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. Author manuscript; available in PMC: 2015 Aug 1.
Published in final edited form as: Bioessays. 2014 Jun 5;36(8):778–787. doi: 10.1002/bies.201400017

Figure 1.

Figure 1

Figure 1

Schematic drawing illustrating the regulation of pineal melatonin synthesis by the light/dark cycles via the SCN. During the daytime, the SCN inhibits melatonin synthesis, whereas at night the SCN sends a signal to the pineal to activate melatonin synthesis by increasing [over 100-fold] the transcription of the Aanat and then the activity of AANAT. AANAT converts serotonin to N-acetyl serotonin, and the Acetylserotonin N-Methyltransferase [ASMT] converts N-acetylserotonin to melatonin. ASMT transcription and activity also increases during the night, albeit to a lesser extent than AANAT.