The dogfish peptides scyliorhinin I and scyliorhinin II bind with differential selectivity to mammalian tachykinin receptors

The dogfish intestinal, linear tachykinin scyliorhinin I (SCYI) and cyclic tachykinin scyliorhinin II (SCYII) bound with differential selectivity to mammalian tachykinin, membrane receptor sites. SCYI bound with highest affinity to NK-1 sites in rat submandibular gland (KI = 0.9 nM) and to NK-2 sites in hamster urinary bladder (KI = 2 nM) whereas SCYII bound with highest affinity to NK-3 sites in rat cerebral cortex (KI = 2.5 nM). These results suggest that SCYI is a dual NK-1/NK-2 tachykinin receptor agonist while SCYII is an NK-3 selective tachykinin receptor agonist.