Localization of methionine-enkephalin, substance P, and somatostatin immunoreactivities in the main olfactory bulb of the hamster.

Methionine-enkephalin, substance P, and somatostatin immunoreactivities are associated with different classes of neurons in the main olfactory bulb of the hamster. In the glomerular layer, methionine-enkephalin immunoreactivity is observed in the somata and dendrites of periglomerular cells whereas substance P immunoreactivity is present in the somata and dendrites of external tufted cells. Substance P immunoreactivity may also be present in the superficial short axon cells. In the deeper layers, methionine-enkephalin immunoreactivity is observed in a mixed population of neurons which appear to be primarily granule cells, whereas somatostatin immunoreactivity is present only in deep short axon cells. Methionine-enkephalin-, substance P-, and somatostatin-positive fibers of central origin are also observed in the main olfactory bulb.