Antidepressant-like effects of a water-soluble extract from the culture medium of Ganoderma lucidum mycelia in rats

BACKGROUND: Ganoderma lucidum is a popular medicinal mushroom used for promoting health and longevity in Asian countries. Previously, we reported that a water-soluble extract from a culture medium of Ganoderma lucidum mycelia (MAK) exerts antioxidative and cerebroprotective effects against ischemia–reperfusion injury in vivo. Here, we evaluated the antidepressant and anxiolytic activities of MAK in rats. METHODS: MAK (0.3 or 1 g/kg, p.o.) was administered in the experimental animals 60 min before the forced swimming, open-field, elevated plus-maze, contextual fear-conditioning, and head twitch tests. Additionally, the mechanisms involved in the antidepressant-like action of MAK were investigated by the serotonin precursor 5-hydroxy-L-tryptophan (5-HTP)- or 5-HT(2A) agonist (±)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane hydrochloride (DOI)-induced head twitch responses. RESULTS: Treatment with MAK (1 g/kg) exhibited antidepressant-like effects in the forced swimming test, attenuated freezing behavior in the contextual fear-conditioning test, and decreased the number of head twitches induced by DOI, but not with 5-HTP. No significant response was observed in locomotion or anxiety-like behavior, when the animals were evaluated in the open-field or elevated plus-maze test, respectively. CONCLUSIONS: These data suggest that MAK has antidepressant-like potential, which is most likely due to the antagonism of 5-HT(2A) receptors, and possesses anxiolytic-like effects toward memory-dependent and/or stress-induced anxiety in rats.