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

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.

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.

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.

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.

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.