Objective      To determine the effect of heat acclimation (HA) on the autophagy and apoptosis of cerebral neurons in mice after heat stroke (HS).       Methods      A total of 48 C57 male mice were randomly divided into control (CON) group

HA group

HS group and HA+HS group. After the establishment of HA and HS models

the brain water content was measured

pathological changes of the brain were observed by HE staining

neuronal degeneration was tested by Fluoro-Jade B (FJB) staining

neuronal apoptosis was detected by TUNEL staining and Western blotting

and the expression of Caspase 3 and LC3 was measured by immunofluorescence assay and Western blotting. The results were compared among the groups.       Results      After exposure to 43 ℃ for 120 min

the brain water content was significantly lower in HA+HS group than HS group [(78.54±0.25)% vs (79.64±0.21)%

P0.05]. Pathological observation displayed swollen cells

rarefied cytoplasm

chromatin concentration and edge accumulation

nuclear pyknosis

rupture and dissolution

obviously cell vacuolation

and exacerbated neuronal degeneration and apoptosis in HS mice

but the damage degrees were milder in the HA+HS mice with remarkably attenuated neuronal degeneration and apoptosis and decreased expression of Caspase 3 (P0.05). Heat exposure elevated the autophagy in the HA

HA+HS and HS groups

but the autophagy and LC3 expression were attenuated after HA preconditioning when compared with HS mice.       Conclusion      HA plays protective role in brain injury in HS-induced mice

and down-regulates the neuronal autophagy and apoptosis.