Pavlovian conditioning of lung anaphylactic response in rats

The present experiment was undertaken to verify if it is possible to impose Pavlovian conditioning on a lung anaphylactic response (LAR) in rats. Two experiments were done. In the 1st, egg albumin (OVA) aerosol inhalation, which induces signs and symptoms of LAR in OVA- sensitized rats, was paired with an audiovisual cue (conditional stimulus, CS). After reexposure to the CS, the signs and symptoms of LAR were quantitatively measured using a scoring system specially developed for this evaluation; the levels of stress response and anxiety were also quantified. Results showed that the rats reexposed to CS only, displayed LAR scores not significantly different from those reexposed to both CS and the antigen; animals of these groups showed significantly higher LAR scores than rats that received no OVA aerosol challenge. High levels of stress and anxiety were observed 30-40 min after the challenge with OVA aerosol. In the 2nd experiment, rats sensitized with OVA and submitted or not to Pavlovian conditioning were observed in the open-field and in the plus maze apparatus in the absence of OVA aerosol but in the presence of the CS; after behavioral observations the animals were sacrificed for serum corticosterone level determination. Both behavioral and biochemical data showed high levels of stress and anxiety in rats for which the antigen was previously paired with the CS; these changes were not observed in animals which received the antigen 24 h after the presentation of the CS (unpaired) or in those exposed to PBS aerosol (the OVA vehicle) only. The present data show not only that LAR can be submitted to Pavlovian conditioning, but also and importantly, that high levels of stress and anxiety are related to the course of LAR.