Immunohistological evidences of Ginkgo biloba extract altering Bax to Bcl-2 expression ratio in the hippocampus and motor cortex of senescence accelerated mice

Ginkgo biloba extract 761 appears to display neuroprotective effect in many nervous diseases and aging. Deterioration of mental functions during aging is always accompanied by loss of neurons, presumably through apoptosis. Here, we studied the effect of G. biloba extract in the expression of Bax/Bcl-2 ratio, an important apoptotic index, in the hippocampus and motor cortex of the aging brain. Bax and Bcl-2 expressions were examined with immunohistochemical methods. Senescence Accelerated Mice Prone Strain 8 was used because the aging process was accelerated with neuropathological alterations similar to those found in the aging human brain. The mice were fed with either G. biloba extract or sucrose from the age of 3 weeks until sacrifice at 3 or 9 months old. In the hippocampus of G. biloba fed 9-month-old mice, the ratio of Bax positive cell to Bcl-2 positive cell (Bax/Bcl-2 expression ratio) was 11.43 +/- 3.11 (mean +/- SD); significantly lower (P<0.05) than the Bax/Bcl-2 expression ratio of 20.99 +/- 5.34 in the sucrose fed mice. The Bax/Bcl-2 expression cell ratios, however, in the motor cortex were not significantly different between the two groups (2.22 +/- 1.35 versus 2.27 +/- 2.02 for the G. biloba and the sucrose fed mice, respectively). The decrease in the Bax/Bcl-2 expression cell ratio following G. biloba treatment might hence be able to protect the aging hippocampus from moving further down the apoptotic pathway. Western blotting confirmed the decrease of Bax in the brain even after a short term and high dose Ginkgo treatment. It is speculated that the G. biloba extract may be a potential neuroprotective agent against apoptosis through the differential expressions of the Bax and Bcl-2 in the hippocampus.