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.