A fluorescence and electronmicroscopic study on certain brain regions rich in monoamine terminals

Abstract

Abstract With the use of both the sensitive fluorescence method of Falck and Hillarp for the histochemical demonstration of monoamines at the cellular level and electron microscopy the synaptic terminals were studied in nucleus caudatus putamen, nucleus tractus solitarii and the substantia grisea periventricularis of the fourth ventricle. In all these regions numerous boutons of a size similar to the varicosities of the monoamine terminal exist. They form mostly synapses with dendrites. The boutons are more or less filled with either small (about 300–350 Å), medium sized (about 450 Å) or — but less commonly — large (about 550–600 Å) agranular vesicles. Larger (about 800–1,000 Å) granular vesicles are found in all three regions studied. In comparison to the agranular vesicles, however, they are practically always few. In animals treated with a large dose of reserpine or nialamide none of the different types of vesicles showed any obvious changes. It is concluded that the monoamine storage granules are not identical with the large granular vesicles, but that they, with the method used, appear as small, agranular vesicles.