Evaluation of the ability of mice to detect VOCs, using a positive operant reinforcement procedure

Abstract

To examine the validity of a newly established “three-odor detection (TOD)” procedure using one of volatile organic compounds (VOCs), limonene, food-restricted male mice were used. Five animals each were assigned to either TOD or single-odor detection (SOD). TOD was composed of two trainings and one test (TEST) session. Mice were trained to discriminate an odor of coffee from no odor and odors of coffee and cheese from no odor in trainings 1 and 2, respectively. In TEST, mice were required to discriminate odors of coffee, cheese, and limonene from no odor. In SOD, mice were required to discriminate an odor of limonene from no odor. Each training or test was conducted once a day until animals achieved a learning criterion (75% correct response rate for 2 consecutive days), or until a maximum number of sessions (20 sessions) was completed. The number of sessions for reaching the learning criterion of animals in TEST (8.2 ± 0.8) was smaller than that of animals in SOD (19.2 ± 0.8). Results indicated that mice in TOD detected low levels of VOCs more rapidly than animals in SOD. I concluded that TOD is a useful procedure for detecting low levels of VOCs.