Pain Recognition by Facial Expression in Mice and Rats€¦ · Sevastre B. - Pain recognition by facial expression in mice and rats 1 Leach M (2012). Pain assessment in laboratory

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Pain Recognition by Facial Expression in Mice and Rats

Bogdan SEVASTRE

University of Agricultural Science and Veterinary Medicine, Faculty of Veterinary Medicine,

Manastur Street. 3-5, 400372, Cluj-Napoca, Romania,

E-mail: [email protected]

mailto:[email protected]

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Background

Sevastre B. - Pain recognition by facial expression in mice and rats

1 Leach M (2012). Pain assessment in laboratory animals using behaviour and facial expression. Workshop on Pain Assessment and Alleviation,

Newcastle University.. 2 Mogil JS, et al.. (2010). The necessity of animal models in pain research. Pain 151: 12–17 3 Waite ME, et al. (2015). Efficacy of Common Analgesiscs for Postsurgical Pain in Rats. Journal of the American Association for Laboratory Animal

Science 54(4): 420-425.

Pain assessment:

” If we accept that animals can experience pain then we have an obligation to develop effective methods of recognizing it and assessing its nature and severity “ [1]

3R

Pain research [2].

Pain control [3] – analgesia (type, dose, administration)

Establishment of severity of procedures

(non recovery / mild / moderate / severe)

” Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such tissue damage“ [IASP, 1979]

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Background


Why not just use extrapolate doses from other species?

Variation in analgesic potency between: species

strains / breeds

sexes

individuals

Thus “universal dose” do not exist to low – Pain!

to high – possible side effects!

millions of rats undergo surgery for research purposes, but only 20% of researches

worldwide reported the administration of analgesics after surgery [4]

4 Stokes EL, Flecknell PA, Richardson CA (2009). Reported analgesic and anaesthesic administration to rodents undergoing experimental surgical

procedures. Laboratory Animals 43:149-154

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Subjective assessment of “clinical signs”

Appearance: coat condition, pilo-erection,

Posture / gait: hunched posture, abnormal gait

Behavior: aggression, hiding

Objective assessment (quantification) of:

Locomotion / Activity

Food / Water intake

Changes in bodyweight

Respiratory rate / Heart rate / Blood pressure

Traditional assessments

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Available for wide range of species (rodents, rabbits, dogs, cats, lambs, caves)

More accurate than traditional methods (pain causes certain behaviors to occur more or less frequently, analgesics influences this specific behavior)

Immediate assessment (no retrospective)

Improved effectiveness of pain assessment !

Behavioral assessments

Why behavioral assessments are not widely used ?

Time consuming

Require advanced training

Only 80% accurate

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Used in non verbal patients (dementia patients, neonates)

Using limited numbers of indicators

Relatively rapid and easy

Not very elaborate training

In humans: Facial Action Coding System (FACS)

Facial expression

. 5 Hamm J. et.al. Automated Facial Action Coding System for Dynamic Analysis of Facial Expressions in Neuropsychiatric Disorders. J Neurosci

Methods. 2011; 200(2): 237–256.

Fig. 1. Examples of facial expressions [5].

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3402717/figure/F1/

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Orbital tightening

Nose bulge

Cheek bulge

Ear position

Whiskers change

5 facial action units (FAUs) [6]

Mouse Grimace Scale (MGS)

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Advantages: high accuracy (72-97%), high reliability

6 Langford, et al. Coding of facial expressions of pain in the laboratory mouse. Nature Methods, in press.

Intensity rating for each action unit (AU)

AU no present = 0

AU moderately visible = 1

AU severe = 2

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.

Fig. 2. The action units in mouse [6].

6 Langford, et al. Coding of facial expressions of pain in the laboratory mouse.

Nature Methods, in press.

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Orbital tightening


.


Fig. 3. Orbital tightening. Eye squeeze represent the contraction of the orbital muscles around the eyes;

any eye closure that reduces the eye size by more than half should be coded as a “2”.

exception sleeping mice

0 1 2

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Nose bulge


.

0 1 2

Fig. 4. Nose bulge. The muscles around the nose will be contracted creating a rounded extension of skin

on the bridge of the nose - nose bulge. In frontal view the bulge generates a V-shape connecting eyes to

nose. exception mice who are actively exploring


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Cheek bulge


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Fig. 5. Cheek bulge. The cheek muscle is contracted and extended relative to the baseline condition; it will

appear to be convex from its neutral position. The distance from eye to whisker pad appear shortened

relative to baseline.


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Ear position


.

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Fig. 6. Ear position. Ears may be pulled back from their baseline position, or may be seen as laid flat

against the head. Normally, the ears are perpendicular to the head and are directed forward. In pain,

the ears tend to rotate outwards and/or back. As a result, the space between the ears appear wider relative

to baseline.

Mice engaged in exploration or grooming also pull ears back, but distance between ears tends to narrow

rather than widen.


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Whiskers change


.

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Fig. 7. Whiskers change. Whiskers move from the baseline position; hey could either be pulled or

pulled forward. Whiskers may also clump together (normally the whiskers tend to be evenly spaced)


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Orbital tightening

Cheek / nose flattening

Ear position

Whisker change

4 facial action units (FAUs) [7]

Rat Grimace Scale (RGS)

. 7Sotocinal et al. (2011). The Rat Grimace Scale: a partially automated method for quantifying pain in the laboratory rat via facial expressions.

Molecular Pain 7:55..

Intensity rating for each action unit (AU)

AU no present = 0

AU moderately visible = 1

AU severe = 2

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.

Fig. 8. The action units in rat [7].


7Sotocinal et al. (2011). The Rat Grimace Scale: a partially automated

method for quantifying pain in the laboratory rat via facial expressions.


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Orbital tightening


.

0 1 2

Fig. 9. Orbital tightening. An eye squeeze is defined as the orbital muscles around the eyes being

contracted. The nictitating membrane may be visible around the eye and becomes more pronounced as the

pain intensifies. If the eye size is reduced by more than half should be coded as a “2”.

Sleeping rats display closed eyes, but of a relaxed nature, whereas a rat in pain may display a closed eye

with tight orbital muscles. Photographs of sleeping rats should not be taken and/or coded

7Sotocinal et al. (2011). The Rat Grimace Scale: a partially automated method for quantifying pain in the laboratory rat via facial expressions.


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Cheek / nose flattening


.

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Fig. 10. Nose / Cheek Flattening. Normally the rats show a clear bulge at the bridge of the nose. The

whisker pads are also rounded and slightly puffed out, leaving a clear crease between the pads and the

cheek. When in pain, the bridge of the nose flattens and elongates, causing the whisker pads to flatten. The

crease between the pads and the cheek is no longer present. In frontal headshots, the nose may appear

narrower and longer



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Ear position


.

0 1 2

Fig. 11. Ear changes (Position, Orientation, Shape). Normally, the ears have a rounded shape, are

perpendicular to the head, face forward, and are angled slightly backward. In pain, the ears tend to fold,

curl inwards and are angled forward. This curling of the ears tends to result in a “pointed” shape of the ears.

In pronounced pain states, the ears are angled outward. As a result, the space between the ears may

appear wider relative to baseline



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Whisker change


.

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Fig. 12. Whiskers change. Rats in pain have whiskers that have moved from the baseline position and

orientation. Whiskers start relaxed and drooping slightly downwards and, as pain progresses, tension in the

pads increases and they become angled back along the head. In pain, the whisker pad is contracted

causing the whiskers to bunch and be directed outwards away from the face. This gives the appearance of

the whiskers as “standing on end”. As follicles become tense, whiskers are closer together and are less

distinct. 7Sotocinal et al. (2011). The Rat Grimace Scale: a partially automated method for quantifying pain in the laboratory rat via facial expressions.


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.

Calculating GS scores (for rats)


photo no. Orbital Nouse/cheek Ear Whisker MGS

1 2 2 1 2 1.75

2 0 0 1 0 0.25

3 1 2 2 1 1.5

Mouse Condition photo no. Orbital Nouse/cheek Ear Whisker MGS

A1 no pain 121 0 0 1 0 0.25

A1 no pain 243 0 0 0 0 0

A1 pain 173 2 1 1 2 1.5

A1 pain 23 1 2 2 1 AVERAGE(D5:G5)

A2 no pain 48

A2 no pain 123

A2 pain 97

A2 pain 7

Mouse MGS no pain MGS pain MGS diffference

A1 0.125 1.5 1.375

A2 0.4 1 0.6

A3 AVERAGE(no pain) AVERAGE (pain) MGS pain - MGS no pain

Step 1

Step 2

Step 3



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.

Calculating GS scores (for rats)


8Dreanca et al. (2016). Post-surgery pain control in rats using the rat grimace scale method. Bulletin UASVM (In Print)

Fig. 13. The effects of Tramadol therapy on pain control in spayed rats according to orbital

tightening (A), nose/cheek flattening (B), ear position (C) and whisker position (D). The proper

analgesic effect was encountered in the animal injected subcutaneously with 50 mg/b.w Tramadol [8].

(mean ± SEM)(3 animals / group) one-way analysis of variance Kruskal-Walis, post test Dunns.

(95% confidence interval) GraphPad Prism 5.0 software

0 2 4 60.0

0.5

1.0

1.5

2.0

2.5Control

OV

OV 25 mg/kg b.w. presurgery

OV 25 mg/kg b.w. postsurgery


Time (h)

pain

inte

nsity

0 2 4 6

0.0

0.5

1.0

1.5

2.0

2.5Control

OV


OV 25 mg/kg b.w postsurgery


Time (h)

pain

inte

nsit

y

0 2 4 60.0

0.5

1.0

1.5

2.0

2.5Control

OV




Time h

pain

inte

nsity

0 2 4 6

0.0

0.5

1.0

1.5

2.0

2.5Control

OV

OV 25 mg/kg b.w presurgery

OV 25 mg/kg mc posttratament

OV 50 mg/kg mc posttratament

Time h

pai

n i

nte

nsi

ty

A

D C

B

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No pain !

Documents

Pain Recognition by Facial Expression in Mice and Rats€¦ · Sevastre B. - Pain recognition by facial expression in mice and rats 1 Leach M (2012). Pain assessment in laboratory