NITRIC-OXIDE INDUCED CYTOTOXICITY ATTENUATION BY THIOPENTONE SODIUM BUT NOT PENTOBARBITAL SODIUM IN PRIMARY BRAIN CULTURES

1 We describe the effects of barbiturates on the neurotoxicity induced by nitric oxide (NO) on foetal rat cultured cortical and hippocampal neurones. Cessation of cerebral blood how leads to an initiation of a neurotoxic cascade including NO and peroxynitrite. Barbiturates are of ten used to protect neurones against cerebrovascular disorders clinica lly. However, its neuroprotective mechanism remains unclear. 2 In the present experiment, we established a new in ville model of brain injur y mediated by NO with an NO-donor, 1 oxy-2-oxo-3-(3-aminopropyl)-3-iso propyl-1-triazene (NOC-5) on grid tissue culture wells. We also invest igated the mechanisms of protection of CNS neurones from NO-induced ne urotoxicity by thiopentone sodium, which contains a sulphhydryl group (SH-) in the medium, and pentobarbitone sodium, which does not contain SH-. 3 Primary cultures of cortical and hippocampal neurones (prepare d from 16-day gestational rat foetuses) were used after 13-14 days in culture. The cells were exposed to NOC-5 at the various concentrations for 24 h in the culture to evaluate a dose-dependent effect of NOC-5. 4 To evaluate the role of the barbiturates, neurones were exposed to 4, 40 and 400 mu M of thiopentone sodium or pentobarbitone sodium with or without 30 mu M NOC-5. In addition, superoxide dismutase (SOD) at 1000 u ml(-1) and 30 mu M NOC-5 were co-administered for 24 h to evalu ate the role of SOD. 5 Exposure to NOC-5 induced neural cell death in a dose-dependent manner in both cortical and hippocampal cultured neur ones. Approximately 90% of the cultured neurones were killed by 100 mu M NOC-5. 6 This NOC-5-induced neurotoxicity was significantly attenua ted by high concentrations of thiopentone sodium (40 and 400 mu M) as well as SOD, but not by pentobarbitone sodium. The survival rates of t he cortical neurones and hippocampal neurones that were exposed to 30 mu M NOC-5 were 11.2 +/- 4.2% and 37.2 +/- 3.0%, respectively, and in the presence of 400 mu M thiopentone sodium, the survival rate increas ed to 65.3 +/- 3.5% in the cortical neurones and 74.6 +/- 2,2% in the hippocampal neurones. 7 These findings demonstrate that thiopentone so dium, which acts as a free radical scavenger, protects the CNS neurone s against NO-mediated cytotoxicity in vitro. In conclusion, thiopenton e sodium is one of the best of the currently available pharmacological agents for protection of neurones against intraoperative cerebral isc haemia.