Classical benzodiazepines are the most frequently prescribed drugs acting on the central nervous system (CNS). They exert their therapeutic effects via binding to the benzodiazepine-site of the type A γ-aminobutyric acid (GABA_A) receptors, which changes the channel opening frequency. The positive modulation of BZ causes behavioral effects such as anxiolysis, sedation, myorelaxation and amnesia and these effects could be governed by the different subtypes of GABA_A receptor. Formula A, a dried decoction of four herbal constituents including Flos Albiziae (F), Caulis Polygoni Multiflori (C), Rhizoma Corydalis Yanhusuo (R) and Radix Bupleuri (B), was documented as an anxiolytic. However, no detail studies with regards to its effectiveness, the possible dispensability of its constitu...[ Read more ]

Classical benzodiazepines are the most frequently prescribed drugs acting on the central nervous system (CNS). They exert their therapeutic effects via binding to the benzodiazepine-site of the type A γ-aminobutyric acid (GABA_A) receptors, which changes the channel opening frequency. The positive modulation of BZ causes behavioral effects such as anxiolysis, sedation, myorelaxation and amnesia and these effects could be governed by the different subtypes of GABA_A receptor. Formula A, a dried decoction of four herbal constituents including Flos Albiziae (F), Caulis Polygoni Multiflori (C), Rhizoma Corydalis Yanhusuo (R) and Radix Bupleuri (B), was documented as an anxiolytic. However, no detail studies with regards to its effectiveness, the possible dispensability of its constituents and possible synergism and antagonism of its anxiolytic effect were performed. In this thesis, dissection and analysis of the decoction of Formula A for its behavioral effects in vivo and in vitro experiments were done. For in vivo experiment, elevated plus maze, holeboard, rotatod, passive avoidance test were done to profile its anxiolytic, sedative, myorelaxant and amnesia respectively. While in vitro experiment of radio-ligand binding assay and whole-cell patch clamp will be carried out to show its interaction with possible binding sites. In the results, extracts of F and C had shown mutual antagonism in their anxiolytic effect while extract FRB was able to induce an enhanced anxiolytic-like effect with heavy sedation. Both extract FCB and Formula A induced an additive anxiolytic-like effect without other detectable accompanying effects. However, Formula A could induce a higher degree of anxiolytic effect as compared to extract FCB. In electrophysiological experiment, Formula A and the mono-extracts C, R and B were shown to induce hyperpolarization in rat cortical neurons; in addition, Formula A and extract C-induced currents could be enhanced by co-administration of diazepam.