Localization and identification of gamma-endorphin and beta-endorphin-like peptides in the hypothalamus and ventral forebrain of the rat

Gamma-endorphin (γE) and related peptides were localized in the brain of the rat, and compared to the distribution of β-endorphin related peptides. γE-like immunoreactivity (γE-LI) was shown to exist only in brain regions known to receive innervation from POMC neurons but not in their pericaria in the arcuate nucleus. Nuclei of the hypothalamus and ventral forebrain contained the major concentration of γE-hl and extracts from these regions were purified and subjected to HPLC in order to identify γE-related peptides. γE, des-tyrosine γE, des-enkephalin-γE, and α-N acetyl γE co-elutable peptides as well as various unidentified forms were evident. This study provides evidence of the endogenous presence of pharmacologically active γE-related peptides in brain regions where they have been postulated to modulate dopaminergic transmission.