Abstract
A method is presented for monitoring the coupling of the alpha(2)-adrenoceptor, as well as other receptors, to their G proteins using the GTP-induced shift in agonist affinity states. In tissue sections GTP, but not ATP, induces a robust decrease in agonist affinity of greater than 100-fold, which is much larger than previously found in membrane preparations. A sensitive and easy procedure to monitor the extent of coupling is to compare the amount of [(3)H]RX821002 binding remaining in the presence of 100 nM brimonidine in the absence and presence of 100 microM GTP. This method should be especially applicable for determining the extent of coupling of receptors to their G proteins in multiple brain regions using autoradiographic procedures.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Adrenergic alpha-2 Receptor Agonists*
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Adrenergic alpha-Agonists / pharmacology
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Adrenergic alpha-Antagonists / pharmacology
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Animals
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Binding, Competitive / drug effects
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Binding, Competitive / physiology
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Brain / cytology
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Brain / drug effects*
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Brain / metabolism
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Brimonidine Tartrate
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GTP-Binding Proteins / drug effects*
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GTP-Binding Proteins / metabolism*
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Guanosine Triphosphate / analogs & derivatives
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Guanosine Triphosphate / metabolism
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Guanosine Triphosphate / pharmacology*
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Idazoxan / analogs & derivatives*
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Idazoxan / pharmacology
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Microtomy / methods
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Nucleotides / chemistry
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Nucleotides / pharmacology
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Protein Binding / drug effects
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Protein Binding / physiology
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Quinoxalines / pharmacology
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Radioligand Assay / methods*
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Rats
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Rats, Sprague-Dawley
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Receptors, Adrenergic, alpha-2 / metabolism*
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Tritium / pharmacology
Substances
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Adrenergic alpha-2 Receptor Agonists
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Adrenergic alpha-Agonists
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Adrenergic alpha-Antagonists
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Nucleotides
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Quinoxalines
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Receptors, Adrenergic, alpha-2
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Tritium
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Brimonidine Tartrate
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Guanosine Triphosphate
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2-methoxyidazoxan
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GTP-Binding Proteins
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Idazoxan