Effects of immune activation on the retrieval of spatial memory

Objective It has been shown that there are extensive interactions between the central nervous system and the immune system. The present study focused on the effects of lipopolysaccharide (LPS) on memory retrieval, to explore the interaction between immune activation and memory. Methods C57BL/6J mice (8 weeks old) were first trained in the Morris water maze to reach asymptotic performance. Then mice were tested 24 h after the last training session and LPS was administered (1.25 mg/kg, i.p.) 4 h prior to the testing. The retrieval of spatial memory was tested by probe trial, and the time spent in the target quadrant and the number of platform location crosses were recorded. ELISA was performed to detect interleukin-1 beta (IL-1 beta) protein level in the hippocampus of mice tested in the water maze. Results Although LPS induced overt sickness behavior and a significant increase in the level of IL-1 beta in the hippocampus of mice, there was no significant difference in the time spent in the target quadrant or in the number of platform location crosses between LPS- treated and control groups in the probe trial testing. Conclusion Immune activation induced by LPS does not impair the retrieval of spatial memory.