The isolation of pure cholinergic nerve terminal sacs (T-sacs) from the electric organ of juvenile Torpedo

Abstract

The problem of synaptosome formation in the electric organ of Torpedo has been re-investigated using tissue from juvenile fish. This tissue is softer than adult material and can be easily homogenized in an Aldridge-type homogenizer. Homogenates so prepared contain a significant number of synaptosome-like structures which can be purified by differential and density gradient centrifugation. The purified particles are enriched in acetylcholine and choline acetyltransferase; they also contain lactate dehydrogenase activity, most of which is in an occluded form. The structure of these particles as revealed by electron microscopy is unusual in that they have no post-synaptic adhesions, relatively few synaptic vesicles and no intraterminal mitochondria. Because of their unusual morphology we have named these particles nerve terminal sacs (T-sacs). A high-affinity, hemicholinium-3 sensitive choline uptake system with an apparent K m of 1–3 μ m is associated with the T-sacs.