Figure 5.

(A) Hispidulin at 10 mM by itself did not elicit any current but potentiated currents elicited by 4 µM GABA at recombinant α1β2γ2S GABA_A receptors expressed in X. leavis oocytes. (B) Concentration dependence of allosteric potentiation by hispidulin demonstrating a biphasic response with potentiation at lower concentrations and inhibition at higher concentrations (>10 µM) of hispidulin. (C) The potentiation of currents elicited by GABA EC_2-5 by hispidulin (10 µM) at α1β2γ2S GABAA receptors is partially inhibited by co-application of the BZD receptor antagonist Ro15-1788 (flumazenil, 1 µM). The GABA EC_2-5 response at benzodiazepine insensitive α1β2 GABA_A receptors is not potentiated by 10 µM hispidulin. From Kavvadias et al. 2004. GABA_A, γ-amino butyric acid-A.