Expression of the thrombin receptor mRNA in rat brain.

Thrombin activates its receptor in a number of cultured cells of neural origin, but the functional significance of this activation in the nervous system is unknown. It is also not known which cells in brain express the thrombin receptor and whether the level of its expression is developmentally regulated. In the present study, Northern blot analysis showed that thrombin receptor mRNA was expressed at higher levels in brain compared to some other tissues, such as skeletal muscle, liver or kidney. The level of expression is substantially higher in the brain of newborn rats compared to that of postnatal day 28 (P28). At embryonic day 18, thrombin receptor mRNA is present throughout in the brain and in dorsal root ganglia as detected by in situ hybridization. The regions of the P28 brain in which the thrombin receptor mRNA was present include the substantia nigra and the ventral tegmental area, the pretectal area, some hypothalamic nuclei and some cells of the cerebral cortex. These results represent one of the first steps needed to understand the role played by the thrombin receptor in the development and function of the nervous system.