Isolation of pure cholinergic nerve endings from Torpedo electric organ. Evaluation of their metabolic properties.

Pure cholinergic nerve endings (synaptosomes) were isolated from the electric organ of Torpedo by a rapid procedure. These synaptosomes are approximately 3 micron in diameter. They contain an occasional mitochondrion, numerous synaptic vesicles, and sometimes an active zone is observed. No postynaptic membrane attachment is found. This nerve ending fraction is extremely pure as shown by morphological controls and biochemical data. It is rich in choline acetyltransferase (450 nmol/h per mg protein) and acetylcholine (ACh) (130 nmol/mg protein). The isolated endings retain their cytoplasmic components and they synthesize ACh and are stable in vitro for several hours, as shown by biochemical measurements and morphological analysis.