Fig. 3. Dependence of RA effect on Ca²⁺ mobilization from internal Ca²⁺ stores. Drugs that inhibit the Ins(1,4,5)P₃ receptor [Xestospongin C (XeC); 2-aminoethoxydiphenylborate (2-APB)] or the ryanodine receptor [8-(dethylamino) octyl 3,4,5-trimethoxybenzoate (TMB-8); ruthenium red] were added to the cell cultures 2030 minutes before the experiment at final concentrations of: XeC, 2 µM; 2-APB, 50 µM; TMB-8, 3 µM; and ruthenium red, 10 µM. The effect of RA on SSC frequency was then evaluated in the presence of XeC (A), 2-APB (B), TMB-8 (C) and ruthenium red (D). Scale bars: 1 nA, 20 seconds. (E) Summary of the drugs effect. For comparison, the horizontal dashed line defines basal activity as `1'. The error bars refer to s.e.m. (n=517). *P<0.05 compared with the control group (Student's t-test).