FELASA 2025 presentation: Assessing lidocaine-based analgesia for mouse ear notching: Insights into strain-specific reactions
From the beginning of 2024, a new national law on animal protection in Finland (1165/2023 3 §) requires laboratory rodent ear notching to be performed only with "appropriate pain relief". However, the European Union directive on the protection of animals used for scientific purposes (2010/63/EU) classifies ear notching as a routine identification method rather than a procedure, leaving no specific guidelines on suitable analgesia at the EU or the national level. This study aimed to evaluate the suitability of a lidocaine-based cream as analgesia (EMLA cream 5%, lidocaine + prilocaine 25+25 mg/g, Aspen Pharmacare Australia) for mice undergoing ear notching.
Materials and methods
The experiment involved 15–33-week-old male and female C57BL/6JRj mice and 17-week-old male BALB/cJRj mice. EMLA was applied 10, 15, 20, or 30 minutes before ear notching. Reactions to notching were observed and categorised into three levels: no reaction (0), mild (flinch, 1) or marked reaction (head shake/vocalisation, 2).
Results
Most C57BL/6JRj mice displayed marked reactions at 10–20 minutes post-application (e.g., 20 min: 83% marked, 8% mild, 17% no reaction, n=13). In mice that were marked with 30 minutes post-application, reactions were significantly reduced (27% marked, 13% mild, and 60% no reaction, n=30). In contrast, BALB/cJRj mice showed minimal responses even at 10 minutes (30% mild, 70% no reaction, n=10).
Conclusions
Preliminary results suggest EMLA is effective if applied 30 minutes before ear notching, but strain-specific behavioural differences must be considered, as BALB/cJRj mice exhibited lower sensitivity. Further research is required to evaluate pain caused by ear notching more comprehensively.
References
Valtioneuvoston asetus eläimille tehtävistä toimenpiteistä ja keinollisen lisäämisen menetelmistä (1165/2023).
Directive 2010/63/EU of the European Parliament and of the Council on the protection of animals used for scientific purposes.
Anni Tenhunen
FELASA 2025
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Authors
Anni Tenhunen, Anna Mari Koponen, Päivi Partanen, Satu Mering
