ABSTRACT
BACKGROUND: Recent studies have shown that preconditioning with hyperbaric oxygen (HBO) can reduce ischemic and hemorrhagic brain injury. We investigated effects of HBO preconditioning on traumatic brain injury (TBI) at high altitude and examined the role of matrix metalloproteinase-9 (MMP-9) in such protection. METHODS: Rats were randomly divided into 3 groups: HBO preconditioning group (HBOP; n = 13), high-altitude group (HA; n = 13), and high-altitude sham operation group (HASO; n = 13). All groups were subjected to head trauma by weight-drop device, except for HASO group. HBOP rats received 5 sessions of HBO preconditioning (2.5 ATA, 100% oxygen, 1 h daily) and then were kept in hypobaric chamber at 0.6 ATA (to simulate pressure at 4000m altitude) for 3 days before operation. HA rats received control pretreatment (1 ATA, room air, 1 h daily), then followed the same procedures as HBOP group. HASO rats were subjected to skull opening only without brain injury. Twenty-four hours after TBI, 7 rats from each group were examined for neurological function and brain water content; 6 rats from each group were killed for analysis by H&E staining and immunohistochemistry. RESULTS: Neurological outcome in HBOP group (0.71 +/- 0.49) was better than HA group (1.57 +/- 0.53; p < 0.05). Preconditioning with HBO significantly reduced percentage of brain water content (86.24 +/- 0.52 vs. 84.60 +/- 0.37; p < 0.01). Brain morphology and structure seen by light microscopy was diminished in HA group, while fewer pathological injuries occurred in HBOP group. Compared to HA group, pretreatment with HBO significantly reduced the number of MMP-9-positive cells (92.25 +/- 8.85 vs. 74.42 +/- 6.27; p < 0.01). CONCLUSIONS: HBO preconditioning attenuates TBI in rats at high altitude. Decline in MMP-9 expression may contribute to HBO preconditioning-induced protection of brain tissue against TBI.
Subject(s)
Altitude , Brain Injuries/prevention & control , Hyperbaric Oxygenation/methods , Ischemic Preconditioning/methods , Analysis of Variance , Animals , Brain Edema/etiology , Brain Edema/prevention & control , Brain Injuries/complications , Brain Injuries/metabolism , Disease Models, Animal , Gene Expression Regulation , Male , Matrix Metalloproteinase 9/metabolism , Neurologic Examination , Random Allocation , Rats , Rats, Sprague-Dawley , Time FactorsABSTRACT
AIM: to investigate the change of nitric oxide synthase (NOS) activity in cochlear stria vascularis (SV) of guinea pig after gentamicin (GM) and Salvia Miltiorrhiza (SM) injection, and to explore the protective role of injectio SM on GM ototoxicity. METHODS: NADPH-diaphorase histochemistry staining and image quantitative analysis technique, combined with auditory brainstem response (ABR) measurement. RESULTS: SM + GM significantly reduced NOS activity in cochlear SV and ABR threshold as compared with CM along (P < 0.01); and ABR threshold shift was in high correlation with NOS activity (rControl = -0.9464; rGM = -0.9117; rSM + GM = -0.8958; P < 0.01). CONCLUSION: SM can reduce NOS activity in cochlear SV so as to alleviate GM ototoxicity, thus ameliorate hearing function.