For the DNA microarray experiments, the rats were orally administered LO at5 mg/kg followed by the screening of differentially expressed genes in the small intestine, spleen, and liver, using a whole genome rat chip and the dye-swap approach. The experimental strategy is illustrated in Fig 1. It was hypothesized that LO administration at a low-dose would induce changes in the gene expression profiles starting with the small intestine, where the oil is perceived and ingested, and probably acting as a site for first pass metabolism, followed by LO transport through the blood to the liver, where further metabolism takes place. As expected, our results indicate that LO influences the expression of numerous genes in these tissues/organs. These results are presented as are source for the scientific community as a first such inventory of genes that are affected by LO in a rat model and discussed in the context of the use of LO for human health and therapeutic properties. Moreover, using bio informatics approaches, these genes have been functionally categorized by their Gene Ontology and are presented and briefly discussed in line with available iterature with an aim of correlating some of the changed gene expressions with LO affects. The main goal of the present study�Cthe establishment of an animal model for investigating the effects of orally administered LO�Cwas fulfilled by using a rat model in conjunction with an omics approach, namely DNA microarray technology for the downstream analysis of target tissues/organs. The hypothesis that a daily ingestion of LO which corresponds to roughly the usual the rapeutic dose in humans would cause differential gene expression at the site of absorption and metabolism, namely, the small Levodopa intestine and liver, was proven by delineating the cellular responses to LO treatment. As the portal vein also connects to the spleen where the blood is then transported to the liver, we also VU 0357121 examined the spleen; moreover, it might also be a secondary target for LO. That these genome-wide changes at the target organs in this study would relate to known genes previously shown to be related to the effect of essential oils was evident from the analysis of up-regulated and down-regulated genes using both GO and biological functions analysis.