Comparing the Rat Grimace Scale and a composite behaviour score in rats

There is a growing interest in the use of voluntarily displayed ongoing behaviours in laboratory animals to assess the pain experience. In rats, two behavioural pain scales, the Rat Grimace Scale (RGS, a facial expression scale) and a composite behaviour score (CBS, a behavioural ethogram reliant on postural changes), are both promising pain assessment methods. Both scales have been used to assess pain in a laparotomy model, however, they have never been compared directly and the knowledge of how different analgesics may affect these two scales is limited. This study aimed to provide a comparison to discriminate the temporal and analgesic response in a laparotomy model. Female Wistar (n = 26) and Sprague Dawley rats (n = 26) were block randomized to receive saline, meloxicam (2 mg/kg) or buprenorphine (0.05 mg/kg) 30 minutes before laparotomy. Rats were video-recorded before surgery (BL) and at 30, 150, 270, and 390 minutes post-operatively. Videos were assessed according to both scales by a trained, blinded observer. Both CBS and RGS scores increased significantly at all post surgical timepoints in the saline group. Both buprenorphine and meloxicam reduced CBS scores to baseline levels following laparotomy; however, RGS scores were only reduced following buprenorphine. RGS scores in the meloxicam group remained similar to scores of the saline group. These findings suggest that the CBS and RGS differ in their sensitivity to discriminating analgesic effects.

人们对利用实验动物自愿表现出的持续行为来评估疼痛体验的兴趣日益增加。在大鼠中，两种行为疼痛量表，大鼠面部疼痛表情量表（RGS，一种面部表情量表）和综合行为评分（CBS，一种基于姿势变化的行为图谱），都是很有前景的疼痛评估方法。这两种量表都已用于评估剖腹手术模型中的疼痛，然而，它们从未被直接比较过，而且关于不同镇痛药如何影响这两种量表的了解有限。本研究旨在进行比较，以区分剖腹手术模型中的时间和镇痛反应。将雌性Wistar大鼠（n = 26）和Sprague Dawley大鼠（n = 26）分组随机化，在剖腹手术前30分钟接受生理盐水、美洛昔康（2 mg/kg）或丁丙诺啡（0.05 mg/kg）。在手术前（基线）以及术后30、150、270和390分钟对大鼠进行视频记录。由一名经过训练且不知情的观察者根据两种量表对视频进行评估。在生理盐水组中，CBS和RGS评分在所有术后时间点均显著升高。丁丙诺啡和美洛昔康都使剖腹手术后的CBS评分降低至基线水平；然而，只有丁丙诺啡使RGS评分降低。美洛昔康组的RGS评分与生理盐水组的评分相似。这些发现表明，CBS和RGS在区分镇痛效果的敏感性方面存在差异。