INTESTINAL MYOELECTRIC ALTERATIONS IN RATS CHRONICALLY INFECTED WITH THE TAPEWORM HYMENOLEPIS-DIMINUTA

Intestinal myoelectric alterations in rats chronically infected with t he tapeworm Hymenolepis diminuta. Am. J. Physiol. 267 (Gastrointest. L iver Physiol. 30): G851-G858, 1994.-This study determined that intesti nal myoelectric activity was profoundly altered during a strictly lumi nal, chronic, tapeworm infection. Chronically implanted bipolar electr odes were attached to five sites on the serosal surface of the rat sma ll intestine. One was placed on the duodenum, three on the jejunum, an d the fifth on the ileum. Electromyographic recording in nonfasted una nesthetized animals was begun at day 5 postsurgery. All electromyograp hic recordings were analyzed for slow wave (SW) frequency, phase III f requency, duration of phase III, and percentage of SW With spike poten tials. Three initial control recordings prior to infection confirmed t he presence of normal interdigestive motility characterized by the thr ee phases (I, II, III) of the migrating myoelectric complex (MMC). Two nonpropulsive myoelectric alterations were observed in infected anima ls: the repetitive bursts of action potentials (RBAP) and periods of s ustained spike potentials (SSP). Myoelectric activity from infected an imals indicated decreased cycling of the interdigestive MMC. RBAP and SSP were more prevalent in the distal small intestine corresponding to tapeworm location. The percent of spike potential activity indicated that there was a reversal in the spike potential gradient on the small intestine. The number of spike potentials was maximal in caudal and m inimal in oral intestine. We propose that overall localized increases in myoelectric spike potential activity represent increased contractil ity and decreased propulsion triggered by the presence of the tapeworm . These motility changes were surprising, since the tapeworm Hymenolep is diminuta does not penetrate the intestinal mucosa. This interaction between parasite and host may prevent expulsion of the tapeworm from the small intestine.