Figure 2.

Endoplasmic reticulum (ER) Ca²⁺ release following caffeine stimulation is stage specific during OPC differentiation. (A) Differential interference contrast (DIC) with Fluo-3 fluorescence of three stages of OL lineage cells, showing typical shape of OPC, imOL and OL. Note that the pictures were acquired at the end point of Ca²⁺ imaging to ensure the morphology of the oligodendroglial cells, thus Fluo-3 fluorescence was extremely strong. (B) Representative examples of Ca²⁺ response following caffeine stimulation. Note that the start point in the x-axis is not the beginning point of recording, baseline recording is omitted from the curve. (C) OPCs and imOLs, which tend to respond with oscillatory Ca²⁺ transients and high flat Ca²⁺ transients, reacted stronger than OLs, which tend to respond with low plateaus Ca²⁺ transients. (D) OPC and imOL had significantly higher Ca²⁺ release peaks after caffeine stimulation compared with mature OLs (*p < 0.05). Time-lapse Ca²⁺ imaging induced by caffeine (20 mM, 0 Ca²⁺) in an OPC (1) (E) and a mature OL (F). Four successive scans were selected from a series of images obtained within 10 min. Transient fluorescence fluctuations, representing local Ca²⁺ release events, were indicated by the pseudocolored peaks in the OPC cell body and processes (arrows), but they occurred only in the soma in mature OLs. The pseudocolor bar in (F) showed the fluorescence intensity of different colors.