Methyl-6-(phenylethynyl)-pyridine (MPEP) induced Ca 2+
release from the endoplasmic reticulum (ER). BV-2 cells were transferred to Ca2+-free medium prior to the experiments and loaded with Fluo-4 AM. (A) Cells were incubated with 100 μM MPEP for 1 hour prior to the addition of 1 μM thapsigargin (▲). Alternatively, as a control, cells were incubated in Ca2+-free medium for 1 hour prior to the addition of 1 μM thapsigargin (●). Addition of thapsigargin and MPEP is indicated by an arrow. (B) Cells were treated with 1 μM thapsigargin for 1 hour, followed by the addition of 100 μM MPEP (●), or they were kept in Ca2+-free medium for 1 hour, followed by the addition of 100 μM MPEP (▲). Fluo-4 AM loaded BV-2 cells were preincubated for 1 hour with 50 μM of the ryanodine receptor (RyR) blocker dantrolene (C) or 5 μM of the IP3R blocker xestospongin C (D) prior to addition of 100 μM MPEP and recording of [Ca2+]i. Relative changes in Ca2+ concentrations using Fluo-4 AM were analyzed and expressed as ΔF/F (in %), with F being the baseline fluorescence and ΔF the variation of fluorescence. Data represent mean ± SD of three independent experiments.