The effects of drugs for affective disorders on the sustained phase of serotonin (5-HT)-induced calcium (Ca2+) response were investigated in single C6BU-1 glioma cells with digital imaging microscopy. The sustained phase was significantly attenuated by 32 µM carbamazepine and 320 µM sodium valproate as well as 100 nM clomipramine and verapamil, whose effects we evaluated in our previous report. The present findings demonstrate that drugs for affective disorders, in their therapeutic concentrations, have common action of inhibiting Ca2+ influx, and suggest that the Ca2+ antagonistic effect may play an important role in the mechanism of the action sites of the drugs for affective disorder