Effects of ononin on cognitive and learning-memory functions in mild cognitive impairment

OBJECTIVE: This study aimed to investigate the potential of ononin in alleviating mild cognitive impairment (MCI) and to determine whether its effects depend on the functional recovery of neurons in the nucleus tractus solitarius (NTS). METHODS: Four-month-old APP/PS1 mice were treated with 30-mg/kg ononin via oral gavage for 8 consecutive days. Cognitive behavior was assessed using the novel object recognition test, Y-maze test, and open field test. Cortical perfusion was measured by laser speckle contrast imaging. The activation of NTS neurons was detected using c-Fos immunofluorescence staining, while dendritic complexity and neuronal firing frequency were evaluated via Golgi staining and patch-clamp electrophysiology, respectively. RESULTS: Ononin treatment significantly improved the novel object recognition index and spontaneous alternation rate in the Y-maze test in APP/PS1 mice. It also enhanced cerebral blood flow perfusion and increased the number of c-Fos-positive cells in the NTS, hippocampal CA1 region, and cortex. Furthermore, ononin increased dendritic intersections and restored dendritic spine density in NTS neurons to normal levels, along with significantly elevating their firing frequency. CONCLUSION: Ononin may ameliorate MCI-like cognitive deficits in APP/PS1 mice by activating NTS neurons, restoring synaptic plasticity, and improving cerebral perfusion. These findings suggest that the NTS could serve as a potential target for early intervention in Alzheimer's disease.