[Role of dopamine as a regulator of vertebrate photoreceptors].

Cyclical changes in retina functioning during a 24-hour daily cycle are largely determined by the influence of two neuromodulators: melatonin and dopamine.

• Dopamine and melatonin mutually inhibit each other's synthesis and are released into the retina in opposite phases.
• Dopamine levels increase during the day and decrease at night, synthesized by specific populations of retinal cells.
• Both neuromodulators affect all major cell types in the outer and inner retinal layers.
• Dopamine activates D1- and D2-type receptors, which may influence pathways involving protein kinase A and cAMP levels.
• Dopamine's action on D2-type receptors can reduce cAMP concentration, suppress melatonin synthesis, and regulate gap junction conduction between rods and cones.

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