Irritable bowel syndrome (IBS) is a disorder of intestinal hypersensitivity and altered motility, exacerbated by stress.
Functional magnetic resonance imaging during painful rectal distension in IBS has demonstrated greater activation of the anterior cingulate cortex, an area relevant to pain and emotions.
Tricyclic antidepressants are effective for IBS.
Dr Mertz and colleagues from Tennessee determined if low dose amitriptyline reduces anterior cingulate cortex activation during painful rectal distension in IBS to confer clinical benefits.
The researchers’ secondary aims were to identify other brain regions altered by amitriptyline, and to determine if reductions in cerebral activation are greater during mental stress.
The research team randomized 19 women with painful IBS to amitriptyline 50 mg or placebo for 1 month.
|Rectal pain induced significant activation of the perigenual anterior cingulate cortex|
The patients were then crossed over to the alternate treatment after washout.
The team compared cerebral activation during rectal distension was compared between placebo and amitriptyline groups by functional magnetic resonance imaging.
The investigators performed distensions alternately during auditory stress and relaxing music.
The researchers found that rectal pain induced significant activation of the perigenual anterior cingulate cortex, right insula, and right prefrontal cortex.
Amitriptyline was associated with reduced pain related cerebral activations in the perigenual anterior cingulate cortex and the left posterior parietal cortex, but only during stress.
Dr Mertz’s team concluded, “The tricyclic antidepressant amitriptyline reduces brain activation during pain in the perigenual (limbic) anterior cingulated cortex and parietal association cortex.”
“These reductions are only seen during stress.”
“Amitriptyline is likely to work in the central nervous system rather than peripherally to blunt pain and other symptoms exacerbated by stress in IBS.”