Deficient habituation to repeated rectal distensions in irritable bowel syndrome patients with visceral hypersensitivity.
BACKGROUND
Irritable bowel syndrome (IBS) patients show evidence of altered central processing of visceral signals. One of the proposed alterations in sensory processing is an altered engagement of endogenous pain modulation mechanisms. The aim was to test the hypothesis that IBS patients with (IBS-S) and without visceral hypersensitivity (IBS-N) differ in their ability to engage endogenous pain modulation mechanism during habituation to repeated visceral stimuli.


METHODS
Brain blood oxygen level dependent (BOLD) response was measured during repeated rectal distension and its anticipation in 33 IBS patients with and without visceral hypersensitivity and 18 healthy controls (HCs). BOLD response to early and late phase of the distension series was compared within and between groups.


KEY RESULTS
While BOLD response was similar during the early phase of the experiment, IBS-S showed greater BOLD response than IBS-N and HCs during the late phase of the distension series. IBS-S showed increasing BOLD response both to the anticipation and delivery of low intensity rectal distensions in brain regions including insula, anterior and mid cingulate cortex. IBS-N showed decreasing BOLD response to repeated rectal distensions in brain regions including insula, prefrontal cortex and amygdala.


CONCLUSIONS & INFERENCES
These findings are consistent with compromised ability of IBS-S to respond to repeated delivery of rectal stimuli, both in terms of sensitization of sensory pathways and habituation of emotional arousal. The fact that both IBS subgroups met Rome criteria, and did not differ in terms of reported symptom severity demonstrates that similar symptom patterns can result from different underlying neurobiological mechanisms.
['Lowén|M B O|MB|', 'Mayer|E|E|', 'Tillisch|K|K|', 'Labus|J|J|', 'Naliboff|B|B|', 'Lundberg|P|P|', 'Thorell|L-H|LH|', 'Ström|M|M|', 'Engström|M|M|', 'Walter|S|S|']
D000328:Adult D059031:Anticipation, Psychological D001007:Anxiety D001921:Brain D016022:Case-Control Studies D003863:Depression D004106:Dilatation D005260:Female D059907:Functional Neuroimaging D006185:Habituation, Psychophysiologic D006801:Humans D043183:Irritable Bowel Syndrome D008279:Magnetic Resonance Imaging D008875:Middle Aged D011312:Pressure D012007:Rectum D020886:Somatosensory Disorders D059265:Visceral Pain D055815:Young Adult
irritable bowel syndrome brain-gut interaction fMRI visceral sensitivity