Assessment of gentamicin-induced vestibulotoxicity by click and galvanic vestibular-evoked myogenic potentials: A guinea pig investigation

• Published in: Neurotoxicology (Park Forest South) 2010, Vol.31 (1), p.121-125
• Main Authors: Cheng, Po-Wen, Lue, June-Horng, Lin, Chi-Te, Day, An-Shiou, Young, Yi-Ho
• Format: Article
• Language: English
• Subjects: Acoustic Stimulation - methods; Animals; Antibacterial agents; Antibiotics. Antiinfectious agents. Antiparasitic agents; Biological and medical sciences; Electromyography - methods; Evoked Potentials, Auditory - drug effects; Functional Laterality; Galvanic vestibular stimulation; Gentamicin; Gentamicins; Guinea Pigs; Medical sciences; NAV1.8 Voltage-Gated Sodium Channel; Neck Muscles - physiopathology; Pharmacology. Drug treatments; Reaction Time - drug effects; Saccular macula; Sodium channel Nav1.8; Sodium Channels - metabolism; Toxicology; Vestibular Diseases - chemically induced; Vestibular Diseases - pathology; Vestibular Diseases - physiopathology; Vestibular ganglion; Vestibular-evoked myogenic potential
• ISSN: 0161-813X; 1872-9711
• DOI: 10.1016/j.neuro.2009.10.009

The aim of this investigation carried out with guinea pigs was to study the possible effects of a gentamicin treatment on the saccular macula and on its afferent vestibular ganglion neurons. The gentamicin-induced impairment was analyzed using vestibular-evoked myogenic potentials (VEMPs) elicited by both click and galvanic vestibular stimulations (GVS). Fifty μl of saline or gentamicin solution (40 mg/ml) was dropped over the round window membrane of the right (control) and left (lesion) cochleae, respectively. Four weeks after surgery, the VEMPs elicited with clicks and GVS were evaluated for each animal. Then, the animals were sacrificed in order to perform morphological and anti-Nav1.8 immunocytochemical analyses. Click- and GVS-VEMPs were obtained in all of the controls, whereas no potentials were obtained from gentamicin-treated animals. Lesions of sensory cells were observed in the saccular macula. In the injured vestibular ganglion, the percentage of voltage-gated sodium channel Nav1.8-like immunoreactive (Nav1.8-LI) neurons was significantly lower (38.9 ± 0.7) than that (53.6 ± 3.2) calculated in controls. Gentamicin-induced impairments of the saccular macula and afferents of guinea pigs can be evaluated by recording both click- and GVS-VEMPs. Both tests provide information on the sacculo-collic reflex pathway and could help a clinical diagnosis of gentamicin intoxication by conventional eardrops in the patient with a perforated eardrum.