Yanai J, Steingart R A, Snapir N, Gvaryahu G, Rozenboim I, Katz A
The Ross Laboratory for Studies in Neural Birth Defects, Department of Anatomy and Cell Biology, The Hebrew University-Hadassah Medical School, Jerusalem, Israel. yanai@
Ann N Y Acad Sci. 2000 Sep;914:402-11. doi: 10.1111/j.1749-6632.2000.tb05214.x.
The present studies employ multitudinous approaches in order to overcome the methodological obstacles in the understanding of the relationship between neurochemical alterations and behavioral deficits induced by heroin during prenatal development. Mice were exposed prenatally to heroin via daily subcutaneous injections of 10 mg/kg, on gestation days 9-18. At age 50 days, the heroin-exposed offspring displayed behavioral deficits as assessed in the eight-arm and Morris mazes, pointing to possible alteration in the septohippocampal cholinergic innervations. Biochemically there was increased presynaptic activity of these innervations as attested to by the increased [3H]hemicholinium-3 (HC-3) binding sites and by K+-stimulated inositol phosphate (IP) formation. Postsynaptically, there was global hyperactivation along the different components of the nerve conduction cascade, including an increase in M1 muscarinic receptor Bmax, a general increase in G-proteins (GP) including the most relevant, G subtype, and an increase in IP formation and in basal protein kinase C (PKC) activity. However, there was desensitization of PKC activity in response to cholinergic agonist in the heroin-exposed offspring. Transplantation of normal embryonic cholinergic cells to the impaired hippocampus reversed the behavioral deficits and both the pre- and postsynaptic hyperactivity and resensitized PKC activity. To support and further strengthen the findings of the neural grafting study, correlation of the heroin-induced behavioral deficits with the biochemical alterations, done within individuals, was applied. The results showed high r values for IP formation, basal PKC, and PKC desensitization. The r values for HC-3 binding were statistically significant but relatively low. Taken together, the findings of the neural grafting and correlation studies bring us closer to understanding the relationship between the prenatal heroin-induced biochemical and behavioral changes. However, mammalian models possess the inherent methodological hindrances, stemming from possible maternal effects. To provide a control for these confounding variables, a chick embryo model was applied in which filial imprinting, a behavior related to a specific hyperstriatal nucleus, served as an endpoint. Heroin was administered to developing chick embryos by injecting the eggs (20 mg/kg) on incubation days (ID) 0 or 5. Prehatch exposure to heroin markedly diminished the ability for filial imprinting in the hatched chicks.
目前的研究采用了多种方法，以克服在理解产前发育期间海洛因引起的神经化学改变与行为缺陷之间关系时所面临的方法学障碍。在妊娠第9至18天，通过每天皮下注射10 mg/kg海洛因，使小鼠在产前接触海洛因。在50日龄时，经海洛因暴露的后代在八臂迷宫和莫里斯迷宫测试中表现出行为缺陷，这表明海马胆碱能神经支配可能发生了改变。生化分析显示，这些神经支配的突触前活性增加，这通过增加的[3H]半胱氨酸-3（HC-3）结合位点以及钾离子刺激的肌醇磷酸（IP）形成得到证实。在突触后，神经传导级联的不同组成部分出现整体过度激活，包括M1毒蕈碱受体Bmax增加、G蛋白（GP）普遍增加，其中最相关的是G亚型，以及IP形成和基础蛋白激酶C（PKC）活性增加。然而，经海洛因暴露的后代中PKC活性对胆碱能激动剂产生了脱敏作用。将正常胚胎胆碱能细胞移植到受损的海马体中，可逆转行为缺陷以及突触前和突触后的过度活跃，并使PKC活性恢复敏感。为了支持并进一步加强神经移植研究的结果，对个体内海洛因诱导的行为缺陷与生化改变进行了相关性分析。结果显示，IP形成、基础PKC和PKC脱敏的r值较高。HC-3结合的r值具有统计学意义，但相对较低。综合来看，神经移植和相关性研究的结果使我们更接近理解产前海洛因诱导的生化和行为变化之间的关系。然而，哺乳动物模型存在固有的方法学障碍，可能源于母体效应。为了控制这些混杂变量，应用了鸡胚模型，其中与特定上纹状体核相关的行为——亲子印记作为一个终点。在孵化第0天或第5天给发育中的鸡胚注射海洛因（20 mg/kg）。孵化前接触海洛因显著降低了孵化出的雏鸡的亲子印记能力。
