[Vestibular nystagmus in rats after hypokinesia and prolonged rotation].

Changes in the latent period, number of beats, duration and frequency of the nystagmus were investigated in rats exposed to angular acceleration of an increasing value (10, 20, 30, and 40 degree/cm2) after a 21-day exposure to hypokinesia per se or hypokinesia in a rotating device (with a radius of 141 cm, rate of rotation of 33.3 rpm, and acceleration value of 2 g). The hypokinetic rats showed nystagmic changes only with the lowest acceleration used (10 degrees/cm2). The hypokinetic animals rapidly adapted to a repeated exposure to angular acceleration during the recovery period. A 21-day exposure to hypokinesia in a rotating device disturbed adaptation to a repeated effect of angular acceleration during recovery. Mechanisms of these effects are discussed. It is concluded that hypokinesia cannot be an adequate model for studying weightlessness effects on the vestibular function.