Mb. Dwinell et al., INTESTINAL MYOELECTRIC ALTERATIONS IN RATS CHRONICALLY INFECTED WITH THE TAPEWORM HYMENOLEPIS-DIMINUTA, American journal of physiology: Gastrointestinal and liver physiology, 30(5), 1994, pp. 70000851-70000858
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.