Synaptosomes Subfractionation

Higher amounts of synoptosome protein con be used if required (e.g., for subsequent subfractionation) but maintaining the protein concentration (see table). When high amounts of synaptosomes are used, a glutamate calibration curve should be performed for a proper calculation of the amount of neurotransmitter released (Nicholls etal., 1987). 

Synaptosomes can be subfractionated into a heavy membrane fraction that contains plasma membranes, synaptic vesicle clusters and most of the contaminating membranes, a light membrane fraction that is enriched in synaptic vesicles and devoid of measurable contamination by mitochondria or neuronal plasma membranes, and a... 

Dagani, F., Zanada, F., Marzatico, F., and Benzi, G. (1985) Free mitochondria and synaptosomes from single rat forebrain. A comparison between two known subfractionating techniques J. Neurochem. 45,653-656. 

This activity is mainly located in particulate components of the primary subcellular fractions. About 35% of the enzyme activity is present in the crude mitochondrial fraction.Further subfractionation has shown that half of the cysteine sulphinate decarboxylase activity, present in this fraction, is localized In synaptosomes... 

After cell fractionation of rat brain the highest specific as well as the major part of the total HGPRT activity is found in the soluble supernatant fraction, as expected. However, when a crude mitochondrial fraction is washed to constant activity and then subfractionated on a discontinuous Picoll-gradient, activity can be enriched in synaptosomes. Whether the enzyme is only entrapped there as a normal constituent of the cytoplasm during the disruption of the nerve endings or whether it serves a more specific function there, remains to be determined. 

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