[3H]methylcarbamylcholine, a new radioligand for studying brain nicotinic receptors

Biochem Pharmacol. 1986 Dec 1;35(23):4199-202. doi: 10.1016/0006-2952(86)90695-7.


A new radioligand, [3H]methylcarbamylcholine, has been developed for the study of the nicotinic cholinergic and nicotine-like binding sites in rat brain membranes. A Scatchard analysis with the radioligand yielded a Kd of 1.1 X 10(-9) M and a Bmax of 4.0 X 10(-14) moles/mg protein which compares with a lower affinity site for (-)-[3H]nicotine having a Kd of 3 X 10(-9) M and a Bmax of 2 X 10(-14) moles/mg. Comparable values for the Kd were obtained from a Hill plot and from calculations based on rate constants for association and dissociation. A comparison of the binding affinities of various nicotine analogues, nicotinic cholinergic agents, and other neurotropic agents revealed a close similarity between the two radioligands, with the exception that quaternization of nicotine or carbamate esters increased affinity by at least an order of magnitude with [3H]methylcarbamylcholine and resulted in a comparable decrease in affinity with [3H]nicotine as the ligand. The binding of [3H]methylcarbamylcholine, like [3H]nicotine, was not displaceable by muscarinic cholinergic antagonists. It was concluded that, although [3H]methylcarbamylcholine and [3H]nicotine bind to a common receptor in brain, the functional and chemical characteristics of the receptor(s) differ in some respects from peripheral nicotinic cholinergic receptors.

Publication types

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

MeSH terms

  • Animals
  • Brain Chemistry*
  • Carbachol* / analogs & derivatives*
  • Choline / analogs & derivatives*
  • Choline / metabolism
  • In Vitro Techniques
  • Kinetics
  • Ligands
  • Nicotine / metabolism
  • Psychotropic Drugs / pharmacology
  • Rats
  • Receptors, Nicotinic / analysis*
  • Tritium


  • Ligands
  • Psychotropic Drugs
  • Receptors, Nicotinic
  • Tritium
  • N-methylcarbamylcholine
  • Nicotine
  • Carbachol
  • Choline