caa a22 4500 469081791 CHVBK 20180323132952.0 cr unu---uuuuu 170328e19920401xx s 000 0 eng 10.1007/BF00338058 doi (NATIONALLICENCE)springer-10.1007/BF00338058 The alpha2-adrenergic receptor system in the hypothalamus of the Pekin duck [Elektronische Daten] [Andreas Müller, Rüdiger Gerstberger] Summary: In the present study, we have employed the monoradioiodinated α2-agonist clonidine ([125I]-CLO) to characterize duck hypothalamic α2-adrenoceptors and to localize α2-specific binding sites in the duck brain. To validate the α2-specificity of [125I]-CLO using an enriched duck hypothalamic membrane fraction, a radioreceptor assay was established by altering the membrane protein concentration, time, temperature and ionic milieu of incubation, and in the presence or absence of protease inhibitors. Competitive displacement studies revealed the following sequence of potency to displace [125I]-CLO: yohimbine>(-)-epinephrine>clonidine> (-)-norepinephrine>phentolamine>(-)-phenylephrine>(-)-isoproterenol>prazosin. The non-hydrolyzable guanosine 5′-triphosphate analog guanylylimidodiphosphate markedly inhibited [125I]-CLO binding suggestive of G-protein involvement. With regard to the histological distribution, diencephalic structures, such as the habenula and the nucleus reticularis of the thalamus, were densely labeled by [125I]-CLO. In the hypothalamus, α2-adrenoceptors were detected in the antidiuretic hormone-synthesizing nucleus paraventricularis, the nucleus praeopticus medialis, the nucleus anterior medialis hypothalami, the nucleus magnocellularis praeopticus, the nucleus commissurae pallii, the nucleus inferior hypothalami and the regio lateralis hypothalami. Circumventricular organs, such as the plexus choroidei, organum subfornicale, organum paraventriculare and the corpus pineale, were endowed with α2-specific binding sites, as were the cell layers of the tectum opticum. In addition, telencephalic structures revealed high receptor densities. The presence of well characterized α2-specific adrenoceptors in hypothalamic structures of the duck brain including associated telencephalic regions supports physiological investigations with regard to functional α2-adrenergic modulation of antidiuretic hormone release in the duck. Springer-Verlag, 1992 Alpha2 receptors nationallicence Hypothalamus nationallicence Circumventricular organs nationallicence Clonidine nationallicence G-protein nationallicence Domestic mallard nationallicence Müller Andreas Max-Planck-Institut für Physiologische und Klinische Forschung, W.G. Kerckhoff-Institut, Parkstrasse 1, W-6350, Bad Nauheim, Federal Republic of Germany aut Gerstberger Rüdiger Max-Planck-Institut für Physiologische und Klinische Forschung, W.G. Kerckhoff-Institut, Parkstrasse 1, W-6350, Bad Nauheim, Federal Republic of Germany aut Cell and Tissue Research Springer-Verlag 268/1(1992-04-01), 99-107 0302-766X 268:1<99 1992 268 441 https://doi.org/10.1007/BF00338058 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00338058 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Müller Andreas Max-Planck-Institut für Physiologische und Klinische Forschung, W.G. Kerckhoff-Institut, Parkstrasse 1, W-6350, Bad Nauheim, Federal Republic of Germany aut NATIONALLICENCE 700 1- Gerstberger Rüdiger Max-Planck-Institut für Physiologische und Klinische Forschung, W.G. Kerckhoff-Institut, Parkstrasse 1, W-6350, Bad Nauheim, Federal Republic of Germany aut NATIONALLICENCE 773 0- Cell and Tissue Research Springer-Verlag 268/1(1992-04-01), 99-107 0302-766X 268:1<99 1992 268 441 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer