Pharmacological activity of the Ginkgo biloba extract (EGb 761) on equilibrium function recovery in the unilateral vestibular neurectomized cat.

Locomotor balance recovery after unilateral vestibular neurectomy has been found strongly accelerated in the cat when the animals received a postoperative treatment with Ginkgo biloba Extract (EGb 761:50 mg/kg/d, i.p.), a result due to the improvement of plasticity mechanisms involved in vestibular compensation. The aim of this study was to determine which of the two main biochemical components (terpenes vs. flavonoids) contained in the extract was the most active in the recovery process, to test the influence of the route of administration, and to look for dose-dependent effects. Experiments were performed in six experimental groups of cats that were compared with each other and with three control groups. Comparisons were done on the recovery profile and time course of equilibrium function restoration, as quantified by the rotating beam test. Four experimental groups were treated with the standardized extract EGb 761 given orally (p.o.:2 groups; 40 mg and 80 mg/kg) or intraperitoneally (i.p.: 2 groups; 50 mg and 25 mg/kg), whereas the two others received only a special extract that did not contain the terpenes (i.p. administration: 25 mg and 10 mg/kg). Treatment was always given until complete recovery of locomotor balance function. The control groups received either no treatment (untreated cats), an oral vehicle (placebo cats), or a sham i.p. injection (sham cats). Results showed that locomotor balance recovery was significantly improved in all the experimental groups as compared to the control groups of cats, which recovered similarly and more slowly. Efficacy of the special extract without the terpenes was comparable to that of the total extract, indicating that the nonterpenic fraction was the most active biochemical constituent in this experimental model of central nervous system (CNS) plasticity. Pharmacological activity of the extract was also significantly better when given i.p. as compared to the p.o. route of administration, and dose-dependent effects were evidenced with the i.p. administration of the special extract without the terpenes, with a lower efficacy for the lowest dose (10 mg/kg). These data confirm that EGb 761 treatment serves as useful therapy in supporting brain functional recovery in this animal model of vestibular compensation and lead to a more precise understanding of the biochemical component that is active in this recovery process.