Autoradiography of serotonin 5-HT1A receptor-activated G proteins in guinea pig brain sections by agonist-stimulated [35S]GTPgammaS binding.
G protein activation mediated by serotonin 5-HT1A and 5-HT(1B/D) receptors in guinea pig brain was investigated by using quantitative autoradiography of agonist-stimulated [35S]GTPgammaS binding to brain sections. [35S]GTPgammaS binding was stimulated by the mixed 5-HT1A/5-HT(1B/D) agonist L694247 in brain structures enriched in 5-HT1A binding sites, i.e., hippocampus (+140 +/- 14%), dorsal raphe (+70 +/- 8%), lateral septum (+52 +/- 12%), cingulate (+36 +/- 8%), and entorhinal cortex (+34 +/- 5%). L694247 caused little or no stimulation of [35S]GTPgammaS binding in brain regions with high densities of 5-HT(1B/D) binding sites (e.g., substantia nigra, striatum, central gray, and dorsal subiculum). The [35S]GTPgammaS binding response was antagonized by WAY100635 (10 microM) and methiothepin (10 microM). In contrast, the 5-HT1B inverse agonist SB224289 (10 microM) did not affect the L694247-mediated [35S]GTPgammaS binding response, and the mixed 5-HT(1B/D) antagonist GR127935 (10 microM) yielded a partial blockade. The distribution pattern of the [35S]GTPgammaS binding response and the antagonist profile suggest the L694247-mediated response in guinea pig brain to be mediated by 5-HT1A receptors. In addition to L694247, 8-hydroxy-2-(di-n-propylamino)tetralin, and flesinoxan also stimulated [35S]GTPgammaS binding; their maximal responses varied between 46 and 52% compared with L694247, irrespective of the brain structure being considered. Sumatriptan, rizatriptan, and zolmitriptan (10 microM) stimulated [35S]GTPgammaS binding in the hippocampus by 20-50%. Naratriptan, CP122638, and dihydroergotamine stimulated [35S]GTPgammaS binding to a similar level as L694247 in hippocampus, lateral septum, and dorsal raphe. It appears that under the present experimental conditions, G protein activation through 5-HT1A but not 5-HT(1B/D) receptors can be measured in guinea pig brain sections.
Dupuis
D S
DS
Department of Cellular and Molecular Biology, Centre de Recherche Pierre Fabre, Castres, France.
Palmier
C
C
Colpaert
F C
FC
Pauwels
P J
PJ
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology; D000818:Animals; D001345:Autoradiography; D001923:Brain Chemistry; D019204:GTP-Binding Proteins / Q000032:analysis* / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism / Q000494:pharmacology*; D006168:Guinea Pigs; D006624:Hippocampus / Q000737:chemistry; D008297:Male; D010069:Oxadiazoles / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D011903:Raphe Nuclei / Q000737:chemistry; D044302:Receptor, Serotonin, 5-HT1B; D011985:Receptors, Serotonin / Q000032:analysis* / Q000502:physiology; D044263:Receptors, Serotonin, 5-HT1; D012686:Septal Nuclei / Q000737:chemistry; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D013462:Sulfur Radioisotopes; D014363:Tryptamines / Q000494:pharmacology
D010069:Oxadiazoles; D010879:Piperazines; D044302:Receptor, Serotonin, 5-HT1B; D011985:Receptors, Serotonin; D044263:Receptors, Serotonin, 5-HT1; D017366:Serotonin Receptor Agonists; D013462:Sulfur Radioisotopes; D014363:Tryptamines; C085632:L 694247; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C056895:flesinoxan; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D019204:GTP-Binding Proteins