Constant illumination causes spatially discrete dopamine depletion in the normal and degenerate retina

Intraretinal signaling by ganglion cell photoreceptors to dopaminergic amacrine neurons

“…In addition to the persistence of sustained responses, we also found that the photoreceptor-driven transient DA neuron light responses were absent from photoreceptor degenerate retinas, providing confirmation of loss of rod and cone function. Taken together, these results provide strong evidence that ipRGCs are the source of light input to sustained DA neurons and present a likely explanation for the persistence of light responsiveness of retinal dopamine levels and rhythms in rod/cone degenerate retinas (38)(39)(40). Although Vugler et al, (40) concluded that this light responsiveness was because of residual cones, based on a lack of morphologically identified ipRGC to DA neuron synapses; we now provide positive functional evidence for ipRGC drive to DA neurons and for a lack of cone-driven responses in DA neurons of photoreceptor degenerate mouse retinas.…”

Circadian organization of the mammalian retina: From gene regulation to physiology and diseases

“…This speculation is attractive as the ipRGCs would then serve entrainment of both the retinal and brain clocks, ensuring synchronization of these two neural oscillators (Zhang et al 2008). Indeed, light-induced dopamine responses and dopamine rhythms have generally been found to be preserved in rod/cone degenerate retinas in which melanopsin ganglion cells could serve as the remaining photoreceptors (Morgan and Kamp 1980; Nir and Iuvone, 1994; Doyle et al 2002b; Vugler et al 2007), presumably due to melanopsin ipRGC drive to dopaminergic neurons, (but see (Cameron et al 2009)). In addition, it has been demonstrated in Xenopus that phototransduction in rods drives the contraction of red cones, again indirectly through dopamine (Besharse and Witkovsky, 1992).…”

Intrinsically Photosensitive Retinal Ganglion Cells

“…10) (but see Refs. 28, 210, 234). Dopamine has diverse effects in the retina, serving as a widespread signal for light adaptation, and DA cells are its only source (226).…”