Ion permeation properties of a cloned human 5-HT3 receptor transiently expressed in HEK 293 cells
Human 5-HT3 receptors expressed in HEK 293 cells were studied using patch-clamp techniques. The permeability ratios of cations to Na+ were Li+, 1.16; K+, 1.04; Rb+, 1.11; Cs+ 1.11; NMDG+, 0.04; Ca2+, 0.49, and Mg2+, 0.37. The permeability sequence of the alkali metal cations was Li+ > Rb+ = Cs+ > K+ > Na+. Increased external concentrations of Ca2+ or Mg2+ decreased 5-HT-induced currents at all potentials tested in a voltage-independent manner. The single-channel conductance of human 5-HT3 receptors measured by fluctuation analysis of whole-cell currents was 790 ± 100fS. Differences in the basic properties of 5-HT3 receptors between species may explain interspecies differences in pharmacological properties.
KeywordsAmino acids Serotonin receptor Serotonin-3 receptor Ion channel Ion permeability
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