Regulation of Melatonin Synthesis in the Ovine Pineal Gland
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Based on studies in the rat, it is now generally believed that pineal serotonin N-acetyltransferase (NAT) activity is the major factor which regulates melatonin synthesis in the pineal gland and its concentration in the circulation on a circadian basis (Axelrod and Zatz, 1977; Klein et al. 1981). NAT activity in the rat increases 50-100-fold at night, causing increased synthesis of melatonin in the pineal gland and about a 10-fold increase in melatonin in the circulation (Reppert and Klein, 1980). The duration of increased melatonin in the circulation is proposed to act as the chemical signal that conveys information about the length of the night to the body. Norepinephrine released from the sympathetic nerve endings in the pineal gland causes the large increase in the NAT activity via a cAMP-dependent mechanism, with alpha and beta adrenergic receptors acting in concert (Klein, 1978).
KeywordsTyrosine Hydroxylase Pineal Gland Melatonin Level Melatonin Production Melatonin Synthesis
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