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

Abstract

In rabbits, dopamine levels in the retina, but not in the caudate nucleus, showed clear diurnal rhythm, with high values seen in the light phase. Thirty min exposition of dark-adapted rabbits to day-light produced no changes in dopamine levels in the retina. In rabbits treated with alpha-methyl-p-tyrosine, the same light exposition decreased the retinal amine level by 18%, while stimulation with intensive, flickering light significantly decreased the retinal dopamine content by 36%. Experiments performed at noon and midnight, under light or dark conditions, showed the retinal dopamine levels to be very similar in groups kept either at light or dark, irrespective of the time of the day, although in animals deprived of light the amine levels were clearly lower than in those exposed to light, both at noon and midnight. Under all experimental conditions there were no significant changes in dopamine level and utilization in the caudate nucleus. The isolated and superfused retina (preloaded with [3H]-dopamine), when stimulated with flashes of white light (2 Hz, 10 min), released [3H]-radioactivity in a Ca2+-dependent manner. It is concluded that in rabbits, light enhances dopamine levels and utilization selectively in the retina, and the observed diurnal changes in the amine metabolism are dependent on the presence or absence of light, and not on the time of the day. The proposed physiological role(s) of the retinal dopaminergic mechanisms is discussed.

Possible neurotransmitter role of noradrenaline in the teleost retina

“…These changes were only observed when measured in the superfusate, but not when measured in tissues. Changes in endogenous DA levels induced by light have also been observed with strong stimulation, i.e., 30-min intensive flickering light (Nowak and Zurawska, 1989). Perhaps because of the different light condition used in the present work, we did not observe changes in DA at the tissue level.…”

Circadian rhythmicity in dopamine content of mammalian retina: role of the photoreceptors

“…Daily rhythms in steady‐state levels of both dopamine and its major retinal metabolite, 3,4dihydroxyphenylacetic acid (DOPAC), with levels higher during the day than at night, have been reported in rat (Melamed et al . 1984; Gibson 1988; Pozdeyev and Lavrikova 2000), rabbit (Nowak and Zurawska 1989), human (Di Paolo et al . 1987) and fish (Kolbinger et al .…”

Dopamine in the Turkey Retina—An Impact of Environmental Light, Circadian Clock, and Melatonin

“…It has been shown that melatonin in vitro inhibits dopamine release and in vivo decreases the retinal content of the catecholamine (Dubocovich 1983;Nowak and Żurawska 1989;Nowak et al 1992;Kazula et al 1993;Boatright et al 1994;Adachi et al 1998;Zawilska et al 2003a, b;Ribelayga et al 2004). In the current study, we demonstrated that injections of melatonin into the vitreous body during daytime significantly reduced, in a dose-dependent manner, the retinal levels of DOPAC.…”