Conditioned place aversion with interleukin-1β in mice is not associated with activation of the cytokine network

Several distinct findings argue in favor of conditioning of some components of the acute phase reaction. However, the possibility of a conditioned cytokine response has not been assessed. In the present study, this possibility was tested by submitting mice to place aversion conditioning with interleukin-1β (2 μg/mouse, ip) as the unconditioned stimulus and an odorous compartment of a two-compartment cage as the conditioned stimulus. After two pairings, conditioned mice developed place aversion towards the odorous compartment. However, this behavioral conditioning was not accompanied by any alteration in peripheral (spleen) and brain (hypothalamus) cytokine levels (interleukin-1, interleukin-6, and interleukin-10). These data do not support the possibility of conditioned alterations in the cytokine network.