@article {Waeber623, author = {Christian Waeber and Michael A. Moskowitz}, title = {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}, volume = {52}, number = {4}, pages = {623--631}, year = {1997}, doi = {10.1124/mol.52.4.623}, publisher = {American Society for Pharmacology and Experimental Therapeutics}, abstract = {[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.}, issn = {0026-895X}, URL = {https://molpharm.aspetjournals.org/content/52/4/623}, eprint = {https://molpharm.aspetjournals.org/content/52/4/623.full.pdf}, journal = {Molecular Pharmacology} }