Melatonin reverses pinealectomy-induced decrease of benzodiazepine binding in rat cerebral cortex |
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Authors: | Pedro R Lowenstein Ruth Rosenstein Daniel P Cardinali |
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Institution: | Centro de Estudios Farmacológicos y de Principios Naturales (CEFAPRIN), Serrano 665, (1414)-Buenos Aires, Argentina |
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Abstract: | Pinealectomy of rats resulted in significant depression of benzodiazepine receptors (assessed by 3H]flunitrazepam binding) in cerebral cortex 3–14 days after surgery without affecting their affinity significantly. A single s.c. injection of melatonin (800 μg/kg body wt) restored the depressed brain benzodiazepine receptor sites. Single melatonin injections (up to 1600 μg/kg) to intact rats did not affect brain benzodiazepine binding when injected at either morning or evening hours. Daily melatonin treatment to intact rats for 5 days augmented benzodiazepine receptor density in brain (morning injections) or its dissociation constant (evening injections). Melatonin added in vitro to rat cerebral cortex membranes only slightly depressed 3H]flunitrazepam binding at 100 μM concentrations. These results point out a link between pineal activity and benzodiazepine receptor function in rats. They also indicate that pharmacological doses of melatonin affect benzodiazepine binding sites in rat cerebral cortex. |
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