Related Experiment Video
Updated: Apr 4, 2026
In vitro Functional Characterization of Mouse Colorectal Afferent Endings
Published on: January 21, 2015
Mechanically evoked cortical potentials: A physiological approach to assessment of anorectal sensory pathways
E V Carrington1, J Evers2, S M Scott3
1School of Medicine and Medical Science, University College Dublin, Dublin, Ireland; GI Physiology Unit, The Wingate Institute of Neurogastroenterology, Queen Mary University of London, London, United Kingdom; National Centre for Bowel Research and Surgical Innovation (NCRBSI), Queen Mary University of London, London, United Kingdom.
Background:
Normal defaecation involves activation of anorectal mechanoreceptors responsive to pressure and stretch. The aim of this study was to develop selective anal and rectal mucosal light-touch stimulation suitable for measurement of cortical evoked potentials (EPs) in order to explore the sensory arm of these pathways.
New Method:
A novel device was manufactured to deliver selective rectal and/or anal light-touch stimulation using a shielded inter-dental brush mounted on a rotating stepper motor (1Hz, 1ms, 15° rotation). Resultant somatosensory EPs recorded with a 32-channel cortical multi-electrode array were compared to those elicited by electrical anorectal stimulation (2mm anal plug electrode [1Hz, 1ms, 10V]).
Results:
Eighteen anaesthetized female Wistar rats (body mass 180-250g) were studied. Electrical and mechanical stimulation provoked similar maximal response amplitudes (electrical anorectal 39.0μV[SEM 5.5], mechanical anal 42.2μV[8.1], mechanical rectal 45.8μV[9.0]). Response latency was longer following mechanical stimulation (electrical anorectal 8.8ms[0.5], mechanical anal 16.4ms[1.1], mechanical rectal 18.3ms[2.5]). The extent of activated sensory cortex was smaller for mechanical stimulation. Sensory inferior rectal nerve activity was greater during anal compared to rectal mechanical in a subgroup of 4 rats. Evoked potentials were reproducible over 40min in a subgroup of 9 rats.
Comparison With Existing Methods:
Cortical EPs are typically recorded in response to non-physiological electrical stimuli. The use of a mechanical stimulus may provide a more localized physiological method of assessment.
Conclusions:
To the authors' knowledge these are the first selective brush-elicited anal and rectal EPs recorded in animals and provide a physiological approach to testing of anorectal afferent pathways.
