Objectives: To demonstrate real-time changes in nitric oxide (NO) production within fetal rat brain during uteroplacental ischemia and subsequent reperfusion, Methods: Using a selective microsensor for NO, changes in NO electrocurrent in the brains of 10 fetal rats at gestational day 20 were observed during and after 30 min occlusion of uterine vessels in anesthetized pregnant rats, Results: The NO electrocurrent reached 397 +/- 71.0% of the control level 30 min after occlusion and increased throughout the observation (p < 0.05) until placental administration of 1 M of L-NAME, In contrast, no significant changes in NO electrocurrent were found in 7 sham operated rats. Conclusion: An NO-specific microelectric sensor detected excessive NO production by fetal rat brains in response to uteroplacental ischemia, Copyright (C) 1999 S.Karger AG, Basel.