A SUGGESTIVE RELATIONSHIP OF NERVE CELL RNA WITH SPECIFIC SYNAPTIC SITES

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Abstract
In electron micrographs of the anterior gray column of the spinal cord of monkeys and of 2 juvenile chimpanzees, aggregates of ribosomes and endoplasmic reticulum, corresponding to ergastoplasm, were frequently noted to be in close apposition to the cell membrane in the region of proximal dendrites. This apposition did not appear to be random, but rather associated with overlying synaptic boutons of definable characteristics, namely, large size (3-6 [mu]), and densely packed and segregated masses of mitochondria and of "synaptic vesicles." Variation in amount of ribosomal material to be seen in subsynaptic relation to large boutons extended from large "Nissl bodies" to a subsynaptic cistern associated with a small scatter of ribosomes. It is possible that the subsurface cistern of Rosenblueth represents one extreme of a functional series of stages. Since ribosomal aggregates tend to avoid the cell and nuclear membranes in normal circumstances, the possibility is suggested that the large boutons on soma or proximal dendrites either possess special metabolic requirements associated with post-junctional protein synthesis, or perhaps a quantitatively greater need than other junctional regions on the adult motoneuron receptive surface. The possible role of subsynaptic ergastoplasm in the developing neuron is also discussed.