High Frequency Rotation Sensation Function Damage Of The Crista Of The Horizontal Semicircular Canal Induced By Gentamicin And Its Morphological Basis

Part oneThe establishment of guinea pigs model of the damage of vestibule horizontal semicircular canal induced by gentamicinObjective:The goal of the present study was to develop a guinea pig model of the damage of vestibule horizontal semicircular canal induced by gentamicin, providing basis for the experiments afterwards. Methods:The guinea pigs were randomly divided into four groups (groupl,2,3 and control group, n=5). The animals of treated groups received gentamicin subcutaneously (50 mg/kg per d) for 1 week (group1),2 weeks (group 2) and 3 weeks (group3), respectively. The animals of control group were administered with equal volume of saline subcutaneously. After VNG and VsEP were examined, the cristae of the horizontal semicircular canals were prepared for scanning and transmission electron microscopy. Results:Electron microscopy was used to observe the crista hair cells of the four groups. In control group, the hair cells were normal. In group 1, almost normal appearance with slight edema of the hair cells was showed. In group 2, some hair cells in the central top of the crista necrosed, but other hair cells in the peripheral area showed normal appearance. In group 3, vestibular hair cells were entirely impaired or necrosis. Conclusions:These results show that the damage induced by gentamicin is concentrated on the top area and then subsequently extends to the peripheral area of vestibular crista. This model establishment method of guinea pigs is simple and effective. Part twoThe Videonystagmography (VNG) recording of guinea pigsObjective:The goal of the present study was to develop the Videonystagmography (VNG) recording of guinea pigs and to explore high frequency rotation sensation function damage of the crista of the horizontal semicircular canal induced by gentamicin. Methods:The guinea pigs were randomly divided into four groups (group 1,2,3 and control group, n=20). The animals of treated groups received gentamicin subcutaneously (50 mg/kg per d) for 1 week (groupl),2 weeks (group 2) and 3 weeks (group3), respectively. The animals of control group were administered with equal volume of saline subcutaneously. Videonystagmography (VNG) evoked by ice water or high frequency rotations after the administration. Nystagmus frequency and duration were recorded. Results:In VNG examination after ice water stimulation, no obvious nystagmus was observed in the animals of group 3, and there was no significant difference in nystagmus frequency and duration among groupl,2 and control group(P>0.05). After high frequency rotations, no obvious nystagmus was yet observed in the animals of group 3. There were significant differences in the nystagmus frequency and duration of the VNG waves between the experimental group 2 and control group (P<0.01), and no difference was found between group1 and control group(P>0.05). Conclusions:These results show gentamicin selectively induces high frequency rotation sensation function damage of the crista of the horizontal semicircular canal. The damage is concentrated on the top area and then subsequently extends to the peripheral area of vestibular crista. Part threeThe vestibular evoked potential (VsEP) recording of guinea pigsObjective:The goal of the present study was to develop the vestibular evoked potential (VsEP) recording of guinea pigs and to explore high frequency rotation sensation function damage of the crista of the horizontal semicircular canal induced by gentamicin. Methods:The guinea pigs were randomly divided into four groups (group 1,2,3 and control group, n=20). The animals of treated groups received gentamicin subcutaneously (50 mg/kg per d) for 1 week (group1),2 weeks (group 2) and 3 weeks (group3), respectively. The animals of control group were administered with equal volume of saline subcutaneously. Vestibular evoked potential (VsEP) evoked by low and high frequency rotations after the administration. The latencies and amplitudes of P1 and P2 waves were recorded. Results:In VsEP examination, there was no significant difference in the parameters of VsEP among group 1,2 and control group (P>0.05), and VsEP was not observed in group 3 after low fequecy rotations. After high frequency rotations, compared with control group, the latencies and amplitudes of P1 and P2 in group 2 significantly decreased (P<0.01), while no changes were found in group 1 (P>0.05). Group 3 had no response of VsEP to high frequency rotations. Conclusions:These results show gentamicin selectively induces high frequency rotation sensation function damage of the crista of the horizontal semicircular canal. The damage is concentrated on the top area and then subsequently extends to the peripheral area of vestibular crista. It can be inferred that the hair cells in the central top area of the crista are involved in high frequency rotation vestibular perception.