Serotonin uptake and release by biochemically characterized nerve endings isolated from rat brain by concomitant flotation and sedimentation centrifugation.

Crude synaptosomal preparations of rat brain were separated by concomitant flotation and sedimentation in a sucrose gradient into fractions containing myelin, nerve endings, and mitochondria, respectively. Two myelin-free nerve ending fractions were obtained which differ in the serotonin content and the activities of the enzymes 5-hydroxytryptophan decarboxylase, monoamine oxidase, choline acetylase, and acetylcholin-esterase. In glucose medium sodium ions stimulate serotonin uptake into the nerve endings while potassium ions in sucrose solution induce the release of this amine.