[The effect of microgravity on the state of compensation in one-side labyrinthisized newts]

Experiments were performed on newts Pleurodeles waltii subjected to one-side labyrinthectomy 1, 2, 5, and 6 mos prior to a spaceflight on board the orbital complex Mir. Duration of the exposure in microgravity was 8, 31 and 73 days. Destruction of one labyrinth in the newts brought about a number of characteristic reactions, i.e. rollover, circling and sideway movements with the head on a solid substrate and spinning about the longitudinal body axis when in water. These reactions were directed exclusively towards the labyrinthectomized side, their intensity faded, and typically in 1.5 mos. following surgery the motor activity of the newts was close to the norm. In the weight-free conditions the animals appeared to lose compensation they had formed on Earth. During 1.5 days of return the newts were unable to walk and their heads were turned towards the labyrinthectomized side. Immersed in water, the animals started spinning also towards this side. Two days later, they regained the ability to walk without assistance but with evident signs of ataxia. In 40 days after flight, the animals still exhibited locomotor disturbances during walk and swimming.