| OBJECTIVE To make the ovariectomized female adult rats model, study the effect of ovariectomy and the steroid hormone intervention on rats spatial learning and memory,and the correlation between the sex steroid hormone levels and the spatial learning and memory. METHODS 80 female SD rats were randomly divided into five groups,16 rats in each group. The five group was as the following, the normal control group,sham operation group(Sham group), the ovariectomized group( OVX group), the ovariectomized with estradiol valerate replacement group( OVX+EV group) and the ovariectomized with estradiol valerate and acrylic acid testosterone replacement group(OVX+E+T group). The rats were anesthetized with sodium pentobarbital(2.5 ml/kg)by intraperitoneal injection. The ovarian surrounding adipose tissue of the rats in sham operation group were removed after the abdominal cavity were opened, then the abdominal cavity were closed. The rats in the model group were ovariectomized and the bilateral fallopian tubes were cut off. The Sham group and the OVX group were intraperitoneally injected saline and intragastric administration of saline with 5 ml/kg respectively. In group OVX+E, intraperitoneal injection of normal saline with 5 ml/kg and intragastric administration of estradiol valerate with 0.1 mg/kg was administered.In group OVX+E+T, 0.1 mg/kg estradiol valerate intragastric administration and intraperitoneal injection of testosterone propionate was conducted. All the 5 groups were administered for five weeks continuously. The Morris water maze was used to observe the pathological changes of the rats behavior, including place navigation test and spatial probe test. The concentration of serum estradiol(E2) and testosterone(T)were detected simultaneously using HPLC-MS method and the relevance of the sex hormone and the learning and memory was analyzed. RESULTS ① With the increase of the number of training, the average escape latency of finding the platform was obviously shortened in rats of all groups. The average escape latency time on the sixth day was(14.32±9.74)s,(15.61±10.08)s,(25.38±12.15)s,(11.92±7.51)s and(10.22±6.83)s respectively. The number of crossing the platform within 1 min on the sixth day of 5 groups of rats was(6.53±1.42),(5.72±1.26),(4.17±1.08),(8.22±2.34)and(9.05±2.83) respectively. Compared with the normal control group, operation stress has no effect on spatial learning and memory of adult female rats.②Removal ofovary can damage the spatial learning and memory of adult female rats. The average escape latency time of Morris water maze test increased in OVX group, mainly in the stage of learningm which illustrated that the effects of ovariectomy on spatial learning and memory ability were mainly reflected in the learning stage. ③ The estradiol can restore the impaired spatial learning and memory of ovariectomized rats. Application of estrogen in ovariectomized rats(group OVX+E) can improve the impaired spatial learning and memory of the ovariectomized rats. The average latency of group OVX+E on fifth day was significantly decreased than group OVX(P < 0.05). ④Testosterone can significantly enhance the spatial learning and memory of adult female rats. Water maze training scores of ovariectomized rats supplemented with estradiol and testosterone(group OVX+E+T) were improved significantly. ⑤ The rats of all groups can form spatial memory after Morris water maze training. The average latency after training was significantly reduced, and the difference was statistically significant(P < 0.05). ⑥ The level of serum E in ovariectomized rats decreased significantly(p<0.01). ⑦ The concentration of serum E level in rats increased significantly after hormone replacement. After co-administration of estradiol and testosterone in Ovariectomized rats, the serum estradiol levels were significantly increased(p<0.01). ⑧ The serum testosterone levels in ovariectomized rats were significantly increased after co-administration of estradiol and testosterone(group OVX+E+T), compared with the control group, Sham group, OVX group, OVX+E group(p<0.01). CONCLUSIONS ① The stress of surgery has no significant effects on spatial learning and memory of adult female rats. ② The ovariectomy can impair the spatial learning and memory of adult female rats. Supplement of estradiol could restore the impaired spatial learning and memory abilities in ovariectomized rats. Testosterone can enhance the ability of learning and memory in adult female rats, and has synergistic effect with estradiol. ③ The levels of E and T and the ability of spatial learning and memory has a positive correlation. |
PDF Full Text Request