Enhancement of serotonin- and bradykinin-evoked calcium ion dynamics in differentiated NG108-15 cells

Dynamic changes in the concentration of intracellular free-calcium ion ([Ca2+]i) by carbachol (CCh) and neurotransmitter candidates was investigated in undifferentiated and differentiated neuroblastoma × glioma hybrid NG108-15 (NG) cells. [Ca2+]i was increased in a dose-dependent manner by bradykinin (BK) and serotonin (5-HT) in differentiated NG cells, and the response to BK and 5-HT was significantly greater than that in undifferentiated NG cells. The EC50 value of BK was approximately 1.5 × 10−8 M in both undifferentiated and differentiated NG cells. The EC50 value of 5-HT in differentiated NG cells was about 5 × 10−6 M. The response to BK and 5-HT was almost completely inhibited by 10 nM Hoe140 (a BK B2 receptor antagonist) and 3 nM tropisetron (a 5-HT3 receptor antagonist), respectively. These results suggest that there are some mechanisms by which the response evoked by BK and 5-HT is up-regulated in differentiated NG cells.