Effects of mild hypothermia on autophagy in hippocampal CA1 neurons in rats after CPR

Objective To establish the cardiac arrest-cardiopulmonary resuscitation model in rats, and to observe the effect of mild hypothermia on autophagy in hippocampal CA1 neurons after ROSC. Methods A total of 36 Wistar rats were randomly divided into two groups: normal temperature treatment group(NT group) and mild hypothermia treatment group(HT group). To establish the cardiac arrest-cardiopulmonary resuscitation(CA-CPR) model in rats by epicardial electrical stimulation induced ventricular fibrillation, and to sacrifice 3 animals in each group to obtain the brain cortex in 2nd and 4th hours after ROSC in order to observe the expression of p-AMPK by electron microscope and LC3 granules through Western blot. The neurological deficit score(NDS) was assessed in 24、48、72 hours respectively after ROSC. To sacrifice the animals so as to take the cerebrum in 72 hours after ROSC, then calculate the apoptotic index of the hippocampal CA1 neurons, which were dyed through TUNEL method. Results The expression of p-AMPK、Beclin-1 and LC3-Ⅱ/LC3-Ⅰratio in Normothermia group were all lower than the Mild hypothermia group(P<0.05), the neurons plasma of hippocampal CA1 area in the Hypothermia group demonstrated obvious LC3 granules formation, the NDS score of the Normothermia group and the Mild hypothermia group in ROSC24h、ROSC48h、ROSC72h were 320vs205、285vs140、266vs120, respectively. The apoptotic index of the hippocampal CA1 area in the Normothemia group in ROSC72h was higher than the Mild hypothermia group, (P<0.05). Conclusions Mild hypothermia after cardiopulmonary resuscitation promotes autophagy of the hippocampal CA1 area neurons in rats and reduce neuronal apoptosis. Key words: Cardiac arrest; CPR; Mild hypothermia; Rat; Autophagy