective tissue structures. This is at variance from Lentle et al. who reported that all haustral indentations appear to propagate (28). We are currently unable to explain the difference between our results.
Two Types of Myogenic Pacemaker Activity in the Proximal Colon Wall
Our experiments provide mechanical evidence for two different frequencies of myogenic pacemaker activity within the proximal colon wall. After neural activity was blocked with TTX and significant distension was applied, in addition to the low-frequency ripples, higher-frequency ripple contractions were detected. Interestingly, these contractions propagated at a significantly greater speed than the lower-frequency ripples (see Figs. 3 and 4). Our findings are also consistent with the work of Lentle et al. (28), who distinguished two frequencies of myogenic motor activity. It is likely that these two oscillations originate at two discrete locations within the colonic wall, with one set of pacemakers perhaps close to the myenteric plexus and the other at the submucosal border, as has been described in the dog colon (38). It is also possible that these second type of ripples we observed may not be due to underlying slow waves (33).
The physiological role of these two frequencies of contractile activity is still unclear. However, a clue to the role of the faster myogenic system may be apparent from Fig. 3. When both pacemaker systems occurred simultaneously and their ripple contractions summated, significant intraluminal pressure changes were generated at the aboral end of the segment. Thus the synchronous activity of these two pacemakers may enable the circular muscle to produce mechanically effective contractions.
Are There Specialized Pacemaker Areas Along the Length of the Colon?
Ruckebusch et al. (34) proposed that there is a special pacemaker area at the colonic flexure (fusus coli), whereas Hukuhara and Neya (25) suggested that a specialized pacemaker area gave rise to the distinct transition from soft viscous content to hard pellet contents at the colonic flexure of the rat and guinea pig. Our results do not support the existence of specialized pacemaker areas anywhere along the colon; contractions could clearly originate at many points in both proximal and distal colon. The shifting points of initiation suggest that there is not a fixed gradient in the intrinsic pacemaker frequency within the isolated segments.
However, the ripples in preparations of terminal distal colon occurred at a higher frequency than those in more proximal regions of the distal colon. The gradient we observed in the rabbit distal colon would favor retrograde (oral) propulsion.
Neurogenic Migrating Motor Complexes in the Proximal Colon
A major result of this study was the identification of CMMC, which occurred at very regular intervals, about every 150 s, and appeared to originate at the tenia transition zone. It is likely that different conditions of the luminal content (e.g., greater volume or viscosity) would generate neurally dependent movements on the oral side of the transition zone (28). The CMMCs in this study were found to propagate all the way along the single tenia region of the proximal colon to the colonic flexure (fusus coli) at a remarkably constant velocity, similar to those reported previously as “haustral progression” at 0.1 mm/s (28) and as “segmental contractions” at 0.1–0.3 mm/s (16, 17). The characteristics of CMMCs in rabbit colon were similar to those described in other species (6, 13, 36, 37, 40). Such activity is likely to form the characteristic shape of the fecal pellets (16, 17, 35). The effect of hexamethonium indicates that nicotinic transmission is required for this cyclic motor activity (28). Nicotinic transmission mediates most fast excitatory synaptic transmission in enteric circuits (9) and thus underlies many neurally dependent enteric motor functions.
Neurogenic Peristalsis (Antegrade) and Antiperistalsis (Retrograde) in the Distal Colon
Liquid distension of the distal colon evoked antegrade peristaltic contractions that became lumen-occlusive and caused large increases in intraluminal pressure at the anal end (Fig. 8), indicating that they are propulsive. Interestingly, although these contractions were found to be dependent on enteric neural circuits [as they were TTX-sensitive (29)], to our surprise fast nicotinic transmission was not required, since hexamethonium did not inhibit them nor their change their speed of propagation (27, 29). Also, mecamylamine (100 μM) failed to block the antegrade or retrograde peristaltic contractions, suggesting that the nicotinic transmission is unlikely to be involved in these peristaltic contractions. TTX-sensitive but hexamethonium-resistant propulsion of colonic contents has also been demonstrated in the guinea pig distal colon (30).
Our experimental arrangement prevented the emptying of the contents and thus simulates an occluded colon. Under these conditions, the peristaltic contractions appeared in irregular clusters, indicating that the underlying neural and muscular processes were cyclical and showed little fatigue. Whether the irregular cyclic activity corresponds to the cyclic motor activity seen in the guinea pig colon when propulsion of pellets is prevented (30, 37) remains to be established.
In more distal regions of the colon, the antiperistaltic contractions were interspersed with the peristaltic contractions. Antiperistaltic (retrograde) contractions have been reported in humans and animals since the early 1900s (3, 4, 7, 11, 18, 42). As in previous studies, the speed of propagation of antiperistalstic contractions was significantly slower than peristaltic contractions. Previous reports did not establish whether retrograde propagating contractions are neural or myogenic in origin. Our data clearly indicate that these motor patterns in the distal colon are neurogenic since they were blocked by TTX.
A question arises as to the nature of the neural control of these peristaltic and antiperistaltic contractions. One possibility is that neural activity is permissive, with the direction of propagation being determined by the muscular apparatus as suggested for the rat colon (24). The lack of recovery of peristaltic or antiperistaltic contractions by carbachol after blocking neural activity suggests that this is not the case and that enteric neural circuits directly generate these motor patterns. It is likely the propagation of these neural contractions involves ongoing mechanical activation of enteric reflex pathways by the advancing contents (neuromechanical process) originally proposed by Bayliss and Starling (5) as the bases of intestinal propulsion.
Interaction Between Neurogenic and Myogenic Patterns
In our experiments, the colonic migrating motor complex in the proximal colon (at ∼0.1 mm/s) was superimposed on the underlying myogenic rhythmic contractions, which propagated at a faster speed (∼1.6 mm/s). Every CMMC resulted from several localized contractions, which were generated by the underlying propagating ripple contractions, as shown in Fig. 2. This pattern is likely to be due to excitatory motoneurons becoming active over an extended area of colon, which then slowly migrates aborally. This excitation is likely to result from the synaptic connectivity in the enteric nervous system (41). As it passes, it augments the slow-wave-generated ripple contractions, generating the full motor complex. The resulting intraluminal pressure recorded at the anal end of the segment showed waning and waxing of rhythmic pressures waves, with maxima corresponding to the deepest indentations of the gut wall seen in the DMaps (see Fig. 2). These pressure “complexes” recorded by the anal pressure transducer (Fig. 2) resemble manometrically recorded motor patterns reported in vivo in the proximal colon of rabbits (16), pigs (23), and sheep (7), and they have been observed in the human colon (19, 32). This type of motility has been temporally associated with movement of colonic content in animals (7, 16, 23) and healthy human subjects (12).
In conclusion, the rabbit colon displays distinct myogenic and neurogenic motor patterns similar to those previously described in other mammals, including humans. Interestingly, this study reveals that the expression of these particular motor patterns differs along the length of the colon, and each pattern is localized to specific anatomical transitions. This suggests that each motor pattern contributes specifically to the optimal progression of contents from semiliquid to solid feces. This study shows how conventional video recording of intestinal motor activity enables the construction of quantitative spatio-temporal maps of motility in which fundamental myogenic and neurogenic patterns of colonic motor activity can be identified, distinguished, and measured. Combining video recordings of colonic wall movements coupled with manometric recordings (15) should facilitate characterization of the complex interactions that must exist between each distinct motor pattern.
P. G. Dinning is supported by National Health and Human Research Council (NHMRC) Grant no. 630502 and the Clinician's Special Purpose Fund of the Flinders Medical Centre; M. Costa is supported by a grant from the FMC Research Foundation. The experiments in this study were carried out in N. J. Spencer's laboratory, funded by NHMRC Grant no. 535034.
No conflicts of interest, financial or otherwise, are declared by the author(s).
Author contributions: P.G.D. and M.C. conception and design of research; P.G.D. and M.C. performed experiments; P.G.D. and M.C. analyzed data; P.G.D., M.C., S.J.B., and N.J.S. interpreted results of experiments; P.G.D. and M.C. prepared figures; P.G.D. and M.C. drafted the manuscript; P.G.D., M.C., S.J.B., and N.J.S. edited and revised the manuscript; P.G.D., M.C., S.J.B., and N.J.S. approved the final version of the manuscript.
We are grateful for the technical support of Mel Kyloh and Sarah Nicholas.
- Copyright © 2012 the American Physiological Society