TY - JOUR T1 - [3H]cytisine binding to nicotinic cholinergic receptors in brain. JF - Molecular Pharmacology JO - Mol Pharmacol SP - 9 LP - 12 VL - 39 IS - 1 AU - L A Pabreza AU - S Dhawan AU - K J Kellar Y1 - 1991/01/01 UR - http://molpharm.aspetjournals.org/content/39/1/9.abstract N2 - 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. ER -