DOPAMINE AND SEROTONIN IN THE TROUT (ONCORHYNCHUS-MYKISS) PITUITARY -MAIN METABOLITES AND CHANGES DURING GONADAL RECRUDESCENCE

Monoamine neurotransmitters and their metabolites in the trout pituita ry have been studied. Dopamine (DA), serotonin (5HT), dihydroxyphenyla cetic acid (DOPAC), and 5-hydroxyindoleacetic acid (5HIAA) were separa ted as pure peaks by HPLC. Peak purity and identity were confirmed by electrochemical behavior. However, measurable amounts of the O-methyla ted DA metabolites 3-methoxytyramine and homovanillic acid were not de tected in pituitary glands of different-aged trout or during the repro ductive cycle. Treatment with L-DOPA or DA increased DOPAC levels, whe reas O-methylated DA metabolites remained undetectable. Thus, MAO may be the major, if not the only, enzyme involved in DA catabolism in tro ut pituitary. A pronounced decline in dopaminergic turnover, measured as the DOPAC/DA ratio, was seen as gonadal recrudescence developed. 5H T or 5HIAA levels were not associated with reproductive status. (C) 19 96 Academic Press, Inc.