Figure 3: Histopathology of CA region of hippocampus in mice after nasal administration of TiO2 NPs for six consecutive months. (a) Control group indicates great nucleus and limpid nucleolus of glial cells and pyramidal cells; (b) 1.25 mg/kg BW TiO2 NP group indicates disperative replication of pyramidal cells, edema of glial cells; (c) 2.5 mg/kg BW TiO2 NP group indicates disperative replication of pyramidal cells, decreased size of cell volume, nuclear irregularity; (d) 5 mg/kg BW TiO2 NP group indicates degeneration, necrosis or abscission of neuron cells.