The antidepressant-like activity of 6-methoxy-2-[4-(2-methoxyphenyl)piperazin-1-yl]-9H-xanthen-9-one involves serotonergic $5-HT_{1A}$ and $5-HT_{2A/C}$ receptors activation

Xanthone derivatives have been shown to posses many biological properties. Some of them act within the central nervous system and show neuroprotective or antidepressant like properties. Taking this into account we investigated antidepressant like activity in mice and the possible mechanism of action of 6-methoxy-2-[4-(2-methoxyphenyl)piperazin-1-yl]-9H-xanthen-9-one (HBK-11) - a new xanthone derivative. We demonstrated that HBK-11 produced antidepressant like effects in the forced swim test and tail suspension test, comparable to that of venlafaxine. The combined treatment with sub effective doses of HBK-11 and fluoxetine (but not reboxetine or bupropion) significantly reduced the immobility in the forced swim test. Moreover, the antidepressant like activity of HBK-11 in the aforementioned test was blocked by p-chlorophertylalanine, and significantly reduced by serotonergic $5-HT_{1A}$ receptor antagunist - WAY-1006335 and $5-HT_{2A/C}$ receptor antagonist - ritanserin. As none of the above treatments influenced the spontaneous locomotor activity, if can be concluded that HBK-11 mediates its activity through a serotonergic system, and its antidepressant like effect involves $5-HT_{1A}$ and $5-HT_{2A/C}$ receptor activation. Furthermore, at antidepressant like doses HBK-11 did not cause the mice to display locomotor deficits in rotarod or chimney rests. Considering the pharmacokinetic profile, HBK-11 demonstrated rapid absorption after i.p. administration, high clearance value, short terminal half-life, very high volume of distribution and incomplete bioavailabilily. The compound studied had good penetration into the brain tissue of mice. Since studied xanthone derivative seems to present interesting, untypical mechanism of antidepressant-like action i.e. $5-HT_{2A/C}$ receptor activation, it may have a potential in the treatment of depressive disorders, and surely requires further studies.