IMMUNOHISTOCHEMICAL ANALYSES OF THE HUMAN OLFACTORY-BULB

These studies explore the distribution of putative neuroactive peptide s in the human olfactory bulb. Localization of synaptophysin-, seroton in-, cholecystokinin-, substance P-, and somatostatin-like staining wa s examined by immunocytochemical protocols. The results provide new in sights into the composition and laminar segregation of subpopulations of neurons and neuronal processes in the human olfactory bulb. The pro minent synaptophysin-like immunoreactivity observed in the glomeruli o f the human olfactory bulb is consistent with the notion that the dens ity of synapses, and hence the density of synaptic vesicles, is highes t in the glomeruli. Serotonin-like immunoreactivity suggested a variab le innervation of glomeruli ranging from a dense tangled ball of fiber s within the glomerulus to a sparse innervation by a single immunoreac tive fiber. There was no evidence of serotonin-like immunoreactive cel l bodies in either the olfactory bulb proper, anterior olfactory nucle us, or proximal regions of the lateral olfactory tract. Cholecystokini n-like immunoreactivity was limited to fibers found largely in the jux taglomerular region of the glomerular layer. In the deeper layers of t he olfactory bulb, cholecystokinin-like immunoreactive fibers did not show any of branching or arborization that was evident in the juxtaglo merular region. Substance P-like immunoreactivity was seen in varicose fibers distributed in all of the human olfactory bulb laminae. In add ition, stained multipolar neurons were found in the area of the anteri or olfactory nucleus. Somatostatin-like immunoreactivity was similar t o that of substance P in that a plexus of stained fibers was found in all laminae of the olfactory bulb. Also, somatostatin-like immunoreact ive cell bodies were found in the area of the anterior olfactory nucle us. However, as compared to substance P, somatostatin had a less dense plexus of immunoreactive fibers in the olfactory bulb. These results increase our understanding of the fundamental organization of the huma n olfactory system. The current data, coupled with prior studies, prov ide a foundation from which to study the cellular pathology of disease s with known olfactory system sequelae such as Alzheimer's, Parkinson' s, and schizophrenia.