alpha-Bungarotoxin-sensitive hippocampal nicotinic receptor channel has a high calcium permeability

Biophys J. 1995 Feb;68(2):516-24. doi: 10.1016/S0006-3495(95)80213-4.


The hippocampal nicotinic acetylcholine receptor (nAChR) is a newly identified ligand-gated ion channel that is blocked by the snake toxin alpha-bungarotoxin (alpha-BGT) and that probably contains the alpha 7 nAChR subunit in its structure. Here its ion selectivity was characterized and compared with that of the N-methyl-D-aspartate (NMDA) receptor channel. The reversal potentials (VR) of acetylcholine- and NMDA-activated whole-cell currents were determined under various ionic conditions. Using ion activities and a Goldman-Hodgkin-Katz equation for VR shifts in the presence of Ca2+, permeability ratios were calculated. For the alpha-BGT-sensitive nAChR, PNa/PCs was close to 1 and Cl- did not contribute to the currents. Changing the [Ca2+]0 from 1 to 10 mM, the VRs of the nAChR and NMDA currents were shifted by +5.6 +/- 0.4 and +8.3 +/- 0.4 mV, respectively, and the nAChR current decay was accelerated. These shifts yielded PCa/PCss of 6.1 +/- 0.5 for the nAChR channel and 10.3 +/- 0.7 for the NMDA channel. Thus, the neuronal alpha-BGT-sensitive nAChR is a cation channel considerably selective to Ca2+ and may mediate a fast rise in intracellular Ca2+ that would increase in magnitude with membrane hyperpolarization.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Acetylcholine / pharmacology
  • Animals
  • Bungarotoxins / pharmacology*
  • Calcium / physiology*
  • Cell Membrane Permeability
  • Cesium / pharmacology
  • Chlorides / physiology
  • Hippocampus / physiology*
  • In Vitro Techniques
  • Ion Channel Gating / drug effects
  • Membrane Potentials
  • Patch-Clamp Techniques
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, Nicotinic / drug effects*


  • Bungarotoxins
  • Chlorides
  • Receptors, Nicotinic
  • Cesium
  • Acetylcholine
  • Calcium