Abstract
We are surrounded by a variety of fragrances such as perfumes and fabric softeners. While these fragrances have been reported to have relaxing effects, in recent years, an increasing number of people suffer from multiple chemical sensitivity (MCS), in which headaches and discomfort are caused by these fragrance substances. However, the mechanism of their action on the brain remain unknown. We hypothesized that not only the olfactory information of fragrance substances, but also the transfer of fragrance substances to the brain via the nasal route, may show direct toxic effects on the brain. Since genetic polymorphisms of drug-metabolizing enzymes are involved in MCS, we also focused on drug-metabolizing enzymes in the brain and attempted to elucidate the toxicity of fragrant substances on the brain.
Mice were exposed intranasally to several fragrance substances commonly contained in perfumes and fabric softeners, and unpleasant behavior was confirmed by behavioral tests and heart rate measurements. After exposure of mice to these fragrance substances, we analyzed the fragrance substances in the brain using GC-MS, and found that the fragrance substances accumulated in various parts of the brain, and that the accumulation of these substances in the brain was greater than in other organs such as the liver. In addition, metabolites of these fragrance substances were detected in the brain, suggesting that the fragrance substances are metabolized by drug-metabolizing enzymes after entering the brain. These fragrance substances or their metabolites also affect the function of neurons and astrocytes. The present study found that fragrance substances may have direct toxic effects on the brain by migrating to the brain and undergoing metabolism.
