Within the brain, the inflammatory cytokine interleukin-1 (IL-1) mediates illness-associated neural, neuroendocrine, and behavioral responses; however, its role in normal neurobehavioral processes is not clear. To examine the role of IL-1 signaling in memory, we infused Long-Evans rats intracerebroventricularly with IL-1β (10 ng/rat), IL-1 receptor antagonist (IL-1ra, 100 μg/rat), or saline immediately following a learning task and tested memory functioning 1–8 days later. In the Morris water maze (MWM), IL-1ra caused memory impairment in the hippocampus-dependent, spatial version, whereas IL-1β had no effect. Neither IL-1β nor IL-1ra influenced the hippocampus-independent, nonspatial version of the MWM. In the passive avoidance response, which also depends on hippocampal functioning, IL-1ra caused memory impairment, and IL-1β caused memory improvement. These results suggest that IL-1 signaling within the hippocampus plays a critical role in learning and memory processes.
Brain Interleukin-1 Is Involved in Spatial Memory and Passive Avoidance Conditioning
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