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Circadian variations in melatonin‐binding sites in discrete areas of the male rat brain
Author(s) -
Zisapel Nava,
Nir Isaac,
Laudon Moshe
Publication year - 1988
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(88)80411-3
Subject(s) - melatonin , hypothalamus , circadian rhythm , medicine , endocrinology , striatum , binding site , darkness , biology , period (music) , central nervous system , chemistry , biochemistry , dopamine , botany , physics , acoustics
The binding of 125 I‐melatonin to synaptosomes prepared from whole brains of male rats of the CD strain and from the brain, hypothalamus and striatum of male rats of the Sabra‐Wistar strain was assessed throughout a 24 h period. The animals were maintained under a daily schedule of 14 h light (05:00–19:00 h) and 10 h darkness. In whole brain preparations the density of binding sites at 18:00 h was higher by about 70% than at 02:00 h with no variations in apparent affinity of the binding sites throughout the daily period. Specific binding of 125 I‐melatonin was found in both hypothalamus and striatum of the male rat with a distinct diurnal variation in binding site density in the hypothalamus only. The density of 125 I‐melatonin‐binding sites in the hypothalamus was maximal between 10:00 and 18:00 h and dropped sharply after the lights went off. The apparent 125 I‐melatonin‐binding affinities in these regions were constant and very similar to those in whole brain preparations. The daily variations in densities of 125 I‐melatonin‐binding sites in discrete brain areas may represent a diurnal rhythmicity in the responsiveness of the neuroendocrine axis to melatonin.