Strain-Related Difference in Susceptibility to Anaphylactic Shock Correlates with Measures of Spontaneous Activity

The onset and severity of anaphylactic reactions in the rat have so far been related to Pavlovian conditioning, previous exposure to stress, and pretreatment with opioid agonists and antagonists. In this study, we compared two strains of rats derived from the same genetic pool (one outbred, Wistar, and one inbred, Wistar-Kyoto) for their susceptibility to anaphylactic shock (AS). In Experiment 1, baseline differences in the overt behavior of the two strains were established. In Experiment 2, following sensitization to ovalbumin, rats of both strains were challenged with antigen by either the intraperitoneal or the intragastric route. Wistar-Kyoto rats were more susceptible to the induction of AS as evidenced by a more pronounced drop in rectal temperature and greater intensity of clinical signs, although there was no evidence for strain-related differences in IgE titres. Experiment 3 replicated and extended the findings of Experiment 2. Again, Wistar-Kyoto rats were found to be more susceptible to the induction of AS. In addition to a greater drop in rectal temperature and intensity of clinical signs, more pronounced changes in gut function were found in the Wistar-Kyoto strain. This was indicated by an elevation of basal short-circuit current (an indication of the transport tone of the tissue mounted in the Ussing chambers). Most importantly, there was a strong linear relationship between measures of overt behaviour and various physiological indices of AS. This finding indicates that the same genetic basis may be responsible for the observed strain-related differences in behavior and susceptibility to AS, and that variations in nonimmunological factors of mast cell activation may also contribute to the observed differences in the susceptibility to anaphylactic reactions.