The 5HT(1A) receptor ligand, S15535, antagonises G-protein activation: a [35S]GTPgammaS and [3H]S15535 autoradiography study.
4-(Benzodioxan-5-yl)1-(indan-2-yl)piperazine (S15535) is a highly selective ligand at 5-HT(1A) receptors. The present study compared its autoradiographic labelling of rat brain sections with its functional actions, visualised by guanylyl-5'-[gamma-thio]-triphosphate ([35S]GTPgammaS) autoradiography, which affords a measure of G-protein activation. [3H]S15535 binding was highest in hippocampus, frontal cortex, entorhinal cortex, lateral septum, interpeduncular nucleus and dorsal raphe, consistent with specific labelling of 5-HT(1A) receptors. In functional studies, S15535 (10 microM) did not markedly stimulate G-protein activation in any brain region, but abolished the activation induced by the selective 5-HT(1A) agonist, (+)-8-hydroxy-dipropyl-aminotetralin ((+)-8-OH-DPAT, 1 microM), in structures enriched in [3H]S15535 labelling. S15535 did not block 5-HT-stimulated activation in caudate nucleus or substantia nigra, regions where (+)-8-OH-DPAT was ineffective and [3H]S15535 binding was absent. Interestingly, S15535 attenuated (+)-8-OH-DPAT and 5-HT-stimulated G-protein activation in dorsal raphe, a region in which S15535 is known to exhibit agonist properties in vivo [Lejeune, F., Millan, M.J., 1998. Induction of burst firing in ventral tegmental area dopaminergic neurons by activation of serotonin (5-HT)(1A) receptors: WAY100,635-reversible actions of the highly selective ligands, flesinoxan and S15535. Synapse 30, 172-180.]. The present data show that (i) [3H]S15535 labels pre- and post-synaptic populations of 5-HT(1A) sites in rat brain sections, (ii) S15535 exhibits antagonist properties at post-synaptic 5-HT(1A) receptors in corticolimbic regions, and (iii) S15535 also attenuates agonist-stimulated G-protein activation at raphe-localised 5-HT(1A) receptors.
Newman-Tancredi
A
A
Department of Psychopharmacology, Institut de Recherches Servier, 125 Chemin de Ronde, F-78290 Croissy-sur-Seine, Paris, France. newman_tancredi@hotmail.com
Rivet
J
J
Chaput
C
C
Touzard
M
M
Verrièle
L
L
Millan
M J
MJ
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000378:metabolism; D000818:Animals; D001345:Autoradiography; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D066298:In Vitro Techniques; D008024:Ligands; D008297:Male; D010879:Piperazines / Q000378:metabolism / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D011985:Receptors, Serotonin / Q000378:metabolism*; D044263:Receptors, Serotonin, 5-HT1; D012701:Serotonin / Q000378:metabolism; D017366:Serotonin Receptor Agonists / Q000378:metabolism / Q000494:pharmacology*; D013462:Sulfur Radioisotopes; D014316:Tritium
D008024:Ligands; D010879:Piperazines; D011985:Receptors, Serotonin; D044263:Receptors, Serotonin, 5-HT1; D017366:Serotonin Receptor Agonists; D013462:Sulfur Radioisotopes; D014316:Tritium; C079549:4-(benzodioxan-5-yl)-1-(indan-2-yl)piperazine; D012701:Serotonin; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D019204:GTP-Binding Proteins