Laminaris During Deafferentation-Induced Dendritic Atrophy

N. laminaris dendrites begin to atrophy almost immediately after they are deafferented. Accompanying this rapid change in shape is a loss of microtubules and neurofilaments at the base of the dendrite, and a decrease in tbe density ofthe dendritic cytoplasm. However, degenerative changes in the dendritic plasma membrane were not evident until 2 days after deafferentation. Thus it was unknown what happened to the volume and membrane lost from the atrophying dendrites before this time. The soma was investigated in this study as a possible recipient of tbe volume of the atrophying dendrite. Soma size increased significantly by 2 hours after deafferentation and continued to increase for 1-8 days after deafferentation. The nucleus, which is normally concentric with the soma, moved continuously to the dorsal pole of the soma, toward the innervated side of the cell. The cytoplasm on the ventral side of the soma showed a decrease in density and loss of cytoskeleton similar to what was found in the initial portion of the ventral primary dendrites in the accompanying paper. These changes are interpreted as indicative of a rapid resorption of the ventral dendrite back into the soma following deafferentation.