The effect of Triton X-100 on bovine brain synaptic membranes.

Bovine brain synaptic membranes which were frozen and then extensively washed showed low affinity [3H]muscimol binding. These membranes contained GABA and calmodulin, apparently tightly bound within the membrane fraction. Membranes which were additionally treated with the detergent Triton X-100 showed high affinity [3H]muscimol binding. These membranes did not appear to contain GABA or calmodulin. Transmission electron microscopy studies demonstrated that the washed membrane fraction contained many synaptosomal and vesicular structures. Triton treatment led to the extensive rupture of these structures. These studies explain the well-reported findings of tightly bound GABA and calmodulin in brain membrane fractions, as being due to the entrapment of these compounds inside sealed membrane-bound structures which are still present after a freeze-thaw and extensive wash treatment, their complete removal requiring Triton-treatment to rupture the vesicles.