Click-evoked potentials on the neck of the guinea pig

Vestibulocollic reflex in humans is called vestibular evoked myogenic potential. To try to establish an animal model of the acoustically evoked vestibulocollic reflex, 18 guinea pigs were used in this study. Eight of the 18 guinea pigs received intramuscular injection of amikacin for 18 days (450 mg/kg/day) before recording to destroy the cochlea pharmacologically. Under general anesthesia with intraperitoneal injection of pentobarbital sodium (40 mg/kg body weight), auditory brainstem responses (ABRs) were recorded. Then potentials on the neck evoked by loud clicks were recorded on the pre-vertebral muscle or on the spinal cord at the level of third cervical vertebral bone using a silver-ball electrode. As a result, a negative peak (NP) with a latency of 6 approximately 8 ms was observed on the neck muscle or on the spinal cord in the control group. The thresholds of the NP were 90-100 dB above those of ABRs. The NP was also observed in the amikacin-administered group using clicks with the same intensity as that for the control group, while the ABR thresholds were highly elevated. These results are in agreement with a vestibular origin of the NP potential.