Vol.100 No.4 contentsPRACTICA OTO-RHINO-LARYNGOLOGICA
Vol. 100 No. 4 April 2007
Ginsenoside Rb1 Protects against Inner Ear Damage
after Transient Ischemia
Kensuke Fujita
(Ehime University Graduate School of Medicine)
Ginsenoside Rb1 (gRb1) is a main ingredient of ginseng root, which has been prescribed to patients for thousands of years in Asian countries without apparent adverse effects. We investigated the protective effects of gRb1 against ischemic damage of the cochlea. Ischemic insult was loaded by occluding the bilateral vertebral arteries for 15 min in a gerbil, which lacks posterior communicating arteries causing the cochlea to be nourished solely by the vertebral arteries. GRb1 was dissolved in isotonic saline. Then, 200 mL of gRb1 solution (50 mg/200 mL) was injected into the left femoral vein 1 h after inducing ischemia. Hearing was assessed by recording the auditory brainstem responses (ABR). Seven days after ischemia, the animal showed a 22.5 dB increase in ABR threshold, 26.5％ loss of the inner hair cells at the basal turn, and 19.3 cells/10000 mm2 spiral ganglion cell density on average in 6 ears. In the ischemia-gRb1 group, the ABR threshold increase was 14.2 dB, inner hair cell loss was 8.6％, and the density of spiral ganglion cells was 25.8 cells/10000 mm2. These findings suggest that gRb1 inhibited ischemic injury of the inner ear.
Key words : ginseng root, ischemia, auditory brainstem response, inner hair cell, spiral ganglion cell