| Objective: To study the effects of thyroid hormone (TH)on the synaptophysin(syn)and nicotinic acetylcholine receptorα4 (nAchRα4)expression in the rat cortex and hippocampus developing period, further investigate the synapses development mechanism of thyroid hormone adjusting and controling the above part central nervous system Methods: In the study, experimental animals were divided into four groups: (1)Hypothyroidism group: The rat of maternal pregnant has given 0.02% methimazole(MM)water since E5, the infant rats were innate hypothyroidism.(2)T4 substitution group: innate hypothyroidism rats were intraperitoneal injected with T4 (0.02ug/ g ·d ) from postnatal 0 days.(3)T4 hyperthyroidism group: innate normol rats were intraperitoneal injected with T4 (0.4ug/ g·d ) from postnatal 0 days(.4)Normal control group: The pregnant rats were made a normol diet and water, its infant rats is used as the normal matched control. SynmRNA and nAchRα4mRNA were measured by in site hybridization. Experimental data were statistically analysed by One—Way ANOVA analysis and LSD test. High peak period mean difference of the four experimental groups were statistically analysed by confidence limit test. Result:(1)Normal control group synmRNA,nAchRα4mRNA expression model have the layer distribute characteristics in rat cortex and hippocampus. (2)SynmRNA expression is very low at P0d, the peak of synmRNA expression is at P4d. With the increment of the day, expression will reduce gradually. At P30d expression level is near to the adulthood rat level(P 120d).(3)NachRα4mRNA expression is very low at P0d, the peak of nAchRα4mRNA expression is at P14d-P21d. Then descend, keeping to the adulthood rat level(P120d).(4)SynmRNA,nAchRα4mRNA expression in hypothyroidism group were significantly lower than those in normal control group(P<0.001); In hypothyroidism group syn mRNA expression high peak delays 3 days, attaining the high peak in the P7d. But nAchRα4mRNA expression high peak time is the same with normal control group, having no the high peak delay. (5)SynmRNA ,nAchR α4mRNA expression in T4 substitution group were significantly higher than those in same days hypothyroidism group at P4d,P7d,P14d,P21d,P30d, but still be lower than the normal group levels(P<0.05 或P<0.01 或P<0.001).(except P7d Syn expression at hippocampus DG,P>0.05)(6)SynmRNA,nAchRα4mRNA expression in T4 hyperthyroidism group were significantly higher than those in same days normal control group at P14d,P21d,P30d(P<0.05 或P<0.01 或P<0.001)(.7)Each brain area syn and nAchRα4 95℅confidence limit of the normal control-hypothyroidism group and T4 substitution-hypothyroidism group high peak period mean difference were above zero ( do not include the zero). Then they have significant. (8) Each brain area syn 95℅confidence limit of the T4 hyperthyroidism-normal control group high peak period mean difference were include zero. Then T4 hyperthyroidism-normal control group have no significant(.9)Each brain area nAchRα4 95℅confidence limit of the T4 hyperthyroidism-normal control group high peak period mean difference were above zero ( do not include the zero). Then T4 hyperthyroidism-normal control group have significant. Conclusion: The synapses development is an important link in the central nervous system growth progress, which growth and mature are closely related with function. Thyroid hormone plays an important role in the development of many neuronal synapses include cholinergic neurons synapses. Syn,nAchRα4 expression change lead to synapses structural abnormality and information delivered the obstacle ,at last effect synapses occurrence and related nerve circut establishment in the cortex and hippocampus, appering the peerless of the neuronal place or mistake nerve thoroughfare, above all those obstructed the brain development and function maturation.It may be one of the braindevelopment obstruction theories mechanisms because of the thyroid hormone change. Timely T4 substitution therapy could an important way to correct hypothyroid brain da...
|
PDF Full Text Request