Colocalization of proenkephalin peptides in rat brain neurons

A serial, thin-section immunocytochemical study of the anatomical distribution of Leu-enkephalin and BAM-22P (an adrenal proenkephalin peptide) demonstrated that both immunoreactivities occur within the same neurons throughout brain. However, neither peptide immunoreactivity could be observed in neurons containing dynorphin A immunoreactivity. These results are consistent with the possibility that the enkephalin precursor in brain is similar to that sequenced in adrenal, but fail to support the hypothesis that the dynorphin precursor is a major source of Leu-enkephalin in brain.