Effects of intraocular irrigation with melatonin on the c-wave of the direct current electroretinogram and on the standing potential of the eye in albino rabbits

Abstract

The direct current electroretinogram (ERG) and the standing potential (SP) were recorded from both eyes of 14 albino rabbits during intraocular perfusion of one of the eyes, which was vitrectomized, with a recently developed eye irrigation solution (PHS) produced by Pharmacia Ophthalmics. PHS was then replaced by a test solution containing melatonin dissolved in PHS (0.002 microM-200 microM). The fluids were subsequently alternated (PHS - melatonin - PHS). During uniocular irrigation with melatonin the mean c-wave amplitude and SP level of the intact control eye were increased (c-wave +24%, p less than 0.01; SP +0.65 mV, p less than 0.05) compared with the values during the initial perfusion with PHS. In contrast, the c-wave amplitude of the irrigated eye was markedly decreased in many rabbits during perfusion with melatonin compared with the initial PHS, but the mean reduction was small and not statistically significant. The mean SP level was reduced (-1.54 mV, p less than 0.001). This difference between the eyes probably depends on the route by which melatonin reaches the retinal pigment epithelium and thus whether it primarily affects the apical (as in the irrigated eye) or the basal (as in the control eye) pigment epithelial membrane. A peak in the b-wave amplitude was observed in both eyes during uniocular irrigation with melatonin when compared with the amplitude measured during the initial perfusion with PHS (irrigated eye: +27%, p less than 0.001; control eye +18%, p less than 0.002).

Dopaminergic and GABAergic amacrine cells are direct targets of melatonin: Immunocytochemical study of mt1 melatonin receptor in guinea pig retina

“…In rat, melatonin administration by a subcutaneous implant increases photoreceptor disk shedding (White & Fisher, 1989). Melatonin promotes melanosome aggregation in the guinea pig RPE (Pang & Yew, 1979), inhibits phagocytosis by chick RPE cells in culture (Ogino et al, 1983), and affects electrical activity of the RPE of chick (Nao-I et al, 1989) and rabbit (Textorius & Nilsson, 1987). In the present study, we did not find detectable mt 1 immunoreactivity in photoreceptors and the RPE in the guinea pig retina.…”

EOG and ERG modifications induced in the chicken eye after blockade of catecholamine and 5-hydroxytryptamine biosynthesis

“…It could be that DA and melatonin interact in the retina as neuromodulators and that these two systems operate in mutual antagonism. It has been reported that in cat and in rabbit [5,15] both dopamine and melatonin are active substances on RPE cells. On the other hand, 5-HT also is modulated by light [2] and increases the SP in the perfused cat eye [5].…”

An exclusive review of melatonin effects on mammalian melanocytes and melanoma

“…Total time of circadian melatonin elevation is the important parameter determining its effect on gonads and pelage, 43 similar reports were observed in female hamsters 44 and mice 45 . Melatonin weakly changes the electrical activity of retinal pigment epithelium 46–48 . Pineal effects on yearly changes in body weight and coat colour are affected via pituitary in Djungarian hamsters 49 .…”