Hyperbaric oxygen therapy improves neurogenesis and brain blood supply in piriform cortex in rats with vascular dementia

Background: Neural stem cell treatment and neurogenesis stimulation have gained attention as potential treatments for vascular dementia (VD). Currently, research mainly focuses on neurogenesis occurring in the sub-ventricular zone and dentate gyrus, while the research of the piriform cortex (Pir) is limited. Few results showed that weak neurogenesis exists in the Pir of adult rats. Since neurogenesis occurs in the Pir and is closely related to cognitive function, this study addressed the question of whether neurogenesis occurs in the Pir of an animal with the VD. Primary objective and hypothesis: This study investigated the effects of hyperbaric oxygen therapy on brain blood supply and neurogenesis in the piriform cortex (Pir) of rats with VD. Main outcomes and results: Compared to non-VD control rats (NC), rats with VD showed reduced rCBF, increased rCBV and slower MTT in the Pir. However, following hyperbaric oxygen (HBO) treatment in VD rats, rCBF increased, rCBV decreased and MTT increased. To determine whether the restoration in brain blood supply was associated with increased neurogenesis, immunohistochemical detection of nestin and doublecortin (DCX) was used. In the Pir of both normal and VD rats, nestin positive cells were localized to layer II (superficial cellular layer) and layer III (deep cellular layer). Nestin expression was increased in Pir cells in VD rats and was even more intensely expressed after the HBO treatment. DCX positive cells were mostly located in layer II from amygdaline fissure to rhinal fissure. Conclusion: These results suggest that HBO therapy can improve the blood supply and promote the neurogenesis in the Pir of adult rats with the VD.