Abstract:
The failure to develop analgesic drugs is attributed not only to the complex and diverse
pathophysiology of pain in humans but also to the poor experimental design and poor preclinical
assessment of pain. Although considerable eforts have been devoted to overcoming the relevant
problems, many features of the behavioral pain assessment remain to be characterized. For example,
a decreased locomotor activity as a common presentation of pain-like behavior has yet to be
described. Studies on mice experimentally induced with carrageenan have provided opportunities
to explore pain-related behaviors in automated home-cage monitoring. Through this approach,
the locomotor activities of mice with carrageenan-induced infammatory pain can be precisely and
objectively captured. Here, we found that the mobile behaviors of mice reduced, and their immobility
increased, indicating that carrageenan induction in mice caused a signifcant decrease in locomotor
activity. These non-refexive pain behaviors were strongly correlated with the refexive pain behaviors
measured via von Frey and plantar tests. Furthermore, the pharmacological intervention using
indomethacin improved the locomotor activity of mice with carrageenan-induced pain. Thus, the
analysis of the locomotor activity in automated home-cage monitoring is useful for studying the
behavioral analgesia and the pharmacological screening of analgesic drugs. The combined evaluation
of refexive and non-refexive pain behaviors enhances the translational utility of preclinical pain
research in rodents.
