Effects of knockout of MT3R/Nqo2 gene on sleep/wake behaviors and EEG power spectrum in rats

Abstract

Objective To observe the sleep/wake behaviors and EEG power spectrum in melatonin type 3 receptor (MT3R/Nqo2) knockout rats with CRISPR/Cas9 gene editing tool in order to explore the receptor mechanism of melatonin in regulation of sleep/wake behaviors. Methods SD rats with MT3R/Nqo2 knockout were created by introducing a mutation in the MT3R/Nqo2 gene frame shift by nonhomologous recombination repair causing the gene dysfunction, and the knockout was confirmed at the genetically, transcriptionally, and morphologically by PCR, RT-PCR, and FISH, respectively.Then the changes in sleep/wake behaviors and in EEG power spectrum were observed in the knockout rats and control rats. Results After MT3R/Nqo2 knockout, the knockout rats showed decreased arousal time and increased NREM and REM sleep time during the first 3 h (ZT12~15) after the onset of the dark phase (active phase) when compared with the control rats (P < 0.05).In addition, a significant increase in the number of sleep/wake transitions, a reduction in the duration of wakefulness, and appearance of wake fragmentation were also observed after MT3R/Nqo2 knockout during this period (P < 0.05).EEG power spectrum analysis revealed that NREM sleep θ band energy was elevated in the knockout rats than the control rats (P < 0.05). Conclusion MT3R/Nqo2 knockout results in abnormal power spectrum of EEG especially high-frequency energy during NREM sleep, disrupts sleep homeostasis, leads to decreased arousal, increased sleep, and fragmented arousals in the first 3 h (ZT12~15) after the onset of the dark phase (active phase) in rats.

Keywords

• melatonin
• mt3r/nqo2
• sleep
• crispr/cas9
• rats
• sprague-dawley
• gene knockout