ACETYLCHOLINE RECEPTORS: NUMBER and DISTRIBUTION IN INTACT and DEAFFERENTED SUPERIOR CERVICAL GANGLION OF THE RAT¹

Abstract

Abstract— α‐Bungarotoxin (α‐BuTX) has been used as a marker for studying the acetylcholine receptors (AChRs) in the superior cervical ganglion (SCG) of the adult rat. Binding of [ 125 I]α‐BuTX to detergent‐solubilized AChRs from rat SCG is a saturable and practically irreversible process. The rate constant of association of the toxin‐receptor complex is 1.66 × 10 5 M −1 S −1 . The receptor is of nicotinic type. One SCG of adult rat binds about 57 fmol of [ 125 I]α‐BuTX corresponding to 9.2 × 10 5 AChRs per sympathetic neuron. Light microscope autoradiography shows that AChRs are mainly localized along neuronal processes (probably dendrites). The perikarya exhibit a weak radioactive reaction, while the nerve fibres are devoid of AChRs. Following preganglionic denervation the number of AChRs never increases and their spatial distribution seems not to change.