Prostaglandin E2 receptor expression in the rat trigeminal-vascular system and other brain structures involved in pain.

Prostaglandin E(2) (PGE(2)) is considered to be a key mediator in migraine pathophysiology. PGE(2) acts via four receptors (EP(1)-EP(4)) but their distribution in the brain districts implicated in migraine has yet to be delineated. We quantified amount of mRNA and protein expression for the EP receptors in both peripheral and central structures involved in pain transmission and perception in migraine: dura mater, cerebral arteries, trigeminal ganglion, trigeminal nucleus caudalis, periaqueductal grey, thalamus, hypothalamus, cortex, pituitary gland, hippocampus and cerebellum. In the trigeminal-vascular system (TVS) we found highest expression of EP(1) and EP(2) protein in the trigeminal nucleus caudalis. EP(3) and EP(4) mRNA expression were highest in the trigeminal ganglion. Within intracranial structures EP(1) mRNA and protein expression were significantly higher in pituitary gland and cerebellum than in dorsal root ganglia (peripheral control), whereas the EP(2) mRNA and protein were highly abundant in the pituitary gland. EP(3) mRNA was mainly found in thalamus and hypothalamus. The most robust mRNA and protein expression for EP(4) receptor was seen in the dorsal root ganglion. In conclusion, all four receptors are located in areas implicated in migraine supporting the possible involvement of PGE(2) in this disease.