An electron-microscopic study of cholinesterase distribution in the rat adrenal medulla

The distribution of cholinesterase activity in the rat adrenal medulla was studied after initial fixation with glutaraldehyde, which preserves the osmiophilia of the noradrenaline-containing cells. Staining for true cholinesterase activity was associated with all the identifiable elements of the preganglionic sympathetic innervation. The morphology and enzyme staining of the endings on the chromaffin cells was similar to that seen in cholinergic synapses in the central nervous system. The endings contained occasional dense-cored vesicles and the possible significance of such vesicles at an undoubted cholinergic synapse is discussed. Staining for pseudocholinesterase activity, by contrast, was associated particularly with the Schwann cells and to a lesser extent with the chromaffin cells, but not with the axons and their processes.