CONTINUOUS NETWORK OF ENDOPLASMIC-RETICULUM IN CEREBELLAR PURKINJE NEURONS

Purkinje neurons in rat cerebellar slices injected with an oil drop sa turated with -dihexadecyl-3,3,3',3'-tetramethylindocarbocyanine perchl orate [DiIC(16)(3)) or DiI] to label the endoplasmic reticulum were ob served by confocal microscopy. DiI spread throughout the cell body and dendrites and into the axon. DB spreading is due to diffusion in a co ntinuous bilayer and is not due to membrane trafficking because it als o spreads in fixed neurons. DiI stained such features of the endoplasm ic reticulum as densities at branch points, reticular networks in the cell body and dendrites, nuclear envelope, spines, and aggregates form ed during anoxia in low extracellular Ca2+. In cultured rat hippocampa l neurons, where optical conditions provide more detail, DiI labeled a clearly delineated network of endoplasmic reticulum in the cell body. We conclude that there is a continuous compartment of endoplasmic ret iculum extending from the cell body throughout the dendrites. This com partment may coordinate and integrate neuronal functions.