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COMPARATIVE STUDIES IN SYNAPTOSOME FORMATION: THE PREPARATION OF SYNAPTOSOMES FROM THE HEAD GANGLION OF THE SQUID, LOLIGO PEALII

Abstract— Relatively high concentrations of ACh have been found in the head ganglion of the squid (Loligo pealii) and the identity of the ACh has been verified by ion‐exchange chromatography. Following homogenization in media iso‐osmotic with sea water about 40 per cent of the ACh survives in particle‐bound form. Experiments using media of varying osmolarity suggest that this bound ACh is osmotically sensitive. A study has been made of the subcellular fractionation of squid head ganglion using sucrose homogenates. A rapid and novel method is described for the preparation of a synaptosome fraction freed from mitochondria. This preparation contains synaptosomes of well‐preserved morphology with occluded cytoplasm and a high specific content of ACh. The synaptosomes are osmotically sensitive and when suspended in water they burst, releasing cytoplasmic constituents and ACh‐containing synaptic vesicles. The synaptic vesicles can be separated from other sub‐synaptic constituents by density gradient centrifugation.