Newland M C, Paletz E M
Department of Psychology, Auburn University, AL 36849, USA.
Neurotoxicology. 2000 Dec;21(6):1003-27.
Methylmercury and polychlorinated biphenyls (PCBs) exemplify the important interactions that should take place between epidemiological and laboratory investigations of developmental neurotoxicants. Often found in the same source, perhaps with multiplicative interactions, it is difficult to isolate specific profiles of effects without advanced behavioral procedures and controlled exposures using laboratory animals. The present review focuses on the effects of developmental exposure to methylmercury or PCBs as expressed in adult animals. The PCBs are subdivided into two structural classes, nonortho-substituted ("coplanar" or "dioxin-like") PCBs and ortho-substituted ("noncoplanar") PCBs, a distinction supported by different behavioral profiles and neural mechanisms of action. Methylmercury's profile is dominated by sensory effects with a likely cortical site of action. Some of these effects may be amplified with aging. Methylmercury's effects on functions generally termed cognitive can be understood by distinguishing between those reflecting the acquisition of a response-consequence relationship from those reflecting memory or contextual influences over behavior. Methylmercury does not appear to impair memory or discriminations, but retards acquisition of a response-reinforcer relationship. Like methylmercury, non-ortho-substituted PCBs do not appear to degrade memory and contextual control. Ortho-substituted PCBs impair performance on certain spatially-based discrimination and memory tasks. Methylmercury and non-ortho-substituted PCBs disturb the temporal pattern seen in fixed-interval schedules, but apparently without a significant change in the pattern of interresponse times. The ortho-substituted PCBs disrupted this pattern, but did so by increasing the number of short interresponse times.
甲基汞和多氯联苯（PCBs）体现了发育性神经毒物的流行病学调查与实验室研究之间应开展的重要相互作用。它们常常存在于同一来源中，或许还存在相乘作用，若不采用先进的行为学方法并利用实验动物进行受控暴露，就很难分离出特定的效应特征。本综述聚焦于发育阶段暴露于甲基汞或多氯联苯对成年动物产生的影响。多氯联苯可细分为两个结构类别，即非邻位取代的（“共平面”或“类二噁英”）多氯联苯和邻位取代的（“非共平面”）多氯联苯，不同的行为特征和神经作用机制支持了这种区分。甲基汞的效应特征以感觉效应为主，其作用部位可能在皮层。其中一些效应可能会随着衰老而增强。通过区分反映反应 - 结果关系习得的功能与反映对行为的记忆或情境影响的功能，可以理解甲基汞对通常称为认知功能的影响。甲基汞似乎不会损害记忆或辨别能力，但会延缓反应 - 强化物关系的习得。与甲基汞一样，非邻位取代的多氯联苯似乎不会破坏记忆和情境控制。邻位取代的多氯联苯会损害某些基于空间的辨别和记忆任务的表现。甲基汞和非邻位取代的多氯联苯会扰乱固定间隔时间表中出现的时间模式，但显然不会使反应间隔时间模式发生显著变化。邻位取代的多氯联苯扰乱了这种模式，但其方式是增加短反应间隔时间的数量。
