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 high2frequency 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.