Modulation of body temperature through taste aversion conditioning.

Injection of rats with bacterial lipopolysaccharide (LPS) results in an initial fall in body temperature followed by a fever. Lithium chloride (LiCl) injection induces a fall in body temperature without subsequent fever production. When these substances were incorporated as unconditioned stimuli in a taste aversion conditioning paradigm, using saccharin flavour as the conditioning stimulus, these differential effects on body temperature were reenlisted on reexposure to saccharin alone 7 days after conditioning. The changes in body temperature on reexposure were similar in direction and kinetics as on the conditioning day although reduced in magnitude. The finding of a true conditioned effect in these studies is in contrast to the paradoxical or compensatory conditioned body temperature responses described elsewhere using different conditioning models. This apparent conflict may be explained on the basis of different unconditioned stimuli acting on efferent versus afferent arms of a negative feedback system. Since body temperature changes often occur in association with immune responses, these findings may have implications to behavioural conditioning of immunity, the outcome of which may reflect the indirect effects on immunity of inadvertent conditioning of thermoregulatory changes.