Abstract
Objective: No study has comprehensively evaluated the effect of postweaning isolation on the social and sexual behaviors of a certain strain of rodents in ethology. The present study aims to explore how and to what extent isolation rearing after postweaning affects the social and sexual behaviors of male CD-1 mice in adulthood systematically.Methods: Male CD-1 mice were randomly assigned to two groups: isolation reared (IS, one mouse per cage, n = 30) and group housed (GH, five mice per cage, n = 15). The mice underwent isolation rearing from postnatal day 23 to day 93. Then, social affiliation, recognition and memory were measured through selection task experiments. Social interaction under a home cage and novel environment were measured via resident–intruder and social interaction test, respectively. Furthermore, sexual preference, homosexual and heterosexual behaviors were measured.Results: Our study found that postweaning isolation increased the social affiliation for conspecifics (p = 0.001), reduced social recognition (p = 0.042) and impaired social memory. As for social interaction, isolated mice showed a remarkably increased aggression toward the intruder male in a home cage or novelty environment. For instance, isolated mice presented a short attack latency (p < 0.001), high attack frequency (p < 0.001) and long attack duration (p < 0.001). In addition, isolated mice exhibited further social avoidance. Contrastingly, isolated mice displayed a reduced sexual preference for female (IS: 61.47 ± 13.80%, GH: 70.33 ± 10.06%, p = 0.038). As for heterosexual behavior, isolated mice have a short mating duration (p = 0.002), long mounting latency (p = 0.002), and long intromission latency (p = 0.015). However, no association was observed between postweaning isolation and homosexual behavior in male CD-1 mouse.Conclusion: Postweaning isolation increased the social affiliation, impaired the social cognition and considerably increased the aggression in social interaction of adult male CD-1 mice. Postweaning isolation induced a decreased sexual preference for female in adulthood. Postweaning isolation extended the latency to mate, thereby reducing mating behavior. No association was observed between isolation and homosexual behavior.
Highlights
Life stress can produce far-reaching deleterious effects on behavior in adult life (Lupien et al, 2009)
In the homosexual behavior test, no association was observed between postweaning isolation and homosexuality in male CD-1 mice
The results indicate that postweaning isolation extends the latency to mate and further leads to reduced mating behaviors in male CD-1 mice
Summary
Life stress can produce far-reaching deleterious effects on behavior in adult life (Lupien et al, 2009). Postweaning social isolation in rat and mouse induces behavioral changes that provide a set of models for abnormal social behaviors. Researchers often test social recognition or memory to reflect the social cognition function. Isolated mice from PND 30 to PND 60 exhibited a decline capability for social recognition and were less likely to discriminate between familiar and unfamiliar conspecifics (Kercmar et al, 2011). This finding indicated isolation affects the social cognition. Social interaction tests involve observing how two unfamiliar rats/mice placed together in a novel environment will explore the new cage and investigate each other (Crawley, 2007). Isolated rats from PND 19 to PND 72 displayed marked elevations in the numbers of contacts and total time spent in contact during social interaction test (Varlinskaya and Spear, 2008; Hermes et al, 2011; Moller et al, 2013)
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