Neuropeptides 5. 501-504, 1985 ANALYSIS OF OPIOID AND NON-OPIOID END PRODUCTS OF PRO-DYNORPHIN IN SUBSTANTIA NIGRA OF THE RAT

The substantia nigra is among the richest pro-dynorphin terminal field regions in the rat brain. We therefore contrasted processing in this area to the known processing in the posterior pituitary. Fractionation of acid extracts of the posterior pituitary by gel filtration followed by analysis by radioimmunoassay indicated that the molar ratio of dynorphin A(l-17) to dynorphin A(l-8) averaged 1:2. The levels of dynorphin A-related end products t0 a-neo-endorphin and bridge peptide (a 2K nonopioid end product of pro-dynorphin) were approximately equimolar; however, the levels of dynorphin B-sized material were 50% lower than dynorphin A levels. Similar analyses of acid extracts of the substantia nigra also indicated that the levels of dynorphin A, a-neo-endorphin, and bridge pept ide were approximately equimolar. In this terminal field the levels of dynorphin B-sized material were approximately 60% lower than dynorphin A. A striking feature of the nigral system was that the molar ratio of dynorphin A(l-17) to dynorphin A(l-8) averaged 1:16. Thus, in the nigra, dynorphin A(l-17) is primarily a biosynthetic intermediate rather than as an end product.