Depletion of Synaptosomal Neurotransmitter Pool by Sudden Cooling

Abstract

An increasing number of reports deal with the uptake, storage and release of putative neurotransmitters by synaptosomes (pinched-off nerve endings)1–6. In most of these, incubated synaptosomes were rapidly cooled to 0°–4° C and washed, in order to measure the uptake or to study the release of the accumulated neurotransmitter1,6,7–10. Synaptosomes are usually collected by filtration through cellulose ester filters (‘Millipore’), followed by washing with ice-cold medium7–10. We noted previously a large loss of accumulated and of endogenous GABA and glutamate during collection of synaptosomes on filters11 and here we suggest that this loss is caused by an alteration of the membrane structure induced by sudden cooling and that the different depletion observed with various neurotransmitters may depend on their intrasynaptosomal compartmentation.