Objective To study the effect of Phenobarbital (PB) on experimental rats,observe the histological changes of immature brain and the expressions of apoptosis-related proteins Bcl-2 and Bax in neurons detected by immunohistochemistry,and to explore the influence and mechanism of PB on brain damage at therapeutic levels to immature brain maturation of rat in order to provide the theoretical and experimental base for clinic.Methods A total of 40 healthy 18-day-old Sprague-Dawley(SD) rats (male or female) were randomly assigned into 2 groups:normal saline (NS) treated as control group(20 cases),PB group(20 cases).Each group was further randomly divided into longterm(4 weeks) treated group and short-term(2 weeks) treated group(10 rats in each group).The rats in PB group received intragastricadministration with PB (30 mg/kg).The rats in control group were handled by injection of NS into stomach and abdomen according to 4 mL/kg.All performances were undertaken for twice every day.At the end of the therapeutic period,body and brain weight were measured when the rats were sacrificed.Histological studies on the tissues of frontal lobes and hippocampus were performed by Hematoxylin-Eosin(HE) staining and Nissl staining.Expressions of apoptosis-related proteins Bcl-2 and Bax in neurons were detected by immunohistochemistry.Results There were no significant differences in body and brain weights or histological studies index among control group as well as PB group before and after treatment for short term(P ＞0.05).Remarkable reduction of brain weight was only observed in immature rats exposed to PB compared to control group for long period,and significant neurodegeneration,neuronal necrosis were observed in immature rats exposed to PB compared to control group(all P ＜ 0.01).The expression of Bax protein in the frontal lobe increased significantly in immature rats receiving PB for long period comparing with control (P＜0.01).In contrast,expression of Bcl-2 protein did not change at therapeutic level.The ratio of Bax/Bcl-2 was obviously increased.Conclusions Chronic treatment with PB will result in significant neuronal apoptosis and necrosis and persistent cognitive impairment and brain damage to immature rates.Brain damage of PB at therapeutic level to immature brain may be irreversible.The significant expression of Bax protein in the frontal lobe and the high rate of Bax/Bcl-2 are probably the main reasons which cause brain weight decreasing and brain damage by PB in immature brain tissue.%目的 通过对苯巴比妥(PB)进行模拟临床用药的动物实验研究,观察不同给药时程幼鼠脑组织的形态结构变化,探讨治疗血浓度下抗癫(癎)药物对幼鼠脑发育的影响及其对认知损害的可能机制,为临床儿童癫(癎)的合理治疗提供科学依据和理论基础.方法 将40只(雌、雄不拘)日龄18 d的健康SD大鼠随机分为2组(每组20只):9 g/L盐水对照组(对照组)、PB组.根据给药时程又将每个给药组分为2周短程及4周长程给药组,共4组,每组10只.PB组予PB 30 mg/kg灌胃；对照组予等体积9 g/L盐水灌胃.以上操作均为2次/d.分别于停药当天将各组幼鼠称体质量后处死,称脑质量,脑组织石蜡包埋,切片HE染色及尼氏染色光镜下观察脑组织形态变化.用免疫组织化学方法检测各组大鼠脑切片海马及额叶皮层凋亡相关蛋白Bcl-2和Bax的表达水平.结果 短程给药后,PB组与对照组比较,其体质量、脑质量及脑组织结构变化差异均无统计学意义(P均＞0.05).而长程给药后,PB组幼鼠脑质量较对照组明显减轻,差异有统计学意义(P＜0.01)；额叶皮层神经细胞减少,且神经元结构明显异常.长程给药后,光镜下观察,PB组幼鼠脑组织额叶皮层Bax蛋白表达高于对照组(P＜0.01),Bcl-2蛋白的表达则无明显改变,Bax/Bcl-2比值明显升高.结论 长程服用PB可引起发育中脑组织明显的组织学损伤及神经元坏死与过度凋亡,而且这种损伤可能是不易恢复的.长程服用PB后幼鼠脑组织额叶皮质Bax蛋白表达显著增强和Bax/Bcl-2比值增高可能是未成熟鼠脑质量减轻和引起脑功能障碍重要原因.
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