Anxiolytic activity of melatonin in mice: involvement of benzodiazepine receptors.
The anxiolytic properties of melatonin are revealed by two behavioral studies. In a free exploratory situation, the holeboard test, melatonin decreased head-dip performance. In an unconditioned conflict test, the light/dark box choice situation, melatonin increased the time spent in the lit box as well as the number of transitions between the two compartments. Melatonin was given in a dose range from 0.5 to 5.0 mg/kg body weight i.p. 30 minutes before testing in daytime. Moreover, the anxiolytic activity of diazepam (2.5 mg/kg i.p.) was evaluated and found to be completely inhibited by the specific benzodiazepine antagonist flumazenil (10 mg/kg i.p. 30 minutes before). In the same manner flumazenil counteracted melatonin activity in the two tests. Involvement of the benzodiazepine/GABAergic system in the anxiolytic activity of melatonin is discussed.
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Laboratoire d'Eutonologie-Hopital Boucicaut, Paris, France.
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D000818:Animals; D014151:Anti-Anxiety Agents / Q000494:pharmacology*; D002755:Choice Behavior / Q000187:drug effects; D003975:Diazepam / Q000037:antagonists & inhibitors / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005442:Flumazenil / Q000494:pharmacology; D008297:Male; D008550:Melatonin / Q000008:administration & dosage / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D051379:Mice; D009043:Motor Activity / Q000187:drug effects; D011963:Receptors, GABA-A / Q000187:drug effects* / Q000502:physiology
D014151:Anti-Anxiety Agents; D011963:Receptors, GABA-A; D005442:Flumazenil; D008550:Melatonin; D003975:Diazepam