Stimulation of the nitric oxide-guanosine 3', 5'-cyclic monophosphate pathway by sildenafil: effect on rectal muscle tone, distensibility, and perception in health and in irritable bowel syndrome

OBJECTIVES: Nitric oxide, a neurotransmitter in the noncholinergic, nonadrenergic nervous system, is a mediator of relaxation of GI smooth muscle and of visceral nociception mainly studied in vitro. Sildenafil stimulates the nitric oxide guanosine 3', 5'-cyclic monophosphate (NO-cGMP) pathway through inhibition of phosphodiesterase 5. The aims of this study were to evaluate in vivo the effect of stimulation of the NO-cGMP pathway on rectal tone, distensibility, and perception in healthy individuals and in patients with irritable bowel syndrome (IBS). METHODS: In eight healthy subjects and four patients with IBS rectal tone, distensibility and perception thresholds were measured with an electronic barostat both before and 60 min after administration of sildenafil (50 mg p.o.). Perception was scored on a graded scale of 0-6. At the end of a distension series an anatomic questionnaire was filled out by the subjects. RESULTS: Sildenafil significantly reduced rectal tone in healthy subjects (intrabag volume predrug: 145.5 +/- 18.7 ml vs postdrug: 164.4 +/- 16.9 ml, p = 0.01) and IBS (111.3 +/- 25.2 ml vs 136.5 +/- 33.3 ml; p = 0.01) but did not alter rectal compliance (healthy subjects: 5.8 +/- 0.4 vs 6.3 +/- 0.6 ml/mm Hg, p > 0.05; IBS subjects: 6.1 +/- 0.6 vs 7.1 +/- 1.0 ml/mm Hg, p > 0.05). Intrabag pressure and rectal wall tension to reach perception thresholds for initial sensation, sensation of stool, and urgency were not altered by sildenafil. However, intrabag volumes to reach these thresholds were significantly increased by sildenafil both in healthy subjects and in patients with IBS. Viscerosomatic referral was unchanged. CONCLUSIONS: Stimulation of the NO-cGMP pathway decreases rectal tone but does not influence rectal distensibility. Relaxation of the rectum is accompanied by an increase in rectal volumes to reach perception thresholds in healthy subjects and in patients with IBS, but no direct effect on rectal perception can be demonstrated.     

The effects of biofeedback on rectal sensation and distal colonic motility in patients with disorders of rectal evacuation: evidence of an inhibitory rectocolonic reflex in humans?

OBJECTIVE: Abnormalities of descending colon motility reported in a subset of patients with rectal evacuation disorders are consistent with a rectocolonic inhibitory reflex. Our aims were to evaluate distal colon motor function and rectal sensation in such patients and assess effects of biofeedback (BF) training on these functions. METHODS: Seven patients (five women, two men; mean age 36 yr) with rectal evacuation disorders were studied before and after 10-days biofeedback training; six healthy volunteers (five women, one man; mean age 30 yr) were studied once. Colonic compliance, motility, sensation thresholds, and perception scores during standardized rectal distentions were measured using two barostat-manometry assemblies inserted into the cleansed colon with the aid of flexible sigmoidoscopy. RESULTS: Sigmoid compliance, fasting, and postprandial motility index, and perception thresholds were similar in controls and patients before and after biofeedback training. Postprandial sigmoid tone tended (p = 0.09) to be lower in patients than controls; after biofeedback, postprandial tone was comparable to that in controls. Rectal urgency scores at 24 mm Hg distention were greater in patients than in controls (p = 0.02 for both). After biofeedback, there were trends for lower perceptions of urgency to defecate (7.6 +/- 1.1 cm pre- vs 5.3 +/- 1.5 post-; p = 0.04) at 24 mm Hg; conversely, gas sensation at 12 mm Hg was higher (1.2 +/- 0.5 cm pre- vs 3.3 +/- 0.6 post-; p = 0.05). CONCLUSIONS: Normalization of rectal evacuation and postprandial sigmoid tone in patients with evacuation disorders by biofeedback training supports the presence of a rectocolonic inhibitory reflex. Effect of biofeedback on rectal sensation in these patients requires further study.     

Acupuncture has a placebo effect on rectal perception but not on distensibility and spatial summation: a study in health and IBS

BACKGROUND: Recent data suggest that acupuncture has effects on gut physiology and perception. Spatial summation is a central mechanism of perception and describes the phenomenon that thresholds for perception are lower if more receptors are stimulated. OBJECTIVES: We assessed perception thresholds for rectal distension and cutaneous referral of symptoms, while inflating one or two rectal balloons and the effect of both electro-acupuncture and placebo-acupuncture on rectal distensibility, perception, and spatial summation. METHODS: A tube with two barostat balloons was placed in the rectum of 12 healthy subjects and nine irritable bowel syndrome (IBS) patients with rectal symptoms. Volume-controlled stepwise distension of the distal balloon only or both balloons was performed first as a control, and thereafter with simultaneous placebo- or electro-acupuncture in dermatomes S3 and S4. A symptom questionnaire and anatomic questionnaire was completed during each distension. RESULTS: Rectal elastance increased from 42.0 +/- 19.6 log mmHg/ml during one-balloon distension to 59.6 +/- 33.1 log mmHg/ml during two-balloon distension (p < 0.05) in healthy subjects, and from 48.8 +/- 14.4 log mmHg/ml (one balloon) to 77.6 +/- 24.2 log mmHg/ml (p < 0.001) in patients with IBS. Electro-acupuncture had no effect on rectal sensation, elastance, and cutaneous referral when compared to placebo-acupuncture. However, acupuncture (both electro- and placebo-) increased volume thresholds for sensation compared to control experiments, while objective parameters like rectal tone and elastance were unaltered. CONCLUSION: Acupuncture has a placebo effect on rectal perception but has no effect on rectal distensibility and visceral referral. Spatial summation affected both rectum distensibility and perception, but was also not altered by acupuncture.     

Rectoanal Sensorimotor Response in Humans During Rectal Distension

PURPOSE: Rectal perception facilitates maintenance of continence and defecation. Whether perception is associated with motor changes in anorectum is unclear. We examined sensory and motor responses of the anorectum during rectal distention. METHODS: Stepwise graded rectal balloon distensions were performed in 23 healthy subjects by placing a six-sensor probe in the anorectum. Manometric changes, rectoanal reflexes, and sensory thresholds were assessed. Studies were repeated in six subjects. RESULTS: All subjects showed rectoanal inhibitory and contractile reflexes, but rectal perception was associated with an anal contractile response (sensorimotor response). In 4 subjects (17 percent) the sensorimotor response first occurred synchronously with a sensation of fullness (Group 1) and in 19 (83 percent) with a desire to defecate (Group 2). Mean balloon volume for inducing the sensorimotor response in Groups 1 and 2 were 80 +/- 14 ml and 96 +/- 26 ml (P > 0.05). The onset, amplitude, duration, and area under curve of the response were similar in both groups. At higher volumes of balloon distention, all subjects (n = 23) reported a desire and an urge to defecate. The sensorimotor response associated with an urge to defecate had higher amplitude (P = 0.01) and higher area under curve (P = 0.001) compared with that associated with a desire to defecate. Repeat studies showed good reproducibility (intraclass correlation coefficient = 0.9; P < 0.05). CONCLUSIONS: A desire to defecate is associated with a unique, consistent, and reproducible anal contractile response: the sensorimotor response. This response could play an integral role in regulating anorectal sensation and function.     

Alterations in rectal sensitivity and motility in childhood irritable bowel syndrome

BACKGROUND & AIMS: Children with chronic abdominal pain have a heterogeneous clinical presentation, but no organic cause can be identified in most of them. Some children present with symptoms of irritable bowel syndrome (IBS). We hypothesized that visceral hypersensitivity and motor abnormalities may be underlying mechanisms in these children. METHODS: Rectal sensation and rectal contractile response to a meal were studied in 8 children with IBS and 8 children with functional abdominal pain (FAP) and were compared with those of 9 healthy volunteers (HVs). RESULTS: The threshold for pain, but not that for first sensation and urge to defecate, was significantly decreased in IBS patients (6 +/- 1 mm Hg) compared with FAP patients and HVs (17 +/- 1 and 22 +/- 2 mm Hg, respectively). In HVs and patients with FAP, ingestion of a meal induced a decrease in rectal volume with an early and late component. This motor pattern was absent in children with IBS. In IBS patients, no rapid volume waves were observed during fasting in contrast to FAP patients (2.7 +/- 0.3/10 min) and HVs (1.8 +/- 0.5/10 min). CONCLUSIONS: Children fulfilling the Rome II criteria for IBS have a significantly lowered threshold for pain and a disturbed contractile response to a meal. Comparable to results reported in adults, sensory and motor abnormalities might play a pathophysiologic role in childhood IBS.     

Subtypes of constipation predominant irritable bowel syndrome based on rectal perception

Background—Patients whocomplain of constipation can be divided into those who have lost thenatural call to stool, but develop abdominal discomfort after severaldays without a bowel movement (no urge); and those who experience aconstant sensation of incomplete evacuation (urge).
Aims—To determine whether the twogroups differ in symptoms, colonic transit, and perceptual responses tocontrolled rectal distension.
Methods—Forty four patients withconstipation were evaluated with a bowel symptom questionnaire, colonictransit (radiopaque markers), and rectal balloon distension. Stool (S)and discomfort (D) thresholds to slow ramp (40 ml/min) and rapid phasicdistension (870 ml/min) were determined with an electronic distensiondevice. Fifteen healthy controls were also studied.
Results—All patients had Romepositive irritable bowel syndrome (IBS); 17 were no urge and 27 urge.Mean D threshold to phasic rectal distensions was 28 (3) mm Hg in nourge, 27 (3) mm Hg in urge (NS), but higher in the control group (46 (2) mm Hg; p<0.01). Sixty seven per cent of no urge and 69% of urgewere hypersensitive for D. Slow ramp distension thresholds were higherin no urge (S: 26 (3); D: 45 (4) mm Hg) compared with urge (S: 16 (2);D: 31 (3) mm Hg; p<0.01), or with controls (S: 15 (1); D: 30 (3); p<0.01).
Conclusions—Hyposensitivity to slowrectal distension is found in patients with IBS who complain ofconstipation and have lost the call to stool even though theirsensitivity to phasic distension is increased.

Keywords:visceral sensation; colonic transit

     

Stimulation of defecation: effects of coffee use and nicotine on rectal tone and visceral sensitivity

OBJECTIVE: Coffee and cigarette use is believed to induce bowel movements, although the literature is controversial and precise measurements of rectal tone and sensitivity with a barostat have never been performed. The aim of this study was to assess the effects of coffee and nicotine on rectal tone, compliance and sensitivity. MATERIALS AND METHODS: Sixteen healthy volunteers were recruited for the coffee (n = 8) and nicotine (n = 8) experiments. The experiments were randomly performed in a placebo-controlled crossover design on separate days. In the coffee experiment, 280 ml strong coffee or warm water was drunk and in the nicotine experiment, nicotine (2 mg) or placebo was given sublingually. A rectal barostat procedure was carried out. A flaccid bag, mounted on a catheter, was inserted in the rectum. Continuous pressure distension was exerted to register basal visceral sensitivity and compliance. After rectal adaptation, the stimulus was given. Rectal tone was measured for 1 h, after which continuous pressure distension was repeated. RESULTS: Rectal tone increased by 45% 30 min after coffee intake (p = 0.031) and by 30% after water intake (p = 0.032), but the effects of coffee and water were not significantly different. Rectal tone did not change significantly after administration of nicotine (7%) or placebo (10%). There was no difference in compliance and visceral sensitivity between coffee and water or nicotine and placebo. CONCLUSIONS: Both coffee and warm water have an effect on defecation by increasing rectal tone, but nicotine (2 mg) did not affect rectal tone. Coffee and nicotine did not influence sensitivity or compliance.     

Rectal afferent hypersensitivity and compliance in irritable bowel syndrome: differences between diarrhoea-predominant and constipation-predominant subgroups

OBJECTIVES: To evaluate the differences in rectal compliance and sensory thresholds for the urge to defecate and discomfort between irritable bowel syndrome (IBS) subgroups and controls, and to correlate these parameters with rectal symptoms. METHODS: A total of 38 IBS patients [Rome II criteria; 19 diarrhoea-predominant IBS (D-IBS), 16 constipation-predominant IBS (C-IBS), three with alternating diarrhoea and constipation IBS (Alt-IBS)] and 10 controls were studied. A barostat was used to measure rectal compliance and sensory thresholds, in the 'unprepared' rectum. The thresholds for the urge to defecate and discomfort were determined using phasic rectal balloon distension in a double random staircase sequence. RESULTS: D-IBS had significantly lower rectal compliance and threshold for the urge to defecate compared with controls [4 ml/mmHg interquartile range (IQR) 3.99 versus 8.4 ml/mmHg IQR 5.69; P=0.001; 8 mmHg IQR 6 versus 20 mmHg IQR 4; P=0.003]. D-IBS also had significantly lower rectal compliance and threshold for the urge to defecate compared with the C-IBS group (5.8 ml/mmHg IQR 4.61; P=0.027; 16 mmHg IQR 12; P=0.003). The volume at the threshold for discomfort was significantly lower in D-IBS compared with controls (163 ml IQR 99.5 versus 212 ml IQR 147.25; P=0.016). The severity of abdominal pain and rectal symptoms showed a significantly negative correlation with rectal sensory thresholds. CONCLUSION: This study shows that the sensory threshold for the urge to defecate and rectal compliance is significantly lower in D-IBS compared with C-IBS and controls. The consequent inability to tolerate rectal faecal loading may account for the symptoms of the passage of frequent, small-volume stools in D-IBS patients.     

Intraesophageal acid perfusion sensitizes the esophagus to mechanical distension: a Barostat study

OBJECTIVE: The pathogenesis of noncardiac chest pain is unclear. Increased gastroesophageal reflux and decreased pain thresholds to intraesophageal balloon distension have been demonstrated in a proportion of such patients. We aimed to investigate whether acid exposure sensitizes esophageal mechanoreceptors in healthy volunteers. METHODS: After an overnight fast, an infinitely compliant balloon, 4.5 cm in length and mounted on a multilumen transnasal manometry catheter, was placed 8.5 cm above the lower esophageal sphincter in 12 healthy male volunteers aged 18-39 yr. After determination of the minimal distending pressure, the balloon was inflated up to 48 mm Hg by means of a computer-controlled barostat (G & J Electronics, Canada). Graded stepwise distensions were interspersed with random decreases in pressure to two-thirds of the previous value. At each pressure level, the subjects were asked to report on sensation and the presence of pain. Baseline distension was repeated to determine reproducibility of the pressure/volume relationship and also the perception and pain thresholds. After the baseline distension sequence, the esophagus was perfused for 20 min (at 7 ml/min) with either normal saline (control) or 0.1 N hydrochloric acid at 37 degrees C on a random basis. RESULTS: Basal sensory thresholds varied widely (first perception 5-36 mm Hg, pain 8 > or = 43 mm Hg). Two subjects did not experience pain up to the maximum distending pressure (42 and 43 mm Hg, respectively, after correction for the minimal distending pressure). Esophageal body compliance was similar on repeat distension. Sensory thresholds were reproducible with different distensions (perception r = 0.99, pain r = 0.95). Saline resulted in no significant changes in perception or pain thresholds. Acid perfusion reduced first perception (median before and after acid, 15 mm Hg and 8 mm Hg, respectively, p = 0.05) and pain threshold (median before and after acid, 32.5 mm Hg and 26.5 mm Hg, respectively, p = 0.05). When compared to changes after saline perfusion, acid perfusion reduced the perception threshold (median change, -3.8 mm Hg vs 0 mm Hg, p = 0.04) and tended to reduce the pain threshold (median change, -3.75 mm Hg vs +0.75 mm Hg, p = 0.09). CONCLUSIONS: Intraesophageal balloon distension using a barostat is a reproducible method of measuring esophageal body compliance and sensory thresholds. Acute exposure to acid seems to sensitize the esophagus to perception from intraluminal balloon distension.     

Hyperglycemia-Induced Attenuation of Rectal Perception Depends upon Pattern of Rectal Balloon Inflation

This study investigated the effects of acutehyperglycemia on conscious rectal perception in responseto two different rectal distension paradigms. Elevenhealthy males were studied in random order on two separate days during euglycemia andhyperglycemia with blood glucose concentrations clampedto 3.8 ± 0.6 and 14.8 ± 0.86 mmol/liter,respectively. In order to evoke sensory responses, rapidphasic and ramplike distensions were applied to anintrarectal balloon. Rectal sensation thresholds forinitial sensation, sensation of stool and discomfort,and sensory intensities were recorded. Additionally,anorectal motor responses were investigated during phasicdistension. Acute hyperglycemia did not modify rectalsensory pressure thresholds and perception scores inresponse to phasic distension. Neither did hyperglycemia alter the resting anal sphincter pressure, thepressure threshold for eliciting the rectoanalinhibitory reflex, or the maximal anal squeeze pressure.In contrast, hyperglycemia attenuated rectal perception in response to ramplike distension. Thepressure thresholds, 10.0 ± 1.8 and 17.0 ±3.6 mm Hg for initial sensation and discomfort,respectively, during hyperglycemia were significantlyhigher than the corresponding thresholds of 4.4 ± 1.4and 11.4 ± 1.9 mm Hg observed during euglycemia(P < 0.01). Higher rectal pressures were observed atall intensities of sensation of stool and discomfortduring hyperglycemia than those obtained duringeuglycemia (P < 0.01). Hyperglycemia did not alterthe compliance of the rectum. The results of this studydemonstrate that acute hyperglycemia attenuates rectal perception, and this attenuation depends uponthe type of distension employed. Our findings alsodemonstrate that anal sphincter motor function is notappreciably modified by hyperglycemia.     

Effect of a second-generation alpha2delta ligand (pregabalin) on visceral sensation in hypersensitive patients with irritable bowel syndrome

BACKGROUND: Visceral hypersensitivity is an important pathophysiological factor in irritable bowel syndrome (IBS). Pre-clinical studies suggest that the alpha(2)delta ligand pregabalin reduces both visceral allodynia and hyperalgesia, but is inactive on basal sensitivity. AIM: To assess the effect of pregabalin on the perception of rectal distension in hypersensitive IBS patients. METHODS: Twenty-six patients with Rome-II-defined IBS (aged 18-46 years, 7 male) were included in a randomized, double-blind, placebo-controlled, parallel-group study in which they received either 3 weeks oral pregabalin (titrated: 50 mg tid days 1-3, 100 mg tid days 4-7, 150 mg tid days 8-11; fixed 200 mg tid days 12-21 +/-4) or placebo control. Rectal sensitivity was assessed using a barostat technique, in which sensory thresholds were determined using the ascending method of limits, followed by tracking both before and after treatment. Only patients with a pain threshold of 相似文献   

Rectal reservoir and sensory function studied by graded isobaric distension in normal man.

The rectal expansion and concomitant sensory function on graded, isobaric, rectal distension within the interval 5-60 cm H2O was investigated in 36 healthy young volunteers. Anal pressure and electromyography (EMG) from the external anal sphincter were simultaneously recorded. Rectal distension caused an initial rapid expansion followed by transient, often repeated, reflex rectal contractions and a slow gradual increase of rectal volume. The maximal volume displaced by the first reflex rectal contraction was 18 (13) ml, which was less than 10% of the volume at 60 s. The pressure threshold for appreciation of rectal filling was 12 cm H2O (95% CL 5-15 cm H2O) and coincided with the threshold for rectoanal inhibition. Urge to defecate was experienced at 28 cm H2O (15-50 cm H2O) distension pressure, which was close to the threshold for maximal rectal contraction, also coinciding with the appearance of the external anal sphincter reflex. The interindividual variation of rectal volume on distension with defined pressures varied widely, indicating a considerable variation of rectal compliance in normal man. No correlation was found between rectal volume and sex or anthropometric variables. The relative variations in pressure thresholds for eliciting rectal sensation and rectoanal reflexes were less than the corresponding threshold volumes. It was concluded that the dynamic rectal response to distension reflects a well graded reflex adjustment ideal for a reservoir.     

Effect of rectal distension on the small intestine with evidence of a recto-enteric reflex

BACKGROUND/AIMS: To study the effect of rectal distension on jejunal and ileal motility aiming at the assessment of the possible role of rectal distension induced by constipation on the transport of the material in the gut. METHODOLOGY: The rectum of 16 healthy volunteers (mean age: 38.6 +/- 11.7 years, 10 men, and 6 women) was distended by a balloon filled with water in increments of 50 mL up to 200 mL and the response of the jejunal and ileal pressures was recorded. The test was repeated distending the anesthetized rectum 20 min and 3 hours after anesthetization. RESULTS: Rectal distension with 50 mL of water effected no jejunal or ileal pressure changes (P > 0.05). One hundred-mililitre (100-mL) rectal distension produced decrease of jejunal and ileal pressures (P < 0.05) which lasted as long as distension was maintained. Rectal distension with 150 and 200 mL caused jejunal and ileal pressure response similar to that of the 100 mL distension (P > 0.05). Distension of the anesthetized rectum effected no significant jejunal or ileal pressure changes. CONCLUSIONS: The results were reproducible in the individual subject. The decline of the intestinal pressure upon rectal distension postulates a reflex relationship between the 2 conditions. This reflex nature is evidenced by reproducibility and by its absence on distension of the anesthetized rectum. We termed this reflex relation: "recto-enteric reflex". It is suggested that under normal physiologic conditions the reflex inhibits the intestinal transit, thus giving the rectum time to evacuate itself. Continuous rectal distension, as occurs in inertia constipation, appears to effect enteric hypotonia, a hypothesis which requires further studies.     

Corticotropin-releasing factor induces rectal hypersensitivity after repetitive painful rectal distention in healthy humans

Background Rectal hypersensitivity induced by repetitive rectal distention (RRD) is reported to be a response specific to patients with irritable bowel syndrome (IBS), and is not observed in healthy controls. We evaluated the rectal pain threshold (PT) and determined whether intravenous corticotropin-releasing factor (CRF) induces rectal hypersensitivity after RRD in healthy humans, that is, whether it mimics the response observed in IBS patients. Methods A double-blind placebo-controlled study design (CRF or vehicle) was used. In the first experiment, PT (mmHg) induced by ramp distention was measured by a barostat. Then CRF (100 μg, n = 5) or vehicle (n = 6) was injected intravenously (iv) followed by RRD, consisting of phasic distentions with sensory tracking, which lasted until the subjects had complained of pain six times. After RRD, PT was measured again. In another experiment, PT was measured, and then CRF (n = 5) or vehicle (n = 5) was injected iv. After 45 min, ramp distention was again induced to determine PT. Results In the placebo group, PT was not modified by RRD (before RRD, 33.0 ± 6.8; after RRD, 33.4 ± 4.5), while it was significantly reduced in the CRF-treated group (before RRD, 32.9 ± 9.0; after RRD, 26.1 ± 7.9, P < 0.05). On the other hand, CRF or vehicle without RRD did not alter PT (before iv-CRF, 35.2 ± 4.2; after iv-CRF, 35.3 ± 4.9; before iv-vehicle, 34.5 ± 7; after iv-vehicle, 35.5 ± 6.8). Conclusions These results indicate that CRF modifies rectal sensation in healthy humans and mimics an IBS-specific visceral response, suggesting the possible contribution of CRF to the pathogenesis of IBS.     

The gastrorectal reflex in women with obstructed defecation

This study evaluated the tonic response of the rectum to a meal in women with obstructed defecation. Fifteen control subjects and 60 women with obstructed defecation were studied. Total colonic transit time was normal in 30 patients (group I) and prolonged in the other 30 (group II). After over-night fasting an "infinitely compliant" polyethylene bag was inserted into the rectum. Rectal tone was assessed by measuring variations in bag volume with a computerized electromechanical air injection system. After an adaptation period of 30 min all subjects consumed a 450-kcal liquid meal. Postprandial recordings were continued for 3 h. In a second recording session we investigated the tonic response of the rectum to an evoked urge to defecate. In a third session rectal sensory perception was assessed. Following the meal all controls showed an increase in rectal tone (mean 74.8 +/- 17%). Patients in whom colonic transit time was normal showed a similar tonic response. In group II the increase in rectal tone was significantly lower (mean 27.8 +/- 10%; P < 0.001). Three patients of this group showed no response to a meal at all. All controls showed an increase in rectal tone during an evoked urge to defecate (mean 39.2 +/- 9%). In both groups this tonic response was absent or significantly blunted (mean 15.3 +/- 6% and 16.4 +/- 5%, respectively; P < 0.001). In both groups rectal sensory perception was significantly impaired. In conclusion, patients with obstructed defecation in whom colonic transit time is normal have an intact gastrorectal reflex. The increase in rectal tone after a meal is absent or blunted in patients with obstructed defecation in whom transit time is prolonged. The tonic response of the rectum to an evoked urge to defecate as well as rectal sensory perception are significantly impaired both in patients with a normal and in those with a prolonged transit time.     

Stimulation of defecation: Effects of coffee use and nicotine on rectal tone and visceral sensitivity

Objective

Coffee and cigarette use is believed to induce bowel movements, although the literature is controversial and precise measurements of rectal tone and sensitivity with a barostat have never been performed. The aim of this study was to assess the effects of coffee and nicotine on rectal tone, compliance and sensitivity.

Material and methods

Sixteen healthy volunteers were recruited for the coffee (n=8) and nicotine (n=8) experiments. The experiments were randomly performed in a placebo-controlled crossover design on separate days. In the coffee experiment, 280?ml strong coffee or warm water was drunk and in the nicotine experiment, nicotine (2?mg) or placebo was given sublingually. A rectal barostat procedure was carried out. A flaccid bag, mounted on a catheter, was inserted in the rectum. Continuous pressure distension was exerted to register basal visceral sensitivity and compliance. After rectal adaptation, the stimulus was given. Rectal tone was measured for 1?h, after which continuous pressure distension was repeated.

Results

Rectal tone increased by 45% 30?min after coffee intake (p=0.031) and by 30% after water intake (p=0.032), but the effects of coffee and water were not significantly different. Rectal tone did not change significantly after administration of nicotine (7%) or placebo (10%). There was no difference in compliance and visceral sensitivity between coffee and water or nicotine and placebo.

Conclusions

Both coffee and warm water have an effect on defecation by increasing rectal tone, but nicotine (2?mg) did not affect rectal tone. Coffee and nicotine did not influence sensitivity or compliance.     

Study of the effect of temperature on the rectal function with evidence of thermorectal reflex

BACKGROUND AND AIMS: Rectal sensation seems to originate from mechanoreceptors which are stimulated by passive rectal filling or active contraction. We investigated the effect of temperature on rectal function. PATIENTS AND METHODS: A balloon was introduced into the rectum of 28 healthy volunteers, filled with 50 ml saline at various temperatures, and rectal pressure was recorded. The test was repeated 30 min and 3 h after rectal anesthetization. RESULTS: Rectal pressure was significantly reduced at 45 degrees and 40 degrees C, showed no change at 37 degrees or 30 degrees C, and was increased at 20 degrees, 10 degrees, and 0 degrees C. At 45 degrees C patients felt rectal pain but no sensation of warmth; at 40 degrees, 37 degrees, and 30 degrees C neither rectal pain nor warm sensation was felt; at 20 degrees C or below rectal pain and cold sensation were perceived. Rectal balloon filling 30 min after anesthetization caused no significant rectal pressure changes or sensation of coldness or warmth; after 3 h, when the anesthetic had waned, the rectal pressure response and sensation were similar to those before anesthetization. CONCLUSIONS: Warm saline appears to cause rectal relaxation and cold saline rectal contraction. Subjects did not perceive sensation of warmth in the rectum but felt cold sensation, which may indicate the presence of cold receptors in the rectal wall. The rectal response to temperature variations is suggested to be reflex in nature as evidenced by its absence on rectal anesthetization. Such reflex, designated "thermorectal reflex," is proposed to mediate the rectal response and is speculated to have clinical significance in rectal dysfunctional and neurogenic disorders.     

Functional hyperprolactinemia and hypophyseal microadenoma in systemic sclerosis

OBJECTIVE: Hyperprolactinemia (HPRL) has been identified in more than half of patients with systemic sclerosis (SSc). However, the association with pituitary adenoma and the status of hypothalamic dopaminergic tone using metoclopramide (MTC) test has not been studied. We investigated the prevalence of prolactin (PRL)-secreting pituitary adenoma and evaluated production of PRL by dynamic testing with MTC in SSc. METHODS: We studied 30 patients with SSc (mean age 38 +/- 10 yrs) and 20 healthy controls (mean age 37 +/- 11 yrs). Serum PRL concentrations were determined by radioimmunoassay in all subjects, and PRL response was measured 30, 60, 90, and 120 min after injection of 10 mg of MTC. Computed tomography (CT) of the sella turcica was performed. RESULTS: The mean basal serum PRL levels before and after stimulation with MTC in SSc patients versus controls were: basal 18.2 +/- 5.4 versus 8.7 +/- 1.6 ng/ml, p = NS; 30 min: 175.0 +/- 5.4 versus 61.0 +/- 42 ng/ml, p < 0.001; 60 min: 160 +/- 64 versus 52 +/- 30 ng/ml, p < 0.001; 90 min: 125 +/- 57 versus 42 +/- 21.0 ng/ml, p < 0.05; 120 min: 108.0 +/- 57 versus 30.0 +/- 10 ng/ml, p < 0.005. CT scan showed microadenomas in 24/30 SSc patients and 1/20 controls (p = 0.001). CONCLUSION: Our study suggests that a group of patients with SSc have a high prevalence of HPRL with increased central dopaminergic tone, and microadenomas. PRL may have a role in the pathogenesis of SSc. Further studies are necessary to confirm our results.     

Rectal tone in response to bisacodyl in women with obstructed defecation

This study investigated the tonic response of the rectum to topical application of bisacodyl in women with obstructed defecation. Forty-five women with obstructed defecation, and 15 female controls were studied. Total colonic transit time was normal in 35 patients, and prolonged in 10. For the purpose of this study an "infinitely compliant" polyethylene bag was inserted into the rectum. Rectal tone was assessed by measuring variations in bag volume with a computerized electromechanical "barostat" system. After an adaptation period of 30 min, a suppository containing 10 mg bisacodyl was inserted into the rectum. Recording was continued for 90 min. In a second recording session rectal tone in response to an evoked urge to defecate was assessed. In a third session we investigated rectal sensory perception. After a mean time interval of 30 +/- 15 min following intrarectal application of bisacodyl, all controls showed a significant increase in rectal tone (mean value: 68.2 +/- 12%). In patients with a normal transit time, a similar increase was observed. In patients with prolonged transit time, the tonic response of the rectum to bisacodyl was significantly lower (mean 21.1 +/- 11%; P < 0.001). Five of these patients showed no response at all. In the second recording session, all controls showed an increase in rectal tone during an evoked urge to defecate (mean 36.3 +/- 7%). In both patient groups this tonic response was absent or significantly blunted (mean 19.2 +/- 6%) (P < 0.001). In both patient groups rectal sensory perception was impaired significantly. In conclusion, rectal tone increases significantly after topical application of bisacodyl in controls as well as in patients with obstructed defecation in whom transit time is normal. This tonic response is absent or significantly blunted in patients with a prolonged transit time. Both the tonic response of the rectum to an evoked urge to defecate and rectal sensory perception are significantly impaired in patients with a normal and those with a prolonged transit time.     

Sexual and physical abuse are not associated with rectal hypersensitivity in patients with irritable bowel syndrome

BACKGROUND: Patients with irritable bowel syndrome (IBS) have reduced pain thresholds for rectal distension. In addition, the prevalence of sexual/physical abuse in referred IBS patients is high and is associated with greater pain reporting, poorer health status, and poorer outcome. This lead to a hypothesis that abuse history may sensitise patients to report pain at a lower threshold. AIM: To compare rectal pain thresholds in women with IBS who had a history of severe abuse to IBS women with no history of abuse. METHODS: We studied 74 IBS patients with a history of severe physical and/or sexual abuse and 85 patients with no history of abuse. Abuse history was assessed by a previously validated self-report abuse screening questionnaire. Rectal sensory thresholds were assessed using an electronic barostat and determined by the ascending method of limit (AML) and by the tracking technique. RESULTS: IBS patients with a history of severe abuse had significantly higher rectal pain thresholds, as measured by AML (F (1, 111) = 6.06; p = 0.015) and the tracking technique (F (1, 109) = 5.21; p = 0.024). Patients with a history of severe abuse also reported a significantly higher threshold for urgency to defecate (F (1, 113) = 11.23; p =.001). CONCLUSION: Severe sexual/physical abuse is associated with higher urge and pain thresholds for rectal distension in IBS patients. This suggests that the greater pain reporting and poorer health status in IBS patients with abuse history are not related to increased rectal pain sensitivity. Further studies are needed to determine the causes of these findings.