SPECIFIC PROCESSING OF ENDORPHINS IN RAT BRAIN

Abstract

Four peptides of similar size, which react with β-endorphin antisera, lipotropin C-Fragment (LPH 61-91), the C'-Fragment (LPH 61-87) and the α, N-acetyl derivatives of these peptides, are known to occur in porcine pituitary. Only the C-fragment exhibits potent opiate activity. We present evidence that the four peptides are also present in rat brain and methods have been developed for study of their regional distribution. Material with ‘β-endorphin’ immunoreactivity was localized by immunofluorescence and the reactive peptides were identified by immunoassay after extraction, gel filtration and ion exchange chromatography. The four peptides were found to be distributed differentially in regions where ‘β-endorphin’ had been demonstrated by immunofluorescence. In the hypothalamus, where intense fluorescence was seen, the C-Fragment was found to be the predominant immunoreactive peptide; in the mid-brain region the four peptides were present in more equivalent proportions; in the hippocampus, where there was a significant amount of β-endorphin fluorescence, the C'-Fragment was the major component. The results indicate that it is the hypothalamus and not the mid-brain or hippocampus which contains the potent opiate peptide.