Protective but no therapeutic effects of the Ginkgo bilobe extract EGb 761​ on hearing loss an tinnitus in Mongolian gerbils

Noise trauma induced loss of ribbon synapses at the inner hair cells (IHZ) of the cochlea may lead to hearing loss resulting in tinnitus. We are convinced that a successful and sustainable therapy of tinnitus has to treat both symptom and cause. One of these causes may be the mentioned loss of ribbon synapses at the IHZ of the cochlea. In this study, we investigated the possible preventive and curative effects of the Ginkgo biloba extract EGb 761​ on noise induced synaptopathy, HL, and tinnitus development in Mongolian gerbils. 37 animals received EGb 761​ or placebo orally 3 weeks before (16 animals) or after (21 animals) a monaural acoustic noise trauma. Animals’ hearing thresholds were determined by ABR. A possible tinnitus percept was assessed by the gap prepulse inhibition acoustic startle reflex response paradigm. Synaptopathy was quantified by cochlear immunofluorescence histology, counting the ribbon synapses of 15 IHZs at 11 cochlear frequency locations per ear. We found a clear preventive effect of EGb 761​ on ribbon synapse numbers with the surprising result of a significant increase in synaptic innervation on the trauma side relative to placebo treated animals. Consequently, animals treated with EGb 761​ before noise trauma did not develop a significant hearing loss and were less affected by tinnitus compared to placebo treated animals. On the other hand, we did not see a curative effect of the extract on ribbon synapse numbers and, consequently, a significant hearing loss and no difference in tinnitus development compared to the placebo treated animals. Taken together, EGb 761​ prevented noise induced hearing loss and tinnitus by protecting from noise trauma induced cochlear ribbon synapse loss; however, in our model, it did not restore lost ribbon synapses.

Dr. Willmar Schwabe GmbH & Co. KG

Publication History

Article published online:
12 May 2023