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Neuroendocrinology Letters incl. Psychoneuroimmunology & Chronobiology


ISSNİ0172ñ780X Copyrightİ©İ1997 NeuroendocrinologyİLetters

NEL Vol. 18 No. 2/3
Review Article

1998; 18:73-84
pii: NEL182397R02


Melatonin: A Synchronizing Signal for the Immune System
by Daniel P. Cardinali, Luis I. Brusco, Laura Selgas and Ana I. Esquifino


Biological time measurement in adult and fetal mammals is critically dependent upon the melatonin signal (Arendt, 1995; Reiter, 1995; Cardinali et al., 1997b). The mechanisms sensitive to melatonin, which mediates the clock message, may reside in the brain, in the biological clock itself, i.e., the suprachiasmatic nuclei (SCN). There are also data indicating that melatonin receptors are universally distributed throughout in the body and can convey circadian-meaningful information to every cell in the organism, playing the role of an "internal Zeitgeber" (Armstrong, 1991).
Among melatonin's versatile functions, immunomodulation has emerged as a major effect of the hormone in vertebrates. The identification of melatonin involvement in immunomodulation was a direct consequence of studies on melatonin and pineal gland participation in regulation of tumor growth, an area in which the late Prof. Derek Gupta made substantial contributions. Indeed, the melatonin rhythm seems to be a very important efferent pathway of the SCN to impose synchronicity to the immune system. The brain, as well as the peripheral immune cells, may
be able to encode an accumulated memory of melatonin signals, thereby defining time intervals at the 24-hour cycle and the annual scale.

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