An automated evaluation system for analyzing antinociceptive effects on intracolonic capsaicin-induced visceral pain-related licking behavior in mice

IntroductionThe development of automated detection systems for animal behaviors is increasing in value in terms of saving time, objective analysis and reducing the need for well-trained experimenters. SCLABA® (Noveltec Inc., Kobe, Japan) is a commercially available analysis system originally developed for analyzing scratching behaviors in rodents, based on distances between points in videotaped images. Here, we used this software to automate analysis of abdominal licking behavior associated with visceral pain in mice.MethodsYellow and green spots were applied to the snout and the lower abdominal region of mice respectively to provide reference points for automated analysis of video recordings. Abdominal licking behavior after intracolonic administration of 0.3% capsaicin solution as a measure of visceral pain was determined based on changes in the inter-spot distance.ResultsA distance threshold between the colored spots was chosen based on manual measurements showing that 99% of minimal distances were below this threshold. Using this threshold, the number of licks determined by the automated analysis significantly and positively correlated with that determined by manual observation (R2 = 0.95 and p < 0.001). The neurokinin-1 receptor antagonist GR205171A dose-dependently inhibited capsaicin-induced licking detected by automated analysis.DiscussionWe demonstrated that visceral pain-related licking behaviors after intracolonic capsaicin treatment can be automatically detected by applying commercially available image analysis software. This automated experimental system is very efficient and useful to evaluate antinociceptive effect of a test compound on visceral pain.