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Abstract
The rat pineal gland shows a significant nocturnal increase in circulating melatonin that reflects night duration.
- The pineal gland transforms circadian rhythms from the suprachiasmatic nucleus into a melatonin signal.
- Arylalkylamine-N-acetyltransferase is the key enzyme controlling melatonin synthesis.
- Norepinephrine stimulates the phosphorylation of a protein that initiates melatonin production at night.
- Additional signaling mechanisms help fine-tune melatonin production to accurately represent darkness duration.
- Signaling mechanisms involve both modifications of existing proteins and the synthesis of new proteins.
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