A Review of Strain and Sex Differences in Response to Pain and Analgesia in Mice

Pain and its alleviation are currently a highly studied issue in human health. Research on pain and response to analgesia has evolved to include the effects of genetics, heritability, and sex as important components in both humans and animals. The laboratory mouse is the major animal studied in the field of pain and analgesia. Studying the inbred mouse to understand how genetic heritable traits and/or sex influence pain and analgesia has added valuable information to the complex nature of pain as a human disease. In the context of biomedical research, identifying pain and ensuring its control through analgesia in research animals remains one of the hallmark responsibilities of the research community. Advancements in both human and mouse genomic research shed light not only on the need to understand how both strain and sex affect the mouse pain response but also on how these research achievements can be used to improve the humane use of all research animal species. A better understanding of how strain and sex affect the response to pain may allow researchers to improve study design and thereby the reproducibility of animal research studies. The need to use both sexes, along with an improved understanding of how genetic heritability affects nociception and analgesic sensitivity, remains a key priority for pain researchers working with mice. This review summarizes the current literature on how strain and sex alter the response to pain and analgesia in the modern research mouse, and highlights the importance of both strain and sex selection in pain research.