Involvement of GABAergic non-benzodiazepine sites in the anxiolytic-like and sedative effects of the flavonoid baicalein in mice.

Baicalein (BA), one of the main flavonoids obtained from the Chinese medicinal herb Scutellaria baicalensis, usually exerts several pharmacological effects. In the central nervous system (CNS), BA exerts a protective effect on neurons against several neuronal insults among other effects, but it is not clear if this effect is due to its metabolite, baicalin. The purpose of the present study was to assess the anxiolytic-like and related properties of BA following its central administration (i.c.v.) in mice. BA (0.02, 0.2pmol) exerted an anxiolytic-like effect at low doses, increasing the time spent in open arms and the head-dipping whereas reducing the stretched-attend postures in the elevated plus-maze. BA also increased the duration of ether-induced sleep without affecting the pentylenetetrazol (PTZ)-induced convulsions. In addition, pretreatment with flumazenil (FMZ), PTZ, dehydroepiandrosterone sulfate (DHEAS), and dl-p-chlorophenilalanine ethyl ester (PCPA) were conducted in order to investigate its mechanism of action. PTZ and DHEAS, but not FMZ or PCPA, antagonized the BA's anxiolytic-like effect. Taken together our results showed that BA, when directly injected into the CNS, promotes anxiolytic-like and sedative effects, pharmacological activities dependent on GABAergic non-benzodiazepine sites but not on the 5-HT system.