Fig. 7. Effect of RA on the intracellular Ca²⁺ concentration. Xenopus nerve-muscle cultures were loaded with Fura-2 AM, and ratio fluorometric measurement of intracellular Ca²⁺ was made on a single motoneuron. Representative traces show F₃₄₀/F₃₈₀ ratio changes induced by perfusion the culture (at time 0) with RA in Ringer's solution (A), Ca²⁺-free Ringer's solution (B), or pretreatment with thapsigargin (TG, 2 µM) followed by perfusion with Ca²⁺-free Ringer's solution (C). (D) Summary of the RA-induced intracellular Ca²⁺ change ([Ca²⁺]_i) in the presence of various inhibitors (U73122, 5 µM; LY294002, 5 µM; genistein, 100 µM, PP2, 10 µM). Representative traces are shown in the inset. Data are presented as mean ± s.e.m. (n=37). *P<0.05 compared with the control group (Student's t-test).