Fig. 5

Assessment of spatial learning and memory in 15-month-old mice using the Morris Water Maze. a Averaged escape latency in the Morris Water maze, training day 1 versus training day 5, with four successive trials per day. NonAD/MTNR+ vehicle treated mice (red line) showed a significant reduction in their escape latency to the submerged platform by day 5. MEL-treated 2xAD/MTNR+ mice (blue line) also had significantly improved performance while none of the other Alzheimer mice showed any significant learning. b Probe test follow-up after Morris Water maze training as determined by percentage of time spent in the goal quadrant. Retention of the memory of the goal quadrant was significantly reduced in the 2xAD mice as compared to the NonAD control mice, irrespective of the presence or absence of melatonin receptors (clear yellow and white bars). Treatment with MEL significantly improved memory in the 2xAD/MTNR+ (yellow, striped bar), but not in the 2xAD/MTNR- mice. Evaluated with 2-way RM ANOVA; n = 4–7; error bars represent SEM; p < 0.05