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Learning to avoid threats in the environment is highly adaptive. However, sometimes a dysregulation of fear memories processing may underlie fear-related disorders. Despite recent advances, a major question of how to effectively attenuate persistent fear memories in a safe manner remains unresolved. Here we show experiments employing a behavioural tool to target a specific time window after training to limit the persistence of a fear memory in rats. We observed that exposure to a novel environment 11 h after an inhibitory avoidance (IA) training that induces a long-lasting memory, attenuates the durability of IA memory but not its formation. This effect is time-restricted and not seen when the environment is familiar. In addition, novelty-induced attenuation of IA memory durability is prevented by the intrahippocampal infusion of the CaMKs inhibitor KN-93. This new behavioural approach which targets a specific time window during late memory consolidation, might represent a new tool for reducing the durability of persistent fear memories. Fil: Katche, Cynthia Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; Argentina Fil: Tomaiuolo, Micol. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; Argentina Fil: Dorman, Guido. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; Argentina Fil: Medina, Jorge Horacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; Argentina Fil: Viola, Haydee Ana Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Fisiología, Biología Molecular y Celular; Argentina

Flavonoids isolated from plants used as tranquilizers in folkloric medicine have a selective affinity, for central benzodiazepine receptors (BDZ-Rs) and some of them possess a pharmacological profile compatible with a partial agonist action. Synthetic derivatives of the common flavone nucleus, give rise to high affinity ligands when electronegative groups are introduced in carbons 6 and/or 3'. Representative compounds such as 6,3'-dinitroflavone and, 6-bromo-3'-nitroflavone exhibit a high affinity for the BDZ-Rs (Ki = 1.5 to 30 nM) and have anxiolytic effects not associated with myorelaxant, sedative or amnesic actions. These compounds or similar ones, could lead to improved therapeutic drugs in the treatment of anxiety.

Salvia guaranitica St. Hil. is a traditional medicinal plant used in Latin America as sedative. We have recently demonstrated the presence of cirsiliol in its extracts and found that this flavonoid is a competitive low affinity benzodiazepine receptor ligand (Marder et al., 1996). This report describes the pharmacological properties of Salvia guaranitica extracts and of its active principle, cirsiliol. A partially purified fraction of this plant, administered intraperitoneally in mice (in a dose equivalent to 3 g of the fresh plant), exhibited sedative and hypnotic effects as measured in the hole board and in the pentobarbital-induced sleep tests, respectively. On the other hand, this fraction had no anxiolytic or myorelaxant effects. In the pentobarbital-induced sleep test, cirsiliol (2-10mg/kg, i. p.) exhibited a dose-dependent hypnotic action. In contrast, it did not produce myorelaxant (up to 30mg/kg) or anticonvulsant (up to 10mg/kg) effects. Cirsiliol was found to be more potent in displacing (3)H Zolpidem binding (K(i) = 20 LiM) than (3)H flunitrazepam binding (K(i) = 200 μM) to benzodiazepine receptors from rat cerebral cortex. It is concluded that Salvia guaranitica extracts and its active principle cirsiliol, possess sedative and hypnotic properties; cirsiliol produces these effects probably acting on the so-called type I benzodiazepine receptor.

Ligands for the central benzodiazepine receptors have been detected in the crude ethanolic extract of Salvia guaranitica. The compounds responsible for the activity were isolated by bioassay-directed fractionation and have been characterised as cirsiliol (5, 3', 4'-trihydroxy 6,7-dimethoxyflavone) and caffeic acid ethyl ester.