Synaptic vesicle fraction devoid of adenosine triphosphatase activity from bovine caudatolenticular nuclei and...

1. As a part of studies on the mechanism by which catecholamines are released from the nerve terminals, the synaptic vesicle fraction was isolated from bovine caudatolenticular nuclei and thalamus by differential centrifugation essentially according to the method of Kadota and Kadota (17). 2. Further centrifugation on a sucrose density gradient of the synaptic vesicle fraction by the method of Whittaker et al. (1) yielded white materials on the upper portion of 0.4 M sucrose, which consisted of vesicles averaging 600-800 A in diameter, and did not show Mg2+-dependent ATpase activity. On the other hand, the denser materials centering on 0.6 M sucrose, consisting of a mixture of microsomes and synaptic vesicles of 400-500 A diameter, showed an ATpase activity activated by either Mg2+ or Ca2+ but not inhibited by ouabain. 3. The white materials on 0.4 M sucrose were almost free of mitochondria, but they contained a large amount of non-heme iron, as reported elsewhere (2). Furthermore, the protein components analyzed on SDS-polyacrylamide gels were similar to those already reported for purified synaptic vesicles (3). 4. Based on these results, the white materials were assumed to be synaptic vesicles devoid of Mg2+-dependent ATPase activity.