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Circadian Phase-Dependent Modulation of cGMP-Gated Channels of Cone Photoreceptors by Dopamine and D2 Agonist
Daily cycle influences how dopamine controls light-sensitive channels in cone cells
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Abstract
Dopamine (DA) and D2 receptor agonists may shift the affinity of cGMP-gated ion channels in chick retinal cone photoreceptors based on the time of day.
- Dopamine and D2 agonists significantly increased the K(D) for cGMP during the night (circadian time 16-19) but not during the day (circadian time 4-7).
- A brief exposure to DA or quinpirole decreased K(D) during the subjective day and had no effect during the subjective night.
- The effect of D2 agonists on K(D) is associated with both the duration of exposure and the circadian timing.
- DA treatment activated the MAP kinase Erk during the day but inhibited it at night.
- D2 agonists activated Ca2+/calmodulin-dependent protein kinase II during the night and inhibited it during the day.
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