Facilitated acquisition of the classically conditioned eyeblink response in male rats after systemic IL-1beta.

Abstract

Exposure to inescapable stressors enhances cue-dependent learning in male rats; enhanced learning is apparent as facilitated acquisition of the classically conditioned eyeblink respouse (CCER). The proinflammatory cytokines, in particular interleukin (IL)-1beta, are presumed to orchestrate a number of acute-phase stress responses in rats, most notably fever, reduced feeding, and inactivity. Little is known of the impact proinflammatory cytokines have on learning and memory processes. Here, we address the effects of IL-1beta treatment on acquisition of the classically conditioned eyeblink response 2 hours [?] after injection in male rats. Training was accomplished with a delay-type paradigm (500-ms conditional stimulus coterminating with a 10-ms periorbital unconditional stimulation). Facilitated acquisition was clearly apparent in rats treated with IL-1beta (3.0 microg/kg). In a second experiment, we compared rats treated with 3.0 microg/kg to those treated with 1.0 microg/kg. Facilitated acquisition was reproduced, but the lower dose did not appreciably affect acquisition. These data further support contentions that IL-1beta has anxiogenic properties, affecting basic new motor learning in a manner similar to that observed after exposure to stress.