Microglial influence on EP1 antagonist-mediated neuroprotection. Neuronal-enriched cultures were cultured in the absence or presence of microglia-containing transwells for 48 hours after which the microglial transwells were removed (pre-conditioning with microglia). The cultures were then treated with NMDA (average [NMDA] = 25 μM for neuronal-enriched cultures and 100 μM for microglia preconditioned media) in the presence or absence of the EP1 antagonist SC51089 (10 μM) and scored for neuronal survival 20 hours later. Neuroprotection is only seen in the neuronal-enriched cultures not exposed to microglia (P < 0.001 ANOVA Tukey-Kramer multiple comparisons test). A line is included in the bar to show the additional amount of survival conferred by addition of the EP1 antagonist. These results show that preconditioning with microglia for 48 hours prior to NMDA treatment is sufficient to inhibit the neuroprotective effect of the EP1 antagonist. This is the average of three independent experiments.