Effect Of Hyperthyroidism On The Expression Of Synaptotagmin-1 In The Prefrontal Lobe Of Adult Rats

ObjectiveTo observe the effect of hyperthyroidism on the expression of synaptotagmin-1 (syt 1) in prefrontal lobe of adult rats. Further to explore the reason and molecular mechanism of the brain impairment.MethodsAll adult male Sprague-Dawley rats were divided into three groups, hyperthyroid (n=11),hypothyroid (n=11),control (n=11).Hyperthyroidism by injecting L-Thyroxine (L-T4) (50 ug/100g body weight) for 3 weeks and the control group by injecting stroke-physiological saline solution for 6 weeks,hypothyroidism was induced by daily intraperitoneal injecting PTU (lmg/100 g body weight) for 6 weeks, Rats chow and tap water were provided ad libitum. After mode were build, getting blood sample 1.5ml from abdominal aorta, using radioimmunity method to assay the levels of serum tri-iodothyronine(T3),serum T4.After the rats were sacrificed, their brains were immediately dissected on ice. The right brains were fixed in 4% paraformaldehyde at 4℃for 7 days for immunohistochemistry. The left PFC was quickly isolated and stored at-80℃for western blot analysis. Immunohistochemical and western blot method were used to determine the levels syt 1 in the prefrontal lobe of rats from different groups. All statistical analysis was performed using SPSS software (version 16.0). Values are expressed as mean±S.E.M. The data among the groups were compared using one-way ANOVA. Statistical significance was defined as P<0.05. Results1.Thyroid hormone levels Serum T3,T4 levels of hyperthyroidism rats were significantly higher than the control group, In the hypothyroid group, the levels of serum T3 and T4 were significantly lower than those in the control group (P<0.05)2. Immunohistochemical method In the hyperthyroidism group, the levels of syt 1 protein in theⅠ,Ⅱ,Ⅲ,Ⅴlayers of prefrontal lobe were significantly decreased comparing to the control group (P< 0.05), only in the internal granular layer was no significant; In the hypothyroid group, the levels of syt 1 protein in theⅠ,Ⅱ,Ⅲ,Ⅳ,Ⅴlayers of prefrontal lobe were significantly lower compared to the control group(P< 0.05).3. Western blot analysis In the hyperthyroidism group, the levels of syt 1 protein of prefrontal lobe were decreased comparing to the control group,but it was no significant (P>0.05), In the hypothyroid group, the levels of syt 1 protein of prefrontal lobe were significantly lower compared to the control group(P<0.05).ConclusionBy immunohistochemical and western blot analysis show that hyperthyroidism can decrease the expression of syt 1 in prefrontal lobe of adult rats.