A Study on Recovery from Smell Dysfunction Induced by 3-Methylindole in Rats

Dhong, Hun Jong

Abstract

BACKGROUND AND OBJECTIVES: Evaluating the olfactory function is as important in animal research as morphological study. However, it is difficult to gauge the smell function in rats because of the underdevelopment of current electrophysiologic measuring devices. The aim of this study is to assess changes in smell dysfunction induced by 3-methylindole (3-MI) in rats using an 8-odor olfactometer. MATERIALS AND METHOD: Eight female Sprague-Dawley rats were used. Ethyl acetate at 10(-4.0) (v/v) concentration was used as an S+ odorant, and six different concentrations (10 (-4.0), 10(-4.5), 10(-5.0), 10(-5.5), 10(-6.0), 10(-6.5)) of butanol mixed with ethyl acetate were used as an S- odorant. S+ and S- stimuli were delivered randomly using the 8-odor olfactometer. After injection of 3-MI at a dosage of 300 mg/kg, mixed odor discrimination test was performed for five weeks.
RESULTS
Normal rats were able to discriminate ethyl acetate from ethyl acetate mixed with butanol to a concentration down to 10(-6.2) (v/v). Immediately after the 3-MI injection, the rats lost all capacity for smell. From 16 days later, the smell function began improving spontaneously. At the end of the fifth week, the discrimination threshold was 10(-5.7) (v/v), which was almost equal to the original level.
CONCLUSIONS
Systematically administered 3-MI caused smell loss in rats. Though not completely, the smell function was recovered spontaneously. An olfactometer is a reliable and accurate device in evaluating the olfactory function in rats.