Table III. IC₅₀ of various cholinergic ligands for binding to the receptor.

Binding of ¹²⁵I-α-bungarotoxin was determined as described under “Materials and Methods” except that the samples were preincubated with competitors for 20 min.

Ligand	Membrane-bound	Purified receptor
Nicotine	4.5 × 10−7 m	5.0 × 10−7 m
d-Tubocurarine	2.6 × 10−6 m	7.4 × 10−7 m
Acetylcholine	2.8 × 10−6 m	3.6 × 10−6 m
Atropine	5.7 × 10−5 m	1.6 × 10−3 m
Hexamethonium		1.3 × 10−3 m
Decamethonium	2.0 × 10−4 m