Memory for context is impaired by a post context exposure injection of interleukin-1 beta into dorsal hippocampus

Prior research has revealed that treatments that elevate the level of the pro-inflammatory cytokine IL-1β in the brain, if given after training, impair contextual but not auditory-cue fear conditioning. The present experiments add to these finding by showing that, (a) IL-1β exerts its effect on contextual fear conditioning by impairing consolidation processes that support the storage of the memory representation of the context; (b) the dorsal hippocampus is a critical site for the effect of IL-1β; (c) the effect of IL-1β cannot be attributed to its effect on glucocorticoid levels; and (d) IL-1β injected into dorsal hippocampus either, immediately, 3, or 24 h, but not 48 h, after training produces this impairment. At this time the mechanisms responsible for this impairment are not understood, but may involve late-phase protein synthesis processes associated with LTP, because later consolidation processes are being disrupted.