Two distinct classes of functional 7-containing nicotinic receptor on rat superior cervical ganglion neurons

J Physiol. 2000 Jun 15;525 Pt 3(Pt 3):735-46. doi: 10.1111/j.1469-7793.2000.t01-1-00735.x.


Nicotinic acetylcholine receptors (nAChRs) that bind alpha-bungarotoxin (alpha Bgt) were studied on isolated rat superior cervical ganglion (SCG) neurons using whole-cell patch clamp recording techniques. Rapid application of ACh onto the soma of voltage clamped neurons evoked a slowly desensitizing current that was reversibly blocked by alpha Bgt (50 nM). The toxin-sensitive current constituted on average about half of the peak whole-cell response evoked by ACh. Nanomolar concentrations of methyllycaconitine blocked the alpha Bgt-sensitive component of the ACh-evoked current as did intracellular dialysis with an anti-alpha 7 monoclonal antibody. The results indicate that the slowly reversible toxin-sensitive response elicited by ACh arises from activation of an unusual class of alpha 7-containing receptor (alpha 7-nAChR) similar to that reported previously for rat intracardiac ganglion neurons. A second class of functional alpha 7-nAChR was identified on some SCG neurons by using rapid application of choline to elicit responses. In these cases a biphasic response was obtained, which included a rapidly desensitizing component that was blocked by alpha Bgt in a pseudo-irreversible manner. The pharmacology and kinetics of the responses resembled those previously attributed to alpha 7-nAChRs in a number of other neuronal cell types. Experiments measuring the dissociation rate of 125I-labelled alpha Bgt from SCG neurons revealed two classes of toxin-binding site. The times for toxin dissociation were consistent with those required to reverse blockade of the two kinds of alpha Bgt-sensitive response. These results indicate that rat SCG neurons express two types of functional alpha 7-nAChR, differing in pharmacology, desensitization and reversibility of alpha Bgt blockade.

Publication types

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

MeSH terms

  • Acetylcholine / pharmacology
  • Aconitine / analogs & derivatives
  • Aconitine / pharmacology
  • Animals
  • Animals, Newborn
  • Antibodies, Monoclonal / pharmacology
  • Bungarotoxins / pharmacology
  • Choline / pharmacology
  • Gene Expression / physiology
  • In Vitro Techniques
  • Insecticides / pharmacology
  • Iodine Radioisotopes
  • Membrane Potentials / drug effects
  • Membrane Potentials / physiology
  • Neurons / chemistry*
  • Neurons / physiology*
  • Nootropic Agents / pharmacology
  • Patch-Clamp Techniques
  • RNA, Messenger / analysis
  • Rats
  • Receptors, Nicotinic / classification*
  • Receptors, Nicotinic / genetics
  • Receptors, Nicotinic / immunology
  • Superior Cervical Ganglion / cytology*
  • Vasodilator Agents / pharmacology
  • alpha7 Nicotinic Acetylcholine Receptor


  • Antibodies, Monoclonal
  • Bungarotoxins
  • Chrna7 protein, rat
  • Insecticides
  • Iodine Radioisotopes
  • Nootropic Agents
  • RNA, Messenger
  • Receptors, Nicotinic
  • Vasodilator Agents
  • alpha7 Nicotinic Acetylcholine Receptor
  • methyllycaconitine
  • Choline
  • Acetylcholine
  • Aconitine