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.
Bibliographical noteFunding Information:
The authors thank Chris Conley and Doug Caruana for excellent technical assistance in conducting the experiments. This project was partly supported by the Smith Laboratory for Collaborative Research in Psychobiology (R.Y.) and a grant from the Natural Sciences and Engineering Research Council of Canada (G.W.). R.Y. is a member of the Eric Roland Center for Neurodegenerative Diseases at the Hebrew University of Jerusalem.
- IL-1 receptor antagonist (IL-1ra)
- Interleukin-1 (IL-1)
- Morris water maze
- Passive avoidance