Odor detection in rats with 3-methylindole-induced reduction of sensory input.

Rats were tested on odor-detection tasks after treatment with 400 mg/kg of 3-methyl-indole. As revealed by anterograde transport of horseradish peroxidase from the olfactory epithelium to the olfactory bulb glomeruli, treatment produced a severe (>97%) loss in sensory input relative to untreated controls. In almost all cases, only glomeruli in a restricted ventromedial segment of the bulb contained control levels of reaction product. In Experiment 1, five of nine experimental rats were anosmic or severely hyposmic, but the remaining four rats were able to detect amyl acetate vapor. In Experiment 2, four of seven experimental rats were anosmic, but the remaining three were able to detect each of four different odors. Among all experimental rats, those that were anosmic had significantly fewer glomeruli with dense anterograde transport than did those that could smell. Among rats that could smell, performance accuracy was related to the number of glomeruli with reaction product.