Regulation of melatonin biosynthesis in vertebrate retina: involvement of dopamine in the suppressive effects of light.

The article shortly reviews literature data and presents our new findings on the regulation of melatonin biosynthesis and level in the vertebrate retina. Special emphasis is given to the role of dopamine as a mediator of the inhibitory effect of light on melatonin synthesis in retinas of lower vertebrates. Other discussed problems include (1) the role of cyclic AMP and calcium ions in the induction of serotonin N-acetyltransferase (NAT; the key regulatory enzyme in melatonin biosynthetic pathway), and (2) feedback regulations and metabolism of retinal melatonin. The presented experimental evidence, compared with similar data obtained for the pineal gland, suggests the existence in the vertebrates retina of some specific for this tissue factors, that locally regulate and control the level of retinal melatonin.