Enkephalin convertase localization by [3H]guanidinoethylmercaptosuccinic acid autoradiography: selective association with enkephalin-containing neurons.

Enkephalin convertase, an enkephalin-forming carboxypeptidase, is potently inhibited by guanidinoethylmercaptosuccinic acid (GEMSA). We have localized enkephalin convertase in rat brain by in vitro autoradiography with [3H]GEMSA. [3H]GEMSA-associated silver grains are highly concentrated in the median eminence, bed nucleus of the stria terminalis, lateral septum, dentate gyrus, hippocampus, central nucleus of the amygdala, preoptic hypothalamus, magnocellular nuclei of the hypothalamus, interpeduncular nucleus, dorsal parabrachial nucleus, locus coeruleus, nucleus of the solitary tract, and the substantia gelatinosa of the spinal trigeminal tract. This distribution corresponds closely with immunocytochemical localizations of enkephalin-containing cells and axons, indicating that enkephalin convertase is selectively involved in enkephalin biosynthesis.