ISSN:
1432-1912
Keywords:
5-HT1C receptors
;
A9 cells potassium conductance
;
Calcium response
;
Fura-2/Fluo-3
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary Functional responses to stimulation of rat 5-HT1C receptors expressed in A9 cells were studied using whole cell voltage clamp and calcium recording techniques. Stimulation of 5-HT1C receptors evoked outward currents clamped at −50 mV. The outward currents were reduced when GTP was excluded from the intracellular recording solution or when GDR-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-HT1C 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-aminopyridine (5 mmol/1). 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 pD2 and KB values of several 5-HT ligands using Fura-2 calcium measurements confirmed the pharmacology of the 5-HT1C receptor. The results show that cloned rat 5-HT1C C receptors expressed in A9 cells activate a calcium-dependent potassium conductance.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00169255
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