碘缺乏甲状腺功能减退对仔鼠海马LTP的影响

Effect of iodine deficiency and hypothyroidism on long-tern potentiation in hippocampus

目的研究碘缺乏、甲状腺功能减退对大鼠仔鼠海马长时程增强(LTP)的影响,为碘缺乏、甲状腺功能减退导致脑发育障碍的发病机制提供实验依据。方法分别选用低碘饲料及他巴唑诱导建立碘缺乏(低碘)及甲状腺功能减退(甲减)大鼠仔鼠动物模型,应用细胞外微电极记录单脉冲刺激海马CA3区在CA1区诱发的群体峰电位(PS),测量高频刺激(HFS)前后单脉冲刺激诱发的PS幅值与PS潜伏期及其变化。结果低碘组、甲减组仔鼠PS潜伏期在HFS前(22.6764±5.4314),(20.0139±3.3028)ms;后(21.4414±4.2231),(20.8598±3.2207)ms,均明显高于相应的对照组(17.4643±2.6242),(16.7467±2.6283)ms(P<0.05)。低碘组HFS(1.8885±0.6418)mV及甲减组HFS前、后PS幅值(2.0291±0.3553),(1.9836±0.5698)mV,均明显低于相应对照组(2.4064±0.4645)、(3.1610±1.0844)mV(P<0.05)。各组HFS后PS幅值与相应的HFS前PS幅值相比,低碘明显降低(P<0.05),9只仔鼠有2只产生LTP,4只产生长时程抑制(LTd);甲减组PS幅值明显降低,6只仔鼠2只产生LTP,4只产生LTD;而对照组PS幅值显著升高(P<0.01),6只仔鼠4只产生LTP,1只产生LTD。结论碘缺乏、甲状腺功能减退可损害仔鼠在体海马LTP的诱导。

Objective To study the effects of iodine deficiency and hypothyroidism on long-term potentiation(LTP) in hippocampus of rat pups,and to discuss the possible mechanism of brain deficits associated with iodine deficiency and hypothyroidism.Methods Iodine deficient rats were administered with iodine-deficient diet and hypothyroid rats were administered with methimazole in drinking water.Population spikes(PS)were recorded in CA1 area in response to single pulse stiumulation applied to CA3 area with extracellular microelectrode technique.The mean PS amplitude and peak latency in response to single pulse stimulation were measured before and after high-frequency stimulation(HFS).Results The mean peak latencies in iodine deficient and hypothyroid groups before(22.6764±5.4314),(20.0139±3.3028)ms and after(21.4414±5.2231),(20.8592±3.2207)ms HFS were signifiantly higher than that in control group(17.4643±2.6242),(16.7467±2.6283)ms(P<0.05).The means PS amplitude in iodine deficiency group after HFS (1.8885±0.6418)mV ad hypothyroid group before and after HFS(2.0291±0.3553),(1.9836±0.5698)mV were singnificantly lower than that in the control group(2.4064±0.4645),(3.1610±1.0844)mV (P<0.05).After the application of the HFS,the mean PS amplitude in the iodine deficiency group decreased significantly(P<0.05),and 2 out of 9 rats showed LTP,however,4 showed long-term depression(LTD);the mean PS amplitude in hypothyroid group decreased,and 2 out of rats showed LTP,however,4 showed LTD;the mean PS amplitude in the control group increased significantly(P<0.01),and 4 out of 6 rats showed LTP,1 showed LTD.Conclusion Iodine deficiency and hypothyroidism of mother rat ma impair the induction of LTP in vivo of their pups.