Abstract: Cyclophosphamide (CY), an immunosuppressive agent, was used as an unconditioned stimulus (UCS) in a conditioned taste aversion (CTA) paradigm with saccharin as the conditioning stimulus (CS) in a two-bottle preference drinking procedure. Conditioned behavioral and immunological responses were observed under both one trial of CS-UCS paring and two trials of CS-UCS paring. Data showed that CTA occurred under both one trial and tWo trials of CS-UCS paring, but conditioned immunosuppression, as assessed by spleen cell proliferation to mitogen and the number of peripheral leukocyte and lymphocyte, required 2 parings. These results suggest that conditioned behavioral and immunological changes might occur independently.

Key words: cyclophosphamide, conditioned immunosuppression, conditioned taste aversion