Lysophosphatidic acid (LPA) signaling is known to play biological roles in many types of animals, and suggested to be involved in the regulation of neuropsychological functions. Medaka (Oryzias latipes) is an experimental fish that can be easily maintained and analysed for their behaviors, and genome project has been completed. However, little information is available for medaka LPA receptors, including Lpar1 to Lpar6. Here, using information from the medaka genome database, we examined the genomic structures, expression and functions of six LPA receptor genes. Our analyses revealed that the genomic structures for Lpar1 and Lpar4 were different from those deduced from the database, and newly determined the first ATG of LPA1 and LPA4. RT-PCR analyses showed that Lpar1, Lpar2b, Lpar4, Lpar5, and Lpar6 were expressed in adult whole brain and pituitary. Finally, functional analyses using mammalian neuronal cells demonstrated that all medaka LPA receptors except for LPA5 responded to LPA treatment with cytoskeletal changes. These findings provide us with useful information for medaka LPA receptor genes and functions, and will prompt to use medaka as experimental models to explore biological significance of LPA signaling in brains.