Vestibular-evoked myogenic potentials recorded from miniature pigs and rats

OBJECTIVE: To report vestibular evoked myogenic potentials from different recording sites (neck extensor or masseter muscles) in miniature pigs and rats. METHODS: Potentials were recorded using 1000 Hz tone bursts from the neck extensor muscle or masseter muscle in normal adult Bama miniature pigs and rats anesthetized with 3% pentobarbital sodium and Sumianxin II. RESULTS: At 80 dB SPL, the first positive wave (P wave) of VEMPs was recognizable in 58% of rats with a latency of 6.45 ± 0.23 ms and an amplitude of 1.45 ± 0.49 μV when recorded from the neck extensor muscle, and in 50% of rats with a latency of 6.38 ± 0.34 ms and an amplitude of 1.57 ± 0.35 μV when recorded from the masseter muscle. In miniature pigs, at the same stimulus intensity, P wave was recognizable in 58% of the animals with a latency of 7.65 ± 0.64 ms and an amplitude of 1.66 ± 0.34 μV when recorded from the neck extensor muscle, and in 50% of the animals with a latency of 7.65 ± 0.64 ms and an amplitude of 0.31 ± 0.28 μV when recorded from the masseter muscle. CONCLUSION: VEMP can be induced from both neck extensor and masseter muscles in the miniature pig and rat. For a given species, the site of recording affects P wave induction rate and amplitude but not latency. Consistency and repeatability analysis suggests that the masseter muscle is a better recording site in miniature pigs while the cervical extensor is a better recording site in rats. For a given recording site, both latency and amplitude of the P wave are slightly greater in miniature pigs than in rats.