Specific protein metabolism in identifiable neurons of Aplysia californica

The patterns of protein metabolism of identified cholinergic (R₂, L₁₀, and L₁₁) and neurosecretory (R_3–13, R₁₄, and Bag cells) cells were analyzed with the use of SDS‐polyacrylamide gel electrophoresis and isoelectric focusing. L₁₁ was unique amongst the three cholinergic neurons in its relatively high rate of incorporation of labeled leucine into proteins at 12,000 daltons. All the neurosecretory cells incorporated relatively large quantities of ³H‐leucine into small proteins (<12,000 daltons), which were concentrated in putative neurosecretory granule fractions of these cells. R_3–13 and R₁₄ synthesized a distinct basic protein which appeared specifically in the branchial nerve which contains the axons of these cells. The combination of these two analytical electrophoretic techniques allowed for the characterization of protein specificity in single nerve cells.