Table 1 Experimental methods of pain assessment in rodent arthritis models
From: Animal models of rheumatoid pain: experimental systems and insights
Assessment method [example references] | Response measured | Pain aspect assessed | Advantages | Disadvantages |
|---|---|---|---|---|
Von Frey test/mechanical hyperalgesia [6, 32, 33, 48,49,50,51,52,53,54, 56, 58, 59, 62] | Pain-evoked behavior: withdrawal threshold from a mechanical stimulus | Mechanical allodynia/hyperalgesia | Quantitative, well-established protocols | Stimulation of mechanical and nociceptive fibers; possible investigator bias/subjectivity |
Hargreaves test/thermonociception [6, 33, 51, 53, 54, 56,57,58,59, 62] | Pain-evoked behavior: withdrawal latency from a thermal stimulus | Thermal allodynia/hyperalgesia | Quantitative, well-established protocols; primary stimulation of nociceptive fibers | Possible investigator bias/subjectivity |
Ambulatory/locomotor behavior [53, 56, 59, 61,62,63,64,65,66] | Pain-suppressed behavior: locomotion in an open field | Locomotor activity/ambulation/exploratory behavior | Automated quantitative measurement; may include affective component | May be affected by nonpain-related outcomes (e.g., motor function) |
Grimace scales [38] | Changes in facial expressions associated with pain | Expression of subjective pain perception | Non-interventional; directly linked to individual pain state; may include affective component | Possible investigator bias/subjectivity; experimenter training needed; further validation in arthritis models required |
fMRI [6] | Functional changes in CNS activity associated with pain | Affective CNS responses to pain | Objective measurements; may include affective component | Expensive equipment; high-level investigator training needed; requirement for restraint/sedation |
Changes in ambulatory posture or weight distribution | Spontaneous gait changes due to joint pain | Objective, quantitative measurements; automated systems available | Specialized equipment needed. | |
Operant conditioning [60] | Behavior emitted to receive a reward despite concurrent exposure to a painful stimulus | Affective and/or motivational components of pain perception | Objective, quantitative; automated systems available; may include affective component | Specialized equipment needed |
Escape/avoidance [45] | Latency to escape noxious stimulus | Affective and/or motivational components of pain perception | Objective, quantitative; automated systems available; may include affective component | Specialized equipment needed |