Dopamine helps the body clock control rod and cone signals to fish eye cells

Dopamine release in the retina is greater during the subjective day than the subjective night.

• Cone horizontal cells are primarily driven by cone signals during the day and by rod signals at night due to a circadian clock.
• Application of dopamine or a dopamine D(2)-like agonist at night increases cone input and removes rod input, mimicking daytime conditions.
• In contrast, a D(2)-like antagonist or an activator of adenylyl cyclase during the day reduces cone input and increases rod input.
• Inhibitors of cAMP-dependent protein kinase or gap junction uncouplers at night also enhance cone input while diminishing rod input.
• D(2)-like receptors are located on photoreceptor cells rather than horizontal cells, suggesting a pathway for dopamine's influence on retinal signaling.

Simplified