Yu Maria S, Eng Margaret L, Williams Tony D, Guigueno Mélanie F, Elliott John E
Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada.
Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada; Environment and Climate Change Canada, Science & Technology Branch, Pacific Wildlife Research Centre, Delta, British Columbia, Canada.
Neurotoxicology. 2017 Mar;59:33-39. doi: 10.1016/j.neuro.2017.01.001. Epub 2017 Jan 7.
Methylmercury (MeHg) readily crosses the blood brain barrier and is a known neuro-toxicant. MeHg accumulation in the brain causes histopathological alterations, neurobehavioral changes, and impairments to cognitive motor functions in mammalian models. However, in birds the neurotoxic effects of MeHg on the developing pre-hatching brain and consequent behavioral alterations in adult birds have not received much attention. Moreover, passerine birds are poorly represented in MeHg neurotoxicology studies in comparison to other avian orders. Hence in this study, we used the egg injection method to investigate the long term effects of in ovo MeHg exposure on brain histopathology and courtship behavior in a model songbird species, the zebra finch (Taeniopygia guttata). Egg treatment groups included: a low MeHg dose of 0.2μg Hg g egg, a high MeHg dose of 3.2μg Hg g egg, and a vehicle control (water). No adverse effects of in ovo MeHg treatment were detected on courtship song quality or on mating behavior in experimental males at sexually maturity which would suggest that observable neurobehavioral effects of MeHg exposure may depend on the timing of exposure during offspring development. However, neuroanatomical analysis indicated an increase in telencephalon volume with increased MeHg concentrations which may suggest a prolonged inflammatory response in this region of the brain.
甲基汞（MeHg）很容易穿过血脑屏障，是一种已知的神经毒素。在哺乳动物模型中，大脑中甲基汞的积累会导致组织病理学改变、神经行为变化以及认知运动功能受损。然而，在鸟类中，甲基汞对发育中的孵化前大脑的神经毒性作用以及成年鸟类随之而来的行为改变并未受到太多关注。此外，与其他鸟类目相比，雀形目鸟类在甲基汞神经毒理学研究中的代表性不足。因此，在本研究中，我们采用卵注射法，研究了在卵内暴露于甲基汞对一种模式鸣禽——斑胸草雀（Taeniopygia guttata）的脑组织病理学和求偶行为的长期影响。卵处理组包括：低甲基汞剂量组，每克卵含0.2μg汞；高甲基汞剂量组，每克卵含3.2μg汞；以及溶剂对照组（水）。在性成熟时，未检测到卵内甲基汞处理对实验雄性的求偶鸣叫质量或交配行为有不利影响，这表明甲基汞暴露的可观察到的神经行为影响可能取决于后代发育过程中的暴露时间。然而，神经解剖学分析表明，随着甲基汞浓度的增加，端脑体积增大，这可能表明大脑该区域存在延长的炎症反应。
