tailieunhanh - Traumatic brain injury and the effects of diazepam, diltiazem, and MK-801 on GABA-A receptor subunit expression in rat hippocampus

Excitatory amino acid release and subsequent biochemical cascades following traumatic brain injury (TBI) have been well documented, especially glutamate-related excitotoxicity. The effects of TBI on the essential functions of inhibitory GABA-A receptors, however, are poorly understood. Methods: We used Western blot procedures to test whether in vivo TBI in rat altered the protein expression of hippocampal GABA-A receptor subunits α1, α2, α3, α5, β3, and γ2 at 3 h, 6 h, 24 h, and 7 days post-injuy. We then used pre-injury injections of MK-801 to block calcium influx through the NMDA receptor, diltiazem to block L-type voltagegated calcium influx,. | Gibson et al. Journal of Biomedical Science 2010 17 38 http content 17 1 38 a NSC The cost of publication In Journal of Blomodlcal Science Is boms by tlM National Science Council Taiwan JOURNAL OF BIOMEDICAL SCIENCE RESEARCH Open Access Traumatic brain injury and the effects of diazepam diltiazem and MK-801 on GABA-A receptor subunit expression in rat hippocampus Cynthia J Gibson 1 Rebecca C Meyer2 and Robert J Hamm3 Abstract Background Excitatory amino acid release and subsequent biochemical cascades following traumatic brain injury TBI have been well documented especially glutamate-related excitotoxicity. The effects of TBI on the essential functions of inhibitory GABA-A receptors however are poorly understood. Methods We used Western blot procedures to test whether in vivoTBI in rat altered the protein expression of hippocampal GABA-A receptor subunits a1 a2 a3 a5 P3 and y2 at 3 h 6 h 24 h and 7 days post-injuy. We then used pre-injury injections of MK-801 to block calcium influx through the NMDA receptor diltiazem to block L-type voltagegated calcium influx or diazepam to enhance chloride conductance and re-examined the protein expressions of a1 a2 a3 and y2 all of which were altered by TBI in the first study and all of which are important constituents in benzodiazepine-sensitive GABA-A receptors. Results Western blot analysis revealed no injury-induced alterations in protein expression for GABA-A receptor a2 or a5 subunits at any time point post-injury. Significant time-dependent changes in a1 a3 P3 and y2 protein expression. The pattern of alterations to GABA-A subunits was nearly identical after diltiazem and diazepam treatment and MK-801 normalized expression of all subunits 24 hours post-TBI. Conclusions These studies are the first to demonstrate that GABA-A receptor subunit expression is altered by TBI in vivo and these alterations may be driven by calcium-mediated cascades in hippocampal neurons. Changes in GABA-A receptors in the .