An automated odor test for rats

The odor-testing apparatus described consists of a circular open-field area opening into four glass tubes, each with an odor source at the far end. When a rat is introduced, each tube is blocked by a grid; when the rat has touched each grid (sampled each odor), the tubes automatically open and recording of preference behavior starts. Two measures of preference are recorded by a photocell outside each tube, the number of visits and the time spent near the odor source. A uniformity test with food odor in all tubes showed that the apparatus did not promote position bias. In two separate sensitivity tests, one with food odor and one with estrous female urine odor, male rats significantly preferred an attractive odor in one tube to odorless controls. The apparatus yields relatively sensitive and reliable odor preference determinations by ensuring sampling of each odor before data are recorded and by eliminating visual, auditory and gustatory cues.