Dopamine retinal

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Steenhard B., Besharse J. (2000). Phase shifting the retinal circadian clock xPer2 mRNS induction by light and dopamine. J. Neurosci 20, 8572-7. 

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Brown JH, Makman MH (1972) Stimulation by dopamine of adenylate cyclase in retinal homogenates and of adenosine-3 5 -cyclic monophosphate formation in intact retina. Proc Natl Acad Sci USA 69 539-543. 

Guimaraes MZ, Hokoc JN, Duvoisin R, Reis RA, De Mello FG (2001) Dopaminergic retinal cell differentiation in culture modulation by forskolin and dopamine. Eur J Neurosci 75 1931-1937. 

Rodrigues Pdos S, Dowling JE (1990) Dopamine induces neurite retraction in retinal horizontal cells via diacylglycerol and protein kinase C. Proc Natl Acad Sci USA 87 9693-9697. 

Dopaminergic amacrine cells with widespread dendritic arborizations increase release of dopamine in response to increases in global illumination. Dopamine diffuses throughout the retina to influence cells as far away as the RPE. The increased release of dopamine by light modifies cell function to opdmize retinal responses in daylight (Witkovsky, 2004). 

Dopamine has been recognized to have neuroprotective actions in glaucoma. Retinal dopaminergic cells can be detected by the immunohistochemical staining of tyrosine hydroxylase, the rate-limiting enzyme in dopamine synthesis. It has been observed that NMDA induced RGC toxicity dramatically decreased tyrosine hydroxylase immunostaining at the June don betw een the inner nuclear layer and inner plexiform layer in glaucoma (Kitaoka and Kumai, 2004). 

Retinal pigmental epithelia (RPE) are dopaminergic support cells in the neural retina. RPE cells on gelatin beads, also called Spheramine, produce levodopa (Watts et al., 2003), but there are no data yet on the consistency of dopamine production by these cells. An open label clinical trial of transplantation of Spheramine was conducted in six patients with PD (Bakay et al., 2004). Spheramine was transplanted into the striatum and show ed clinical effects over 24 months. Spheramine is now undergoing double bhnd placebo controlled trials in advanced PD. 

Specific cell injury or cell functional disorder occur with individual drugs or drug classes, e.g. tardive dyskinesia (dopamine receptor blockers), retinal damage (chloroquine, phenothiazines), retroperitoneal fibrosis (methysergide), NSAIDs (nephropathy). Cancer may occur, e.g. with oestrogens (endometrium) and with immunosuppressive (anticancer) drugs. 

The bottom of the binding pocket is in a position equivalent to the binding site of small cationic neurotransmitters (dopamine, adrenaline, serotonin, acetylcholine,etc.) and to the ionone ring of retinal in opsins. 

Alternative approaches have been considered using genetically modified cells, for example fibroblasts from the skin, or retinal cells as sources of dopamine production. These approaches are still very much in the experimental stages. 

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