The Circadian Clock in the Retina Controls Rod-Cone Coupling

Abstract

SUMMARY Although rod and cone photoreceptor cells in the vertebrate retina are anatomically connected or coupled by gap junctions, rod-cone coupling is thought to be weak. By using a combination of tracer labeling and electrical recording in the goldfish retina and tracer labeling in the mouse retina, we show that the retinal circadian clock, a local endogenous process, and not the retinal response to the visual environment, controls the extent and strength of rod-cone coupling by activating dopamine D2-like receptors in the day, so that rod-cone coupling is weak during the day but remarkably robust at night. The results demonstrate that circadian control of rod-cone coupling serves as a synaptic switch between the rod and cone pathways, so that cones and neurons postsynaptic to cones receive very dim light signals from rods at night, but not in the day. The increase in the strength and extent of rod-cone coupling at night may enhance the reliability of the rod light response and facilitate the detection of large dim objects.

Parkinson's disease, visual hallucinations and apomorphine: A review of the available evidence

“…Therefore, dopamine seems to be essential in mediating light-adaptive mechanisms in retinal function [42,43].…”

“…These findings suggest that other mixed D1-like and D2-like dopamine agonists, such as pergolide and cabergoline, could exert similar anti-hallucinogenic effects. However, the evidence to date suggest a distinct effect for the ergolines pergolide and cabergoline indicating that the serotonergic antagonistic properties of apomorphine's piperdine moiety makes an additional and significant contribution [43].…”

Electrical synapses between AII amacrine cells in the retina: Function and modulation

“…Tuning is thought to take place both in the OPL, for coupling between horizontal cells (Hampson et al, 1994) and between photoreceptors (Ribelayga et al, 2008), as well as in the IPL. In the IPL, there is evidence that the electrical synapses that couple AII amacrine cells are regulated, potentially via dopamine released from specific amacrine cells.…”

Neuropsin (OPN5)-mediated photoentrainment of local circadian oscillators in mammalian retina and cornea

“…The SCN clock itself is entrained by external light cycles through retinal rods, cones, and melanopsin (OPN4)-expressing, intrinsically photosensitive retinal ganglion cells (ipRGCs) (2,3). The retina also manifests a local circadian clock, which regulates many important functions, such as photoreceptor disk shedding, photoreceptor gap-junction coupling, and neurotransmitter release (4)(5)(6). Surprisingly, local retinal photoentrainment does not require the SCN, and it also does not require rods, cones, or ipRGCs (7,8).…”