Fig. 4. The GP-GP_o values of Laurdan in model membranes at 37°C. (A) GP-GP_o of Laurdan in membranes of DMPC, SOPC and rat brain lipids. The GP-GP_o values of lipid membranes except those of DMPC membranes decreased with increasing dose of H₂O₂ (2 hours treatment) (P<0.05), indicating that the vesicle membranes became more liquid crystalline-like. (B) The effect of H₂O₂ treatment at 37°C on GP-GP_o values of Laurdan integrated in membranes composed of lipids and cholesterol. (C) GP-GP_o values of Laurdan in brain lipid vesicles pretreated with the p38 MAPK inhibitor SB203580. SB203580 (20 µM, 30 minutes) did not protect artificial brain vesicles from a phase change. Values are the mean ± s.d. of three independent experiments.