Previous studies have revealed that zinc-enriched(ZEN) terminals are present in all parts of the CNS thoughwith great differences in intensity. The densest populationsof both ZEN terminals and ZEN somata are found in telencephalicstructures, but also structures like the spinal corddemonstrate impressive ZEN systems spreading terminalsseveral segments around the respective ZEN somata.The present study evaluates whether sympathetic neuronsin the superior cervical ganglia (SCG) are ZEN neurons,i.e. contain vesicles that have zinc transporter 3 (ZnT3) proteinsin their membranes and contain zinc ions.ZnT3 immunoreactivity (IR) was found in the somata andprocesses in the postganglionic neurons of mouse SCG.Only a small fraction of neurons (less than 5%), expressedvarying degrees of ZnT3. Colchicine treatment, however, increasedthe number of ZnT3-positive neurons three-fold, suggestingan accumulation of ZnT3 protein in the somata. Asmall proportion of the postganglionic axons revealed dottedaccumulations of ZnT3 IR along their courses. Double labelingshowed that all ZnT3-positive neurons and axons werealso tyrosine hydroxylase-positive with strong immunofluorescence,while no colocalization was found between ZnT3and the vesicular acetylcholine transporter (VAChT) or neuropeptideY IR. VAChT-positive preganglionic neurons werefound to terminate on ZnT3 neuronal somata.6-Methoxy 8-para toluene sulfonamide quinoline fluorescenceand zinc selenium autometallography (ZnSeAMG) revealedthat a subgroup of SCG cells contained free or looselybound zinc ions. It is therefore concluded that ZnT3 and zincions are present in a subpopulation of TH-positive, NPYnegativeneurons in the rodent SCG, supporting the notionthat vesicular zinc ions may play a special role in the peripheralsympathetic adrenergic system.