C-peptide immunoreactive neurons in human brain.

C-peptide/C-peptide-like immunoreactivity was shown to be present in the cytoplasm of the soma and the proximal part of apical dendrites of some pyramidal cells in the Neocortex (Gyrus precentralis) and Hippocampus of man. C-peptide (connecting peptide) is a metabolic product in insulin biosynthesis and its localization in neurons is a proof for extrapancreatic insulin production.