2.4. Electroencephalogram (EEG) recording
In order to collect EEG data in the acute and chronic stages of PTE (Pitkänen et al., 2014), mice underwent electrode implantation prior to seizure induction by KA. A bipolar electrode was implanted into CA3 region (AP-2.9 mm; ML-3.0 mm; V-3.0 mm) for EEG recording. After seven days’ recovery, the baseline EEG trace was recorded 30 min before FeCl3 injection. Subsequently, an injection tube (62204, RWD Life Science) was inserted into the guide cannula which was placed in the somatosensory cortex (AP-1.3 mm; ML-2.0 mm; V-1.6 mm) for injection with 5 μl of a 50 mM solution of FeCl3 or 1 pmol Fer-1. Five minutes later, mice were subjected to 2 h EEG monitoring session. EEG data in the acute and chronic stages of PTE were both collected for 3 d with 2 h per day. Electrical seizures were defined as regular spike clusters lasting more than 10 s, spike frequency greater than 3 Hz and amplitude at least three times higher than the baseline according to the previous investigation (Zhao et al., 2020).