Pavlovian conditioning of immunosuppression modifies adjuvant arthritis in rats.

Abstract

Ten days prior to induction of adjuvant arthritis (by injection of complete Freund's adjuvant into a rat's hind paw), three groups of rats were dosed with cyclophosphamide (CY), an immunosuppressive drug. A saccharin/vanilla solution (SV) was presented either 2 days (Group NC) or immediately before CY treatment (Groups C and C2). Three further SV presentations started either 30 min (Groups C and NC) or 2 days after antigenic stimulation (Group C2). The groups did not differ with respect to the degree of swelling in the injected paws. In contrast, Group C differed significantly from Groups NC and C2 with respect to the uninjected hind paws: Group C showed no external signs of a proliferation of inflammation, whereas approximately half of the animals in the other two groups developed small lesions. A second experiment, similar to the first, yielded the same results. These results essentially confirm previous findings on conditioned immunosuppression and extend them to an inflammatory joint disease.