G‐protein activation at 5‐HT 1A receptors by the 5‐ht 1F 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: 03.02.2009
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1038/sj.bjp.0701832

G‐protein activation by the 5‐ht 1F 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 [ 35 S]‐GTPγS binding responses in cell lines stably expressing human 5‐HT 1A (h 5‐HT 1A ) receptors. LY334370 (10 μ M ) caused little or no stimulation of [ 35 S]‐GTPγS binding in guinea‐pig brain regions enriched in 5‐ht 1F binding sites (e.g., claustrum, caudate/putamen and thalamic nuclei), as identified by labelling with 10 n M [ 3 H]‐sumatriptan plus 10 n M 5‐carboxamidotryptamine (5‐CT). Application of LY334370 (10 μ M ) to guinea‐pig brain sections resulted in an increase of [ 35 S]‐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‐HT 1A receptors as found with lisuride (10 μ M ), and labelling of 5‐HT 1A receptors by 140 p M [ 125 I]‐4‐(2′‐methoxy‐phenyl)‐1‐[2′‐(n‐2′′‐pyridinyl)‐p‐iodobenzamido]‐ethyl‐piperazine (p‐MPPI). The LY334370‐mediated [ 35 S]‐GTPγS response was antagonized by the selective, silent 5‐HT 1A receptor antagonist N‐[2‐[4‐(2‐methoxyphenyl)1‐piperazinyl]ethyl]‐N‐(2‐pyridinyl)cyclohexanecarboxamide (WAY100635, 1 μ M ) in each of the brain structures investigated. The distribution pattern of the [ 35 S]‐GTPγS binding response and the antagonist profile suggest that the LY334370‐induced response in guinea‐pig brain is mediated by 5‐HT 1A receptors. The maximal LY334370‐induced [ 35 S]‐GTPγS binding response (83 to 94%) in membranes of recombinant C6‐glial/h 5‐HT 1A and HeLa/h 5‐HT 1A cells was close to that of 5‐HT, suggesting LY334370 to exert high intrinsic activity at h 5‐HT 1A receptors. In conclusion, in guinea‐pig brain sections and recombinant cell lines the 5‐ht 1F receptor agonist LY334370 causes G‐protein activation that is mediated by 5‐HT 1A receptors. Caution should be taken when employing this ligand as a putative selective 5‐ht 1F agonist.