Behavioural responses to single and repeated restraint in male and female rats

The effects of single and repeated restraint (RT) on non-social behaviour were investigated in male and female rats. The animals underwent either 15-min or 30-min single RT (Experiment 1), or daily 30-min RT for 7 days (Experiment 2). Behavioural parameters recorded included locomotion and exploration in the hole-board and anxiety in the elevated plus-maze. Effects of RT depended on sex, parameter and schedule of RT administration. After 15-min single RT, anxiety increased and exploration decreased in males; after 30-min single RT, motor activity decreased in both sexes, and anxiety increased in females. After repeated RT, exploration and anxiety were unmodified in males, indicating habituation. Residual emotionality was suggested by increased time spent self-grooming and preferential locomotion in the peripheral squares of the open field. In females, habituation was observed in locomotion and anxiety. Interestingly, parameters which did not habituate suggested decreased emotionality: exploration increased, and ambulation in central squares was preferred to peripheral locomotion. Caution is needed in taking these marginal modifications of female behaviour as facilitatory effects, possibly concurring to increase individual fitness. In summary, both single and repeated RT caused less behavioural deficits in females than in males. Effects on exploration were sex-dependent, and different after single and repeated stress. Locomotion in peripheral vs. central squares, and self-grooming, were also affected by RT sex-dependently, but with similar effects after single and repeated stress. In contrast with the above-mentioned items, modifications of anxiety appeared uninfluenced by sex.