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Several lines of indirect evidence have suggested that nitric oxide may play an important role during light adaptation of the vertebrate retina. We aimed to verify directly the effect of light on nitric oxide release in the isolated carp retina and to investigate the relationship between nitric oxide and dopamine, an established neuromodulator of retinal light adaptation. Using a biochemical nitric oxide assay, we found that steady or flicker light stimulation enhanced retinal nitric oxide production from a basal level. The metabotropic glutamate receptor agonist L-amino-4-phosphonobutyric acid, inhibited the light adaptation-induced nitric oxide production suggesting that the underlying cellular pathway involved centre-depolarizing bipolar cell activity. Application of exogenous dopamine to retinas in the dark significantly enhanced the basal production of nitric oxide and importantly, inhibition of endogenous dopaminergic activity completely suppressed the light-evoked nitric oxide release. The effect of dopamine was mediated through the D1 receptor subtype. Imaging of the nitric oxide-sensitive fluorescent indicator 4,5-diaminofluorescein di-acetate in retinal slices revealed that activation of D1 receptors resulted in nitric oxide production from two main spatial sources corresponding to the photoreceptor inner segment region and the inner nuclear layer. The results taken together would suggest that during the progression of retinal light adaptation there is a switch from dopaminergic to nitrergic control, probably to induce further neuromodulatory effects at higher levels of illumination and to enable more efficient spreading of the light adaptive signal.

Original publication

DOI

10.1111/j.1460-9568.2005.04051.x

Type

Journal article

Journal

Eur J Neurosci

Publication Date

04/2005

Volume

21

Pages

2199 - 2208

Keywords

Adaptation, Ocular, Animals, Calcium Channel Blockers, Carps, Darkness, Dopamine, Dopamine Agonists, Dopamine Antagonists, Dose-Response Relationship, Drug, Drug Interactions, Electrochemistry, Enzyme Inhibitors, Excitatory Amino Acid Agonists, Excitatory Amino Acid Antagonists, Fluorescein, Fura-2, Indazoles, Lighting, Linear Models, Nitric Oxide, Photic Stimulation, Retina, Time Factors