A simple biochemical approach to differentiate synaptosomes and non-synaptic mitochondria from rat brain.

A simple and rapid low speed density gradient centrifugation method has been described to isolate relatively pure synaptosomes and non-synaptic mitochondria from rat brain cerebral cortex. The purity of the fractions isolated were tested biochemically by considering some marker enzymes, i.e., lactate dehydrogenase, plasma membrane Na+K+ATPase and acetylcholinesterase for the synaptosomes and succinate dehydrogenase for the mitochondrial fraction. The adrenergic receptor properties in the synaptosomal membrane were evaluated by observing the effect of different beta- and alpha 2-adrenergic receptor agonists and antagonists as function of synaptic plasma membrane Na+K+ATPase activity. Isoproterenol (beta-agonist) and yohimbine (alpha 2-antagonist)-induced changes in the synaptosomal Na+K+ATPase activity were counteracted by beta-antagonist propranolol and alpha 2-agonist clonidine, respectively. In the non-synaptic mitochondria the corresponding effects were insignificant. The study illustrates an easy, rapid and low-speed preparatory method to obtain synaptosomal and non-synaptic mitochondrial fractions of high purity.