Fluorescence histochemistry of monoamine‐containing cell bodies in the brain stem of the squirrel monkey (<i>Saimiri sciureus</i>). The locus caeruleus

Abstract

Abstract A study of the locus caeruleus is presented as the first in a series of papers describing the monoamine‐containing cell bodies in the brain stem of the squirrel monkey ( Saimiri sciureus ) using the fluorescent histochemical technique. Found most caudally in the roof of the ventriculus quartus, the locus caeruleus attains its greatest density of cell bodies medial to the tractus mesencephalicus n. trigemini at the level where the tract lies medial and ventral to the brachium conjunctivum. More rostrally, the cells are found dorsal, medial, and ventral to the brachium conjunctivum. Finally, in a location to a few cells closely associated with the fibers of the nervus trochlearis. Careful examination of closely packed cells medial to the tractus mesencephalicus n. trigemini reveals that almost all of the cell bodies of this region fluoresce, thus displaying a positive reaction for monoamines. On the basis of the fluorescent histochemical technique, therefore, the authors conclude that this region which often is indicated in the literature as the nucleus tr. mesenceph. n. trigemini is actually composed of the catecholamine‐containing cells of the locus caeruleus.