Massé Ian O, Moquin Luc, Provost Chloé, Guay Samuel, Gratton Alain, De Beaumont Louis
Research Center, Hôpital du Sacré-Cœur de Montréal;
Research Center, Douglas Institute.
J Vis Exp. 2019 Jul 12(149). doi: 10.3791/59585.
Persistent cognitive and motor symptoms are known consequences of concussions/mild traumatic brain injury (mTBIs) that can be partly attributable to altered neurotransmission. Indeed, cerebral microdialysis studies in rodents have demonstrated an excessive extracellular glutamate release in the hippocampus within the first 10 min following trauma. Microdialysis offers the clear advantage of in vivo neurotransmitter continuous sampling while not having to sacrifice the animal. In addition to the aforementioned technique, a closed head injury model that exerts rapid acceleration and deceleration of the head and torso is needed, as such a factor is not available in many other animal models. The Wayne State weight-drop model mimics this essential component of human craniocerebral trauma, allowing the induction of an impact on the head of an unrestrained rodent with a falling weight. Our novel and translational rat model combines cerebral microdialysis with the Wayne State weight-drop model to study, in lightly anesthetized and unrestrained adult rats, the acute changes in extracellular neurotransmitter levels following concussion. In this protocol, the microdialysis probe was inserted inside the hippocampus as region of interest, and was left inserted in the brain at impact. There is a high density of terminals and receptors in the hippocampus, making it a relevant region to document altered neurotransmission following concussion. When applied to adult Sprague-Dawley rats, our combined model induced increases in hippocampal extracellular glutamate concentrations within the first 10 min, consistent with the previously reported post-concussion symptomology. This combined weight-drop model provides a reliable tool for researchers to study early therapeutic responses to concussions in addition to repetitive brain injury, since this protocol induces a closed-head mild trauma.
持续性认知和运动症状是脑震荡/轻度创伤性脑损伤（mTBI）的已知后果，部分可归因于神经传递改变。事实上，对啮齿动物的脑微透析研究表明，创伤后的前10分钟内海马体中细胞外谷氨酸释放过多。微透析具有在不牺牲动物的情况下对体内神经递质进行连续采样的明显优势。除了上述技术外，还需要一种能使头部和躯干快速加速和减速的闭合性颅脑损伤模型，因为许多其他动物模型中没有这样一个因素。韦恩州立大学的重量落体模型模拟了人类颅脑创伤的这一关键组成部分，允许用下落的重物对无束缚的啮齿动物头部施加撞击。我们新颖的转化大鼠模型将脑微透析与韦恩州立大学的重量落体模型相结合，以研究轻度麻醉且无束缚的成年大鼠脑震荡后细胞外神经递质水平的急性变化。在本实验方案中，将微透析探针插入作为感兴趣区域的海马体内，并在撞击时留在脑内。海马体中存在高密度的终末和受体，使其成为记录脑震荡后神经传递改变的相关区域。当应用于成年Sprague-Dawley大鼠时，我们的联合模型在最初10分钟内诱导海马体中细胞外谷氨酸浓度升高，这与先前报道的脑震荡后症状一致。这种联合重量落体模型为研究人员提供了一个可靠的工具，除了重复性脑损伤外，还可用于研究对脑震荡的早期治疗反应，因为该实验方案可诱导闭合性轻度颅脑创伤。
