RT Journal Article SR Electronic T1 5-Hydroxytryptamine1A and 5-Hydroxytryptamine1B Receptors Stimulate [35S]Guanosine-5′-O-(3-thio)triphosphate Binding to Rodent Brain Sections as Visualized by In Vitro Autoradiography JF Molecular Pharmacology JO Mol Pharmacol FD American Society for Pharmacology and Experimental Therapeutics SP 623 OP 631 DO 10.1124/mol.52.4.623 VO 52 IS 4 A1 Christian Waeber A1 Michael A. Moskowitz YR 1997 UL http://molpharm.aspetjournals.org/content/52/4/623.abstract AB [35S]Guanosine-5′-O-(3-thio)triphosphate ([35S]GTPγS) binding to G proteins was measured byin vitro autoradiography in guinea pig and rat brain sections after activation by 5-hydroxytryptamine (5-HT) receptor agonists. 5-Carboxamidotryptamine stimulated binding strongly in hippocampus and lateral septum and weakly in substantia nigra. This effect was blocked in the substantia nigra by the 5-HT1B/1Dreceptor antagonist GR-127,935 and in the former two regions by the 5-HT1A antagonist NAN-190. 5-HT1B/1D receptor agonists stimulated binding in substantia nigra and in areas containing 5-HT1A receptors. In guinea pig substantia nigra, 5-(nonyloxy)-tryptamine maximally stimulated [35S]GTPγS binding by 54%, with an EC50 value of 62 nm; at 100 μm, this agonist increased binding by ∼200% in hippocampus (with a 2-fold weaker EC50 value). The distribution of [3H]8-OH-DPAT binding sites was identical to that of the [35S]GTPγS labeling stimulated by the 5-HT1A agonist (R)-8-hydroxy-2-dipropylaminotetralin [(R)-8-OH-DPAT)]. (R)-8-OH-DPAT, (S)-8-OH-DPAT, and buspirone stimulated [35S]GTPγS binding in hippocampus by 340%, 140%, and 78%, with EC50 values of 71, 51, and 132 nm. Enhanced [35S]GTPγS binding was not detected in the presence of 5-HT1F, 5-HT2, 5-HT4, and 5-HT7 receptor agonists. Because activation of μ-opioid, muscarinic M2, histamine H3, and cannabinoid receptors was also visualized successfully, these data suggest that only receptors coupled to pertussis toxin-sensitive G proteins can be seen by [35S]GTPγS binding autoradiography. This study also shows that different 5-HT receptors coupled to these proteins can show a wide range of [35S]GTPγS binding stimulation. Although the functional significance of these variations is unclear, this technique offers advantages over receptor autoradiography because it does not require high affinity radioligands and provides a measure of agonist efficacies in various brain regions.