Transmitter histochemistry of the rat olfactory bulb. II. Fluorescence histochemical, autoradiographic and electron microscopic localization of monoamines.

The rat olfactory bulb was studied with the Falck-Hillarp formaldehyde fluorescence technique, including recent modifications, autoradiography and electron microscopic cytochemistry (permanganate fixation). Some periglomerular cells and few superficial tufted cells take up and accumulate catecholamines and precursors. They probably represent dopamine cells. In the glomeruli, probable 5-hydroxy-tryptamine nerve terminals could be identified. In the granular and external plexiform layers, noradrenaline axon terminals were present. At the ultrastructural level, monoamine boutons were in synaptic contact with dendritic spines of granule cells and in the glomeruli, probable 5-hydroxytryptamine boutons formed synapses with periglomerular cell dendrites. Therefore, monoamine afferents to the bulb may exert their influence via interneurons.