Synaptic vesicles, preparation from synaptosomes

The procedure for the preparation of synaptosomes and small synaptic vesicles (SSV) from rat brain cortex follows established methods with minor modifications (Schiavo and Montecucco, 1995). 

If ACh is synthesized extravesicularly as all experiments seem to indicate at present, there must exist a mechanism for the uptake of ACh into the synaptic vesicles. This mechanism has not yet been convincingly established. Experiments in vivo with infusion of labelled choline give labelling of ACh in synaptic vesicles (Chakrin and Whittaker, 1969 Barker et al., 1970) whereas the results from isolated synaptosome preparations are controversal. 

Preparation of sub-synaptosomal fractions showed that after labelling vivo, phosphatidate of Fraction E which contains marker enzymes for endoplasmic reticulum and plasma membrane (but not in higher concentration than some other fractions) had the highest specific radioactivity (Table 1). The most active phosphatidylinositol was in the synaptic vesicle fraction. Electrical stimulation provoked loss of these particular pools of phospholipid, while there was little effect on either phospholipid in the remaining fractions, as can be seen from the Table. 

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