Resolution of multiple affinity states of 5-hydroxytryptamine-1A receptors labelled by [3H]-8-hydroxy-2-(di-n-propilamino) tetralin in rat hippocampal membranes.
1. We examined the binding of [3H]-8-hydroxy-2-(DI-n-propilamino)tetralin ([3H]-8OH-DPAT) to 5-hydroxytriptamine-1A (5-HT1A) receptors in rat hippocampal membranes. 2. Computer analysis of [3H]-8OH-DPAT displacement curves in the absence and in the presence of 100 microM guanosine-5'-O-(3-thiotriphosphate) (GTP gamma S) were best fitted with a three-site model with apparent dissociation constants (Kd) of 0.45, 2.8 and 30 nM; the corresponding binding capacity (Bmax) existing in the three affinity states were 4, 2 and 12 pmol/g of tissue (wet weight), respectively. 3. These results suggest that [3H]-8OH-DPAT binding can be resolved as complex isotherms and we provided evidence that [3H]-8OH-DPAT labels 2 high-affinity GTP gamma S-sensitive and one low-affinity GTP gamma S-sensitive state of 5-HT1A receptors.
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Laboratoire de Neuroendocrinologie Experimentale, INSERM Unite 297, Faculte de Medecine Nord, Marseille, France.
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D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology*; D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D018492:Dopamine Antagonists / Q000494:pharmacology; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D008566:Membranes / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D011985:Receptors, Serotonin / Q000187:drug effects / Q000378:metabolism*; D017366:Serotonin Receptor Agonists / Q000494:pharmacology*; D013134:Spiperone / Q000494:pharmacology; D013816:Thermodynamics
D018492:Dopamine Antagonists; D011985:Receptors, Serotonin; D017366:Serotonin Receptor Agonists; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D013134:Spiperone; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin