The human olfactory bulb is a promising structure for the investigation of central nervous system disorders, including dementias of various etiologies. In Alzheimer’s disease, anosmia is among the earliest clinical manifestations. Although olfactory disturbances have also been reported in schizophrenia, alterations within the olfactory system remain insufficiently studied. The aim of this study was to identify changes in the olfactory bulbs of patients with schizophrenia. Olfactory bulbs obtained from patients with schizophrenia (n = 23) and individuals without identified nervous system pathology (n = 23) were examined. Patients with schizophrenia demonstrated a statistically significant decrease in the immunoreactive area of myelin basic protein and a significant increase in the immunoreactive area of glial fibrillary acidic protein compared with the control group. In addition, the thickness of the layer of incoming olfactory nerve fibers was significantly reduced in the schizophrenia group. Overall, our findings demonstrate neuroglial alterations in the human olfactory bulb in schizophrenia. Together with observations from other brain regions, these results may indicate that the identified changes are systemic rather than localized in nature.

Background. Numerous studies link olfactory impairment to accelerated cognitive decline in neurodegenerative diseases, yet the mechanism by which the olfactory bulb participates in these processes remains unclear. βIII-tubulin is one of the most commonly used neuronal markers, but data on its distribution in the olfactory bulb are limited. Aim. To analyze the distribution of βIII-tubulin in the olfactory bulbs of men and women during aging. Methods. The study was performed on autopsy material. Olfactory bulbs were obtained from 10 men and 14 women of elderly (60–74 years, n = 11) and senile (75–89 years n = 13) ages. Histological sections were stained with hematoxylin and eosin, Nissl stain, and Mallory’s trichrome for cytoarchitectonic analysis. Immunohistochemical analysis was performed using primary antibodies against neuron-specific βIII-tubulin. Morphometric and statistical analyses were carried out. Results. βIII-tubulin immunoreactivity was mainly detected in the olfactory nerve fiber layer and the glomerular layer. Analysis of sex differences revealed a significant (p = 0.006) predominance of the βIII-tubulin reaction area in olfactory bulb sections obtained from women. This aligns with research findings showing that women have nearly twice as many neurons in their olfactory bulbs and typically exhibit better odor identification ability compared to men. Despite a trend towards a decrease in βIII-tubulin levels with age, no statistically significant differences were found. Conclusion. The study revealed sexand age-related variability in the distribution of βIII-tubulin in the human olfactory bulb. Therefore, these factors should be taken into account when performing functional olfactory diagnostics.