Increase of hypoxic tolerance in rat hippocampal slices following 3-nitropropionic acid is not mediated by endogenous nerve growth factor.

Chemical preconditioning with low dose inhibition of succinic dehydrogenase by 3-nitropropionic acid (3-np) increases tolerance against succeeding hypoxia. Supraphysiological doses of nerve growth factor (NGF) repeatedly were shown to protect against ischemic damage. We investigated whether increased tolerance against hypoxia results from increased or accelerated production of endogenous NGF. Average recovery of population spike amplitude after 15 min of hypoxia and 45 min of reoxygenation was 31 +/- 9% (mean +/- SE) in control hippocampal slices. After pretreatment with 3-np (single i.p. injection of 20 mg/kg body weight 1 h to 3 days prior to slice preparation), recovery exceeded 90% (P < 0.01). However, NGF content did not increase upon slice preparation, hypoxia in vitro, and pretreatment with 3-np in vivo 1 h to 1 day prior to slice preparation with and without additional hypoxia in vitro. We conclude that early-onset tolerance to hypoxia induced by 3-np treatment is not caused by induction of endogenous NGF production.