[Utility of organotypic raphe slice cultures to investigate the effects of psychotropic drugs on the function of serotoninergic neurons].

A number of behavioral, neurochemical and electrophysiological studies have emphasized the importance of the serotonergic neurons in the pathophysiology of psychiatric disorders and the therapeutic actions of psychotropics. However, no in vitro serotonergic culture systems have successfully analyzed the long-term effects of psychotropics or the neural interaction between serotonergic and excitatory/inhibitory neurons. Recently, we have established rat organotypic raphe slice cultures, which have functional serotonergic neurons with the ability to release 5-HT in response to stimulation and to reuptake 5-HT through serotonin transporter and retain neural and synaptic functions. Here, we show the following results in the raphe slice cultures: 1) acute and sustained treatments with 3,4-methylenedioxymethamphetamine induce the 5-HT efflux via serotonin transporter and AMPA receptor-mediated exocytotic 5-HT release, respectively; 2) sustained treatment with antidepressants enhances the exocytotic 5-HT release, which is dependent on AMPA receptor stimulation, but not on desensitization of 5-HT(1A/1B) autoreceptors; 3) the augmentation therapy of an atypical antipsychotic, olanzapine, with antidepressants is caused by the decrease in the raphe inhibitory GABAergic tone through 5-HT6 receptor antagonism. Our findings suggest that the raphe slice cultures are suitable for analyzing the neural and molecular mechanisms underlying the efficacy of psychotropics in vitro.