Repeated acute exposures to hypergravity during early development subtly affect CD-1 mouse neurobehavioural profile

Exposure to altered gravitational environment, especially during critical ontogenetic phases, may induce persistent nervous system modifications and behavioural anomalies. This study evaluated the effects of hypergravity exposure on the development of the nervous system and assessed the relevance of parity in the mother's responses to altered gravitational stimuli. CD-1 mouse pups of both sexes delivered by primiparous and biparous dams were exposed to 1h of 2 G rotationally induced hypergravity from PND2 to PND9. Sensorimotor responses and somatic growth were daily measured (PND2-PND15), ultrasonic vocalisations recorded on PNDs 2, 5 and 9, and homing behaviour evaluated on PND12. In addition, spatial orientation ability was assessed in a T-maze on PND18, while mice exploratory behaviour and locomotor activity were evaluated in an open-field test (PND21). Long-term effects of hypergravity exposure on both spatial learning (Morris water-maze test) and brain levels of NGF and BDNF were also investigated at adulthood. Rotation per se induced a delay in somatic growth, sensorimotor responses and ultrasonic vocalisation profile, while hypergravity highlighted sex differences in open-field behaviour. Strategies to solve a spatial learning task, rather than learning per se, were affected by early exposure to rotation, while hypergravity selectively altered behavioural profile in the reversal phase of the test. Early exposure to rotation per se also decreased hypothalamic BDNF levels, while hypergravity reduced NGF levels in the frontal cortex. Previous maternal experience did not interact with hypergravity exposure, while differences between offspring of primiparous and biparous dams were observed in sensorimotor development and exploratory behaviour.