褪黑素对噪声应激大鼠学习记忆的保护作用

目的 探讨噪声应激对大鼠记忆功能的影响及可能机制.方法 将50只大鼠用随机数字法分为空白组和2个实验组、2个对照组.空白组不给任何处理,实验组及对照组暴露于120dB噪声应激1d或3d,8h/d,并于每次噪声应激前分别腹腔注射褪黑素(MT,15mg/kg)或等量生理盐水.应激结束后,用旷场反应箱测试大鼠的行为,用Morris水迷宫法测试大鼠学习记忆,用试剂盒检测大鼠大脑皮层和海马中一氧化氮(NO)、超氧化物歧化酶(SOD)和丙二醛(MDA)含量.结果 无论噪声应激1d或3d,旷场反应测试大鼠兴奋性和探索性行为实验组运动总距离(TMD)(1322.50±504.32)cm,(1819.55±458.37)cm,较快运动时间(FMT)(68.49±23.90)s,(87.34±16.01)s,距中心距离(DTC)(63.56±2.75)cm,(60.13±1.87)cm,内环内时间(ITT)(7.87±2.06)s,(9.60±2.89)]均明显小于对照组TMD(2042.03±449.19)cm,(2325.73±384.90)cm,FMT(109.32±21.84)s,(124.65±16.74)s,DTC(58.00±1.53)cm,(55.05±5.13)cm,ITT(12.84±3.62)s,(14.92±2.75)s,(P＜0.05,P＜0.01)];水迷宫中的逃避潜伏期实验组大鼠(10.69±3.37)s,(18.87±4.74)s]均明显小于对照组(23.86±7.66)s,(33.55±7.20)s,(P＜0.01)];大鼠大脑皮层和海马组织中NO和MDA含量实验组皮层NO(3.35±0.40)μmol/gprot,(4.50±0.41)μmol/gprot,海马NO(2.24±0.18)μmol/gprot,(3.15±0.21)μmol/gprot,皮层MDA(1.34±0.44)nmol/mgprot,(2.39±0.18)nmol/mgprot,海马MDA(0.13±0.07)nmol/mgprot,(0.53±0.10)nmol/mgprot]明显低于对照组皮层NO(3.35±0.40)μmol/gprot,(5.03±0.44)μmol/gprot,海马NO(2.93±0.31)μmol/gprot,(3.38±0.24)μmol/gprot,皮层MDA(2.24±0.26)nmol/mgprot,(4.21±0.21)nmol/mgprot,海马MDA(0.47e0.29)nmol/mgprot,(1.33±0.187)nmol/mgprot,(P＜0.05,P＜0.01)],SOD含量实验组皮层(763.95±214.36)U/mgprot,(491.33±35.85)U/mgprot,海马(817.02±232.39)U/mgprot,(644.85±28.02)U/mgprot]明显高于对照组皮层(556.50±101.51)U/mgprot,(327.35±30.54)U/mgprot,海马(279.74±117.02)U/mgprot,(108.75±15.52)U/mgprot,(P＜0.05,P＜0.01)].结论 褪黑素对噪声应激大鼠记忆障碍有改善作用,这种作用可能与抑制噪声应激大鼠大脑皮层和海马中NO及MDA的升高,并提高SOD活性作用有关.

Protective effects of melatonin on learning and memory in rats by noise stress

Objective To explore the effect of melatonin(MT) on the behavior of rats treated with noise stress and the related bio-mechanism. Methods Fifty rats were randomly divided into a blank group,two experimental groups and two control groups. The blank group was untreated. The experimental and control groups were exposed to 120dB noise stress for 1 day or 3 days, 8 hours per day, and treated with 15 mg/kg melatonin by intraperitoneal injection,or the same volume of physiological saline 30 minutes before noise stress. After noise stress,the rats' behavior was measured by open field test, learning and memory ability of rats was investigated with the method of Morris water maze and then nitric oxide (NO), superoxide dismutase (SOD) and malondialdehyde (MDA) contents in cerebral cortex and hippocampus of the rats were measured by TBA and Griess method respectively. Results No matter noise stress time was 1 day or 3 days, the excitability and explorative behavior of the 2 experimental groups(total movement distance (TMD) (1322.50 ± 504.32) cm, (1819.55 ± 458.37) cm, faster movement time (FMT) (68.49 ± 23.90) s, (87.34 ± 16.01) s, distance to center (DTC) (63.56 ± 2. 75) cm, (60. 13 ±1.87)cm, inner toriod time(ITT) (7.87 ±2.06)s,(9.60 ±2.89)s) in the open field test decreased significantly compared with those of the control group (TMD (2042.03 ± 449. 19) cm, (2325.73 ± 384.90) cm,FMT (109.32 ±21.84)s,(124.65 ± 16.74)s, DTC (58.00± 1.53)cm,(55.05 ±5.13)cm, ITT (12.84 ±3.62) s, (14.92 ± 2.75) s, P ＜ 0. 05, P ＜ 0.01);the escape latency of the experimental groups (( 10. 69 ±3.37) s, (18.87 ± 4.74) s) in Morris water maze was significantly shorter than that of the control group (( 23.86± 7.66)s, (33.55 ± 7.20)s, P＜ 0.05, P＜0.01). The contents of NO or MDA in cerebral cortex and hippocampus of the experimental groups (NO in cerebral cortex (3.35 ± 0.40) μmol/gprot, (4.50 ± 0.41) μmol/gprot, NO in hippocampus (2.24 ±0.18) μmol/gprot,(3.15 ±0.21) μmol/gprot, MDA in cerebral cortex(1.34 ±0.44)nmol/mgprot, (2.39 ± 0. 18) nmol/mgprot, MDA in hippocampus (0. 13 ± 0. 07) nmol/mgprot, (0.53 ± 0. 10)nmol/mgprot) were lower than those of the control group (NO in cerebral cortex (3.35 ± 0. 40) μmol/mgprot,(5.03 ± 0.44)μmol/mgprot, NO in hippocampus (2.93 ± 0. 31) μmol/gprot, (3.38 ± 0.24) μmol/gprot, MDA in cerebral cortex (2.24 ± 0.26) nmol/mgprot, (4.21 ± 0.21) nmol/mgprot, MDA in hippocampus (0.47 ± 0.29)nmol/mgprot, (1.33 ± 0. 187) nmol/mgprot, P ＜ 0.05, P ＜ 0. 01) respectively and the contents of SOD in cerebral cortex and hippocampus of the experimental groups (in cerebral cortex (763.95 ± 214.36) U/mgprot, (491.33 ±35.85) U/mgprot, in hippocampus (817.02 ± 232.39) U/mgprot, (644.85 ± 28.02) U/mgprot) were higher than those of the control group(in cerebral cortex (556.50 ± 101.51) U/mgprot, (327.35 ± 30.54) U/mgprot, in hippocampus (279.74 ± 117.02) U/mgprot, (108.75 ± 15.52) U/mgprot, P ＜ 0.05, P＜ 0.01) respectively. Conclusion Melatonin is effective in improving the ability of learning and memory in the rats of noise stress,possibly by inhibiting the increase of NO and MDA and increasing the SOD activity in cerebral cortex and hippocampus of the rats.