Hi! Melatonine is indicated in Europe for sleep disorders in patients > 65 years old .
The secretion of melatonin is regulated by light. Apparently, the following mechanism is observed: absence of light => increase of NE => action on beta1 and alpa-adrenergic receptors of the pineal gland = > activation of N-acetyltransferase => synthesis and release of melatonin (Touitou Y., 2005).
My question is this: When we give the patient melatonin tablets (or a melatonin agonist as the agomelatine), should we be concerned about a potential inhibitory feedback on endogenous melatonin secretion (as is the case for corticosteroids and inhibition of the hyphalamic-pituitary axis): Do we have info about the regulation of this key enzyme, the N-acetyltransferase, by melatonine ? Do cells of pineal gland express melatonin receptors ?
Thank you in advance for your reply :) !
No, there is no classical negative feedback at all. However, exogenous melatonin might advance or delay the endogenous pineal melatonin production accordingly to the intake time. See work by Alfred Lewy defining dim light melatonin onset and melatonin phase response curve. Alternatively, please, read our review recently published in Endocrine Review.
Dear Dr Cipolla, thnk you for your help .
I woul love to read your review " MELATONIN AS A HORMONE: NEW PHYSIOLOGICAL AND CLINICAL INSIGHTS" but, I do not have access.
Best ,
Marie.
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