Premium
Localization and quantification of melatonin receptors in the diencephalon and posterior telencephalon of the sheep brain
Author(s) -
Chabot V.,
Caldani M.,
Reviers M.M.,
Pelletier J.
Publication year - 1998
Publication title -
journal of pineal research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.881
H-Index - 131
eISSN - 1600-079X
pISSN - 0742-3098
DOI - 10.1111/j.1600-079x.1998.tb00365.x
Subject(s) - diencephalon , cerebrum , melatonin , stria terminalis , coronal plane , nucleus , biology , receptor , melatonin receptor , endocrinology , hypothalamus , anatomy , medicine , pineal gland , central nervous system , neuroscience , biochemistry
Chabot V, Caldani M, de Reviers MM, Pelletier J. Localization and quantification of melatonin receptors in the diencephalon and posterior telencephalon of the sheep brain. J. Pineal Res. 1998; 24:50–57. © Munksgaard, Copenhagen Abstract In an attempt to better understand the mechanisms by which melatonin controls neuroendocrine activity, we tried to define with accuracy the brain areas where the density of melatonin receptors is the highest in sheep and to establish their characteristics. The specific labelling of 125 I‐melatonin was first revealed by autoradiography on brain sections of the posterior telencephalon and diencephalon in three ewes. The extent and position of the five structures where the binding was found to be the highest (i.e., the pars verticalis and pars horizontalis of the nucleus tractus diagonalis, the septal area, the bed nucleus of the stria terminalis, and the ventromedial hypothalamic area) were then accurately defined by image analysis. In comparison to the landmarks given by image analysis, photographs of coronal sections of another ewe permitted the accurate definition of the limits of the structures to be punched in a second step. In six ewes, each of the five structures previously identified were punched from frozen coronal sections and binding of 125 I‐melatonin to membrane preparations was studied individually by Scatchard analysis. The correlation coefficient between the B/F ratio and binding (B) was in the range of 0.96–0.98, indicating that a precise quantification was possible in these different structures. The Bmax was the highest in the bed nucleus of the stria terminalis, the septal area, and the ventromedial hypothalamic area (1.38, 1.25, and 0.95 fmol/mg protein, respectively). All Kd values were less than 10 pM and the Hill coefficient was close to 1, indicating the presence of a single class of receptor to 125 I‐melatonin. These results indicate the reliability of a method used to measure with accuracy low concentrations of melatonin receptors in brain structures. In addition, the ventromedial hypothalamic area was found to be rich in melatonin receptors. This region is known to be involved in the central gonadotrope control in sheep.