Inglis W L, Semba K
Department of Anatomy and Neurobiology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada.
Brain Res. 1997 Apr 25;755(1):17-27. doi: 10.1016/s0006-8993(97)00101-7.
Excitotoxins are valuable tools in neuroscience research as they can help us to discover the extent to which certain neurones are necessary for different types of behaviour. They have distinctive neurotoxic effects depending on where they are infused, and this study was conducted to delineate the neurotoxic profiles of excitotoxins in the laterodorsal tegmental nucleus (LDTg). Two 0.1 microl infusions of 0.1 M ibotenate, 0.1 M quinolinate, 0.04-0.1 M NMDA, or 0.05-0.015 M AMPA, were made unilaterally into the LDTg under either pentobarbitone or Avertin anaesthesia. The injection needle was oriented at an angle of 24 degrees from vertical in the mediolateral plane. After 23-27 days, sections through the mesopontine tegmentum were processed using standard histological procedures for NADPH-diaphorase histochemistry, tyrosine hydroxylase or 5-hydroxytryptamine immunohistochemistry, and Cresyl violet. Lesions were assessed in terms of the size of the damaged area (identified by reactive gliosis), the extent of cholinergic cell loss in the mesopontine tegmentum (by counting NADPH-diaphorase-positive neurones), and neuronal loss induced in the locus coeruleus and dorsal raphe nucleus. Ibotenate induced compact lesions in the LDTg (more than 80% cholinergic loss) and did little damage to the locus coeruleus and dorsal raphe nucleus. Quinolinate and low doses of AMPA and NMDA made very small lesions with less than 35% cholinergic loss, while at higher doses, AMPA and NMDA induced large areas of reactive gliosis but killed only a proportion of the cholinergic neurones. AMPA appeared to have a particular affinity for noradrenergic neurones in the locus coeruleus, with the 0.015 M dose injected into the LDTg typically destroying the majority of these neurones. The results are discussed in the context of what is known about the mechanisms of excitotoxins and the glutamate receptor profile of mesopontine neurones.
兴奋性毒素是神经科学研究中的重要工具，因为它们能帮助我们了解某些神经元对不同类型行为的必需程度。根据注入部位的不同，它们具有独特的神经毒性作用。本研究旨在描绘兴奋性毒素在脑桥背外侧被盖核（LDTg）中的神经毒性特征。在戊巴比妥或阿佛丁麻醉下，将0.1微升的0.1 M异博定、0.1 M喹啉酸、0.04 - 0.1 M N-甲基-D-天冬氨酸（NMDA）或0.05 - 0.015 Mα-氨基-3-羟基-5-甲基-4-异恶唑丙酸（AMPA）单侧注入LDTg。注射针在中外侧平面与垂直方向成24度角。23 - 27天后，使用标准组织学程序对脑桥中脑被盖进行切片处理，用于烟酰胺腺嘌呤二核苷酸磷酸黄递酶（NADPH-d）组织化学、酪氨酸羟化酶或5-羟色胺免疫组织化学以及甲酚紫染色。通过受损区域的大小（由反应性胶质细胞增生确定）、脑桥中脑被盖中胆碱能细胞损失的程度（通过计数NADPH-d阳性神经元）以及蓝斑核和中缝背核中诱导的神经元损失来评估损伤情况。异博定在LDTg中诱导形成致密损伤（胆碱能损失超过80%），对蓝斑核和中缝背核的损伤较小。喹啉酸以及低剂量的AMPA和NMDA造成的损伤非常小，胆碱能损失不到35%，而高剂量时，AMPA和NMDA诱导大面积的反应性胶质细胞增生，但仅杀死一部分胆碱能神经元。AMPA似乎对蓝斑核中的去甲肾上腺素能神经元具有特殊亲和力，向LDTg中注入0.015 M剂量的AMPA通常会破坏这些神经元中的大多数。结合已知的兴奋性毒素机制和脑桥中脑神经元的谷氨酸受体特征对结果进行了讨论。
