Pharmacology and biophysical properties of alpha 7 and alpha 7-alpha 8 alpha-bungarotoxin receptor subtypes immunopurified from the chick optic lobe

Eur J Neurosci. 1994 Aug 1;6(8):1281-91. doi: 10.1111/j.1460-9568.1994.tb00318.x.


Two chick optic lobe alpha-bungarotoxin receptor subtypes (alpha 7 and alpha 7-alpha 8) were immunopurified using polyclonal antibodies raised against synthetic peptides of chick alpha 7 and alpha 8 alpha-bungarotoxin receptor subunits. The alpha 7 subtype contained the M(r) 57,000 alpha 7 subunit, and represented 60-70% of the alpha-bungarotoxin receptors; the alpha 7-alpha 8 subtype contained the M(r) 57,000 alpha 7 and alpha 8 subunits, and represented only 20-25% of the receptors. Both subtypes also had an additional M(r) 52,000 subunit. The affinity of these subtypes for alpha-bungarotoxin as well as antagonists was similar. However, the alpha 7-alpha 8 subtype displayed consistently higher affinities for agonists. When reconstituted in planar lipid bilayers, the alpha 7-alpha 8 subtype displayed several conductance states of 10-50 pS; the alpha 7 subtype had only one conductance state of 45 pS. The alpha 7-alpha 8 subtype was activated by lower agonist concentrations than the alpha 7 subtype. When expressed in Xenopus oocytes, the alpha 8 subunit formed functional homomeric receptors that desensitized rapidly. These channels were blocked by alpha-bungarotoxin and displayed a higher affinity for agonists than the alpha 7 homomeric receptor. Taken together, these data indicate that at least two alpha-bungarotoxin subtypes are present in the chick optic lobe. They operate as ligand-gated channels and display different agonist sensitivities and kinetics/conductance properties.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Blotting, Western
  • Brain Chemistry / drug effects
  • Brain Chemistry / physiology*
  • Bungarotoxins / chemistry*
  • Calcium / metabolism
  • Carbachol / pharmacology
  • Chickens
  • Chromatography, Affinity
  • Electrophoresis, Polyacrylamide Gel
  • Electrophysiology
  • Immunochemistry
  • Ion Channel Gating / drug effects
  • Lipid Bilayers
  • Precipitin Tests
  • Receptors, Cholinergic / metabolism
  • Receptors, Nicotinic / chemistry
  • Receptors, Nicotinic / drug effects*
  • Xenopus
  • alpha7 Nicotinic Acetylcholine Receptor


  • Bungarotoxins
  • Lipid Bilayers
  • Receptors, Cholinergic
  • Receptors, Nicotinic
  • alpha7 Nicotinic Acetylcholine Receptor
  • Carbachol
  • Calcium