Investigating the Effect of Melatonin on the Human Photopic ERG

Abstract

Abstract: : Purpose: Last year we reported that oral administration of melatonin in beagle dogs resulted in a decreased photopic ERG whereas no effect was observed on the rod ERG¹. This time, we are presenting the effect of oral melatonin administration on the photopic ERG in humans. Methods: In 12 humans (6 males and 6 females), photopic ERG luminance response functions (7 intensities ranging from –1.1 to 0.84 log cd/m^–2.s, background 30 cd/m^–2 ) were obtained in dilated eyes (tropicamide 1%) one time after oral administration of a placebo and one time after oral administration of melatonin (15mg). The trials were contrebalanced Vmax (maximal amplitude achieved) and log K (retinal sensitivity) were calculated from the derived Naka–Rushton luminance response functions. Results: ANOVA yielded a significant Treatment (melatonin vs. placebo) and Time (before vs. after) interaction (p=0.0043). There was no change in Vmax amplitude after the placebo (86.6 ±9.8µV versus 88.0 ±8.7µV) and a significant decrease of 7.9 %, 50 min after melatonin (87.4 ±13.4µV versus 80.5 ±13.0µV; p<0.01). No change in log K was observed. Conclusions: We are confirming, this time in humans, that melatonin administered during the daytime (when least produced naturally) appears to have a negative effect on the cone ERG. It has been proposed that in daytime dopamine production favors cone activity and that melatonin and dopamine inhibit each other. Herefore, it is possible that melatonin could have impact cone functioning through retinal dopamine inhibition. REFERENCE: ¹Effects of melatonin in the dog's ERG. S.G. Rosolen, C.Chalier, J.Saucet, F.Rigaudière, J.–F.LeGargasson, P.Lachapelle, K.Danilenko, M.Hebert. ARVO 2004

Keywords: melatonin • electroretinography: non-clinical • photoreceptors