Retinal Ganglion Cells: A new Site for Melatonin Synthesis

M.E. GUIDO; R.E. ROSENSTEIN

Visual and Circadian Phototransduction

Ed. S.R. Pandi-Perumal, Mount Sinai School of Medicine

Lugar: Mount Sinai School of Medicine, N York, USA; Año: 2007;

Preface Several lines of evidences indicate that melatonin could provide widespread modulatory influences on retinal pathophysiology. Moreover, numerous studies have firmly established that melatonin synthesis occurs in the retina of vertebrates, including mammals. In this sense, available evidence supports the idea that circadian clocks located in retinal photoreceptors drive retinal melatonin rhythms independently of the rest of the retina. However, the possibility that other retinal cell type(s) are also able to synthesize melatonin has been recently reported. In the present chapter, we will present evidences supporting that retinal ganglion cells (RGCs) are capable of synthesizing melatonin and that this synthesis shows a circadian variation that peaks during the day. Intriguingly, this diurnal production of melatonin in the RGCs occurs in antiphase to the peak of melatonin production by the pineal gland and retinal photoreceptors. In addition, we will discuss herein that RGCs are autonomous circadian oscillators and fundamental components of the vertebrate circadian timing system as well as the physiological implications for such oscillatory behavior.