title: Melatonin reverses pinealectomy-induced decrease of benzodiazepine binding in rat cerebral cortex.
abstract: Pinealectomy of rats resulted in significant depression of benzodiazepine receptors (assessed by [(3)H]flunitrazepam binding) in cerebral cortex 3-14 days after surgery without affecting their affinity significantly. A single s.c. injection of melatonin (800 ?g/kg body wt) restored the depressed brain benzodiazepine receptor sites. Single melatonin injections (up to 1600 ?g/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 [(3)H]flunitrazepam binding at 100 ?M 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.
authors.affiliation: Centro de Estudios Farmacológicos y de Principios Naturales (CEFAPRIN), Serrano 665, (1414)-Buenos Aires, Argentina.
authors.forename: P R
authors.initials: PR
authors.lastname: Lowenstein
authors.forename: R
authors.initials: R
authors.lastname: Rosenstein
authors.forename: D P
authors.initials: DP
authors.lastname: Cardinali