Participation of Melatonin in Retinal Physiology

R.E. ROSENSTEIN, J. BENOZZI, C. JALIFFA, M.I. KELLER SARMIENTO, M.P FAILLACE

Fort Lauderdale, Florida

Congreso; ARVO Meeting 2001; 2001

The Association for Research in Vision and Ophtalmology (ARVO)

The effect of melatonin on [3H]glutamateuptakeand release in the golden hamster retina was studied.In retinas excised in the middle of the dark phase,i.e., at 2400 h, melatonin (0.1 and 10 nM) significantlyincreased [3H]glutamateuptake, and this effect persistedin a Ca2~-freemedium. On the other hand, melatoninsignificantly increased [3H]glutamaterelease in retinasexcised at 2400 h, but this effect was Ca2~sensitive.Melatonin significantly increased 45Ca2~ uptake by acrude synaptosomal fraction from retinas of hamsterskilled at 2400 h. In retinas excised at 1200 h, melatoninhad no effect on [3H]glutamateuptake, [3H}glutamaterelease, or 45Ca2~uptake at any concentration tested.CyclicGMP analogues, i.e., 8-bromoguanosine 3’,5’-cyclicmonophosphate and 2’-O-dibutyrylguanosine 3’,5’-cyclic monophosphate, significantly increased [3H]-glutamateuptake, [3H]glutamaterelease, and 45Ca2~uptakeby tissue removed at 1200 and 2400 h, suggestingthat the effects of melatonin could correlate with a previouslydescribed effect of melatonin on cyclic GMP levelsin the golden hamster retina. Taking into account thekey role of glutamate in visual mechanisms, the resultssuggest the participation of melatonin in retinal physiology.Key Words: Melatonin—Glutamate----Calcium—Hamster retina.