GABAA receptor modulation and neuropharmacological activities of viscosine isolated from Dodonaea viscosa (Linn)

The objective of the present study was to evaluate the modulation of GABA-evoked currents by the flavonoid viscosine at recombinant GABA(A) receptors, and subsequently to study its anxiolytic, sedative and anticonvulsant activities. Viscosine (1-300 mu M) positively modulated GABA-evoked currents at human alpha 1 beta 2 gamma 2L and alpha 2 beta 2 gamma 2L GABA(A) receptors expressed in Xenopus oocytes in a flumazenil insensitive manner. In behavioral studies, viscosine at doses of 10-100 mg/kg (i.p.) exerted significant anxiolytic effects in the elevated plus maze, light-dark and open field tests (*p < 0.05, **p < 0.01 ***P < 0.001 n = 6, One-way ANOVA post-Dunnett's test), and sedative effects at high doses (100 mg/kg i.p.) in hole board and thiopental induced sleep time tests. The anxiolytic effect in the elevated plus maze test was not blocked by flumazenil whereas pentylenetetrazole (PTZ) completely attenuated the effect, indicating that the activity was mediated via the non-benzodiazepine sites of GABA(A) receptors. Furthermore, viscosine at doses of 10-100 mg/kg (i.p.) exerted anticonvulsant effects in a dose-dependent manner in PTZ, picrotoxin and bicuculline induced seizure paradigms (*P < 0.05, **P < 0.01,***p < 0.001 n = 6, One-way ANOVA post-Dunnett's test). In conclusion, the results of the present study suggest that the anxiolytic and anticonvulsant actions of viscosine are likely mediated via its positive allosteric modulatory action of GABA at different GABA(A) receptor subtypes. (C) 2015 Elsevier Inc All rights reserved.