Evaluation of neurogranin levels in a rat model of diffuse axonal injury

Abstract

Diffuse axonal injury (DAI), one of the most common and devastating type of traumatic brain injury, is the result of the shear force on axons due to severe rotational acceleration and deceleration. Neurogranin (NRGN) is a postsynaptic protein secreted by excitatory neurons, and synaptic dysfunction can alter extracellular NRGN levels. In this study, we examined NRGN levels in serum and cerebrospinal fluid (CSF) after experimental DAI in terms of their diagnostic value. Experimental DAI was induced using the Marmarou technique in male Wistar albino rats. Serum and CSF NRGN levels of the sham group, one‑hour, six‑hour, 24‑hour, and 72‑hour post‑DAI groups were measured by ELISA method. DAI was verified by staining with hematoxylin‑eosin and β‑amyloid precursor protein in the rat brain samples. While no histopathological and immunohistochemical changes were observed in the early hours of the post‑DAI groups, the staining of the β‑APP visibly increased over time, with positivity being most frequent and intense in the 72‑hour group. It was found that serum NRGN levels were significantly lower in the 6‑hour group than in the sham group. The serum NRGN levels in the 24‑hour group were significantly higher than those in the sham group. This study showed a dichotomy of post‑DAI serum NRGN levels in consecutive time periods. NRGN levels in CSF were higher in the one‑hour group than in the sham group and returned to baseline by 72 hours, although not significantly. Our study provides an impression of serum and CSF NRGN levels in a rat DAI model in consecutive time periods. Further studies are needed to understand the diagnostic value of NRGN.