Fig. 5. Neither Ins(1,4,5)P₃- nor I_Ca-evoked [Ca²⁺]_c increases significantly altered _m of individual mitochondria. I_Ca activation (A, by depolarizing from –70 to +10 mV, 500 ms, n=9, white squares) or local photolysis of caged Ins(1,4,5)P₃ (B, , n=10, white circles) each increased [Ca²⁺]_c (Ci and Di). Neither caused significant alteration in _m (as shown by TMRE fluorescence, normalized to starting values, F/F₀) compared with control (n=9, black triangles, P>0.05 for all data points). Occasionally, the _m of individual mitochondria decreased during the period of observation of either I_Ca-evoked [Ca²⁺]_c elevation (Ci, [Ca²⁺]_c changes; Cii, holding potential, V_m; Ciii, _m of six individual mitochondria) or Ins(1,4,5)P₃-evoked [Ca²⁺]_c elevation (Di, [Ca²⁺]_c changes; Dii, activated by photolytic release of Ins(1,4,5)P₃ at ; Diii, _m of eight individual mitochondria); however, this was equally as likely to occur before, during or after [Ca²⁺]_c elevation.