Fig. 6. Absence of MAPK activity and IP₃R1 MPM2 phosphorylation influences the ability of mouse eggs to mount oscillations and affects IP₃R1 function. (A)[Ca²⁺]_i responses induced by SrCl₂ (10 mM) and (B) PLC (0.1 µg/µl) were compared in oocytes matured in the absence (left panels) or presence (right panels) of U0126 (25 µM). (C) The content of the Ca²⁺ stores was examined in oocytes maturated in the absence (left panel) or presence of U0126 (right panel) by monitoring [Ca²⁺]_i responses induced by the addition of thapsigargin (first arrow; TG; 10 µM) in Ca²⁺-free media. Ca²⁺ influx was examined in the same oocytes after the addition of CaCl₂ up to a final concentration of 5 mM (second arrow).