title: Daily variations in melatonin binding sites in the masu salmon brain.
abstract: Daily variations in melatonin binding sites in the brain of underyearling masu salmon Oncorhynchus masou were examined by radioreceptor assay using 2-[125I]iodomelatonin as the radioligand. Fish were reared under a natural photoperiod in July and sampled eight times at 3 h intervals from 12:00 to 09:00 h. Plasma melatonin levels showed robust daily rhythms in both precocious males and immature females, with high and low levels during night and day, respectively. The affinity (Kd) and density (Bmax) of melatonin binding sites in the brain also showed similar variations. There were significant positive correlations between the plasma melatonin levels and the Kd or the Bmax in immature females and between the Kd and Bmax values in both precocious males and immature females. These results indicate that melatonin binding sites in the brain showed daily variations under a natural photoperiod in masu salmon.
authors.affiliation: School of Fisheries Sciences, Kitasato University, Ofunato, Iwate 022-0101, Japan. amanoma@kitasato-u.ac.jp
authors.forename: Masafumi
authors.initials: M
authors.lastname: Amano
authors.forename: Masayuki
authors.initials: M
authors.lastname: Iigo
authors.forename: Kazumasa
authors.initials: K
authors.lastname: Ikuta
authors.forename: Shoji
authors.initials: S
authors.lastname: Kitamura
authors.forename: Kunio
authors.initials: K
authors.lastname: Yamamori
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000378:metabolism*; D001923:Brain Chemistry; D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D007456:Iodine Isotopes / Q000378:metabolism; D008297:Male; D008550:Melatonin / Q000378:metabolism*; D017683:Oncorhynchus; D012737:Sex Factors
chemical_list: D007456:Iodine Isotopes; D008550:Melatonin