Background: Prostaglandin D2 (PGD2) is a strong vasodilator of extracerebral arteries, but causes only mild headache in healthy volunteers. Aims: 1.) To elucidate the mRNA expression profile of DP1, DP2 receptors and PGD2 synthase (L-PGDS) in the trigeminovascular system (TVS); and other pain processing structures in rat brain; 2.) To study the effect of the DP1 receptor antagonist, MK-0524, on PGD2-induced vasodilation of middle meningeal artery (MMA) in rat closed cranial window (CCW) model; 3.) To investigate if an i.v. infusion of prostaglandin (PG) mix, PGD2, PGE2 and PGI2 (iloprost), in awake rats activates nociceptive/neuronal activation markers in the TVS. Methods: qPCR, the genuine rat CCW model, and the western blot technique were used to investigate the above mentioned aims. Results: mRNA for DP1, DP2 and L-PGDS was expressed differentially in all examined tissues. The DP1 receptor was highly expressed in trigeminal ganglion and dorsal rootganglion. MK-0524 significantly (62%, p<0.05) blocked the PGD2- induced dilation of MMA. No increase in p-ERK protein level was observed in the TVS after infusion of PG mix in awake rats. Neuronal activation markers, cFOS and EGR-1, were not changed in the trigeminal nucleus caudalis. Conclusions: PGD2 induced vasodilation of MMA is mainly mediated by activation of DP1 receptors. Furthermore, high expression of DP1 mRNA in TG and DRG suggest that PGD2 might play a role in migraine pathophysiology. However, infusion of PG mix in awake rats did not activate nociceptive/neuronal markers in the TVS.