Department of Oral and Maxillofacial Surgery, University of Florida, Gainesville.
Department of Orthodontics, University of Florida, Gainesville.
J Vis Exp. 2022 Jul 26(185). doi: 10.3791/64221.
Pain has sensory and affective components. Unlike traditional, reflex-based pain assays, operant pain assays can produce more clinically relevant results by addressing the cognitive and motivational aspects of pain in rodents. This paper presents a protocol for assessing mechanical hypersensitivity following chronic constriction injury of the infraorbital nerves (CCI-ION) in rats using an orofacial operant pain system. Before CCI-ION surgery, rats were trained in an orofacial pain assessment device (OPAD) to drink sweetened condensed milk while making facial contact with the metal spiked bars and lick-tube. In this assay, rats can choose between receiving milk as a positive reinforcer or escaping an aversive mechanical stimulus that is produced by a vertical row of small pyramid-shaped spikes on each side of the reward access hole. Following 2 weeks of training in the OPAD and before the CCI-ION surgery, baseline mechanical sensitivity data were recorded for 5 days for each rat during a 10 min testing session. During a session, the operant system automatically records the number of reward bottle activations (licks) and facial contacts, contact duration, and latency to the first lick, among other measures. Following baseline measurements, rats underwent either CCI-ION or sham surgery. In this protocol, mechanical hypersensitivity was quantified by measuring the number of licks, latency to the first lick, the number of contacts, and the ratio of licks to facial contacts (L/F). The data showed that CCI-ION resulted in a significant decrease in the number of licks and the L/F ratio and an increase in the latency to the first lick, indicating mechanical hypersensitivity. These data support the use of operant-based pain assays to assess mechanical pain sensitivity in preclinical pain research.
疼痛具有感觉和情感成分。与传统的基于反射的疼痛测定方法不同，操作性疼痛测定方法可以通过解决啮齿动物疼痛的认知和动机方面，产生更具临床相关性的结果。本文介绍了一种使用口腔操作性疼痛系统评估眶下神经慢性缩窄性损伤（CCI-ION）后机械性超敏反应的方案。在 CCI-ION 手术前，大鼠在口腔疼痛评估装置（OPAD）中接受训练，使其在与金属刺棒和舔管进行面部接触的同时饮用加糖炼乳。在该测定中，大鼠可以选择接受牛奶作为正强化物，或者逃避由奖励进入孔两侧每侧的垂直排小金字塔形刺针产生的厌恶机械刺激。在 OPAD 中接受 2 周训练并在 CCI-ION 手术前，在 10 分钟测试期间，为每只大鼠记录 5 天的基线机械敏感性数据。在一次测试中，操作性系统会自动记录奖励瓶激活（舔舐）和面部接触的次数、接触持续时间以及首次舔舐的潜伏期等其他指标。在基线测量之后，大鼠接受 CCI-ION 或假手术。在本方案中，通过测量舔舐次数、首次舔舐的潜伏期、接触次数以及舔舐与面部接触的比率（L/F）来定量机械性超敏反应。数据表明，CCI-ION 导致舔舐次数、L/F 比值显著减少，首次舔舐的潜伏期增加，表明存在机械性超敏反应。这些数据支持使用基于操作性的疼痛测定方法来评估临床前疼痛研究中的机械性疼痛敏感性。
