Research articleInhalation of a racemic mixture (R,S)-linalool by rats experiencing restraint stress alters neuropeptide and MHC class I gene expression in the hypothalamus

- Inhalation of (R,S)-linalool affected overall gene expression in the hypothalamus.
- (R,S)-linalool inhalation altered the expression of genes related to synaptic transmission.
- Oxytocin and neuropeptide Y were upregulated by (R,S)-linalool inhalation.
- Several MHC class I molecules were also upregulated by inhaled (R,S)-linalool.

Some odorants have physiological and psychological effects on organisms. However, little is known about the effects of inhaling them, particularly on the central nervous system. Using DNA microarray analysis, we obtained gene expression profiles of the hypothalamus from restraint stressed rats exposed to racemic (R,S)-linalool. Hierarchical clustering across all probe sets showed that this inhalation of (R,S)-linalool influenced the expression levels of a wide range of genes in the hypothalamus. A comparison of transcription levels revealed that the inhalation of (R,S)-linalool restored the expression of 560 stress-induced probe sets to a normal status. Gene Ontology (GO) analysis showed that these genes were associated with synaptic transmission via neurotransmitters including anxiolytic neuropeptides such as oxytocin and neuropeptide Y. These genes also included several major histocompatibility complex (MHC) class I molecules necessary for neural development and plasticity. Moreover, Upstream Regulator Analysis predicted that the hormone prolactin would be activated by the inhalation of (R,S)-linalool under stress. Our results reveal some of the molecular mechanisms associated with odor inhalation in the hypothalamus in organisms under stress.