title: Characterization of 5-HT1A receptor-mediated [35S]GTPgammaS binding in rat hippocampal membranes.
abstract: Stimulation of [35S]GTPgammaS binding by serotonin (5-hydroxytryptamine, 5-HT) receptor ligands was characterized in rat hippocampal membranes. The optimized assay contained 30-50 microg protein, 300 microM GDP and 0.1 nM [35S]GTPgammaS, incubated at 37 degrees C for 20 min. At 10 microM, the 5-HT1A receptor agonist R(+)-8-hydroxy-2-(di-n-propylamino)tetralin [R(+)-8-OH-DPAT] stimulated GTPgammaS binding from 27.1 +/- 2.5 to 45.7 +/- 4.2 fmol/mg protein. Increasing the protein concentration did not affect the absolute difference between basal and maximal GTPgammaS binding nor the EC50, but decreased the percent stimulation. The non-selective agonists serotonin and 5-carboxamidotryptamine were 30-35% more efficacious, whereas the partial agonists buspirone and S(-)-8-hydroxy-2-(di-n-propylamino)tetralin stimulated GTPgammaS binding by 19 +/- 1 and 43 +/- 3%, respectively, compared to R(+)-8-OH-DPAT. Neither the 5-HT2 receptor agonist [(+/-)1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane HCl] (DOI) nor the 5-HT1A receptor antagonists WAY 100,635 (n-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-n-(2-pyridinyl) cyclohexanecarboxamide trihydrochloride) and spiperone altered basal GTPgammaS binding. WAY 100,635 abolished the effect of R(+)-8-OH-DPAT, but only reduced the effect of serotonin by 88 +/- 3%. Finally, methiothepin antagonized R(+)-8-OH-DPAT-stimulated GTPgammaS binding and reduced basal GTPgammaS binding by itself. The reduction was not affected by WAY 100,635. We have characterized a method to assess functional activity at 5-HT1A receptors in rat hippocampal membranes by measuring agonist-induced [35S]GTPgammaS binding.
authors.affiliation: Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City 66160-7417, USA. ralper@kumc.edu
authors.forename: R H
authors.initials: RH
authors.lastname: Alper
authors.forename: D L
authors.initials: DL
authors.lastname: Nelson
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D005625:Frontal Lobe / Q000187:drug effects / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism*; D006153:Guanosine Diphosphate / Q000494:pharmacology; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008719:Methiothepin / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D011485:Protein Binding; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011985:Receptors, Serotonin / Q000378:metabolism*; D044263:Receptors, Serotonin, 5-HT1; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D013134:Spiperone / Q000494:pharmacology; D013462:Sulfur Radioisotopes; D013696:Temperature
chemical_list: D010879:Piperazines; D011725:Pyridines; D011985:Receptors, Serotonin; D044263:Receptors, Serotonin, 5-HT1; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D013462:Sulfur Radioisotopes; D006153:Guanosine Diphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D013134:Spiperone; D008719:Methiothepin; C090413:N-(2-(4-(2-methoxyphenyl)-1-piperazinyl)ethyl)-N-(2-pyridinyl)cyclohexanecarboxamide