| background and objectives: Irritable bowel syndrome (IBS) is one of the most common functional gastrointestinal disorders, characterized by abdominal pain associated with altered bowel habit (ie, diarrhea and/or constipation,abdomen pain,bloating) . Much evidence suggests that the pathogenesis of IBS involves abnormal brain-gut interactions, characterized by a hyperresponsiveness and/or a hypersensitivity . However, it is unclear whether this occurs at the level of the gut, the autonomic nervous system(ANS), or the central nervous system(CNS) . There is evidence to support the importance of both visceral stimuli (eg, colonic distention) and nonvisceral stimuli (eg, psychological stressors). Individuals with IBS are reported to experience more symptoms compatible with psychopathologic disorders, abnormal personality traits, and psychological distress. Conversely, individuals with psychiatric disorders report higher levels of gastrointestinal symptoms compatible with IBS.The disease severity in IBS is highly influenced by psychiatric comorbidity. The mechanism of this influence is generally unknown, even if the brain-gut axis seems to be involved. Recent research has indicated that IBS patients have aberrant perception of visceral stimuli in the CNS. Some data from clinic suggest psychotherapy and antidepressants are effective in patients with severe IBS, but the cost-effectiveness of either treatment in routine practice has not been established. As theprimary link between brain and gut, autonomic dysfunction plays a role in the pathophysiology of IBS.The aim of this study was to assess autonomic response to somatic stimuli( cold-water test), psychologicall stressor and visceral stimuli (rectum distension), identify the psychosocial conditions (anxiety and depression) of patients with IBS and healthy objects, as well evaluate effects of antidepressant treatment of SaintJohn's Wort extract in IBS. It was hypothesized that patients with IBS would show exaggerated autonomic responses to the psychological stressor and experience more symptoms compatible with psychopathologic disorders.Materials and Method: Thirty female patients with IBS (according to Rome II ) and twenty healthy women participated in the two-day study protocol . Hamilton Depression Scale (HAMA) and Hamilton Anxiety Scale (HAMD) scores were used to measure their anxiety and depression conditions by two psychologist .All patients and controls underwent a cold-water test and a colon distension experiment of a pain-threshold pressure(60mmHg) in the same condition a day after while wearing a Holter 24-hr electrocardiograph monitor. Autonomic nervous system function was assessed using frequency domain measures of heart rate variability(HRV). Five-minite-short-time heart rate variability spectrum analysis of electrocardiogram(ECG) recordings were analyzed at baseline and during somatic stimuli( cold-water test), psychological stressor and visceral stimuli (rectum distension). ECG data were continuously recorded by use of a computerized data collection system . Power of low frequency band spectrum/power of high frequency band spectrum (LF/HF) ratio were collected. Spectral analysis of heart rate variability was used as a measure of the sympathovagal regulation of the heart rate.Baseline: Before cold-water test all IBS patients and healthy controls rest in bed for 30 minutes while wearing a Holter 24-hr electrocardiograph monitor, we took 5 minutes of the 30 minutes as baseline analysis time.Cold-water test: All IBS patients and healthy controls immersed their hands in 4°C cold water for 60 seconds, and then took them out for 15 seconds; repeated 5 times. Rectum distension : A manometric catheter was inserted to the rectum apart fromanus 9 cm and a balloon was placed in the rectum. After baseline for lOmin, the rectum was stimulated by balloon distention. Balloon distention was repeated 5 times, and each stimulation consisted of a 6-s inflation,lasting for 45-s with a pressure of 60mmHg and a 8-s deflation.Psychological stressor: We regarded rectum distension as a psychological stressor to the testees .5 minutes before rectum distension were analysis time of psychological stressor. IBS groups repeated the tests above after 8-weeks'antidepressant treatment of Saint.John's Wort Extract. SPSS10.0 was used to evaluate the statistical significance. Results: 1) IBS-group showed a higher scores and had more abnormal rate(X2HAMA=18.75,p<0.01; X2hamd=17.88, p<0.01) in HAMA(4.75±2.37 vs 20.5± 5.56, p<0.01) and HAMD(7.45±5.78vs22.3±6.20, p<0.01) graded, the results had much significant difference comparing with controls.2) )IBS-group also showed a significant increase in the power of low frequency band spectrum / the power high frequency band spectrum ratio(LF/HF) during the period of somatic stimuli( cold-water test)( 0.98±0.28 vs 3.10±1.33, p<0.01), psychological stressor(5 minutes before colon distension)(1.76±0.54vs5.57±1.74,p<0.01) and visceral stimuli (rectum distension)( 1.24±0.31vs4.42±2.00,p<0.01),which was significantly different from controls ,but the difference of LF/HF during the time of baseline was not significant(0.60±0.17vsl.47±0.63,p>0.05).3) After 8-weeks antidepressant treatment, L/H ratio showed a significant decrease in IBS-group during the somatic stimuli(1.18± 0.33vs3.10±1.33,p<0.05) and visceral stimuli(2.60±0.92vs4.42±2.00,p<0.05), which was significantly different from them before treatment ,but had not significantly changed during the psychological stressor(2.10 ±0.71vs5.57±1.74,p>0.05), the HAMD ,HAMA scores significantly improved (20.5+ 5.56vsl3.40±3.13,p<0.01)( 22.3±6.20vsl4.37±3.91,p<0.01), the HAMD ,HAMA scores abnormal rate significantly declined ( X2hama=5.711,p<0.05;X2hamd=6.786,p<0.05 ) comparing with them 8 weeks before <,4) There was a significantly negative correlation between the HAMD ,HAMA scores andL/H during the stressor(p<0.01),but not in the baseline(r=0.237,r=0.162,p>0.05). Conclusions: 1) These findings support the notion that an abnormal autonomic nervous system activities response to physical and psychological stimuli may play a role in the pathophysiolgy of IBS.2) Psychosocial features have an important effect on symptoms severity and patient status in IBS3) There is a direct association between the severity of depressive symptoms and the modulation of cardiovagal activity.4) Antidepressant treatment can improve the conditions of psychology and the reactivity to stress in patients with IBS. |
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