Circadian regulation of retinomotor movements. I. Interaction of melatonin and dopamine in the control of cone length. J Gen Physiol 1985 Nov;86(5):671-89
Date
11/01/1985Pubmed ID
2999294Pubmed Central ID
PMC2228813DOI
10.1085/jgp.86.5.671Scopus ID
2-s2.0-0022360406 (requires institutional sign-in at Scopus site) 266 CitationsAbstract
In lower vertebrates, cone retinomotor movements occur in response to changes in lighting conditions and to an endogenous circadian clock. In the light, cone myoids contract, while in the dark, they elongate. In order to test the hypothesis that melatonin and dopamine may be involved in the regulation of cone movement, we have used an in vitro eyecup preparation from Xenopus laevis that sustains light- and dark-adaptive cone retinomotor movement. Melatonin mimics darkness by causing cone elongation. Dark- and melatonin-induced cone elongation are blocked by dopamine. Dopamine also stimulates cone contraction in dark-adapted eyecups. The effect of dopamine appears to be mediated specifically by a dopamine receptor, possibly of the D2 type. The dopamine agonist apomorphine and the putative D2 agonist LY171555 induced cone contraction. In contrast, the putative D1 agonist SKF38393-A and specific alpha 1-, alpha 2-, and beta-adrenergic receptor agonists were without effect. Furthermore, the dopamine antagonist spiroperidol not only blocked light-induced cone contraction, but also stimulated cone elongation in the light. These results suggest that dopamine is part of the light signal for cone contraction, and that its suppression is part of the dark signal for cone elongation. Melatonin may affect cone movement indirectly through its influence on the dopaminergic system.
Author List
Pierce ME, Besharse JCMESH terms used to index this publication - Major topics in bold
AnimalsCell Movement
Circadian Rhythm
Dark Adaptation
Dopamine
Drug Interactions
In Vitro Techniques
Melatonin
Photoreceptor Cells
Synaptic Transmission
Xenopus laevis