Impaired Interleukin-1β and c-Fos Expression in the Hippocampus Is Associated with a Spatial Memory Deficit in P2X ₇ Receptor-Deficient Mice

Abstract

Recent evidence suggests that interleukin-1β (IL-1β), which was originally identified as a proinflammatory cytokine, is also required in the brain for memory processes. We have previously shown that IL-1β synthesis in the hippocampus is dependent on P2X ₇ receptor (P2X ₇R), which is an ionotropic receptor of ATP. To substantiate the role of P2X ₇R in both brain IL-1β expression and memory processes, we examined the induction of IL-1β mRNA expression in the hippocampus of wild-type (WT) and homozygous P2X ₇ receptor knockout mice (P2X ₇R ^−/−) following a spatial memory task. The spatial recognition task induced both IL-1β mRNA expression and c-Fos protein activation in the hippocampus of WT but not of P2X ₇R ^−/− mice. Remarkably, P2X ₇R ^−/− mice displayed spatial memory impairment in a hippocampal-dependant task, while their performances in an object recognition task were unaltered. Taken together, our results show that P2X ₇R plays a critical role in spatial memory processes and the associated hippocampal IL-1β mRNA synthesis and c-Fos activation.