Nasal obstruction during adolescence induces memory/learning impairments associated with BDNF/TrkB signaling pathway hypofunction and high corticosterone levels.

The hippocampus is an important brain region involved in memory and learning. Brain-derived neurotrophic factor (BDNF), tyrosine kinase receptor B (TrkB), and phospho-p44/p42 mitogen-activated protein kinase (MAPK) are known to contribute to hippocampal memory/learning. The present study aimed to clarify the effects of nasal obstruction during the growth period on memory/learning in an animal model, using combined behavioral, biochemical, and histological approaches. Male BALB/C mice underwent unilateral nasal obstruction (UNO) by cauterization at 8 days of age and were subjected to Y-maze and passive avoidance tests at 15 weeks of age. The serum corticosterone levels were measured using an enzyme-linked immunosorbent assay, and brain tissues were subjected to hematoxylin-eosin staining and histological analysis or homogenization and Western blot analysis. Compared with control mice, UNO mice had lower blood oxygen saturation levels and exhibited apparent memory/learning impairments during behavioral testing. Additionally, the UNO group had higher hippocampal BDNF levels and serum corticosterone levels, lower hippocampal TrkB and phospho-p44/p42 MAPK levels, and reduced neuron numbers relative to controls. Our findings suggest that UNO during adolescence affects the hippocampus and causes memory/learning impairments.