Repeated local inflammation of the GI tract: Does it influence the development of persistent visceral hyperalgesia?

Abstract

Introduction: It} palients with inllammatory bowd disorders sensory ttreesholds increase (Gut 200047:497 In animals, a persistent increase in visceral sensitivity occurs after a single episode of a chemically induced colitis. Whether repeated chemically induced inflammations are associated with an increase of sensory thresholds is mtknown Aims: To study the eltect of repeated transient local inflammation on visceral sensory function in a rat nmdd Methods: We perkmned colorectal distensions (CRD) with a barostat device in lasted, con~ions male Lewis rats (n=40, age 8 months) and assessed the visceromotor reflex (VMR) to tortic distension (60 mmHg/3 rain) by abdominal wail electromyogl~phy (EMG). Following an initial iaduction of transient chemical coliti& instillation of trinitrobenzenesulphonic acid (TNB) was repeated alter another 2 weeks (study group A) versus 2 weeks and 4 weeks (study group g). EMG response to 4 CRDs at separate days was recorded starting i4 days alter the second (study group A) versus the him inflammation (study group B) Resuhs: For all time points, the VMR to CRD was significautly higher in animals after TNB treatment than in control animals (saline). in the TNB group, the visceral stimulation iolLowing the second inflammatory event (study group A) was associated with a significant increase of the EMG activity over the time from 1651 + 124 uV to 1899 + 237 uV. However, after the third TNB administration (study group B-~, the VMR to C~'D decreased from 1316+ 146 uV to 1132__+142 uV (pC.05). in saline-treated animals, consecutive CRDs resu l~ in a progressive decrease of the EMG response from 982 + 85 uV to 759 + 62 uV (study group A) and from 809__+/2 uV to 685__+71 uV (study grou-p-B) (pC.05) S'~unmary and Conclnsion: Colonic instillation of TNB resulted in a persistent increase of the VMR to CRD. Following relmated acid instilhttion with sufficient time in between TNB applications, the VMR Io CRD slightly decreased after more than two TNB exposures but remained higher compared to EMG responses in saline-treated animals