A. Block of bradykinin-induced increase in [Ca2+]i by caffeine on the primary human glioblastoma cells and astrocytes. Summary of block of GPCR agonist-induced Ca2+ responses by caffeine on various cell types. B. mRNA expression of IP3Rs and GAPDH was tested by semi-quantitative RT-PCR in various human glioblastoma cell lines (U87MG, U178MG, U373MG, T98G, M059K), human neuroblastoma cell line (SH-SY5Y), human embryonic kidney cell line (HEK293T), and human astrocyte. Correlation between expression of IP3R subtype 3 normalized to GAPDH in each cell type and caffeine block of agonist induced Ca2+ responses. (r 2=0.891, p<0.001) C. Semi-quantitative RT-PCR of IP3R subtypes in normal human brain and human glioblastoma tissue samples. Averages of densitometric measurement of IP3R mRNA expression in human samples, normalized to the normal human brain tissue sample (*p<0.001, **p<0.0001 by student’s t-test).