Experimental timelines are shown above graphs. (a) Rats were injected bilaterally into the dorsal hippocampus with vehicle or the indicated concentrations of mannose-6-phosphate (M6P) immediately after IA training (↑), and memory was tested 1 day and 1 week later (n = 6–12, five independent experiments). (b) Vehicle, IGF2 (30 μg/kg), or M6P (850 μg/kg) was administered systemically (s.c., ↑) 20 min before contextual fear conditioning training to GFP- or Cre-injected mice. Percent (%) of time spent freezing were measured 1 day or 1 week after training (n = 5–7, five independent experiments). Two-way repeated measures ANOVA followed by Sidak’s post hoc tests. ****p<0.0001; see Source data one for detailed statistical information.