[Hippocampal stereotactic injection of cerebrospinal fluid from single-prolonged stress mice induces PTSD-like...

This study aimed to investigate the impact of cerebrospinal fluid (CSF) from single-prolonged stress (SPS) model mice on the neurobehavioral outcomes in normal mice, and to explore the underlying mechanisms. CSF was extracted from SPS mice (SPS-CSF), and norepinephrine (NE) levels were measured using high-performance liquid chromatography-electrochemical detection (HPLC-ECD). A cannula was used for direct hippocampal injection of SPS-CSF, followed by behavioral experiments such as the elevated plus maze and fear extinction tests to assess changes in anxiety and fear memory in SPS-CSF injected mice. Hematoxylin and eosin (HE) staining was employed to evaluate neuronal pathology in the hippocampus. Western blotting and immunofluorescence were used to detect changes in the expression of astrocytic and synaptic proteins. Transmission electron microscopy (TEM) was adopted for synaptic ultrastructural analysis. Additionally, the effect of intraperitoneal ketamine (KET) injection on the behavioral changes induced by SPS-CSF was assessed. The results showed that SPS mice exhibited typical anxiety-like behavior, and NE levels in the CSF of SPS mice were significantly higher than those in control animals. Repeated injections of SPS-CSF into normal mice led to anxiety-like behavior and impaired fear memory extinction. After SPS-CSF administration, neuronal damage was observed in the hippocampus, along with decreased glial fibrillary acidic protein (GFAP) expression and reduced synaptic protein levels. Interestingly, the behavioral changes induced by SPS-CSF persisted for several weeks, and these changes could be blocked by KET. These findings suggest that stereotactic injection of SPS-CSF into the hippocampus can induce anxiety-like behavior and abnormal fear memory in normal mice, with mechanisms involving the regulation of astrocytes and synapses. This model indicates a potential "infectious" nature of SPS-CSF and provides a novel approach for future research on post-traumatic stress disorder (PTSD).