Glutamate release and neuronal injury after intrathecal injection of localanesthetics

High concentrations of local anesthetics are neurotoxic, but the mechanism for this neurotoxicity is obscure. Here, we report increased concentrations of glutamate in the cerebrospinal fluid after intrathecal injections of hi gh concentrations of tetracaine (a local anesthetic). The peak concentratio ns of glutamate after administration of 1%, 2%, and 4% tetracaine were 4-fo ld, 6-fold, and 10-fold higher than baseline values, respectively. Animals in the 1% group were all neurologically normal one week after tetracaine in jection. In the group receiving 4%, no animal was able to hop and vacuolati on of the white matter and/or central chromatolysis of the motor neurons we re observed. Because high concentrations of glutamate are known to be neuro toxic, our results may provide some insight into the mechanisms for neuroto xicity of intrathecal local anesthetics. NeuroReport 11:1105-1109 (C) 2000 Lippincott Williams & Wilkins.