Acquisition and extinction of conditional immunoenhancement following training with cyclophosphamide

Paired-group mice were injected with pentobarbital (a pharmacological conditioned stimulus, CS) prior to injection of cyclophosphamide (Cy), an immunosuppressive drug. Unpaired-group mice received Cy 24 h after the CS. CS-alone mice received only pentobarbital. When reexposed to the CS in conjunction with an antigenic challenge, unpaired-group mice displayed suppressed antibody titers, while paired-group mice displayed titers similar to those …