The structure and function of the endoplasmic reticulum (ER) in neurons and glia are being investigated using newly developed techniques which make it possible to investigate the dynamic properties of the ER in living cells by video and laser scanning confocal microscopy. New techniques have been developed using sea urchin eggs as a model system. Sea urchin eggs have the advantages of being readily available, having a prominent ER, and being easy to microinject. A novel technique for specifically staining ER in living cells shows that the ER undergoes actin~dependent movements, that a striking change in its organization occurs as it becomes capable of releasing calcium at the time of calcium release, and that the appearance of microtubules has a profound effect on its organization. This technique has been applied to Purkinje neurons of the cerebellum in acute slices, where it shows that there is a continuous compartment of ER that extends from the cell body throughout the dendritic tree. The structure and dynamics of the ER is currently being investigated in hippocampal neurons in culture, where the ER may have a role in the establishment of axonal and dendritic polarity. A second initiative uses calcium~sensitive fluorescent indicators to investigate calcium regulation by the ER. Calcium increase during ciliary reversal has been detected, and calcium regulation in neurons in frog tadpoles is being investigated with these techniques.
