Altered Behaviour of Hamsters by Prolonged Hypergravity: Adaptation to 2.5 G and Re-adaptation to 1 G

Abstract

We studied the functional adaptation process in 40 hamsters subjected to either prolonged hypergravity to normal gravity. Subadult golden hamsters (n = 20) exposed to a hypergravity condition of 2.5 G for 6 months were tested to investigate the effect of hyper gravity on the perceptive motor skills and compared with control hamsters (n = 20). The motor coordination of the hypergravity hamsters hardly changed; locomotion was normal and swimming was possible. Equilibrium maintenance was disturbed during the first 3 months as was shown by the higher crossing time (p < 0.001) and higher fall frequency (p < 0.001) for the hypergravity group. Significant differences were also found in orientation during swimming (p = 0.007) and turning behaviour in the rotation task (p < 0.001) and in the no-rotation task (p = 0.029). After 6 months, 10 hamsters of both groups were tested for another 4 months, also the hypergravity hamsters were living at 1 G. Differences in orientation in the two groups did not change during swimming and turning behaviour during the rotation task (p = 0.026). Based on our findings, we conclude that the hamsters functionally adapted to hypergravity, which led to an altered performance of several tasks. The condition continued after 4 months of normal gravity.

Altered Behaviour in Hamsters Conceived and Born in Hypergravity

“…Other studies have reported the behavioural disturbances in animals postnatally exposed to hypergravity [4][5][6]9,30,31] sults obtained from these studies will be compared with the results obtained from the present one.…”

“…The HL and HS hamsters remained low in body weight and looked smaller even after a long period in normal gravity. More evidence that HG animals are smaller is found in the work of Amtman and Oyama [1] who found a repression of linear growth in the overall size of rats exposed to 2.76 G. The persistent body weight decrease was also found in hamsters postnatally exposed to hypergravity [31]. This alteration occurred in both pre-and postnatally hypergravity exposed animals and thus proved to be independent of the gravity level in which the embryonal development took place.…”

“…The authors suggested that sustained body weight decrease was the result of a physiological regulation to adjust the animal to hypergravity. Hamsters born in hypergravity and hamsters postnatally exposed to hypergravity weighed less than the CON hamsters even after months of normal gravity showing a persistent alteration of the body weight [31].…”

“…The shape of the maze was similar to our earlier experiments [30,31]. If the hamsters were capable of finding the ladder in the lane, their orientation ability in the maze was assessed.…”

“…Animals postnatally exposed to hypergravity also showed disruption of behaviour in tasks that require normal vestibular functioning [4,5,9,31]. Swimming and air-righting are tasks that depend on correct peripheral vestibular information for normal performance [10,12,21,33].…”