Neuropeptide Y-like immunoreactive neurons in the human olfactory bulb

Neuropeptide Y-like (NPY) immunoreactivity was localized in the adult human olfactory bulb by the unlabeled antibody enzyme (peroxidase anti-peroxidase; PAP) technique in vibratome sections. The majority of NPY-immunoreactive somata was localized in the white matter surrounding the anterior olfactory nucleus. Immunoreactive neurons were less numerous within the anterior olfactory nucleus and within the olfactory bulb layers. NPY-immunoreactive fibres were present in the white matter, the anterior olfactory nucleus, and in the olfactory bulb layers. Fibres within the white matter were generally aligned in a straight path parallel to the long axis of the olfactory bulb and tract. Fibres within the anterior olfactory nucleus showed no clear orientation and displayed numerous branching points. Coiled plexus of NPY-immunoreactive fibres were present in the glomerular layer of the olfactory bulb. Additional characteristics of the NPY-immunoreactive neurons were studied after decolouring the chromogen and restaining the sections with aldehydefuchsin to demonstrate the presence of lipofuscin granules and also with gallocyanin chrome alum to stain the Nissl substance. This analysis showed that the neurons belong to the class of non-pigmented nerve cells.