GABA(A) receptor subtype selectivity underlying anxiolytic effect of 6-hydroxyflavone

Area of Science:

• Neuroscience
• Pharmacology
• Natural Products

Background:

• 6-Hydroxyflavone (6HF) is a natural flavonoid with known affinity for the benzodiazepine (BZ) site of type A gamma-aminobutyric acid (GABA(A)) receptors.
• Previous research indicated moderate binding affinity, suggesting potential modulatory effects on GABAergic neurotransmission.

Purpose of the Study:

• To investigate the functional effects of 6HF on native GABA(A) receptors.
• To determine the subtype selectivity of 6HF at the BZ site.
• To evaluate the in vivo anxiolytic potential and associated side effects of 6HF.

Main Methods:

• Patch clamp electrophysiology was used to study GABA-induced currents in cortical neurons and HEK 293T cells expressing specific GABA(A) receptor subtypes.
• Pharmacological characterization involved assessing the effects of 6HF and flumazenil.
• Behavioral tests in mice, including the elevated plus-maze, hole-board, passive avoidance, horizontal wire, rotarod, and pentylenetetrazol-induced seizure tests, were conducted.

Main Results:

• 6HF partially potentiated GABA-induced currents in cortical neurons, an effect blocked by flumazenil, confirming action via the BZ site.
• 6HF showed a preference for alpha(2)- and alpha(3)-containing GABA(A) receptor subtypes over alpha(1)- and alpha(5)-containing subtypes.
• In vivo, 6HF demonstrated anxiolytic-like effects without causing sedation, cognitive impairment, muscle relaxation, motor incoordination, or anticonvulsant effects.

Conclusions:

• 6-Hydroxyflavone modulates GABA(A) receptors, particularly those containing alpha(2) and alpha(3) subunits.
• 6HF exhibits a favorable preclinical profile with anxiolytic efficacy and a lack of common benzodiazepine-associated adverse effects.
• These findings position 6HF as a potential therapeutic agent for anxiety disorders.