Correlation of inbred mouse sensitivity to nitrous oxide antinociception with brain nitric oxide synthase activity following exposure to nitrous oxide.
Inhibition of nitric oxide synthase (NOS) antagonizes nitrous oxide (N2O)-induced antinociception in mice. This study was conducted to compare brain NOS activity in high responding C57BL/6 mice, low responding DBA/2 mice and S5 mice selectively bred for low responsiveness to N2O. Exposure to 70% N2O suppressed acetic acid-induced abdominal constrictions in C57BL/6 mice but not DBA/2 or S5 mice. N2O exposure also elevated NOS activity in brains of C57BL/6 mice but not DBA/2 or S5 mice. The absence of these effects in DBA/2 or S5 mice is further support for the hypothesis that nitric oxide (NO) may play a critical role in N2O-induced antinociception in mice.