EFFECTS OF CLOMIPRAMINE AND VERAPAMIL ON 5-HT-INDUCED INTRACELLULAR CALCIUM CHANGES IN INDIVIDUAL C6 RAT GLIOMA-CELLS

The effects of antidepressants and calcium (Ca2+) antagonists on serot onin (5-HT)-induced Ca2+ increase were investigated in single C6BU-1 g lioma cells with digital imaging microscopy. Application of 5-HT (100 nM - 100 mu M) caused a rapid and reversible rise of intracellular Ca2 + concentration ([Ca2+](i)) in a concentration-dependent manner. In th e absence of extracellular Ca2+, the sustained phase of the [Ca2+](i) response was strongly reduced, which was greater than the suppression of the initial peak. This suggests that the peak value is mainly due t o internal Ca2+ storage sites, and the sustained phase is mainly compo sed of Ca2+ influx. The sustained phase was significantly attenuated b y 100 nM clomipramine and verapamil. The present findings demonstrate that clomipramine and verapamil, in their therapeutic concentrations, have a common action of inhibiting Ca2+ influx, and suggest that the c alcium antagonistic effect may play an important role in clinical effe cts of antidepressants.