br Materials and methods br Results br Discussion Here we

Materials and methods
Results
Discussion Here we show expression of the EP1 receptor in the hippocampus of mice and the functional influence of the EP1 receptor on kainic TCS HDAC6 20b mg induced seizures. Mice lacking a functional EP1 receptor gene displayed a lower tendency to enter status epilepticus when injected with high concentrations of kainic acid although they exhibited a similar behavioral seizure threshold compared to their wildtype counterparts, suggesting that EP1 receptor activation increases the probability for entry of mice into status epilepticus. Moreover, for EP1-KO and wildtype mice selected for the same behavioral seizure intensity during status epilepticus, the EP1-KO showed a smaller cytokine burst one day later and less neurodegeneration 4days later. These results together suggest that EP1 activation regulates the response to kainate both directly by increasing the probability to enter status epilepticus, and indirectly by intensifying the consequences of status epilepticus. Analysis of acute mortality caused by status epilepticus revealed no difference for mice lacking a functional EP1 gene compared to wildtype mice indicating that the EP1 receptor does not contribute to the overall survival of mice. However, we found neuroprotection of hippocampal pyramidal neurons in the CA1 and CA3 layers after status epilepticus in the EP1-KO mouse, which is striking because mice lacking EP1 displayed a similar behavioral seizure phenotype as wildtype mice (Fig. 2D). Therefore, EP1 activation during or after status epilepticus appears to contribute to subsequent CA1 and CA3 pyramidal cell neurodegeneration. One day after kainic acid induced status epilepticus in the EP1-KO mouse, we also observed that the induction of 11 inflammatory mediators in the forebrain was blunted. The induction of the pro-inflammatory mediators CCL2, CCL3, CCL4 and IL-6 were strongly attenuated in the EP1-KO mice, suggesting that the robust overall brain inflammation may be reduced in the EP1-KO mice following status epilepticus. COX-2 induction was also significantly reduced in EP1-KO mice suggesting that these early effects might be dependent consequences of COX-2 regulation. Although COX-2 is upstream of the EP1 receptor in the prostaglandin signaling pathway the reduction of COX-2 seen in the EP1-KO mice compared to wildtype following kainate induced status epilepticus is not surprising as it is known that COX-2 is an activity-dependent enzyme, responding to cytoplasmic Ca levels that can rise upon activation of the EP1 receptor, or coactivation of EP1 and kainate receptors. In the EP1-KO intracellular Ca might not rise high enough during status epilepticus to induce COX-2 to the same extent as in WT mice. In summary, the EP1 receptor partially mediates the robust inflammatory response following kainic acid induced status epilepticus. The GPCR–Gαq–PKC pathway, activated by mGlu1/5 (Rojas et al., 2013), mAChR (Benveniste et al., 2010) and now EP1, represents a general post-translational regulatory mechanism for heteromeric kainate receptors bearing the GluK4 or GluK5 subunits. The observed EP1-induced and PKC-mediated potentiation of heteromeric GluK2/GluK5 but not homomeric GluK2 strengthens the idea that the GluK5 subunit may be a regulatory subunit in the kainate receptor complex as was shown for heteromeric kainate receptor potentiation by muscarinic M1, M3 and group I mGlu receptors (Benveniste et al., 2010, Rojas et al., 2013). EP1 receptor activation engages this pathway to potentiate heteromeric but not homomeric kainate receptors, pointing to a mechanism by which the potentiation of kainate receptors by EP1 receptor activation likely occurs through phosphorylation by PKC of specific residues in high affinity kainate receptor subunits. Here, we demonstrated that PGE2 potentiates kainate receptor-induced Ca signals in neuron rich mouse and rat cortical cultures in a PKC-dependent manner, confirming that EP1 receptor activation potentiates native kainate receptor-mediated calcium signaling.