Behavioural changes induced by early and long-term gravito-inertial force modification in the rat.
The study concerns rats conceived, born and raised in a hypergravity environment (HG: 2 g) for 3 months using a centrifuge. They were then exposed to terrestrial gravity (1 g) and submitted to behavioural tests investigating their spontaneous locomotor activity (open-field), their posture (support surface), and their vestibular function (air-righting reflex). Performances were compared to age-matched control rats housed at 1 g for the same time period. Results showed static and dynamic behavioural deficits as early as the rats were exposed to normal gravity. They exhibited strongly increased motor activity in open-field, with longer travelled distances and more scattered trajectories; in addition, the HG rats displayed more numerous rearings than controls did. They showed postural changes characterized by an enlarged support surface and they did not succeed in the air-righting reflex, due to increased time-delay for head righting. None of these changes were permanent. Indeed, for all tests, the HG rats tested after 3 weeks spent in normal terrestrial gravity exhibited behaviours similar to those of the controls. HG-induced changes in the functional properties of the vestibular system may explain the deficits showed by the HG rats once exposed to normal gravity. The adaptation process to 1 g leading to the appearance of normal behaviour takes about 3 weeks. It likely implicates a central re-evaluation of the sensory inputs and an updating of the motor commands.
Bouët
V
V
UMR 6149, Laboratoire de Neurobiologie Intégrative et Adaptative, CNRS/Université de Provence, 52, Faculté de St Jérôme, Case 361, 13397 Marseilles Cedex 20, France.
Gahéry
Y
Y
Lacour
M
M
D000222:Adaptation, Physiological / Q000502:physiology; D000818:Animals; D005106:Exploratory Behavior / Q000502:physiology; D005260:Female; D018471:Hypergravity; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D004856:Postural Balance / Q000502:physiology*; D011187:Posture; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D011434:Proprioception / Q000502:physiology*; D051381:Rats; D012018:Reflex / Q000502:physiology; D014724:Vestibular Function Tests