The method and effect of rapid establishment of a mild cognitive impairment model

To further the exploration of the pathogenesis of mild cognitive impairment (MCI), we aimed to determine the appropriate dose for a rapidly established MCI rat model using D-galactose (D-gal), with lasting cognitive effects.

In Experiment 1, we evaluated various D-gal concentrations (100-2,000 mg/kg/day), and determined that, compared with saline injections of the same volume. In Experiment 2, we evaluated the duration of the effect of 1,000 mg/kg/day D-gal injections for 1 week, with MWM testing initiated at 1 day, 1 month, and 3 months after completion of the injection regime in three model groups, respectively.

In Experiment 1, D-gal injections at a concentration of 1,000 mg/kg/day for 1 week was adequate to induce a significantly worse Morris water maze (MWM) test performance and pathomorphologic changes in the hippocampus, with MWM testing initiated 1 day after completion of the injection regime. In Experiment 2, Before modeling, the overall condition (fur, mental state, foraging behavior, and activity level), body weight, swimming speed, and swimming time did not significantly differ between the control (saline injections) and model groups (D-gal injections). After modeling, MWM test performance was considerably worse (longer escape latencies and fewer platform crossings within 90 seconds) in the model groups than in the control group, without significant differences among model groups. Furthermore, movement trajectories were similar among model groups.

These results demonstrate that subcutaneous injections of D-gal 1,000 mg/kg/day for 1 week produce changes consistent with the characteristics and pathological processes of MCI. Thus, high-dose D-gal injection allows the rapid establishment of an MCI model that is effective and sustainable.