PRAZIQUANTEL TREATMENT NORMALIZES INTESTINAL MYOELECTRIC ALTERATIONS ASSOCIATED WITH HYMENOLEPIS DIMINUTA-INFECTED RATS

Hymenolepis diminuta-associated alterations in rat intestinal myoelect ric patterns are abolished following therapeutic administration of the anthelmintic praziquantel (PZQ). Host intestinal smooth muscle myoele ctric patterns, reflecting smooth muscle contractility and intestinal phasic motility, were recorded using in vivo serosal electrodes, surgi cally implanted on the duodenum, jejunum, and ileum. Repeated electrom yographic recording from unrestrained and unanesthetized rats began 5 days after electrode implantation surgery. Three initial control recor dings from each rat confirmed the appearance of normal intestinal myoe lectric patterns, characterized by the interdigestive migrating myoele ctric complex (MMC). All animals were subsequently infected with H, di minuta and myoelectric recordings beginning after day 8 postinfection confirmed the appearance of diminished frequency of the MMC and 2 nonm igrating myoelectric patterns, i.e., repetitive bursts of action poten tials and sustained spike potentials. PZQ was used to remove the tapew orms from rats 12 days after Hymenolepis diminuta infection, as intest inal myoelectric changes become maximal at this time in tapeworm-infec ted rats. PZQ administered to uninfected rats at either of 2 dose leve ls did not affect host interdigestive myoelectric activity. After remo val of the parasite with PZQ, electromyographic recordings indicated a return to normal uninfected electrical patterns within 24 hr of drug treatment. We have demonstrated that the presence of Hymenolepis dimin uta is necessary to induce and maintain abnormal intestinal myoelectri c patterns. The altered motor properties of tapeworm-infected rat inte stine and the rapid reconversion to preinfection myoelectric patterns provides a new and unique model to examine the regulatory mechanisms o f intestinal motility and its control by luminal parasites.