Isolation of rat brain subcellular fraction enriched in putative neurotransmitter receptors and synaptic junctions

A simple reliable method was developed for the rapid isolation of a synaptic plasma membrane-enriched fraction from rat brain. The procedure involves the direct lysis of a crude mitochondrial fraction followed by a combined flotation-sedimentation density gradient centrifugation in a fixed-angle centrifuge rotor. All fractions have been characterized with respect to relative enrichment of (Na+-K+)ATPase activity as well as putative cholinergic neurotransmitter receptors determined by [125I]alpha-bungarotoxin and [3H]quinuclidinyl benzilate binding. The 2- to 4-fold relative enrichment of putative receptor binding sites correlated well with the 4-fold enrichment of morphologically identifiable synaptic junctions in the synaptic plasma membrane enriched fraction.