Characterization of functional responses in A9 cells transfected with cloned rat 5-HT(1C) receptors

Boddeke, H. W. G. M., Hoffman, B. J., Palacios, J. M., Knot, H. & Hoyer, D., 12-Nov-1993, In : Naunyn-Schmiedeberg's Archives of Pharmacology. 347, 2, p. 119-124 6 p.

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Functional responses to stimulation of rat 5-HT(1C) receptors expressed in A9 cells were studied using whole cell voltage clamp and calcium recording techniques. Stimulation of 5-HT(1C) receptors evoked outward currents clamped at -50 mV. The outward currents were reduced when GTP was excluded from the intracellular recording solution or when GDP-β-S was added. 8-Bromo cyclic AMP (5 mmol/l) neither produced an effect per se nor affected the 5-HT-induced outward current in A9 cells, thus excluding cAMP as a second messenger involved in 5-HT(1C) receptor activation. Phorbol myristic acetate (PMA; 10 μmol/l) did not affect the electrical activity of the transfected A9 cells but reduced the 5-HT-induced current amplitude to 71 ± 9% of the control value (n = 12). This indicates that activation of protein kinase C does not play a direct role in the 5-HT-induced response in these cells. The 5-HT induced currents mainly involved potassium ions, although a small contribution of chloride ions was also observed. The 5-HT-induced current was inhibited by the K+channel blocking agents tetraethylammonium (1 mmol/l), apamin (0,5 μmol/l) and 4-amino-pyridine (5 mmol/l). The 5-HT-induced currents recorded at -50 mV were unaffected by removal of extracellular calcium, but inclusion of the calcium chelator BAPTA (5 mmol/l) in the intracellular solutions abolished the current. Measurement with the calcium indicator Fluo-3 revealed a 5-HT-induced increase in intracellular calcium which was not affected by removal of extracellular calcium but declined after repeated stimulation. Determinated of pD2and K(B) values of several 5-HT ligands using Fura-2 calcium measurements confirmed the pharmacology of the 5-HT(1C) receptor. The results show that cloned rat 5-HT(1C) receptors expressed in A9 cells activate a calcium-dependent potassium conductance.
Original languageEnglish
Pages (from-to)119-124
Number of pages6
JournalNaunyn-Schmiedeberg's Archives of Pharmacology
Issue number2
Publication statusPublished - 12-Nov-1993


  • 5-HT(1C) receptors, A9 cells potassium conductance, Calcium response, Fura-2/Fluo-3, (3 chlorophenyl)piperazine, 1 (3 trifluoromethylphenyl)piperazine, 4 aminopyridine, 4 iodo 2,5 dimethoxyamphetamine, 6 chloro 2 (1 piperazinyl)pyrazine, 8 bromo cyclic AMP, calcium, guanine nucleotide binding protein, guanosine 5' o (2 thiodiphosphate), guanosine triphosphate, ketanserin, mianserin, phorbol 13 acetate 12 myristate, serotonin, serotonin 2C receptor, serotonin agonist, serotonin antagonist, tetrylammonium, animal cell, article, calcium cell level, cell strain, chloride current, concentration response, controlled study, electrophysiology, molecular cloning, mouse, nonhuman, potassium conductance, priority journal, transfusion, voltage clamp technique

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