DRD2 and sleep disorder: For example, the CSF samples showed higher levels of mRNAs (Log2 FC > 6.0) from neurotransmitter genes that have been implicated in promoting wakefulness such as histamine receptor (HRH3), dopamine (DRD2) [58], and gamma-aminobutyric acid receptors (GABR, Log2FC 5.0–7.0), which are implicated in sleep disorders [39].