[3H]cytisine binding to nicotinic cholinergic receptors in brain

Mol Pharmacol. 1991 Jan;39(1):9-12.


Cytisine, a ganglionic agonist, competes with high affinity for brain nicotinic cholinergic receptors labeled by any of several nicotinic 3H-agonist ligands. Here we have examined the binding of [3H]cytisine in rat brain homogenates. [3H]Cytisine binds with high affinity (Kd less than 1 nM), and specific binding represented 60-90% of total binding at all concentrations examined up to 15 nM. The nicotinic cholinergic agonists nicotine, acetylcholine, and carbachol compete with high affinity for [3H]cytisine binding sites, whereas among nicotinic receptor antagonists only dihydro-beta-erythroidine competes with high affinity (in the nanomolar range). Comparison of binding in several brain regions showed that [3H]cytisine binding is higher in the thalamus, striatum, and cortex than in the hippocampus, cerebellum, or hypothalamus. The pharmacology and brain regional distribution of [3H]cytisine binding sites are those predicted for neuronal nicotinic receptor agonist recognition sites. The high affinity and low nonspecific binding of [3H]cytisine should make it a very useful ligand for studying neuronal nicotinic receptors.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Acetylcholine / pharmacology
  • Alkaloids / pharmacokinetics
  • Alkaloids / pharmacology*
  • Animals
  • Azocines
  • Binding, Competitive
  • Carbachol / pharmacology
  • Cerebral Cortex / drug effects*
  • Cerebral Cortex / metabolism
  • Nicotine / pharmacology
  • Quinolizines
  • Rats
  • Receptors, Nicotinic / drug effects*
  • Tritium


  • Alkaloids
  • Azocines
  • Quinolizines
  • Receptors, Nicotinic
  • Tritium
  • cytisine
  • Nicotine
  • Carbachol
  • Acetylcholine