The affinity of @entity6708 -gated ion channels (CNGCs) for @entity6708 in @entity1573 retinal cone photoreceptors is under circadian control. Here we report that @entity935 (DA) and D2 receptor agonists evoke phase-dependent shifts in the affinity of CNGCs for activating ligand. Inside-out patch recordings from cultured @entity1573 cones were performed at circadian time (CT) 4-7 and CT 16-19 on the second day of constant darkness. Exposing intact cells to DA or the D2 agonist @entity11640 for 2 hr before patch excision caused a significant increase in the K(D) for @entity6708 during the night (CT 16-19) but had no effect during the day (CT 4-7). DA or @entity11640 treatment had no effect on the Hill slope or the average number of channels per patch. The effect of DA was blocked by the D2 antagonist @entity12174 and was not mimicked by D1 agonists or blocked by D1 antagonists. By contrast, a brief (15 min) exposure to DA or @entity11640 caused a decrease in K(D) during the subjective day and had no effect during the subjective night. Thus, the effect of D2 agonists depends on both the duration of agonist exposure and the time of day. Application of DA or @entity11640 evoked a transient activation of the MAP kinase Erk (extracellular signal-related kinase) during the day but caused a sustained inhibition during the night. Conversely, D2 agonists caused activation of @entity141 /calmodulin-dependent protein kinase II during the night and inhibited this enzyme during the day. A circadian oscillator in cones appears to regulate the nature of the transduction cascade used by D2 receptors.

Circadian phase-dependent modulation of @entity6708 -gated channels of cone photoreceptors by XXXX and D2 agonist.

@entity6708 :: ('CHEBI:16356', 'Chemical') :: ['cGMP'] @entity11640 :: ('MESH:D019257', 'Chemical') :: ['quinpirole'] @entity12174 :: ('MESH:C045989', 'Chemical') :: ['eticlopride'] @entity935 :: ('MESH:D004298', 'Chemical') :: ['dopamine'] @entity1573 :: ('9031', 'Species') :: ['chick'] @entity141 :: ('CHEBI:29108', 'Chemical') :: ['Ca2+']
@entity935 :: (MESH:D004298,Chemical) :: ['dopamine']
