Sleep slow-wave oscillations trigger seizures in a genetic epilepsy model of Dravet syndrome
Sleep is the brain state when cortical activity decreases and memory consolidates. However, in human epileptic patients, including genetic epileptic seizures such as Dravet syndrome, sleep is the preferential period when epileptic spike-wave discharges (SWDs) appear, with more severe epileptic symptoms in female patients than male patients, which influencing patient sleep quality and memory. Currently, seizure onset mechanisms during sleep period still remain unknown. Our previous work has shown that the sleep-like state-dependent synaptic potentiation mechanism can trigger epileptic SWDs(Zhang et al., 2021). In this study, using one heterozygous (het) knock-in (KI) transgenic mice (GABAA receptor {gamma}2 subunit Gabrg2Q390X mutation) and an optogenetic method, we hypothesized that slow-wave oscillations (SWOs) themselves in vivo could trigger epileptic seizures. We found that epileptic SWDs in het Gabrg2+/Q390X KI mice exhibited preferential incidence during NREM sleep period, accompanied by motor immobility/ facial myoclonus/vibrissal twitching, with more frequent incidence in female het KI mice than male het KI mice. Optogenetic induced SWOs in vivo significantly increased epileptic seizure incidence in het Gabrg2+/Q390X KI mice with increased duration of NREM sleep or quiet-wakeful states. Furthermore, suppression of SWO-related homeostatic synaptic potentiation by 4- (diethylamino)-benzaldehyde (DEAB) injection (i.p.) greatly decreased seizure incidence in het KI mice, suggesting that SWOs did trigger seizure activity in het KI mice. In addition, EEG delta-frequency (0.1-4 Hz) power spectral density during NREM sleep was significantly larger in female het Gabrg2+/Q390X KI mice than male het Gabrg2+/Q390X KI mice, which likely contributes to the gender difference in seizure incidence during NREM sleep/quiet-wake as that in human patients.