Effect of an extract of Ginkgo biloba on rat brain energy metabolism in hypoxia.

The purpose of the present investigation was to determine brain energy metabolism under hypoxic conditions as influenced by an extract of Ginkgo biloba (EGB). Male Sprague-Dawley rats treated with EGB were exposed to hypobaric or hypoxic hypoxia, and at various time points during or after hypoxia the levels of high-energy phosphates and some substrates of glycolysis were measured in brain cortical tissue. Rats treated with EGB (100 mg/kg, intraperitoneally) survived hypobaric hypoxia for a much longer period than controls (e.g. controls: 3.9 +/- 1.8 min, EGB-treated: 23.6 +/- 10.5 min). The brain glucose level was elevated by EGB in most experimental series, and the lactate concentration was slightly lower than in control brains. The lowering of lactate/pyruvate ratio was due to the decreased level of lactate and to the enhanced concentration of pyruvate as well. When hypoxia was sufficiently severe the breakdown of high-energy phosphates was less pronounced in EGB-treated animals. After oral application of EGB for 14 days the rats survived hypobaric hypoxia for 25.7 +/- 2.5 min whereas controls survived for 11.5 +/- 5.1 min. However, brain energy metabolism was not significantly influenced by this oral treatment. It is suggested that changes in brain energy metabolism and blood flow may contribute to the protective effect of EGB against hypoxia.