title: Anxiolytic effect of wogonin, a benzodiazepine receptor ligand isolated from Scutellaria baicalensis Georgi.
abstract: The search for novel anxiolytics devoid of undesirable side-effects typical of classical benzodiazepines (BDZs) has been intense, and flavonoids, as a relative new class of ligands, have been shown to possess anxiolytic effects in vivo. The present study evaluated the pharmacological properties of a naturally occurring monoflavonoid, 5,7-dihydroxy-8-methoxyflavone or wogonin. The affinity (K(i)) of wogonin for the benzodiazepine site (BZD-S) on the gamma-aminobutyric acid(A) (GABA(A)) receptor complex was 0.92 microM. Using electrophysiological techniques, we showed that wogonin enhanced the GABA-activated current in rat dorsal root ganglion neurons, and in Xenopus laevis oocytes expressing recombinant rat GABA(A) receptors, the enhancement was partially reversed by the co-application of a 1 microM concentration of the BZD-S antagonist anexate (Ro15-1788). Acute toxicity and behavioral effects were examined in mice. Acute lethal activity was low, with an LD(50) of 3.9 g/kg. Oral administration of wogonin (7.5 to 30 mg/kg) elicited an anxiolytic response that was similar to that elicited by diazepam in the elevated plus-maze; a dose-dependent increase in open arm entries and time spent in open arms was observed. More importantly, its anxiolytic effect was blocked by the co-administration of Ro15-1788. In the holeboard test, not only did wogonin-treated mice experience an increased number of head-dips but they also spent more time at it, showing no signs of sedation. Furthermore, wogonin did not cause myorelaxant effects in the horizontal wire test. Taken together, these data suggest that wogonin exerts its anxiolytic effect through positive allosteric modulation of the GABA(A) receptor complex via interaction at the BZD-S. Its anxiolytic effect was not accompanied by sedative and myorelaxant side-effects typical of BDZs.
authors.affiliation: Department of Biochemistry, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
authors.forename: Kwok Min
authors.initials: KM
authors.lastname: Hui
authors.forename: Michael S Y
authors.initials: MS
authors.lastname: Huen
authors.forename: Hong Yan
authors.initials: HY
authors.lastname: Wang
authors.forename: Hui
authors.initials: H
authors.lastname: Zheng
authors.forename: Erwin
authors.initials: E
authors.lastname: Sigel
authors.forename: Roland
authors.initials: R
authors.lastname: Baur
authors.forename: Hong
authors.initials: H
authors.lastname: Ren
authors.forename: Zhi Wang
authors.initials: ZW
authors.lastname: Li
authors.forename: J Tze-Fei
authors.initials: JT
authors.lastname: Wong
authors.forename: Hong
authors.initials: H
authors.lastname: Xue
mesh_terms: D000818:Animals; D014151:Anti-Anxiety Agents / Q000302:isolation & purification / Q000494:pharmacology* / Q000633:toxicity; D001665:Binding Sites; D004365:Drugs, Chinese Herbal / Q000494:pharmacology; D004594:Electrophysiology; D005260:Female; D044950:Flavanones; D005419:Flavonoids / Q000302:isolation & purification / Q000494:pharmacology* / Q000633:toxicity; D008024:Ligands; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D023421:Models, Animal; D009043:Motor Activity / Q000187:drug effects*; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D011597:Psychomotor Performance / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D011963:Receptors, GABA-A / Q000187:drug effects / Q000378:metabolism*; D031364:Scutellaria baicalensis / Q000737:chemistry*; D014982:Xenopus laevis
chemical_list: D014151:Anti-Anxiety Agents; D004365:Drugs, Chinese Herbal; D044950:Flavanones; D005419:Flavonoids; D008024:Ligands; D011963:Receptors, GABA-A; C085514:wogonin