Document Detail

The relationship between ocular melatonin and dopamine rhythms in the pigeon: effects of melatonin inhibition on dopamine release.
MedLine Citation:
PMID:  9878866     Owner:  NLM     Status:  MEDLINE    
Our previous study has shown that the phases of circadian rhythms of ocular melatonin and dopamine are always opposite and intraocular melatonin injection suppresses dopamine release. Therefore, it is possible that dopamine rhythms result from inhibitory action of melatonin. We have examined this possibility in the following experiments. In the first experiment effects of continuous light on melatonin and dopamine release were examined. The data indicated that continuous light exposure resulted in loss of circadian rhythmicity of melatonin and dopamine by suppressing melatonin and enhancing dopamine levels throughout the day. To further examine the effects of light in the second experiment, 2 h light pulse was applied during the night, then temporal changes of melatonin and dopamine release were studied. The light pulse rapidly suppressed melatonin release, whereas it rapidly increased dopamine release. These changes occurred within 30 min in both melatonin and dopamine. However, the recovery after the cessation of the light stimulus was slower in melatonin than dopamine. In the third experiment it was tested if dopamine release was increased by lowering melatonin release with an intraocular injection of the D2 agonist, quinpirol. Although quinpirol strongly inhibited melatonin release independently of the time of injection, dopamine did not always increase by the inhibition of melatonin. These results indicate that ocular dopamine rhythms are not simply produced by melatonin inhibitory action.
A Adachi; Y Suzuki; T Nogi; S Ebihara
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Brain research     Volume:  815     ISSN:  0006-8993     ISO Abbreviation:  Brain Res.     Publication Date:  1999 Jan 
Date Detail:
Created Date:  1999-02-26     Completed Date:  1999-02-26     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0045503     Medline TA:  Brain Res     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  435-40     Citation Subset:  IM    
Copyright Information:
Copyright 1999 Elsevier Science B.V.
Department of Animal Physiology, Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya 464-0814, Japan.
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MeSH Terms
Circadian Rhythm / drug effects,  physiology*
Dopamine / metabolism*
Eye / metabolism*
Melatonin / antagonists & inhibitors*,  metabolism*
Ocular Physiological Phenomena / drug effects*
Quinpirole / pharmacology
Vitreous Body / metabolism,  physiology
Reg. No./Substance:
73-31-4/Melatonin; 85760-74-3/Quinpirole

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