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An electrophysiological investigation of the properties of a murine recombinant 5‐HT 3 receptor stably expressed in HEK 293 cells
Author(s) -
Gill Catherine H.,
Peters John A.,
Lambert Jeremy J.
Publication year - 1995
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1995.tb13335.x
Subject(s) - methysergide , 5 ht3 receptor , biophysics , ketanserin , chemistry , electrophysiology , patch clamp , receptor , 5 ht receptor , hek 293 cells , pharmacology , antagonist , biology , biochemistry , serotonin , neuroscience
1 The pharmacological and biophysical properties of a recombinant 5‐HT 3 receptor have been studied by use of patch‐clamp techniques applied to HEK 293 cells stably transfected with the murine 5‐HT 3 R‐A cDNA. 2 At a holding potential of −60 mV, 77% of cells investigated responded to ionophoretically applied 5‐HT with an inward current. Such currents were unaffected by methysergide (1 μ m ), or ketanserin (1 μ m ), but were antagonized in a concentration‐dependent and reversible manner by the selective 5‐HT 3 receptor antagonist, ondansetron (IC 50 = 440 p m ) and the non‐selective antagonists (+)‐tubocurarine (IC 50 = 1.8 n m ) and metoclopramide (IC 50 50 n m ). 3 The 5‐HT‐induced current reversed in sign (E 5‐HT ) at approximately – 2 mV and exhibited inward rectification. The influence of extra‐ and intracellular ion substitutions upon E 5‐HT indicates the 5‐HT‐evoked current to be mainly mediated by a mixed monovalent cation conductance. 4 Calcium and magnesium (0.1–10 n m ) produced a concentration‐dependent, voltage‐independent, inhibition of the 5‐HT‐induced response. Zinc (0.3–300 μ m ) exerted a biphasic effect with low concentrations enhancing, and high concentrations depressing, the 5‐HT‐evoked current. 5 Fluctuation analysis of inward currents evoked by a low (1 μ m ) concentration of 5‐HT suggests the current to be mediated by the opening of channels with a conductance of 420 fS. 6 The pharmacological and biophysical properties of the 5‐HT 3 R‐A are similar to those previously described for 5‐HT 3 receptors native to murine neuroblastoma cell lines, with the exception that the function of the recombinant receptor was enhanced by low concentrations of zinc. This observation suggests that the properties of the native receptor are not completely represented by the 5‐HT 3 R‐A subunit alone.