Effects of EP1 receptor on cerebral blood flow in the middle cerebral artery occlusion model of stroke in mice

The lipid mediator prostaglandin E2 (PGE2) exhibits diverse biologic activity in a variety of tissues. Four PGE2 receptor subtypes (EP1-4) are involved in various physiologic and pathophysiologic conditions, but differ in tissue distribution, ligand-binding affinity, and coupling to intracellular signaling pathways. To characterize the role of the EP1 receptor, physiologic parameters (mean arterial blood pressure, pH, blood gases PaO2 and PaCO2, and body temperature), cerebral blood flow (CBF), and neuronal cell death were studied in a middle cerebral artery occlusion model of ischemic stroke in wild-type (WT) and EP1 knockout (EP1-/-) mice. The right middle cerebral artery was occluded for 60 min, and absolute CBF was measured by [14C] iodoantipyrine autoradiography. The effect of EP1 receptor on oxidative stress in neuronal cultures was investigated. Although no differences were observed in the physiologic parameters, CBF was significantly (P < 0.01) higher in EP1-/- mice than in WT mice, suggesting a role for this receptor in physiologic and pathophysiologic control of vascular tone. Similarly, neuronal cultures derived from EP1-/- mice were more resistant (90.6 +/- 5.8% viability) to tert-butyl hydroperoxide-induced oxidative stress than neurons from WT mice (39.6 +/- 17.2% viability). The EP1 receptor antagonist SC-51089 and Calcium Channel blocker verapamil each attenuated the neuronal cell death induced by PGE2. Thus, the prostanoid EP1 receptor plays a significant role in regulating CBF and neuronal cell death. These findings suggest that pharmacologic modulation of the EP1 receptor might be a means to improve CBF and neuronal survival during ischemic stroke.