IMMUNOHISTOCHEMICAL LOCALIZATION OF BIOACTIVE PEPTIDES AND AMINES ASSOCIATED WITH THE CHROMAFFIN TISSUE OF 5 SPECIES OF FISH

Biogenic peptides and amines associated with the chromaffin tissue in Atlantic cod (Gadus morhua), rainbow trout (Oncorhynchus mykiss), Euro pean eel (Anguilla anguilla), spiny dogfish (Squalus acanthias) and At lantic hagfish (Myxine glutinosa) were identified utilizing immunohist ochemical techniques. Within the posterior cardinal vein (PCV) in cod, trout and eel, a subpopulation of chromaffin cells displayed immunore activity to tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (D beta H) but not to phenylethanolamine-N-methyltransferase (PNNT). TH- like immunoreactivity was observed within cells in hagfish hearts. Ner ve fibres displaying vasoactive intestinal peptide (VIP) immunoreactiv ity and pituitary adenylyl cyclase activating peptide (PACAP) immunore activity innervated cod, trout and eel chromaffin cells. In eel, neuro peptide Y (NPY)like and peptide YY (PYY)-like immunoreactivity was loc ated within cells in the PCV, including chromaffin cells. Serotonin-li ke immunoreactivity was observed within eel and cod chromaffin cells a nd in hagfish hearts. In the dogfish axillary bodies, nerves displayin g TH-like, VIP-like, PACAP-like, substance P-like and galanin-like imm unoreactivity were observed. These results are compared with those of other vertebrates, and potential roles for these substances in the con trol of catecholamine release are suggested.