One or two Ca2+ stores in the neuronal endoplasmic reticulum?

It is generally accepted that the endoplasmic reticulum (ER) has one continuous lumen and operates as one unified Ca2+ store, but new data from Chen-Engerer et al. in hippocampal neurons now challenge this idea and indicate that receptors for inositol trisphosphate (IP3) and ryanodine may be located in two functionally distinct Ca2+ stores. Are both these stores in the ER