AbstractRegional binding of norepinephrine to tissue structures occurs in sections of brain tissue incubatedin vitrowith tritiated norepinephrine, followed by radioautography. The binding probably represents one of the mechanisms involved in the uptake and storage of catecholamines by nerve cells. Applying this method to a study of human brains showed excessively strong binding of norepinephrine at the surface membranes of pigmented nerve cells in the substantia nigra, nucleus coeruleus, nucleus dorsalis vagi, and others. Such excessive binding was not found in nonpigmented nuclei in the human brain nor in rat brain. The arrangement of sites of binding at the cell membranes strongly suggested synaptic endings. Melanin pigmentation of nerve cells may be related to the amount of catecholamine‐containing synapses at the surface of the neuron