Effect of honokiol on activity of GAD65 and GAD67 in the cortex and hippocampus of mice

Honokiol, an active agent extracted from magnolia bark, has been reported that induces anxiolytic action in a mouse elevated plus-maze test. However, the mechanism of anxiolytic action induced by honokiol remains unclear. This study was to investigate the change in two forms of glutamic acid decarboxylase (GABA synthesized enzymes) GAD65 and GAD67 in the cortex and hippocampus areas while the anxiolytic actions induced by chronic administration of honokiol in mice. Mice treated with 7 daily injection of honokiol (1 mg/kg, p.o.) caused anxiolytic action which was similar to that was induced by 7 daily injection of diazepam (2 mg/kg, p.o.) in the elevated plus-maze test. In addition, the activity of hippocampal GAD65 of honokiol treated mice was significantly increased than that of the vehicle or diazepam treated groups. These data suggest that honokiol causes diazepam-like anxiolytic action, which may be mediated by altering the synthesis of GABA in the brain of mice.