Functional properties of a cloned 5-hydroxytryptamine ionotropic receptor subunit: comparison with native mouse receptors

J Physiol. 1994 Dec 1;481 ( Pt 2)(Pt 2):311-23. doi: 10.1113/jphysiol.1994.sp020441.


1. A comparative study of the whole-cell and single-channel properties of cloned and native mouse 5-hydroxytryptamine ionotropic receptors (5-HT3) was undertaken using mammalian cell lines expressing the cloned 5-HT3 receptor subunit A (5-HT3R-A), superior cervical ganglia (SCG) neurones and N1E-115 cells. 2. No pharmacological difference was found in the sensitivity to the agonists 5-HT and 2-methyl-5-HT, or to the antagonists d-tubocurare and 3-tropanyl-3,5-dichlorobenzoate (MDL-72222). 3. Current-voltage (I-V) relationships of whole-cell currents showed inward rectification in the three preparations. Rectification was stronger both in cells expressing the 5-HT3R-A subunit and in N1E-115 cells when compared with SCG neurones. 4. No clear openings could be resolved in 5-HT-activated currents in patches excised from cells expressing the 5-HT3R-A subunit or N1E-115 cells. Current fluctuation analysis of whole-cell and excised-patch records revealed a slope conductance of 0.4-0.6 pS in both preparations. Current-voltage relationships of these channels showed strong rectification that fully accounted for the whole-cell voltage dependence. 5. In contrast, single channels of about 10 pS were activated by 5-HT in patches excised from SCG neurones. The weak voltage dependence of their conductance did not account completely for the rectification of whole-cell currents. A lower unitary conductance (3.4 pS) was inferred from whole-cell noise analysis. 6. We conclude that the receptor expressed from the cloned cDNA is indistinguishable from the 5-HT3 receptor of N1E-115 cells, suggesting an identical structure for these two receptors. The higher conductance and different voltage dependence of the 5-HT3 receptor in SCG neurones might indicate the participation of an additional subunit in the structure of native ganglionic 5-HT3 receptors. Homo-oligomeric 5-HT3R-A channels may also be present as suggested by the lower conductance estimated by whole-cell noise analysis.

Publication types

  • Comparative Study

MeSH terms

  • Animals
  • Cloning, Molecular
  • Electrophysiology
  • Genetic Vectors
  • Ion Channels / drug effects
  • Ion Channels / metabolism
  • Mice
  • Neuroblastoma / metabolism
  • Neurons / drug effects
  • Neurons / metabolism
  • Patch-Clamp Techniques
  • Receptors, Serotonin / drug effects
  • Receptors, Serotonin / metabolism*
  • Semliki forest virus
  • Serotonin Antagonists / pharmacology
  • Serotonin Receptor Agonists / pharmacology
  • Superior Cervical Ganglion / cytology
  • Superior Cervical Ganglion / drug effects
  • Superior Cervical Ganglion / metabolism
  • Tumor Cells, Cultured


  • Ion Channels
  • Receptors, Serotonin
  • Serotonin Antagonists
  • Serotonin Receptor Agonists