Conditioned immune responses to taste and environmental cues signalling cyclophosphamide

Lewis, Stevan Joel (1995) Conditioned immune responses to taste and environmental cues signalling cyclophosphamide. Masters thesis, Memorial University of Newfoundland.

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Abstract

Injection of cyclophosphamide (Cy), an immunosuppressive drug, in conjunction with a conditional stimulus (CS) has repeatedly been shown to produce Pavlovian conditioning. However, reports vary on the critical issue of whether the conditioned response augments the immunosuppressive effect of Cy or counteracts it. In this study, the effects of CS type and post CS reexposure saline injections on the direction of conditioned immune responses were measured using a passive hemagglutination reaction. One hundred and twenty Sprague-Dawley rats were randomly assigned to a conditioning protocol using either a taste CS (saccharin, SAC) or a distinctive environmental CS (Plexiglas tubs). For some animals, CS exposure coincided with intraperitoneal (i.p.) injections of Cy (paired groups) or saline (saline groups). For others, Cy injections occurred 24 h after exposure to the CS (unpaired groups). Groups were further divided following CS reexposure such that, half of the animals in each group received an injection of saline. Contrary to some previous reports, both taste and environmental CSs that were paired with injections of Cy support a conditioned immunosuppression of Ab production rather than conditioned immunoenhancement. This conditioned immunosuppression occurred without a measurable conditioned taste aversion, and did not affect Cy-induced reductions in weight gain. Also, injections of Cy reduced fluid consumption 24 h, but not 48 h, later. These findings are inconsistent with some current interpretations of conditioned immune responses and are examined in terms of simultaneous and sequential conditioning procedures.

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