G‐protein activation at 5‐HT1A receptors by the 5‐ht1F ligand LY334370 in guinea‐pig brain sections and recombinant cell lines

• Published in: British journal of pharmacology Vol. 124; no. 2; pp. 283 - 290
• Main Authors: Dupuis, Delphine S, Colpaert, Francis C, Pauwels, Petrus J
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.05.1998; Nature Publishing
• Subjects: 5‐ht1F and 5‐HT1A receptor; [35S]‐GTPγS binding and autoradiography; Aminopyridines - metabolism; Animals; Autoradiography; Benzamides - pharmacology; Binding Sites; Binding, Competitive; Biological and medical sciences; Brain - drug effects; Brain - metabolism; GTP-Binding Proteins - metabolism; Guanosine 5'-O-(3-Thiotriphosphate) - metabolism; Guinea Pigs; guinea‐pig brain; G‐protein activation; HeLa Cells; Hippocampus - metabolism; Humans; Indoles - pharmacology; Male; Medical sciences; Neuropharmacology; Neurotransmitters. Neurotransmission. Receptors; Pharmacology. Drug treatments; Piperazines - metabolism; Piperazines - pharmacology; Pyridines - pharmacology; Raphe Nuclei - drug effects; Raphe Nuclei - metabolism; Receptors, Serotonin - drug effects; Receptors, Serotonin - metabolism; Receptors, Serotonin, 5-HT1; recombinant h 5‐HT1A cell lines; Serotonin - analogs & derivatives; Serotonin - metabolism; Serotonin Antagonists - metabolism; Serotonin Antagonists - pharmacology; Serotonin Receptor Agonists - pharmacology; Serotoninergic system; Sumatriptan - metabolism; Agonist; GTP; Serotonin; Rodentia; Central nervous system; Activation; 5-HT1 Serotonine receptor; Catecholamine; In vitro; Biological activity; Vertebrata; Biological fixation; Mammalia; Guinea pig; Animal; Established cell line; Brain (vertebrata); G protein
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1038/sj.bjp.0701832

G‐protein activation by the 5‐ht1F receptor agonist 5‐(4‐fluorobenzoyl)amino‐3‐(1‐methylpiperidin‐4‐yl)‐1H‐indole fumarate (LY334370) was investigated by use of autoradiography of receptor‐activated G‐proteins in guinea‐pig brain sections and [35S]‐GTPγS binding responses in cell lines stably expressing human 5‐HT1A (h 5‐HT1A) receptors. LY334370 (10 μM) caused little or no stimulation of [35S]‐GTPγS binding in guinea‐pig brain regions enriched in 5‐ht1F binding sites (e.g., claustrum, caudate/putamen and thalamic nuclei), as identified by labelling with 10 nM [3H]‐sumatriptan plus 10 nM 5‐carboxamidotryptamine (5‐CT). Application of LY334370 (10 μM) to guinea‐pig brain sections resulted in an increase of [35S]‐GTPγS binding in hippocampus (123±17%), lateral septum (58±14%), dorsal raphe (57±10%), entorhinal (37±11%) and cingulate cortex (28±10%). This distribution fits with the G‐protein activation mediated by 5‐HT1A receptors as found with lisuride (10 μM), and labelling of 5‐HT1A receptors by 140 pM [125I]‐4‐(2′‐methoxy‐phenyl)‐1‐[2′‐(n‐2′′‐pyridinyl)‐p‐iodobenzamido]‐ethyl‐piperazine (p‐MPPI). The LY334370‐mediated [35S]‐GTPγS response was antagonized by the selective, silent 5‐HT1A receptor antagonist N‐[2‐[4‐(2‐methoxyphenyl)1‐piperazinyl]ethyl]‐N‐(2‐pyridinyl)cyclohexanecarboxamide (WAY100635, 1 μM) in each of the brain structures investigated. The distribution pattern of the [35S]‐GTPγS binding response and the antagonist profile suggest that the LY334370‐induced response in guinea‐pig brain is mediated by 5‐HT1A receptors. The maximal LY334370‐induced [35S]‐GTPγS binding response (83 to 94%) in membranes of recombinant C6‐glial/h 5‐HT1A and HeLa/h 5‐HT1A cells was close to that of 5‐HT, suggesting LY334370 to exert high intrinsic activity at h 5‐HT1A receptors. In conclusion, in guinea‐pig brain sections and recombinant cell lines the 5‐ht1F receptor agonist LY334370 causes G‐protein activation that is mediated by 5‐HT1A receptors. Caution should be taken when employing this ligand as a putative selective 5‐ht1F agonist.