An improved invertebrate synaptosomal preparation with cholinergic properties.

Our laboratory has previously characterized a high affinity choline uptake system (HAChUS) in Limulus tissues and synaptosomes. We report here on the characterization of the HAChUS in synaptosomes prepared selectively from central nervous system tissues shown to be enriched for presumed cholinergic functions; namely the protocerebrum, corpora pedunculata and abdominal ganglia. Synaptosomes were prepared from these tissues by means of a modification of the subfractionation procedure developed by Dowdall and Whittaker. In our modification, we harvested a PP2L fraction exclusively from the S2 fraction. Compared to the P2L fraction, the PP2L was greater than three times more efficient in [3H]choline uptake and was significantly more sensitive to inhibition with micromolar concentrations of hemicholinium-3. The PP2L fraction HAChUS was shown to have characteristics common to the HAChUS of identified cholinergic tissues.