Effect of specific α7 nAChR agonist and antagonist on PGE2 synthesis by activated rat microglial cultures. Microglial cells were subcultured as in Fig. 3, and nicotine (0.1–1 μM) added 30 min before LPS stimulation (10 ng/ml). Supernatants were collected after 24 h and analyzed for PGE2 content. Data, with induction expressed as a percentage of LPS-induced PGE2 production, are shown as mean ± SEM for 5 independent experiments, run in duplicate. The levels of PGE2 were undetectable in basal conditions, and were 24 ± 6 ng/mg protein after LPS-stimulation for 24 h. *p < 0.05 vs LPS; **p < 0.02 vs LPS.