Effects of polydatin on learning memory and the expression of synaptophysin in hippocampus induced by hypoxic-ischemic brain injury in neonatal rats

Abstract

Objective To explore the protective effects and possible mechanisms of Polydatin (PD)on hypoxic-ischemia brain injury(HIBD) in neonatal rat by means of spatial learning memory and the expression of synaptophysin in hippocampal CA1. Methods Thirty-seven neonatal SD rats were divided into 3 groups at random: normal sham-operated group( no hypoxia and ischemia); HIBD group( no medication) ;PD treatment group. 7-old-day rat' s model of HIBD was established by left carotid artery ligation and 2 h hypoxia. Morris water maze test was used to evaluate cognitive function in the rats after 28-day-old( 21-day later after HI). Immunohistochemical method was used to measure the expression of synaptophysin after the end of Morris water maze test. Results Morris water maze results showed that the mean escape latency of the shamgroup (SG) ,HIBD group (HIBD) and PD treatment group (PD) were (39. 55 ±8. 08) s, (52. 37 ±8.03) s and (43.29 ± 7. 63 ) s respectirely. For PD and SG, the mean escape latency was significantly shorter than the HIBD (P ＜0.05). After training,the mean escape latency in the three groups of rats was shortened gradually. The frequency of platform crossings were 5. 29 ±2.62、2. 36 ± 1.80、4. 25 ± 1. 66 in the SG,HIBD and PD respectirely. The frequency of platform crossings in PD was higher than that of HIBD ( P ＜ 0. 05 ). The swimming time in target quadrant were ( 15.74 ± 3.85) s, ( 10. 63 ± 3.66) s and ( 14. 32 ± 2. 52 ) s in SG, HIBD and PD respectirely. For HIBD ,the swimming time in target quadrant was significantly shorter comparing to SG and PD ( P ＜ 0. 05 ). The expression of synaptophys in hippocampal CA1 in PD ( 0. 295 2 ± 0. 044 3 )were evidently higher than that in the HIBD group (0.261 2 ±0.032 3) at 3 week after operation (P ＜0. 05). Conclusion Spatial learning memory deficits and the decrease of synaptophys in hippocampal CA1 could be induced by hypoxic-ischemia. Polydatin could improve the learning and memory ability in neonatal rats following hypoxic-ischemia brain damage. The mechanisms of improvement with Polydatin treatment is associated with the enhancement of expression of synaptophys. Key words: Polydatin ; Hypoxic-ischemic brain injury ; Spatial learning memory ; Synaptophysin ; Rat