Dopamine turnover in rat retina: A 24-hour light-dependent rhythm

Dopamine in the rabbit retina and striatum: Diurnal rhythm and effect of light stimulation

“…Although the studied dopaminergic parameters in the retina showed the same diurnal changes under 12-h light-dark (LD) cycle in both laboratories, there was a clear difference between the results obtained by both groups when experiments were performed on rats kept under constant darkness throughout the day (dark-dark cycle; DD). Whereas Wirz-Justice et al (1984) observed similar diurnal variations in DA metabolism under LD and DD conditions, Melamed et al (1984) did not find any significant diurnal changes in the amine turnover under DD cycle. Consequently, the conclusions regarding the driving factor were different: the crucial role of an endogenous pacemaker and light by the former and latter authors, respectively, was suggested.…”

“…DA-receptor agonists inhibit the nighttime melatonin synthesis in the retina (Iuvone and Besharse, 1986;Iuvone et al, 1987;Zurawska and Nowak, unpublished data), thus, resembling the action of light; 4. melatonin potently inhibits both electrically-and light-evoked DA release (Dubocovich, 1983;Nowak, 1987) and DA metabolism (Pierce et al, 1984) in the retina; 5. under natural environmental (i.e. day-night) conditions, diurnal rhythm of DA level (and turnover) in the retina (Melamed et al, 1984;Wirz-Justice eta!., 1984;present data), and circadian variations in activity of melatonin generating system in both the retina and pineal gland (Harem and Menaker, 1980;Reiter, 1984;Pang, 1986;Nowak and Zurawska, 1987;Nowak et at., 1988) show reciprocal direction. In sum, the data suggest the existence in the retina of a mutual interaction between the dopaminergic (amacrine and perhaps interplexiform cells) and melatoninergic (most probably photoreceptors; see Bubenik et al, 1978;Wiechmann and Hollyfield, 1987) cells, and the role of the former (dopaminergic) cells would be the creation of a proper chemical signal about environmental illumination, which would serve as a cue for the body c}readian clock(s).…”

“…Recently, it has been shown in the rat retina that levels and turnover of DA, an established neurotransmitter both in the brain and in the retinal arnacrine cells (see Ehinger, 1983;Dowling, 1986), fluctuate during the 24-h period, with higher values seen during the light phase (Melamed et al, 1984;WirzJustice et al, 1984). Although the studied dopaminergic parameters in the retina showed the same diurnal changes under 12-h light-dark (LD) cycle in both laboratories, there was a clear difference between the results obtained by both groups when experiments were performed on rats kept under constant darkness throughout the day (dark-dark cycle; DD).…”

Loss of light in the eyes: A window to melancholia

“…Several lines of research have suggested that the mammalian retina has a circadian organization, with rat dopaminergic retinal neurons showing daily rhythms of dopaminergic turnover [40], which is influenced largely by the presence of melatonin [41] but not by the presence of the light [42]. This led Doyle et al [41] to suggest that an internally regulated circadian clock determines dopamine metabolite turnover.…”

Myopia, Light and Circadian Rhythms

“…As in the brain, retinal dopamine shows a diurnal rhythm with peak levels during the day and low levels during the night in non-human vertebrates (Nowak, Zurawska et al 1989;Megaw, Boelen et al 2006), and in human retinas (Di Paolo, Harnois et al 1987). The diurnal variation in dopamine levels persists in constant darkness in mice, indicating that it has a circadian rhythm of release (Doyle, Grace et al 2002), although others have found no circadian rhythm but a light activated fluctuation in retinal dopamine (Melamed, Frucht et al 1984).…”