ANGIOTENSINOGEN-LIKE EPITOPES ARE PRESENT IN THE CNS OF APLYSIA-CALIFORNICA AND CO-LOCALIZE WITH UROTENSIN-I-LIKE AND UROTENSIN-II-LIKE IMMUNOREACTIVITIES IN THE CEREBRAL GANGLIA

IMMUNOHISTOCHEMISTRY was used to demonstrate urotensin I(UI), urotensi n II (UII), and angiotensinogen (Ao)-like immunoreactivities (ir) in t he CNS of Aplysia californica. The fish UI is a 41 amino acid peptide that has 50% identity with mammalian corticotropin-releasing factor (C RF). Identity also exists between UI and angiotensinogen in a tetrapep tide at the N-terminus. Ao-ir neurones were found in the F cluster of the Aplysia cerebral ganglia. Beaded Ao-ir fibres were seen in the neu ropile and commissure of the cerebral, pleural and pedal ganglia. Ao n eurosecretory material was also seen in the perineural region of the p roximal supralabial nerve. Previously we have demonstrated UI and UII immunoreactivities were present in the CNS of Aplysia. A comparison of adjacent sections of the cerebral ganglia immunostained sequentially for UI, UII and Ao revealed that all three immunoreactivities co-exist ed in the same cells of the F cluster of the cerebral ganglia. Liquid- phase immunoabsorption of the Ao antiserum revealed that porcine or hu man angiotensinogen but not UI or UII were able to quench Ao immunosta ining. Conversely UI and UII staining were quenched by white sucker (C atatomus commersoni) UI and goby (Gillichtys mirabilis) UII, respectiv ely, but they were not modified by angiotensinogen. These results sugg est that UI-, UII-, and Ao-like peptides might co-exist as separate en tities in the cerebral ganglia of Aplysia californica where they can a ct in an integrated and/or independent modulatory way.