The change of metabotropic glutamate receptor 5 expression level in rats with late-stage traumatic brain injury and the therapeutic effect of taurine

Abstract

Objective To investigate the change of metabotropic glutamate receptor 5 (mGluR5) expression level in rats with late-stage (the 7th day) traumatic brain injury (TBI) and the role of taurine. Methods The left cerebral TBI rat models were made by using lateral fluid percussion method. A total of 30 specific pathogen free (SPF) male Sprague-Dawley (SD) rats were randomly divided into 3 groups: sham operation group (control group), TBI model group (TBI group) and taurine treatment group (taurine group). Wet and dry weight method was used to measure the brain water content. Real-time fluorescent quantitative polymerase chain reaction (PCR) and Western blotting were used to detect the change of mRNA and protein expression of aquaporin 4 (AQP4) and mGluR5 in each group. Results Compared with control group, the brain water content ( t = 4.893, P = 0.002), AQP4 mRNA ( t = 6.523, P = 0.000) and protein ( t = 4.366, P = 0.008) expression were upregulated, while mGluR5 mRNA ( t = 5.776, P = 0.001) and protein ( t = 3.945, P = 0.014) expression were downregulated in TBI group. After taurine treatment, the brain water content ( t = 2.151, P = 0.140), AQP4 mRNA ( t = 1.144， P = 0.432) and protein ( t = 0.367, P = 0.804) decreased to normal, while mGluR5 mRNA ( t = 1.824, P = 0.216) and protein ( t = 1.185, P = 0.414) increased to normal. Correlation analysis showed brain water content was negatively correlated with mGluR5 mRNA ( r = -0.617, P = 0.014) and mGluR5 protein ( r = -0.665, P = 0.007), while it was positively correlated with AQP4 protein ( r = 0.658, P = 0.008). Conclusions Taurine can significantly increase the mGluR5 expression level of brain issue in the late-stage (the 7th day) of TBI and decline brain edema and brain water content. It may be a potential protective agent as an inhibitory neurotransmitter. DOI: 10.3969/j.issn.1672-6731.2016.08.008