Document Detail

Melatonin-induced depression of locomotor activity in hamsters: time-dependency and inhibition by the central-type benzodiazepine antagonist Ro 15-1788.
MedLine Citation:
PMID:  1654569     Owner:  NLM     Status:  MEDLINE    
The aim of the present study was to determine whether melatonin-induced depression of locomotor activity in hamsters is time-dependent and to analyze the inhibitory effects of the central-type benzodiazepine (BZP) antagonist Ro 15-1788 on melatonin-induced depression of locomotor behavior. Activity was monitored and registered by means of an optical actometer. Two phases of locomotor behavior were found. The initial phase, found both at noon and during the evening, exhibited an absence of diurnal variability, while a second long-lasting phase of activity exhibited a peak at early night. The IP injection of melatonin (minimal effective dose: 100 micrograms/kg) inhibited the early phase of activity at 1200 or 2000 h. Inhibition of the late phase of activity was found at 2000 or 0400 h, but not at midnight. When assessed at 2000 h, melatonin depression of the early phase of locomotor activity attained significance after 5 days of injection, while its effect on the late phase of activity attained significance during the second day of injection. The administration of Ro 15-1788, although unable by itself to modify locomotor activity, significantly attenuated the inhibitory effects of melatonin. These results indicate the existence of a time-dependency for melatonin activity on locomotor behavior similar to that known to occur for other effects of the hormone, and further support a link between melatonin and the activity of central type BZP receptors.
D A Golombek; E Escolar; D P Cardinali
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Physiology & behavior     Volume:  49     ISSN:  0031-9384     ISO Abbreviation:  Physiol. Behav.     Publication Date:  1991 Jun 
Date Detail:
Created Date:  1991-10-23     Completed Date:  1991-10-23     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0151504     Medline TA:  Physiol Behav     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1091-7     Citation Subset:  IM    
Departamento de Fisiología, Facultad de Medicina, Universidad de Buenos Aires, Argentina.
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MeSH Terms
Brain / drug effects*
Circadian Rhythm / drug effects*
Dose-Response Relationship, Drug
Flumazenil / pharmacology*
Melatonin / antagonists & inhibitors,  pharmacology*
Motor Activity / drug effects*
Receptors, GABA-A / antagonists & inhibitors*
Reg. No./Substance:
0/Receptors, GABA-A; 73-31-4/Melatonin; 78755-81-4/Flumazenil

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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