AJP - Gastrointestinal and Liver Physiology, Vol 254, Issue 4 477-G482, Copyright © 1988 by American Physiological Society
Cerebral evoked potentials after endorectal mechanical stimulation in humans
L. Collet, P. Meunier, R. Duclaux, S. Chery-Croze and P. Falipou
Laboratoire de Physiologie Sensorielle, Centre Hospitalo-Universitaire Lyon-Sud, Pierre-Benite, France.
Although numerous clinical studies have proved that impaired rectal
sensation is a major factor in fecal continence dysfunctions, objective
studies in this field are still lacking. To provide information on normal
rectal afferents, a study of cerebral potentials evoked by mechanical
stimulation of the rectal wall was carried out in 10 healthy volunteers (5
male, 5 female; age, 33-52 yr). The stimulating device consisted of a
rectal balloon rhythmically inflated and deflated by means of an animal
breathing ventilator. Recordings were obtained 2 cm behind the vertex (C'z,
International system 10-20). The responses were averaged from 300 to 800
sweeps. The average was triggered either on inflation ("on effect") or on
deflation ("off effect"). Inflation volume and pressure were adjusted to
induce a clear but not painful pulsing sensation. Reproducible responses
were recorded by both on and off effects. The evoked potentials were
polyphasic with a succession of positive and negative waves (peak latencies
between 78 and 310 ms). The shape of the response (morphology, latency, and
amplitude) was perfectly reproducible in the same subject. With regard to
intrasubject reproducibility, variability was displayed: only the early
waves (latency less than 100 ms) were perfectly reproducible; late waves
exhibited variable latency and morphology. The present findings are the
first demonstration of the possibility of recording an evoked potential on
the scalp after a mechanical stimulation of the rectum.
