The Model of Alzheimer’s Disease and Drug Administration

Aβ25–35 was dissolved in sterile water at a concentration of 1 mg/ml and stored at −20°C until use. Before administration to the animals, the prepared Aβ solution was thawed and incubated for 4 days at 37°C to form aggregates. Injections into cerebral ventricles were performed as described earlier (Tikhonova et al., 2020). The mice were anesthetized by administration of a 2.5% solution of avertin (2,2,2-tribromoethanol and 2-methyl-2-butanol, 100 μl/10 g, i.p.; Sigma-Aldrich Co.). The Aβ solution or sterile water was injected bilaterally with a Hamilton syringe (25 μl, model 1702 RN SYR, with a 22s ga needle, 2 in.), using a micropump (injection rate 0.8 μl/min). The needle was left at the injection site for 2 min after the injection. A total of 10 μl of the solution (9.4 nmol) were injected. The following coordinates adapted from the mouse brain atlas were used (Paxinos and Franklin, 2013): AP: -0.5 mm, ML: ±1 mm, and DV: −3 mm from the bregma, midline, and skull surface, respectively.

The rationale behind the CEF dosage (100 mg/kg/day) adopted in the current study was based on our recent studies showing neuroprotective effects of CEF in correcting behavioral and neuronal deficits (Tikhonova et al., 2017) and modifying the expression of genes related to the system of Aβ metabolism in the brain (Tikhonova et al., 2018) in another AD model (OXYS rats). Mice were weighed weekly during the experiment to adjust the drug dosage. The drug administration that preceded the testing of behavior or the collection of bio-samples was performed in 1 day prior to the corresponding manipulation in order to avoid the acute effects of CEF.