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The hormone in mammals may be DHEA.

Posted by pbio on 07 May 2009 at 22:16 GMT

Author: James Howard
Position: Biologist
Institution: independent
Submitted Date: March 22, 2007
Published Date: March 30, 2007
This comment was originally posted as a “Reader Response” on the publication date indicated above. All Reader Responses are now available as comments.

It is my hypothesis 0f 1985 that sleep in mammals / humans is controlled by the “melatonin – DHEA cycle.” DHEA is high during the day; melatonin is high during the night. Besides stimulating brain activity, I suggest DHEA inhibits melatonin release during the day. DHEA is high during the day, but, as DHEA production declines towards nighttime, the inhibition of melatonin is released. Melatonin production has continued during the day so the first release of melatonin is high. I suggest this produces the first, deep-slow-wave sleep.

When melatonin increases, it reduces prolactin (PRL). DHEA is stimulated by PRL so the sudden increase in melatonin significantly reduces DHEA so brain stimulation is decreased and sleep occurs. During sleep a small amount of DHEA must be released to ensure maintenance of the brainstem. This is produced by continued cycling of the melatonin – DHEA cycle. Each release of melatonin reduces PRL which then rebounds to ensure DHEA production. Each subsequent release of melatonin is reduced so each rebound of PRL is increased. This cycling of melatonin and DHEA necessary for brainstem maintenance produces REM activity. That is, as DHEA is slightly stimulated, it stimulates brain activity. This is interpreted as “dreams.” As the night continues, less melatonin is released so the depth of sleep is reduced as DHEA increases. Slow-wave-sleep decreases with time because of this mechanism. When the melatonin supply is exhausted, a large pre-awakening PRL release stimulates a large release of DHEA which produces consciousness and, again, inhibits melatonin release. The cycle is complete.

No competing interests declared.