Fig. 3. Depolarisation but not cADPR contracted single colonic myocytes. Photolysed cADPR ( 50 µM) failed to increase F/F₀ (C) or to contract colonic myocytes [P>0.05 (Di)]. Depolarisation to +10 mV [holding potential –70 mV (A)] induced an inward I_Ca (B and expanded timescale inset) and a Ca²⁺ transient (C). Following the increase in [Ca²⁺]_c (F/F₀), (Dii) shows the mean changes in cell length produced by depolarization (P<0.05) and (Di) the failure of cADPR to induce contraction (n=10-18, P>0.05). Alignment of time with the videotaped contractile behaviour of the cell (E) was achieved by cell illumination with a flash lamp (Ei) or an LED triggered by depolarisation (Eii).