セロトニン作動性幻覚薬の抗うつ作用における責任回路研究

抄録

Serotonergic psychedelics such as psilocybin, the psychoactive substance found in the magic mushroom, have hallucinatory effect through stimulation of the cortical serotonin 5-HT_2A receptor (5-HT2A). Recently, FDA has called psilocybin a 'breakthrough therapy' for severe depression. We have already demonstrated that 5-HT2A in the lateral septum (LS) plays a responsible role in antidepressant-like effect of psilocin, an active metabolite of psilocybin, whereas hallucinatory effect of psilocin was attributed to 5-HT2A stimulation in the visual cortex (V1) in mice. Here, we investigated the neural network responsible for antidepressant effect of psilocin. The histological study with anterograde and retrograde transports of adeno-associated viruses showed that 5-HT2A in LS abundantly expressed in GABAergic neurons, which projects to the dorsomedial hypothalamic nucleus (DM) in mice. Therefore, we investigated the functional role of 5-HT2A-positive LS-DM pathway in antidepressant effect by optogenetic and chemogenetic approaches. Selective inhibition of 5-HT2A-positive LS-DM pathway eliminated the antidepressant-like effect of psilocin in mice in forced-swim test as well as social defeat stress test. On the other hand, activation of the LS-DM pathway induced antidepressant-like effect in mice. Lastly, microinjection of bicuculline, an antagonist of GABA_A receptor, into the DM diminished such effect of psilocin in mice. These suggest that 5-HT2A-positive LS-DM GABAergic network contributes to antidepressant effect of serotonergic psychedelics.