[The co-localization of monoamines and enkephalins in the central nervous system]

After examination of some particular methodological problems concerning the visualization of monoaminergic and "enkephalin containing" central neurones, the colocalisation of enkephalins in certains monoaminergic neurones is reported. Thus, in rat and cate raphe nuclei many serotoninergic cell bodies display enkephalin-like immunoreactivity (ELI). In the cat locus coeruleus complex most catecholaminergic neurones contain ELI. Further, the synthesis in situ of enkephalins is strongly suggested by the fact that synenkephalin-like immunoreactivity is also detected in these monoaminergic neurones. Synenkephalin is the N terminal part to the bovine medullosurrenal pro-enkephalin. Monoamine-enkephalin colocalisation has been shown in peripheral neurones and adrenal medulla. The possible functionnal significance of the coexistence of monoamine-enkephalins in neurones is discussed. In particular, some hypothetical levels of interaction are considered.