A recent (2021) publication reveals deliberate pain inflicted on adult male mice in experiments carried out at the University of Queensland.(1) The purpose was to induce pain in an attempt to replicate human pain felt after surgery, or administration of anti-tumour chemotherapeutic agent, and treat the pain with pharmacological compounds subcutaneously (under the skin).
In one group, under anaesthesia, mice had the plantaris muscle in the leg incised (cut with surgical instrument) to cause pain. After the incision, the wound was closed and the mice were moved back to their cages where they were repeatedly subjected to pressure being placed on the paw causing paw withdrawal. They were observed to lift, shake and lick their paws. In other groups, the mice had pain induced by the administration of anti-tumour chemotherapeutic compounds.
Conotoxin (a neurotoxic peptide from the venom of the marine cone snail) was injected into the paw to study locomotor activity and side effects. This compound is already used for pain relief after surgery however this study was to investigate the effect of subcutaneous (under the skin) injection administration rather than via the spine.
The perception of pain is subjective and in humans is difficult to measure, explaining why, on presenting for treatment of pain, one is asked by the physician to indicate “On a scale of 1 to 10 how bad do your rate your pain”? This cannot be done in animals.
There are various studies available using non animal methods to assess pain. For example, in 2011 researchers in India developed and validated a radiant heat pain model for future screening of various analgesic agents by recording pain threshold and pain tolerance in health human subjects.(2) In 2018 an in silico study of peptides from venoms was undertaken(3) and in 2020, scientists undertook a chemical study of tarantula toxin and human receptors.(4)
The University of Queensland pain experiment in mice was federally funded by various National Health & Medical Research Council grants.
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References:
- Hasan et al, Subcutaneous ω-Conotoxins Alleviate Mechanical Pain in Rodent Models of Acute Peripheral Neuropathy. Drugs 2021, 19, 106.2021 https://pubmed.ncbi.nlm.nih.gov/33670311/
- Naidu et al, Development of a simple radiant heat induced experimental pain model for evaluation of analgesics in normal healthy human volunteers. Indian Journal of Pharmacology. 2011;43(6):632-637. doi:10.4103/0253-7613.89816
- Agwa et al, 2018 https://dx.doi.org/10.1074%2Fjbc.RA118.002553