Abstract
Differential centrifugation of disrupted nerve-ending particles (NEPs) from rat brain stem yielded a vesicular fraction containing norepinephrine (NE) and 5-hydroxytryptamine (5-HT). For starting material NEPs purified by gradient density centrifugation were less satisfactory than the crude "mitochondrial" (P2) fraction of homogenates. To disrupt the NEPs, a wide range of conditions of hypotonicity and sonification was investigated. Strenuous sonification caused an almost complete solubilization of the NE and 5-HT.
Under optimal conditions the vesicular (P2-V) fractions obtained by ultrasonic or hypotonic disruption contained about 25% of the NE, 20% of the 5-HT and 10% of the protein in the crude NEP preparation.
Electron microscopic examination revealed that the P2-V fractions from both ultrasonic and hypotonic disruption were composed almost entirely of vesicles of about the same size and appearance as those seen at synaptic junctions. In fixed and sectioned material the dense-core vesicles often associated with adrenergic nerve endings were exceedingly rare. At least 3 morphologically distinct kinds of vesicles could be observed in negatively stained P2-V preparations. They were differentiated primarily on the basis of the thickness of their walls, although one type also was distinguishable by a matrix containing many small granules. Vesicles extruding a granular material were observed rather frequently.
Footnotes
- Received December 16, 1963.
- Accepted February 5, 1964.
- The Williams & Wilkins Company
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