FOS and epilepsy: In the two epilepsy models as mentioned above, the decrease of class I HDACs initiates the acetylation of histone H4 protein in rat hippocampal neurons and thereby activates the factors involved in epileptogenesis such as immediate early genes (IEGs) (e.g. c-fos and c-jun) and growth factors (e.g. brain-derived neurotrophic factor (BDNF)) [101].