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Comparative Study
. 2019 May 31;14(5):e0209467.
doi: 10.1371/journal.pone.0209467. eCollection 2019.

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

Cassandra B Klune  1 , Amy E Larkin  2 , Vivian S Y Leung  3 , Daniel Pang  3
Affiliations
Comparative Study

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

Cassandra B Klune et al. PLoS One. .

Abstract

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.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Rat Grimace Scale scores are reduced by the administration of buprenorphine after laparotomy.
Saline (n = 21), meloxicam (n = 16) and buprenorphine (n = 15) groups at all time points. Data presented as mean ± SEM. BL = baseline. Asterisks above bars indicate within group differences from baseline. Asterisks with brackets indicate differences between groups. Horizontal broken line at y = 0.67 indicates analgesic intervention threshold [11].
Fig 2
Fig 2. Composite behaviour scores (cumulative frequency of back-arching, writhing and staggering) are reduced by both meloxicam and buprenorphine following laparotomy.
Saline (n = 21), meloxicam (n = 16) and buprenorphine (n = 15) groups at all time points. Data presented as mean ± SEM. BL = baseline. Asterisks stars above bars indicate within group differences from baseline. Asterisks with brackets indicate differences between groups.
Fig 3
Fig 3. RGS scores of individual rats at all post-surgical timepoints in comparison to their baseline scores.
Saline (n = 21), meloxicam (n = 16) and buprenorphine (n = 15) rats at all time points. Horizontal broken line at y = 0.67 indicates analgesic intervention threshold [11].
Fig 4
Fig 4. CBS scores of individual rats at all post-surgical timepoints in comparison to their baseline scores.
Saline (n = 21), meloxicam (n = 16) and buprenorphine (n = 15) rats at all time points.
Fig 5
Fig 5. RGS and CBS scores are positively correlated.
Data from all groups and all timepoints are plotted (260 xy pairs) with each point representing an individual rat. r = 0.36 (95% CI, 0.25 to 0.47), p < 0.0001.
See this image and copyright information in PMC

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Grants and funding

This work was supported by: Natural Sciences and Engineering Research Council (NSERC) Discovery Grant (ID: 424022-2013, http://www.nserc-crsng.gc.ca, DP), Fondation Lévesque (DP), NSERC Undergraduate Student Research Awards (CK), Markin Undergraduate Student Research Program of the University of Calgary (CK), Investigative Medicine veterinary student rotation of the Faculty of Veterinary Medicine, University of Calgary (AL). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.