Proceedings of The Physiological Society

University of Manchester (2010) Proc Physiol Soc 19, PC263

Poster Communications

Preliminary evidence for altered rectal visceral sensitivity to non-invasive magnetic neurostimulation

T. Algladi1, M. Harris1, E. Michou1, P. J. Whorwell1, J. McLaughlin1, S. Hamdy1

1. Epithelial Sciences, Translational Medicine, The University of Manchester, Manchester, United Kingdom.

Visceral pain is a major clinical problem being a primary feature of functional gastrointestinal disorders. Treatments for this condition are limited, but there is increasing evidence that neural stimulation may be able to alter pain thresholds in the somatic literature. However, little is known about the properties of neurostimulation applied to visceral pain and its role in altering sensitivity. Repetitive transcranial stimulation (1 Hz) has shown an inhibitory effect on cortical excitation in both the gastrointestinal and somatic systems in healthy control subjects [1]. In addition, peripheral short-term magnetic stimulation delivered over the lumbosacrum induces post-stimulus effects on the excitability of motor projections to the anal sphincter [2]. The aim of this study is to ascertain whether non-invasive magnetic stimulation applied to the motor cortex and/or lumbosacrum can modulate rectal sensation. Participants: 10 healthy volunteers (5 females and 5 males, age range 20 and 56 years) participated in this study. Sensory measurements were performed via an electrode stimulating catheter was positioned in the rectum. The catheter’s electrode was positioned at 10 cm from the anal verge. Sensory and pain thresholds rectum were determined using short trains of electrical stimuli [3], repeated three times to assess reliability. The assessments of sensory and pain thresholds of the rectum were performed at baseline before intervention and then immediately, 30 and 60 min after each intervention. The interventions comprised 6 differing neurostimulation regimens delivered via magnetic stimulation in random order over different days and formed 3 repetitive lumbosacral magnetic stimulation (rLSMSs) (1 Hz, 10 Hz and sham) and 3 repetitive transcranial magnetic stimulation (rTMSs) (1 Hz, 10 Hz and sham) on separate visits, minimally 1 week apart between each visit. Data were (mean±SEM) analysed by two way ANOVA showed a significant increase in sensory and pain thresholds in the rectum at 60min following 1 Hz rLSMS ((sensation = 13.3±1.3 vs. 17.3±3.4 mA, p=0.045) , (pain = 19.2±1.7 vs. 25.7±4.4 mA, p=0.042)). By comparison, there was also increase in pain thresholds in the rectum only following 10 Hz rTMS at 60min (17.2±2.8 vs. 20.9±4.3 mA, p=0.052). All other interventions including sham had no measureable effect. The application of magnetic stimulation to either cortical and lumbosacral areas is able to modulate visceral pain in a frequency and site dependent manner and holds the promise of being applied to patients with abdominal pain in as a future therapeutic intervention.

Where applicable, experiments conform with Society ethical requirements