title: Transient serotonin-immunoreactive neurons coincide with a critical period of neural development in coho salmon (Oncorhynchus kisutch).
abstract: In coho salmon (Oncorhynchus kisutch), smolt transformation has been shown to be associated with sequential surges of neurotransmitters in the brain. In order to determine if the surge of serotonin (5-HT) is correlated with structural changes, we have used immunocytochemistry to observe changes in the serotonin immunoreactivity before, during and after the 5-HT surge. The following stages were studied: 12-month-old freshwater presmolts, 17-month-old freshwater presmolts, 18-month-old saltwater smolts, 19-month-old saltwater postsmolt, 24-month-old postsmolt, and adult spawners. In the 17-month-old samples, but not at any other stage, we found a set of transient (serotonin-immunoreactive) 5-HT-immunoreactive neurons in the lateral preoptic area, as well as a discrete population of 5-HT-immunoreactive neurons in the lateral part of the dorsal right habenular nucleus. In addition, a higher density of serotonergic fibers was found in the telencephalon at this stage compared to the following two stages. Since the transient 5-HT-immunoreactive structures presented here do not appear simultaneously with the 5-HT total brain concentration surge, we conclude that they are unlikely to be the source of the 5-HT surge, but are probably related to other developmental changes in the brain associated with smolt transformation.
authors.affiliation: Institute of Marine Science, University of Alaska, Fairbanks 99775-1080.
authors.forename: L O
authors.initials: LO
authors.lastname: Ebbesson
authors.forename: B
authors.initials: B
authors.lastname: Holmqvist
authors.forename: T
authors.initials: T
authors.lastname: Ostholm
authors.forename: P
authors.initials: P
authors.lastname: Ekström
mesh_terms: D000818:Animals; D000906:Antibodies; D001921:Brain / Q000033:anatomy & histology / Q000166:cytology / Q000254:growth & development*; D001923:Brain Chemistry; D007150:Immunohistochemistry; D009474:Neurons / Q000737:chemistry; D012474:Salmon / Q000254:growth & development*; D012701:Serotonin / Q000032:analysis*
chemical_list: D000906:Antibodies; D012701:Serotonin