The Role Of NMDAR Regulated By PKC In Aluminum-induced Impairment Of Learning And Memory In Rats

Objective:To explore the mechanism of NMDAR in learning and memory damage of SD rats after acute and subchronic Aluminum exposure. Methods:1.Acute Al exposure(1)(1)The rats were divided into 5 groups randomly, including operation control group、saline control group and low-, medium-, high-dose groups, with 10 rats in each group. The operation control group was not treated,the rats were received 5ul of saline or Al(mal)3 via intracerebroventricular injection within 5 minutes.They received 7 days.(2) Rats were randomly divided into 5 groups: control group, saline group, PMA group, Al group, PMA + Al(mal)3 group, the rats of each group received 5ul of saline、PMA、64mmol/L Al(mal)3 and PMA + Al(mal)3.To study the role of PKC in impairment on learning and memory induced by aluminum in rats.(2) Morris water maze was used to detect learning and memory abilities of rats,including place navigation test(learning) and space probe test(memory);The Open-field test was employed to test the ability of rats to adapt to a new environment.(3) The relative expression level of PKC、NMDAR1、NMDAR2A、NMDAR2B、Ca MKII、Phospho- Ca MKII(Thr286) in hippocampus were detected by western blot.(4)The relative expression level of NMDAR1、NMDAR2A、NMDAR2B m RNA in hippocampus were detected by RT-PCR.2.Subchronic aluminum exposure(1)50 male SD rats were randomly divided into blank group、solvent control group、15mmol/L Al(mal)3 group、30mmol/L Al(mal)3 group and 60mmol/L Al(mal)3 group, The rats were received intraperitoneal injection for 2 month. The blank group was not treated.(2) The relative expression level of PKC、NMDAR1、NMDAR2A、NMDAR2B、Ca MKII、Phospho- Ca MKII(Thr286) in hippocampus were detected by western blot.(3) The relative expression level of NMDAR1、NMDAR2A、NMDAR2B m RNA in hippocampus were detected by RT-PCR.. Results:1.The result of acute Al exposure(1)The results of Morris water maze:(1)navigation test showed that with the increase of training days,the escape latency of each group was reduced gradually,the difference of escape latency was statistically significant among five point(P<0.01); In every training day, the escape latency of rats in each group was increased with the increasing exposure dose,compared to operation control group.the escape latency of each does group was prolonged obviously except the first day, and the difference is statistically significant(P<0.01),there is no interaction between does and time(F=0.692, P=0. 833). The probe test showed that the first time through the platform in high dose group was increased by 68.12% compared with the control, the time spent in the target quadrant was decreased by 23.9%(P<0.05). Times of passing through the platform was no significant difference.Open-field test showed that compared with the blank group,the rats in the center time was increased by 56.5%(P<0.05);the rearing and grooming were decreased by 36.8% and 37.9%(P<0.05).(2)Compared with Al exposure group, the first time through the platform was decreased by 34.8% and the time spent in the target quadrant was increased by 26.9% in PMA+ Al(mal)3 group(P<0.05),Open-field test showed that compared with Al exposure group,the time in center、rearing and grooming have no difference in PMA + Al(mal)3 group(P > 0.05).(2)The results of Western-blot:(1) The expression of NR1 and NR2 A were a downward trend with the increasing exposure dose.Compared with the control group, the expression of NR1 and NR2 A were decreased by 29.9% and 32.9% respectively in high dose group; NR2 B is also a downward trend, but there was no significant difference(P = 0.537). The expression of PKC and p- Ca MKII(Thr286) in high dose group was than the operation control group, The expression in high dose group was decreased by 20.9% and 34.7%(P<0.05).(2) PMA alone does not affect the expression of NMDA receptors subunits,the expression of PKC 、 NR1 and NR2 B in PMA+ Al(mal)3 group were increased by 15.8%、34.9% and 34.3%(P<0.05), Compared with Al exposure group,the expression of PKC and P-Ca MKII(Thr286) in PMA+Al(mal)3 were increased by 23.5% and 40.2%.(3)The results of RT-PCR:(1)Compared with the operation control group,the expression of NR1 and NR2 A m RNA was decreased by 48% and 38% in high exposure group.2.The result of Subchronic Al exposure(1)The results of subchronic Al exposure: The expression of NMDA receptor subunits was a downward trend with increasing dose.Compared with the blank control group, The expression of NR1、NR2A and NR2 B in high dose group were decreased by 22.0%、29.7%、29.8%.The expression of PKC、Phospho- Ca MKII(Thr286) were decreased by 29.3% and 31.5% in high dose group,and the expression level of Ca MKII was not changed.(2)Compared with the control group,the expression of NR1 and NR2 A m RNA decreased more than 50% in high exposure groups,The expression of NR2 B m RNA was not influenced。 Conclusions:1.Acute aluminum exposure can impair learning and memory in SD rats, the damage is more serious with the increase of the exposure dose.2.The decrease of NMDAR2 B in acute aluminum exposure was not caused by the change of the level of transcription,mainly due to NR2 B regulated by PKC, which was further confirmed in the subchronic aluminum exposure.3.Aluminum induced learning and memory impairment may be relevant with decrease in the expression of NMDA receptor subunits:Al exposure can inhibit transposition and activation of PKC,may influence NMDA receptor channel opening and the formation of NMDAR/Ca MKII complex, which damage the learning and memory.