Increased cerebrospinal fluid glutamate and taurine concentrations are associated with traumatic brain edema formation in rats

Glutamate-mediated excitotoxicity results in cell swelling and contributes to brain edema formation. Since increased extracellular taurine reflects gl utamate-induced cell swelling in vitro, elevated CSF taurine could therefor e unmask glutamate-mediated cytotoxic edema formation under in vivo conditi ons. For this, the temporal profile of brain edema and changes in cisternal CSF glutamate and taurine levels were determined in 28 rats following foca l traumatic brain injury. Compared to six non-traumatized rats, CSF glutama te (4.8+/-0.3 vs. 10+/-0.9 mu M) and taurine levels (12+/-1.3 vs. 41+/-3 mu M) were significantly increased at 8 h after trauma (P<0.001). Over time, CSF glutamate and taurine were significantly increased by 24 (glutamate: 38 +/-4.4 mu M) and 48 h (taurine: 51+/-4 mu M), respectively. While CSF gluta mate closely reflected changes in hemispheric water content, alterations in CSF taurine occurred diametrically to those seen for glutamate. Under the present study design, increased CSF taurine could reflect glutamate-induced cell swelling. In addition, neuronal release of taurine with its inhibitor y and antiexcitotoxic functions could explain the observed diametric change s in CSF glutamate, CSF taurine, and hemispheric water content. Therefore, increasing taurine could be a therapeutic approach in attenuating post-trau matic glutamate-mediated cell damage. (C) 2000 Elsevier Science B,V. All ri ghts reserved.