Anamnestic stimulus-specific myoelectric responses associated with intestinal immunity in the rat.

Changes in small intestinal motility reflective of local anaphylaxis are hypothesized to be associated with the rapid, immune-mediated rejection of infective larvae of the nematode Trichinella spiralis. This hypothesis was tested by comparing intestinal myoelectric activity in primarily and secondarily infected rats; the latter group represented immunized hosts, i.e., immunized by initial contact with the parasite. Patterns of slow waves, action potentials, interdigestive migrating myoelectric complexes, and migrating action-potential complexes induced by secondary infection differed from those associated with primary infection. Patterns in both cases differed from those in uninfected rats. Secondary but not primary infection evoked changes in myoelectric patterns within 15 min after administration of infective larvae. These changes could not be elicited by inoculation with dead larvae, larval excretory-secretory antigens, or a heterologous parasite, Eimeria nieschulzi. Results indicate that altered smooth muscle contractile activity is part of an anamnestic, stimulus-specific response to T. spiralis in immunized rats. These changes may represent the in vivo equivalent of the anaphylactically mediated intestinal smooth muscle contraction elicited in vitro in the Schultz-Dale reaction.