Minett Michael S, Eijkelkamp Niels, Wood John N
Molecular Nociception Group, Wolfson Institute for Biomedical Research, University College London, Gower Street, London, United Kingdom.
Molecular Nociception Group, Wolfson Institute for Biomedical Research, University College London, Gower Street, London, United Kingdom; Laboratory of Neuroimmunology and Developmental Origins of Disease, University Medical Center Utrecht, Utrecht, The Netherlands.
PLoS One. 2014 Aug 7;9(8):e104458. doi: 10.1371/journal.pone.0104458. eCollection 2014.
Transgenic mouse behavioural analysis has furthered our understanding of the molecular and cellular mechanisms underlying damage sensing and pain. However, it is not unusual for conflicting data on the pain phenotypes of knockout mice to be generated by reputable groups. Here we focus on some technical aspects of measuring mouse pain behaviour that are often overlooked, which may help explain discrepancies in the pain literature. We examined touch perception using von Frey hairs and mechanical pain thresholds using the Randall-Selitto test. Thermal pain thresholds were measured using the Hargreaves apparatus and a thermal place preference test. Sodium channel Nav1.7 knockout mice show a mechanical deficit in the hairy skin, but not the paw, whilst shaving the abdominal hair abolished this phenotype. Nav1.7, Nav1.8 and Nav1.9 knockout mice show deficits in noxious mechanosensation in the tail, but not the paw. TRPA1 knockout mice, however, have a loss of noxious mechanosensation in the paw but not the tail. Studies of heat and cold sensitivity also show variability depending on the intensity of the stimulus. Deleting Nav1.7, Nav1.8 or Nav1.9 in Nav1.8-positive sensory neurons attenuates responses to slow noxious heat ramps, whilst responses to fast noxious heat ramps are only reduced when Nav1.7 is lost in large diameter sensory neurons. Deleting Nav1.7 from all sensory neurons attenuates responses to noxious cooling but not extreme cold. Finally, circadian rhythms dramatically influence behavioural outcome measures such as von Frey responses, which change by 80% over the day. These observations demonstrate that fully characterising the phenotype of a transgenic mouse strain requires a range of behavioural pain models. Failure to conduct behavioural tests at different anatomical locations, stimulus intensities, and at different points in the circadian cycle may lead to a pain behavioural phenotype being misinterpreted, or missed altogether.
转基因小鼠行为分析加深了我们对损伤感知和疼痛背后分子及细胞机制的理解。然而，声誉良好的研究团队产生关于基因敲除小鼠疼痛表型的相互矛盾的数据并非罕见。在此，我们聚焦于测量小鼠疼痛行为时一些常被忽视的技术方面，这可能有助于解释疼痛文献中的差异。我们使用von Frey毛发检测触觉感知，并使用Randall - Selitto测试检测机械性疼痛阈值。使用哈格里夫斯仪器和热偏好测试测量热痛阈值。钠通道Nav1.7基因敲除小鼠在有毛皮肤而非爪子上表现出机械性缺陷，而剃除腹部毛发可消除此表型。Nav1.7、Nav1.8和Nav1.9基因敲除小鼠在尾巴而非爪子上表现出有害机械感觉缺失。然而，TRPA1基因敲除小鼠在爪子而非尾巴上出现有害机械感觉丧失。对热和冷敏感性的研究也显示出因刺激强度而异的变异性。在Nav1.8阳性感觉神经元中删除Nav1.7、Nav1.8或Nav1.9会减弱对缓慢有害热斜坡的反应，而只有当大直径感觉神经元中Nav1.7缺失时，对快速有害热斜坡的反应才会降低。从所有感觉神经元中删除Nav1.7会减弱对有害冷却的反应，但对极冷的反应则不然。最后，昼夜节律显著影响行为结果测量，如von Frey反应，其在一天内变化达80%。这些观察结果表明，全面表征转基因小鼠品系的表型需要一系列行为疼痛模型。未能在不同解剖位置、刺激强度以及昼夜周期的不同时间点进行行为测试可能导致疼痛行为表型被误解或完全遗漏。
