RESULTS
I2-IR ligand LSL60101 and donepezil improve memory deficits in 5XFAD mice.
Short- and long-term working memory were evaluated by NORT. 7-month-old 5XFAD mice presented robust cognitive deficits when compared to WT. LSL60101 treatment resulted in a rapid and sustained recovery of cognitive function by increasing the DI in both 2h and 24h memory tests (Figure 1b-c). Donepezil enhanced but did not sustain memory function in 5XFAD mice, as a significant increase of the DI was found after 2h, but not at 24h memory test (Figure 1c). Co-treatment did not improve cognition in comparison with individual treatments (Figure 1b-c). Treatments had no significant effects on WTs cognitive performance (Figures 1b-c).
For spatial learning and memory evaluation, the MWM was performed. After 5 days of training, all experimental groups presented curves with progressively shorter path length on consecutive days. Of note, the path length to the platform was significantly decreased in LSL60101 treated 5XFAD mice when compared to 5XFAD controls (Figure 1d). In the probe trial, 5XFAD mice showed a decreased percentage of time spent in the platform quadrant while the mice spent significantly more time in the quadrant opposite to the platform (Figure 1e,1h). LSL60101 treatment significantly increased the time spent in the platform quadrant in the 5XFAD treated mice when compared to both vehicle and donepezil treated 5XFAD, whereas LSL60101 treatment had no effect on WTs (Figures 1e, 1f,1h). Neither donepezil nor co-treatment improved 5XFAD mice spatial memory (Figures 1d, 1e). Although WT treated mice performed better (Figures 1d,1f,1h). All treatments decreased the path length to the platform albeit not significantly, due to different performance of individual mice (Figure 1g).
I2-IR ligand LSL60101 does not affect behavioural and emotional disturbances in 5XFAD mice in contrast to donepezil.
We also investigated the effect of the treatments on the 5XFAD and WT mice anxiety-like behaviour by performing the OF and EPM tests. No differences in locomotor activity were observed among the WT and 5XFAD groups (Figure 2a). 5XFAD mice presented a significant increase in the time spent in the centre of the open field compared to WT mice (Figure 2b). No effect was observed on the WT mice behaviour after treatments. 5XFAD treated with donepezil but not with LSL60101 showed a significant decrease in the time spent in the centre compared to 5XFAD controls, reverting to the WT healthy phenotype (Figure 2b). Co-treatment LSL60101/donepezil displayed the same results that showed donepezil alone, in all parameters evaluated (Figure 2b and Supplementary table S3). Similarly, in the EPM, 5XFAD mice spent significantly more time in the open arms and less in the closed arms in comparison with age-matched WTs (Figures 2d, 2e). Donepezil had a positive effect by reverting the 5XFAD EPM parameters evaluated to those showed by WT group (Figures 2d-f, Supplementary table S4). I2-IR ligand treatment alone did not affect any of the EPM parameters studied, whereas co-treatment maintained the donepezil values. Treatments did not induce significant changes in EPM parameters evaluated in WT mice (Supplementary Table S4).