Immunoreactive peptides related to dynorphin B (= rimorphin) in the rat brain

We have developed a radioimmunoassay for synthetic dynorphin B, a novel opioid tridecapeptide, which shares a common precursor molecule with dynorphin1-17 (= dynorphin A) and the neo-endorphins. The levels of immunoreactivity towards this peptide in rat brain and pituitary show a pattern quantitatively and qualitatively similar to those found for dynorphin A and alpha-neo-endorphin in earlier studies. The antiserum used was highly specific with only dynorphin-32 and dynorphin B-29, both of which contain the dynorphin B sequence, showing substantial cross-reactivity. Gel filtration of whole rat brain extracts in combination with HPLC analysis provide strong evidence for the existence of these latter two peptides in rat brain.