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Keywords:

  • patch-clamp;
  • transfection;
  • laser confocal microscopy;
  • Ca2+ transients;
  • single-channel conductance

Abstract

To study how subunit composition affects the functional properties of neuronal nicotinic acetylcholine receptors (nAChRs), we examined the behaviour of acetylcholine (ACh)-induced single-channel currents in human BOSC 23 cells transiently transfected with various subunit cDNA combinations. For all nAChRs examined (chick and rat α3β4, chick α<3/β2, α4β2, α4β4, α7and α8, expression levels were high enough to allow measurements of acetylcholine-evoked whole-cell currents and nicotine-elicited Ca2+ transients as well as the functional characterization of nAChR channels. Unitary acetylcholine-evoked events of α8 nAChR had a slope conductance of 23 pS, whereas two conductance classes (19–23 and 32–45 pS) were identified for all other nAChR channels. The mean channel open times were significantly longer for homomeric α7 and α8 nAChRs (6–7 ms) than for heteromeric nAChRs (1–3 ms), with the exception of α3α4nAChRs (8.4 ms for rat, 7 ms for chick). At least two species of heterologously expressed nAChRs (α3α4and α3α2) exhibited single-channel characteristics similar to those reported for native receptors. The variety of nAChRs channel conductance and kinetic properties encountered in human cells transfected with nAChR subunits contributes to the functional diversity of nAChRs in nerve cells.