Postweaning Isolation Rearing Alters the Adult Social, Sexual Preference and Mating Behaviors of Male CD-1 Mice

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.

Keywords: isolation rearing; male CD-1 mice; mating behavior; postweaning; sexual preference; social behavior.

FIGURE 1

Results of social affiliation test. (A) Recognition indexes of stimulus mouse and empty cage. (B) Recognition indexes of stimulus mouse and object. ^∗∗∗ indicate p < 0.001. Bar represent mean. Error bar represent standard deviation (SD).

FIGURE 2

Discrimination index of isolation-reared and group-housed mice in the social recognition tests. ^∗Indicate p < 0.05. Bar represent mean. Error bar represent SD.

FIGURE 3

The exploration time of isolation-reared and group-housed mice in the social memory tests. ^∗Indicate p < 0.05. Bar represent mean. Error bar represent SD.

FIGURE 4

Box plots of attack latency and duration in the resident–intruder tests. (A) Attack latency of isolation-reared and group-housed mice. (B) Attack duration of isolation-reared and group-housed mice. ^∗∗∗Indicate p < 0.001. Bar represent minimum or maximum. ^□Represent mean.

FIGURE 5

Results of sexual preference test. (A) The exploration time of isolation-reared and group-housed mice toward stimulus male and female. (B) The sexual preference indexes of isolation-reared and group-housed mice. ^∗Indicate p < 0.05. Bar represent mean. Error bar represent SD.

FIGURE 6

Results of heterosexual behavior test. (A) Box plot of the mounting latency of isolation-reared and group-housed mice. (B) Box plot of the intromission latency of isolation-reared and group-housed mice. (C) The total mating duration of isolation-reared and group-housed mice. ^∗∗Indicate p < 0.01.