[Classical conditioning of anaphylaxis in sensitized guinea pigs]

An attempt of classical conditioning of anaphylaxis by odor was carried out, using actively sensitized guinea pigs with an inhalation of ovalbumin (OA). One month after sensitization, animals were divided into the conditioned group; group C, and the unconditioned group; group U, consisted of 6 animals, respectively. Dimethylsulfied (DMS: sulfur odor), was inhaled in group C as a conditioned stimulus with OA which is an unconditioned stimulus, while only OA was inhaled in group U. Four days after these procedures, saline was inhaled in group C and DMS was solely inhaled in group U in order to equalize the total inhaled dose of OA and DMS in both groups. These sessions were repeated once a week for seven weeks. After final sessions, all animals were inhaled DMS, saline and OA separately, and blood samples were drawn after each inhalation to measure plasma histamine levels. After an inhalation of DMS only, plasma histamine levels of group C and U were 47.5 +/- 9.7 and 25.7 +/- 1.2 ng/ml, respectively. In group C, plasma histamine levels were 32.9 +/- 4.7 at the inhalation of saline and 59.0 +/- 9.2 ng/ml at OA inhalation. Plasma histamine level after an inhalation of DMS only was significantly higher in group C than that in group U (p < 0.05). These results suggest that the conditional stimulus (DMS inhalation) may induce histamine release in the absence of any antigenic stimulus and support the evidence for mast cell-neuron interaction.