Dopaminergic modulation of retinal processing from starlight to sunlight

Dopamine D1 and D4 receptors contribute to light adaptation in ON-sustained retinal ganglion cells

“…There is also good evidence to suggest that light adaptation induces significant changes in resting ganglion cell spike rates (Barlow and Levick 1969;Freeman et al 2008), which could be mediated by the changes in spontaneous currents measured here. Because dopamine is released during light adaptation and modulates retinal activity via activation of both D1Rs and D4Rs (Roy and Field 2019;Witkovsky 2004), it makes sense that treatment with either a D1R or D4R agonist seems to mediate a portion of light adaptation's effects. but fails to completely recapitulate them.…”

“…For more than half a century visual neuroscientists have known that dopamine is integral to retinal light adaptation, but the full scope of its sites of action and neuromodulatory effects remain inadequately understood and quantified (Roy and Field 2019;Witkovsky 2004). In the retina, dopamine is produced by a specific population of dopaminergic amacrine cells that are located within the inner nuclear layer (Jackson et al 2012;Witkovsky 2004).…”

Dopamine, Alpha-Synuclein, and Mitochondrial Dysfunctions in Parkinsonian Eyes

“…Most DA amacrine cells (DACs) also synthetize GABA. DACs constitute only a small part of amacrine cells and they often co-express GABA and glycine (May et al, 2008;Roy and Field, 2019). DACs have long axon-like processes reaching the IPL, the GCL and sometimes the OPL and processes that overlap and branch forming a densely packed network of dendrites (Figure 1).…”

“…DA exerts its action through direct synaptic contacts and through volumetric diffusion. Given its long-distance and dense network it has the potential to influence the activity at different levels and on different cell subtypes in the retina (Witkovsky, 2004;Roy and Field, 2019). DA acts on five G-protein-coupled receptor subtypes grouped in D-like receptors (D1 and D5) and D2-like (D2, D3, D4) linked to the activation (D1-like) and inhibition (D2like) of cyclic-AMP (Seeman and Van Tol, 1994;Witkovsky, 2004).…”

“…receptors uncouples H1-type horizontal cells; both mechanisms increasing the direct response of cones in photopic conditions. By contrast, the absence of DA favors the rod-cone conductance and shunting of the cone electrical signal (Veruki and Wassle, 1996;Puopolo et al, 2001;Witkovsky, 2004;Roy and Field, 2019). Interestingly, a mouse model where the synthesis of DA was specifically prevented in the retina was generated by conditional inactivation of the tyrosine hydroxylase (TH) gene, which encodes the DA synthesis rate limiting enzyme.…”