Zhou Yong-Hua, Wang Xiao-Bo, Jiang Shou-Fu, Xu Yong-Liang, Tao Jian-Ping, Zhang Xiao-Ping, Zhang Ying, Gao Qi
Zhongguo Ji Sheng Chong Xue Yu Ji Sheng Chong Bing Za Zhi. 2011 Oct;29(5):333-8.
To detect the learning and memory ability in mice model of latent Toxoplasma gondii infection with object recognition test and Morris water maze test.
Thirty-six Kunming mice were divided into control group, infection group with 6 cysts each mouse (low infection group), and infection group with 12 cysts each mouse (high infection group) averaged. Mice in the two infection groups were orally infected with T. gondii Prugniaud (PRU) low virulence strain. Object recognition test was conducted at the 63rd day after infection. After the first day of adaptation and the second day of familiarization in the test, the time expended on exploring new and familiar objects was recorded on the third day and the discrimination index (DI) was calculated. Morris water maze test was conducted at the 66th day. The ability of spatial learning, spatial memory retention and working memory capacity was evaluated by place navigation test, spatial probe test, and working memory test, respectively. The mice were sacrificed at the 74th day after infection. The left cerebral hemisphere of mice was fixed, sliced, and stained with eosin-hematoxylin for pathological examination. The right hemisphere was used to detect the activity of superoxide dismutase (SOD) and malondialdehyde (MDA) content.
The results of object recognition test showed that the discrimination index of high infection group and low infection group was (14.3 +/- 5.2)% and (17.5 +/- 5.6)%, respectively, significantly lower than the control [(28.9 +/- 7.1)%] (P < 0.01). In the place navigation test, the latency to find the platform in the two infection groups was longer than the control, with significant difference on the second and third day (P<0.05). In the spatial probe test, the percentage of the distance across the platform quadrant in the total swimming distance of high infection group and low infection group were (19.9 +/- 5.0)% and (23.9 +/- 6.8)%, respectively, significantly lower than the control [(27.4 +/- 3.6)%] (P < 0.05). In the working memory test, at the fourth day of test the latency of high infection group and low infection group [(365 +/- 14.2) s and (35.3 +/- 13.7) s] was significantly longer than the control [(30.4 +/- 12.5) s] (P<0.05). In all the tests, there was no statistical significance between low infection group and high infection group (P > 0.05). The brain sections of two infection groups showed cysts of T. gondii, proliferation of glial cells, widened gap around small blood vessels, and a phenomenon of "vascular cuff". The activity of SOD in the mice brains of two infection groups was significantly lower than the control, while MDA level was significantly higher (P < 0.05). SOD and MDA showed no significant difference between two infection groups (P > 0.05).
Latent infection of T. gondii may lead to learning and memory impairment in mice.
采用物体识别试验和莫里斯水迷宫试验检测潜伏性弓形虫感染小鼠模型的学习和记忆能力。
将36只昆明小鼠平均分为对照组、每只小鼠感染6个包囊的感染组（低感染组）和每只小鼠感染12个包囊的感染组（高感染组）。两个感染组的小鼠经口感染弓形虫Prugniaud（PRU）低毒株。感染后第63天进行物体识别试验。在试验中适应第1天和熟悉第2天后，记录第3天探索新物体和熟悉物体所花费的时间，并计算辨别指数（DI）。感染后第66天进行莫里斯水迷宫试验。分别通过定位航行试验、空间探索试验和工作记忆试验评估空间学习能力、空间记忆保持能力和工作记忆能力。感染后第74天处死小鼠。取小鼠左侧大脑半球固定、切片，苏木精-伊红染色进行病理检查。取右侧大脑半球检测超氧化物歧化酶（SOD）活性和丙二醛（MDA）含量。
物体识别试验结果显示，高感染组和低感染组的辨别指数分别为（14.3±5.2）%和（17.5±5.6）%，显著低于对照组[（28.9±7.1）%]（P<0.01）。在定位航行试验中，两个感染组找到平台的潜伏期均长于对照组，在第2天和第3天有显著差异（P<0.05）。在空间探索试验中，高感染组和低感染组穿过平台象限的距离占总游泳距离的百分比分别为（19.9±5.0）%和（23.9±6.8）%，显著低于对照组[（27.4±3.6）%]（P<0.05）。在工作记忆试验中，试验第4天高感染组和低感染组的潜伏期[（365±14.2）秒和（35.3±13.7）秒]显著长于对照组[（30.4±12.5）秒]（P<0.05）。在所有试验中，低感染组和高感染组之间无统计学差异（P>0.05）。两个感染组的脑切片均显示有弓形虫包囊、胶质细胞增生、小血管周围间隙增宽以及“血管袖套”现象。两个感染组小鼠脑内SOD活性显著低于对照组，而MDA水平显著高于对照组（P<0.05）。SOD和MDA在两个感染组之间无显著差异（P>0.05）。
弓形虫潜伏感染可能导致小鼠学习和记忆障碍。
