Trichinella spiralis: intestinal myoelectric activity during enteric infection in the rat.

The objective was to characterize changes in the host's small intestinal smooth muscle contractile activity caused by the enteric stages of the nematode, Trichinella spiralis, during primary infection. Myoelectric activity was recorded from electrodes permanently implanted on the seromuscular surface of the small bowel in conscious, unrestrained rats during the first 2 weeks postinfection (PI). Several myoelectric parameters examined collectively indicated that smooth muscle function of the small bowel was altered by infection. A decrease in contractile activity was indicated by reductions in electrical slow wave and spike potential frequencies that were maximal 6-12 days postinfection. Normal coordinated contractile behavior was also impaired, as evident from a reduction in the frequency of migrating myoelectric complexes. An infection-induced qualitative change occurred designated as a migrating action potential complex. This unusual spiking activity swept down the bowl rapidly, occurred with greatest frequency 2-6 days PI, and coincided with the disruption of the normal migrating myoelectric complex. It is concluded that recordings of intestinal myoelectric activity provide sensitive, quantifiable correlates of contractile patterns throughout the intestinal phase of trichinellosis in a single host.