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 flow leads to an initiation of a neurotoxic cascade including NO and
peroxynitrite.
Barbiturates are often used to protect neurones against
cerebrovascular disorders clinically. However, its neuroprotective mechanism remains unclear. 2. In the present experiment, we established a new in vitro model of
brain injury mediated by NO with an NO-donor,
1-hydroxy-2-oxo-3-(3-aminopropyl)-3-isopropyl-1-triazene (NOC-5) on grid tissue culture wells. We also investigated the mechanisms of protection of CNS neurones from NO-induced neurotoxicity by
thiopentone sodium, which contains a sulphydryl group (SH-) in the medium, and
pentobarbitone sodium, which does not contain SH-. 3. Primary cultures of cortical and hippocampal neurones (prepared 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 microM of
thiopentone sodium or
pentobarbitone sodium with or without 30 microM
NOC-5. In addition,
superoxide dismutase (SOD) at 1000 u ml(-1) and 30 microM
NOC-5 were co-administered for 24 h to evaluate the role of SOD. 5. Exposure to
NOC-5 induced neural cell death in a dose-dependent manner in both cortical and hippocampal cultured neurones. Approximately 90% of the cultured neurones were killed by 100 microM
NOC-5. 6. This NOC-5-induced neurotoxicity was significantly attenuated by high concentrations of
thiopentone sodium (40 and 400 microM) as well as SOD, but not by
pentobarbitone sodium. The survival rates of the cortical neurones and hippocampal neurones that were exposed to 30 microM
NOC-5 were 11.2+/-4.2% and 37.2+/-3.0%, respectively, and in the presence of 400 microM
thiopentone sodium, the survival rate increased to 65.3+/-3.5% in the cortical neurones and 74.6+/-2.2% in the hippocampal neurones. 7. These findings demonstrate that
thiopentone sodium, which acts as a
free radical scavenger, protects the CNS neurones against NO-mediated cytotoxicity in vitro. In conclusion,
thiopentone sodium is one of the best of the currently available pharmacological agents for protection of neurones against intraoperative cerebral ischaemia.