Antigen-specific tachycardia and hypotension in rodents

Tachycardia and hypotension, two cardiovascular responses to anaphylaxis, were specifically induced by antigen in mice and rats, respectively. Intravenous injection of poly (Glu60Ala30Tyr10) (GAT) elicited tachycardia within 30-40 sec in GAT-primed B6 mice. Moreover, a minute amount of GAT (0.2 micrograms) was enough to sensitize the mice to subsequent GAT-induced tachycardia. Challenging doses ranging from 100 ng to 500 micrograms. could elicit tachycardia. The kinetics of tachycardia induction was different from that of antibody production or delayed-type hypersensitivity. Tachycardia was induced from day 6 after immunization, while delayed-type hypersensitivity developed as early as day 4, and anti-GAT antibodies were undetectable on day 6 and would not reach a maximum until day 8. Specific antigen-induced hypotension was also observed in rats. Furthermore, cardiovascular changes in both species could be passively transferred by heat-treated (56 degrees C, 30 min) sera from immunized animals. These benchmarks of antigen-induced cardiovascular changes in mice or rats could be used as models to study the immune control of cardiovascular changes in anaphylactic responses.