Changes of cognitive ability in elderly rats induced by sevoflurane exposure and their relation with TLR4-MyD88 signal pathway

Objective To explore the changes of cognitive ability in elderly rats induced by sevoflurane exposure, and their relation with Toll like receptor 4 (TLR4)-MyD88 signal pathway. Methods Forty-eight male SD rats, weighting 550-750 g, in accordance with the random number table, were divided into 4 groups (n=12): control group (C group), sevoflurane treatment group (S group), sevoflurane plus TAK242 treatment group (TS group), and sevoflurane plus ST2825 treatment group (SS group). The rats in S, TS and SS groups were subjected to inhale 4% sevoflurane for 6 h, but the rats in C group were inhaled by air-oxygen only. The rats in TS and SS group were injected with 20 μL TAK242 (1 g/L) or 20 μL ST2825 (1 g/L) via lateral ventricle 10 min before sevoflurane exposure, respectively. The cognitive ability was assessed by Morris water maze test and open field test; the levels of hippocampal tumor necrosis factor (TNF)-α and interleukin (IL)-1β were assessed by ELISA; the Aβ expressions was assessed by Western blotting. Results As compared with those in the C group, significant increase of escape latency, time of the animals spent in the central square, and TNF-α, IL-1β and Aβ expressions, but decrease of number of crossing the grid, and smaller number of standing on the back legs were noted in the S group (P<0.05). As compared with S group, TS and SS group had significantly decreased escape latency, time of the animals spent in the central square, and TNF-α, IL-1β nd Aβ expressions, but statistically larger number of crossing the grid and number of standing on the back legs (P<0.05). Conclusion The cognitive dysfunction of elderly rats induced by sevoflurane exposure could be associated with TLR4-MyD88 signal pathway. Key words: Toll like receptor 4; Sevoflurane; Neurotoxicity; Cognition