Figure 4. BzATP does not release Ca²⁺ from intracellular stores.

A, confocal image of two myelinated nerve fibres within an isolated rat spinal root stained with the Ca²⁺-sensitive dyes Calcium Green-1 and Fura Red. The mean grey value of the paranodal Schwann cell area (selected region of interest indicated in the right panel) and its ratio was used for the analysis. B and C, changes in [Ca²⁺]_i were measured during application of BzATP (150 μM) and UTP (300 μM) into the standard bathing solution and after depletion of intracellular Ca²⁺ stores with cyclopiazonic acid (CPA, 5 μM for 5 min). Note that only the UTP-induced intracellular Ca²⁺ transient was completely and reversibly blocked by CPA.