Influence of Long-term Repetitive Rotatostimulations on Lateral Semicircular Canals

Abstract

Sixty-five guinea pigs were used to investigate the influence of rotatostimulations on the lateral crista ampullaris. After repeated turning stimulations with the cupulometric mode (the terminal turning velocity: 180"lsec) for 2 6 7 2 hours, the morphological changes in the crista ampullaris on the ampullopetal flow side were compared with those on the ampullofugal flow side by using scanning and transmission electron microscopy. Postrotatory nystagmus recorded by ENG during this experiment revealed the response decline phenomenon in all animals, and the caloric test performed after the rotatostimulation showed 'canal paresis' in the ear on the ampullopetal flow side. In a group stimulated for 24 hours, no particular damage on the crista ampllaris was noticed. However, in a group stimulated for 72 hours, local damage was dominant in the central part of the crista, which showed a tendency to extend towards the planum semilunatum according to an increment of changes. These findings were more remarkable on the ampullopetal flow side than on the ampullofugal flow side, suggesting the predominant effect of the ampullopetal endolymph flow in the lateral semicircular canal.

Long‐term behavioral effects observed in mice chronically exposed to static ultra‐high magnetic fields

“…Although habituation effects were reported for a limited number of repeated exposures (3 × 30 min in 14.1 T), such a mechanism is most likely insufficient to prevent a long-term vestibular system impairment because the habituation and adaptation processes suppress the perception, but not the stimulation itself. 51 These suggestions are in agreement with previously published reports that prolonged or intense stimuli, such as chronic weightlessness, 52 rotation, 53 changes in atmospheric pressure, 54 or even a percussive auditory stimulus 55 can cause long-lasting damage to the semicircular canals or otolith organs. 23 The assumption of vestibular apparatus impairment is supported by our observation that the direction of spinning (clockwise or counterclockwise) remains the same in mice for each animal that showed a consistent tight-circling behavior (Figure 6).…”

Repeated exposure attenuates the behavioral response of rats to static high magnetic fields

“…An alternative, however, is that responses are dampened after repeated exposure because the high magnetic fields persistently alter or damage the peripheral vestibular apparatus. Prolonged or intense stimuli, such as chronic weightlessness [50, 51], rotation [52], changes in atmospheric pressure [53], or even a percussive auditory stimulus [54] can cause long-lasting damage to the semicircular canals or otolith organs. In Experiment 3 we observed a long-term decrement (after 36 days) in the induction of locomotor circling, although not in CTA acquisition.…”

Validity of Ewald's law in the horizontal semicircular canals and the vestibular nuclei : Electron microscopic observation and quantitative (14C)-2-deoxy-D-glucose study.

“…Moreover, our recent scanning electron microscopic study (Hozawa et al 1984) suggested the predominance of the ampullopetal physical effect. Namely, the dominant morphological change of sensory cells, such an complete or incomplete loss of kinocilium and stereocilia could be observed in the tip of the crista ampllaris near the canalicular side.…”