Evidence that the ginkgo biloba extract, EGb 761, neither accelerates nor enhances the rapid compensation of the static symptoms of unilateral vestibular deafferentation in guinea pig.

The concentrated Ginkgo biloba extract, EGb 761, has previously been reported to enhance and accelerate vestibular compensation following unilateral vestibular deafferentation (UVD), in particular, compensation of the dynamic postural symptoms such as locomotor dysequilibrium. However, many of these studies have not included a complete analysis of the static symptoms of UVD, such as spontaneous nystagmus (SN), yaw head tilt (YHT), and roll head tilt (RHT), nor have they included a dose-response analysis or vehicle controls for EGb 761. The aim of the present study was to examine the effects of the EGb 761 extract on static vestibular compensation in guinea pig, using a dose-response analysis and both vehicle and saline controls. Analysis of variance showed that there was a significant decrease in SN frequency (P < 0.05) and a significant change in the rate of SN compensation (P < 0.05), using 3 i.p. injections of EGb 761 (25, 50, or 100 mg/kg), or vehicle, or saline, at 0, 25, and 40 h post-UVD. However, post-hoc testing revealed that this was due entirely to significant differences between the saline and vehicle groups at 35, 40, and 50 h post-UVD (P < 0.05 in all cases) and between the saline and the 100 mg/kg and 25 mg/kg EGb 761 groups at 35 and 50 h post-UVD, respectively (P < 0.05 for both comparisons); there were no significant differences between the vehicle and drug groups at any time. YHT and RHT were not significantly different between the drug, saline, and vehicle groups. In a second set of experiments, the 50 and 100 mg/kg EGb 761 i.p. injection frequencies were doubled. However, once again, neither SN nor YHT were significantly different between the EGb 761 groups and the vehicle controls. These results suggest that 1) EGb 761 does not significantly enhance or accelerate compensation of the static symptoms of UVD in guinea pig and 2) the EGb 761 vehicle may exert some effects on its own. Therefore, EGb 761 may be of limited use in the treatment of acute vestibular dysfunction in humans.