Capsaicin and anaphylactic reactions in the guinea-pig

The influence of capsaicin on anaphylactic reactions in the guinea-pig was studied both in vivo and in vitro. In guinea-pigs actively sensitized with ovalbumin, Herxheimer microshock was elicited by antigen aerosol and the preconvulsion time recorded. The preconvulsion time was reduced by about 30% in animals pretreated with capsaicin (1 mg/kg) injected i.p. 30 min before antigen aerosol, whereas it remained unchanged when the drug was administered two days before aerosol treatment. Capsaicin shows a partial protective effect when the provocative aerosol was administered 3 h after the last of three doses of capsaicin (100 micrograms/kg, i.p.), which had been injected for three consecutive days. Ileum longitudinal muscle strips were used for in vitro anaphylaxis studies. These were isolated from guinea-pigs actively sensitized with ovalbumin and histamine release evoked by antigen was measured. Preparations perfused with capsaicin (10(-6)-10(-4) M) and desensitized to the drug, showed a lower anaphylactic release of histamine. This effect was dose-dependent, with the histamine release reduced by 35% at higher concentrations (10(-5)-10(-4) M) of capsaicin. The mechanism of the influence of capsaicin on anaphylactic reactions is discussed briefly.