Colchicine-binding activity and neurotubule integrity in a rat sympathetic ganglion

The colchicine-binding activity of rat superior cervical ganglia was examined. Ganglia were cooled and re-warmed in the presence of either Cu²⁺ or of metabolic inhibitors. Electronmicroscopy showed that these treatments depolymerized the neurotubules. This depolymerization of neurotubules did not affect the colchicine-binding activity of ganglion homogenates but caused a two-fold increase in colchicine-binding by whole ganglia. This suggests that colchicine binds only to depolymerized neurotubule subunits and that colchicine-binding by whole ganglia can be used as a measure of polymerization of the neurotubule protein.The major part of the colchicine-binding activity of ganglion homogenates was found in the soluble fraction and was unstable. In the absence of divalent cations, 10⁻⁴ M vinblastine stabilised the soluble colchicine-binding activity.