Fine structure of the locus coeruleus in the mouse

In a light microscopic study we used the wet fluorescent method and counted numbers of fluorescent LC cells and obtained 1326±64 in one side, and many processes of LC cells reached and expanded into the latero-dorsal tegmental nucleus and nucl. parabrachialis medialis and lateralis. By EM study of glyoxylic acid and permanganate fixed material, LC cells (the principal cells, (16.8±2.9)x(27.8±5.1) μm), which cotained small and large cored vesicles characteristic for NA, were divided into 2 types. The one was rich in Golgi apparatuses, ER and other cell organelles, the other being poor in these cell organelles. Another type of cells, devoid of cored vesicles, were small in size (12x15μm) and poor in cell organelles. In the neuropil of LC, the % of axon terminals containing NA cored vesicles amounted to 2.2 (±0.67)% % of all axon terminals (a total of 10,545). Counted NA terminals (a total of 232) showed apposition to dendrites at 43%, free endings at 52%, contacts to LC cells at 5%. Moderate number of dendrites containing cored vesicles contacted with LC cell bodies or their dendrites especially in the caudal part of LC.