Figure 1.
The Sleep Homeostat
Sleep regulatory substances (SRS) form complex biochemical pathways involving positive and negative feedback loops, changes in gene transcription, as well as the processing of intermediary products. These SRSs act in concert with many other molecules to facilitate local sleep state oscillations. SRSs act over multiple time scales. Multiple components of the homeostat will likely have to be simultaneously assessed for use as a biomarker for sleepiness. Abbreviations: ATP, adenosine triphosphate; CD39, ecto-nucleotidase CD39; CD73, 5[prime]-ecto-nucleotidase CD73; IL-4, interleukin-4; IL-10, interleukin-10; IL-37, interleukin-37; CRH, corticotrophin releasing hormone; sTNFR, soluble tumor necrosis factor α receptor; sIL1R, soluble interleukin-1 receptor; TGF, transforming growth factor β; IL1, interleukin-1 β; TNF, tumor necrosis factor α; BDNF, brain derived neurotrophic factor; NF-kB, nuclear factor κ β; A1AR, adenosine A1 receptor; NOS, nitric oxide synthase; COX, cyclo-oxygenase; GHRH, growth hormone releasing hormone; NO, nitric oxide; PG, prostaglandin.
